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Clinical Features and Outcomes of Holoprosencephaly in Korea
Clinical Features and Outcomes of Holoprosencephaly in Korea Jung Min Ko, MD* and Sung Hwan Kim, MD, PhD† The clinical spectrum of holoprosencephaly is broad, and its etiology is heterogeneous. To investigate the clinical spectrum of holoprosencephaly in Korea, we performed a database analysis of 55 cases of holoprosencephaly, including 12 diagnosed postnatally, all from a single institution. The 55 patients were categorized into several types: 37 alobar, eight semilobar, eight lobar, and two middle interhemispheric variant. Associated brain (41.8%) and craniofacial (74.5%) features varied substantially. Of 40 patients studied according to karyotype, chromosomal aberrations were detected in 18 (45.0%). Twenty-seven (49.1%) patients, diagnosed postnatally, exhibited milder types of holoprosencephaly and less profound craniofacial malformations than in prenatal diagnoses. Moreover, in postnatally diagnosed patients, the subgroup surviving longer than 1 month also exhibited a milder holoprosencephaly type and lower incidence of associated craniofacial malformations. The most frequent clinical signs in living children with holoprosencephaly included microcephaly, global developmental delay, and seizures. Holoprosencephaly represents a heterogeneous entity with different clinical manifestations and etiologies. A high index of suspicion, coupled with appropriate imaging studies, can enable accurate diagnoses and prognoses of holoprosencephaly. Ó 2010 by Elsevier Inc. All rights reserved. Ko JM, Kim SH. Clinical features and outcomes of holoprosencephaly in Korea. Pediatr Neurol 2010;43:245-252.
Introduction Holoprosencephaly is a structural anomaly of the brain in which the developing forebrain fails to divide into two sep-
From the *Department of Medical Genetics, and †Division of Pediatric Neurology, Department of Pediatrics, Ajou University School of Medicine, Suwon, South Korea.
Ó 2010 by Elsevier Inc. All rights reserved. doi:10.1016/j.pediatrneurol.2010.05.001 0887-8994/$—see front matter
arate hemispheres and ventricles. It occurs between days 18 and 28 of gestation, and affects both the forebrain and the face. This condition is estimated to occur in 1:250 embryos [1] and in 1:10,000 to 1:20,000 births [2]. Three ranges of increasing severity have been characterized: lobar, semilobar, and alobar holoprosencephaly. Another milder subtype of holoprosencephaly, referred to as the middle interhemispheric variant or syntelencephaly, is also reported [3-5]. A spectrum of craniofacial anomalies accompanies holoprosencephaly in approximately 80% of affected individuals, including cyclopia, proboscis, median or bilateral cleft lip and palate, ocular hypotelorism, and single central incisor. Developmental delays are evident in virtually all individuals with holoprosencephaly, and chronic seizures were associated in 40% as a complication [6]. The outcome of the disease is principally dependent on its severity and the associated medical and neurologic complications. Almost without exception, severely affected children do not survive beyond early infancy [6], but a significant proportion of more mildly affected children survive longer than 1 year [7]. Approximately 25-50% of individuals with holoprosencephaly also manifest a numeric or structural chromosomal abnormality [8]. Eighteen percent to 25% of individuals with monogenic holoprosencephaly manifest a recognizable syndrome, and the remainder exhibit nonsyndromic holoprosencephaly [9]. Thus far, more than seven genes have been positively implicated in nonsyndromic holoprosencephaly: SHH, ZIC2, SIX3, TGIF, PTCH, GLI2, and TDGF1 [10-13]. Nevertheless, in approximately 70% of patients, the molecular basis of the disease remains unknown, possibly suggesting the existence of several other candidate genes or environmental factors, such as maternal diabetes, drugs, or infection. In this study, we describe 12 cases of postnatally diagnosed holoprosencephaly in a single Korean institution
Communications should be addressed to: Dr. Kim; Division of Pediatric Neurology, Department of Pediatrics; Ajou University School of Medicine; San 5, Woncheon-dong; Youngtong-gu, Suwon 443-721, South Korea. E-mail: [email protected] Received January 17, 2010; accepted May 3, 2010.
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Table 1. Clinical characteristics in 12 cases of holoprosencephaly
Patient
Sex
GA (wk)
Birth Weight (kg)
Age at Diagnosis
Diagnostic Method
Holoprosencephaly Type
1 2 3 4 5 6 7 8 9 10 11 12
M F M M F M M F F F M F
37.5 38 41 34 36 43 38 37.5 36 32 37 38
3.44 1.87 3.1 1.5 3.8 2.5 3.1 2.72 2 2.36 2.4 3.06
1 day 1 day 1 day 1 day 1 day 15 days 1.4 years 6 months 1 day 4 years 4.5 years 1 year
Magnetic resonance imaging US US Autopsy Autopsy Autopsy Magnetic resonance imaging Magnetic resonance imaging Autopsy Magnetic resonance imaging Magnetic resonance imaging Magnetic resonance imaging
A A A A A S S S S L M M
Abbreviations: A = Alobar CL = Cleft lip CP = Cleft palate GA = Gestational age GDD = Global developmental delay HP = Hypopituitarism, including growth hormone deficiency HT = Hypotelorism L = Lobar M = Middle interhemispheric variant
Lissencephaly Dorsal cyst Dorsal cyst Dorsal cyst, Lissencephaly Pachygyria Schizencephaly Dorsal cyst Cortical dysplasia
MC = Microcephaly MO = Microphthalmia ONH = Optic nerve hypoplasia PP = Precocious puberty S = Semilobar SN = Single nostril SNHL = Sensorineural hearing loss SZ = Seizure US = Ultrasonography
between the years 1990 and 2009, along with a brief review of other Korean literature on this subject. Patients and Methods Study Population AJOU UNIVERSITY HOSPITAL CASES Between January 1990 and September 2009, 12 patients with holoprosencephaly were diagnosed at the Department of Pediatrics at Ajou University Hospital. All patients were evaluated and followed by one pediatric neurologist. Clinical data (including gestational age, birth weight, maternal age at delivery, age at diagnosis, method of diagnosis, type of holoprosencephaly, associated brain anomalies, associated facial anomalies, karyotype, family history, prognoses, and follow-up period) were collected via retrospective reviews of medical records. This study was approved by the Institutional Review Board at Ajou University Hospital, and informed consent was obtained from all parents before enrollment. Types of holoprosencephaly were classified into four grades of severity, according to the classification of Demyer [14] and the findings of neuroimaging studies [3,15]: alobar, semilobar, lobar, and middle interhemispheric variant. In alobar holoprosencephaly, the most severe form of this condition, only a single ventricle is evident, and the cerebral hemispheres are not separated. In semilobar holoprosencephaly, the left and right frontal and parietal lobes are fused, and the interhemispheric fissure is only present posteriorly. In lobar holoprosencephaly, the right and left cerebral hemispheres and lateral ventricles are largely separate, but the most rostral aspect of the telencephalon and the frontal lobes are fused, especially ventrally. The middle interhemispheric variant involves a failure of separation in the posterior frontal and parietal lobes, with a varying lack of cleavage of the basal ganglia and thalami, and absence of the body portion of the corpus callosum [3,15]. CASES FROM THE REVIEWED LITERATURE Forty-three prenatally or postnatally diagnosed cases of holoprosencephaly were identified in Korea via online database searches (KoreaMed) [16]. Inclusion criteria
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Associated Brain Anomaly
for this database study entailed cases of holoprosencephaly that were confirmed via neuroimaging (magnetic resonance imaging or high-quality computed tomography) reviews of postnatally diagnosed patients, and by typical sonographic findings such as abnormalities of the falx cerebri and face or other associated central nervous system malformations for prenatally diagnosed patients. In each prenatally diagnosed patient, an autopsy confirmed the initial sonographic diagnosis. The clinical variables examined in the 12 patients at Ajou University Hospital were also collected and analyzed.
Methods In total, 55 Korean patients (12 from Ajou University Hospital, and 43 from the reviewed literature) were divided into two groups: (1) 27 postnatally diagnosed, and (2) 28 prenatally diagnosed using sonography and confirmed by autopsy. Clinical characteristics were compared between the two groups. Moreover, in the postnatally diagnosed group, we compared variables between the subgroup that survived more than 1 month and the subgroup that died before age 1 month.
Statistical Analysis Statistical analyses were performed using SPSS for Windows, version 11.5 (SPSS, Inc., Chicago, IL). A Student t test was conducted to assess the possible relationships between maternal age and the group according to age at diagnosis, and the Mann-Whitney U test was used to compare gestational age, birth weight, and maternal age between the two postnatally diagnosed subgroups, according to duration of survival after birth. The frequencies of categorical variables such as sex ratio, type of holoprosencephaly, presence of craniofacial malformations, and family history were compared between the prenatally and postnatally diagnosed groups, using the Fisher exact test.
Craniofacial Anomalies HT, CL, CP HT, CL, CP, MO CL, CP, MO Cyclopia, Proboscis
HT, CP, SN, MO
Karyotype
Prognosis
46,XY 69,XXY 46,XY 46,XY 46,XX/hypdiploid 46,XY 46,XY 46,XX 46,XX 47,XXX 46,XY 46,XX
Survived Died (age 1 day) Died (age 1 day) Died (age 1 day) Died (age 1 day) Died (age 15 days) Survived Survived Died (age 1 day) Survived Survived Survived
Results Clinical Characteristics of 12 Patients With Holoprosencephaly From Ajou University Hospital All 12 patients (6 boys and 6 girls) included in this study were diagnosed postnatally, and their mean age at diagnosis was 1.6 years (range, 1 day to 4.5 years). Among these patients, six (50%) were referred because of severe facial dysmorphism, and were diagnosed on the day of birth. One patient who exhibited no facial anomalies was diagnosed by autopsy at age 16 days. Among five (41.7%) patients diagnosed after the neonatal period, none evidenced any facial dysmorphism. The mean age of mothers at time of delivery was 27.9 years (range, 22-34 years). One mother had become pregnant by in vitro fertilization, and none of the mothers had any history of chronic diseases (including diabetes mellitus) before or during the pregnancy. The mean gestational age at delivery was 37.3 weeks (range, 32-43 weeks). Four patients were delivered before 37 weeks of gestation, and one patient was delivered after 42 weeks of gestation. The mean birth weight was 2.7 kg (range, 1.5-3.8 kg). Seven (58.3%) patients were diagnosed via magnetic resonance imaging or high-quality computed tomography scans, and autopsies were conducted as a diagnostic tool in the other five patients, all of whom died during the neonatal period. The cerebral and facial features of patients are listed in Table 1. With regard to type of holoprosencephaly, five alobar (41.7%), four semilobar (33.3%), one lobar (8.3%), and
Complications in Survivors MC, GDD, HP, ONH
Epilepsy
Follow-Up (yr)
Generalized tonic seizures
6.9
MC, GDD MC, GDD, hypertonia, SNHL MC, GDD, PP, SNHL MC, GDD, HP MC, GDD
0.1 3.5 Complex partial seizures Complex partial seizures
5.9 0.1 0.1
two middle interhemispheric variant (16.7%) cases were identified. Associated cerebral anomalies were identified in eight (66.7%) patients. In those with alobar holoprosencephaly, variably sized dorsal sacs were detected in three patients, and lissencephaly was detected in one patient. Pachygyria and schizencephaly were detected in two patients with semilobar holoprosencephaly, respectively. Cortical dysplasia was detected in one patient with the middle interhemispheric variant. Four of five patients with alobar holoprosencephaly exhibited facial anomalies. The most severe facial phenotype, which involved cyclopia and proboscis, was present in one patient with alobar holoprosencephaly, and cebocephaly was evident in one semilobar patient. Midline cleft palate was detected in four patients (three alobar and one semilobar), and three also manifested cleft lip. Microphthalmia with distinct orbits were detected in two patients (one alobar and one semilobar). Karyotype analysis was performed in all 12 cases, and three (25%) demonstrated abnormal karyotypes such as 69,XXY, mosaicism of 46,XX and hypodiploidy, and 47,XXX. The first two karyotypes were discovered in the patients with alobar holoprosencephaly, and the third was detected in one of the lobar cases. The male/female sex ratio for all cases was 1.0:1.0. Although one patient who died 1 hour after birth manifested indistinguishable genitalia, chromosome analysis confirmed the 46,XX karyotype. Among our 12 patients, one (8.3%) was a familial case. The parents had a preterm delivery history of an anencephalic infant 2 years previously. No additional affected individuals were present on either side of the family, and the
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karyotype of this case was normal. Thus, an autosomal recessive inheritance of holoprosencephaly was suggested in this familial case. Although all 12 patients were born alive, four of the alobar cases and one of the semilobar cases died 24 hours after birth. One semilobar patient, who died at age 16 days because of respiratory difficulty and sepsis, was diagnosed at autopsy as manifesting holoprosencephaly. Neuropathologic examination at the microscopic level could not be performed in six autopsies. Six patients survived for more than 1 year. Five of these patients were diagnosed more than 1 month after birth and manifested no facial dysmorphism, and the sixth was the alobar patient who demonstrated hypotelorism coupled with cleft lip and palate. The mean duration of follow-up for these patients living with holoprosencephaly was 2.8 years (range, 1 month to 6.9 years). All six patients who survived for longer than 1 year have survived to date. Microcephaly (below the third percentile) and global developmental delay were identified in all six, and symptomatic seizures, controlled with antiepileptic drugs, developed in three (50%) patients. Their seizure types were neonatal-onset generalized tonic seizure in one patient of the alobar type, and complex partial seizures in the other two patients. Their electroencephalogram findings revealed slow background activities and focal spikes in all three patients with epilepsy, frontal fast activities in one patient with neonatal-onset generalized tonic seizure, and slow spike-and-wave complexes in two patients with complex partial seizures. The other three (50%) patients who had not previously experienced any seizures exhibited normal sleep and waking patterns according to electroencephalograms. Short stature with hypopituitarism and bilateral sensorineural hearing loss were each detected in two patients. Optic nerve hypoplasia in the spectrum of septo-optic dysplasia and central precocious puberty were each evident in one patient. Clinical Characteristics of 43 Holoprosencephaly Patients From Online Koreamed Database Among the 43 reported Korean patients with holoprosencephaly, 13 (30.2%) were male, and 20 (46.5%) were female. Phenotypic sex was not mentioned in the reports on the other seven (16.3%) patients, and the other three (7.0%) patients exhibited ambiguous genitalia. The mean gestational age at diagnosis was 26.6 6.6 weeks for 28 (50.9%) patients who were prenatally diagnosed, and 1.0 2.8 years for the 27 (49.1%) patients who were postnatally diagnosed. Mean maternal age at birth was 28.7 4.9 years, and mean gestational age at birth and birth weight were 39.0 1.7 weeks and 2.6 0.5 kg for postnatally diagnosed patients, respectively. One mother had a history of diabetes mellitus during her pregnancy. The tools used initially for diagnosis included ultrasonography in 29 (67.4%) patients (including all 28 diagnosed prenatally), magnetic resonance imaging in 10 (23.3%) patients, and autopsy in
248 PEDIATRIC NEUROLOGY Vol. 43 No. 4
four (9.3%) cases, without any imaging studies. The type of holoprosencephaly was classified as alobar in 32 (74.4%) patients, semilobar in four (9.3%) patients, and lobar in seven (16.3%) patients. Brain anomalies associated with holoprosencephaly were evident in 15 (34.9%) patients. Among them, dorsal sac (20.9%), hydrocephalus (16.3%), and lissencephaly (9.3%) were the most frequently detected anomalies. Craniofacial malformations were present in 36 (83.7%) patients, whereas in seven (16.3%) patients, isolated holoprosencephaly without any craniofacial malformation was evident. The eyes, the oral cavity and palate, and the nose were the most commonly affected organ systems, at frequencies of 69.8%, 41.9%, and 46.5%, respectively. Hypotelorism and cyclopia, as well as anophthalmia, provided the majority of ocular malformations, and cleft lip and/or palate proved to be the most frequent malformations. Proboscis and single nostril were the most frequently detected nasal malformations. Karyotyping was performed in 28 (65.1%) of 43 patients. Chromosomal aberrations that appeared to be a cause of holoprosencephaly were detected in 15 (53.6%) of 28 patients. Trisomy 13, which was detected in four patients, was the most frequently observed chromosomal aberration, and structural abnormalities of chromosome 13 were also evident in two other patients. The mother of one patient with 46,XY,rec(13)dup(13q)(p13;q21.3) was a carrier of a balanced chromosomal rearrangement. Structural abnormalities of chromosome 7 and triploidy were evident in three and two patients, respectively. Six patients with normal karyotypes had a positive family history of holoprosencephaly in their siblings, and the pattern of inheritance in these families appeared to be autosomal recessive. In 25 of 28 prenatally diagnosed patients, the pregnancy was terminated by missed abortion (7.1%) or induced preterm labor (82.1%). Three (10.7%) patients were delivered at full term, and one of them died on postnatal day 1. In the 15 postnatally diagnosed cases, seven (46.7%) died during postnatal month 1, and the other eight patients survived for a mean follow-up duration of 1.2 0.8 years. The principal causes of neonatal death comprised central apnea or respiratory difficulty. Frequently observed signs in survivors included microcephaly (100%), psychomotor developmental delay (62.5%), and epilepsy (50.0%). Other associated signs were also identified, including growth hormone deficiency or other pituitary hormone deficiencies (12.5%), hypertonia (12.5%), sensorineural hearing loss (12.5%), optic nerve hypoplasia (12.5%), and hypotonia (12.5%). Comparisons Between Two Groups According to Time of Diagnosis The 55 patients in total were classified into two groups: prenatally diagnosed, and the postnatally diagnosed. We then compared each clinical variable to identify differences between the two groups (Table 2). Differences in types of
Table 2. Types of holoprosencephaly observed in 55 patients
Type Alobar Semilobar Lobar MIH
Total (n = 55) n % 37 8 8 2
67.3 14.5 14.5 3.6
Prenatally Diagnosed Patients n
Total
23 3 2 0
14 5 6 2
Postnatally Diagnosed Patients Death <1 mo Survival $1 mo 11 2 1 0
3 3 5 2
Abbreviation: MIH = Middle interhemispheric variant
holoprosencephaly and the presence of craniofacial malformations were demonstrated to be statistically significant (Table 3). More severe types of holoprosencephaly were evident in the prenatally diagnosed group than in the postnatally diagnosed group, and this association proved meaningful, with a P value of 0.018. In addition, more craniofacial malformations were detected in prenatally diagnosed patients at a significantly greater frequency than in postnatally diagnosed patients (P = 0.026). We were unable to detect any differences in regard to maternal age at birth, the incidence of associated brain anomalies and chromosomal aberrations (Table 4), and the presence of a positive family history. Comparison Between Two Subgroups According to Duration of Survival After Birth in Postnatally Diagnosed Patients Among 55 patients in total, 27 with postnatal diagnoses were classified into two subgroups according to duration of survival after birth. In 14 patients, death occurred less than 1 month after birth, and 13 patients survived more than 1 month after birth. Differences in types of holoprosencephaly and the presence of craniofacial malformations were statistically significant. More severe types of holoprosencephaly were evident in the subgroup which survived more than 1 month after birth, and this association proved meaningful, with a P value of 0.022. Furthermore, significantly more craniofacial malformations were detected in the subgroup that died less than 1 month after birth than in the subgroup that survived (P = 0.041). None of the patients with cyclopia or proboscis survived more than 1 month after birth. Although birth weight tended to increase in the surviving subgroup (2.83 0.45 kg in the surviving subgroup vs 2.42 0.65 kg in the subgroup that died; P = 0.08), no differences between the two subgroups were evident in terms of sex ratio, gestational age, maternal age, the incidence of associated brain anomalies and chromosomal aberrations, and the presence of a positive family history. Discussion Holoprosencephaly is a genetically heterogeneous anomaly, and its phenotype is implicated in a variety of syndromes and chromosomal anomalies. Although
holoprosencephaly is divided into four types according to severity of the disease, these types should be envisioned as nodes on a continuous spectrum of abnormal hemispheric separation, rather than as clear and distinct divisions [9]. The most severe type of holoprosencephaly is alobar, and children with this type can present with severe craniofacial malformations, such as cyclopia or proboscis. The lobar or middle interhemispheric variant types are associated with milder facial dysmorphisms, including single central incisor and cleft lip and/or palate. The severity of facial malformation was demonstrated to correlate with brain anomalies [6,9,17], and our results indicated a similar tendency. However, many exceptions occur. The reason for facial dysmorphism does not involve a forebrain malformation, but rather the rostrocaudal gradient of the longitudinal axis. If the gradient reaches as far as the midbrain, a facial dysmorphism occurs because of defective mesencephalic neural crest migration, and if the gradient reaches only to the diencephalon or is confined to the telencephalon, facial dysmorphism may not occur [4,18]. The proportion of patients with the alobar type of holoprosencephaly in our study was 67.3%, and this finding does not differ from those in other reports [19]. However, less severe forms (e.g., middle interhemispheric variant or lobar) can now be readily identified because of rapid advances in neuroimaging, and the prevalence of each type will be altered. Although these morphologic categories are attractive because they are easy to identify on neuroimaging, they do not denote an etiology, and do not provide clues to specific genetic defects, because various genes and environmental factors are associated with the development of holoprosencephaly. In this study, 50.9% of patients were diagnosed prenatally with holoprosencephaly, and this rate of detection was somewhat lower than in previous studies [20], in which prenatal diagnoses were achieved in more than 70% via routine ultrasonography scans. Our data were collected over 20 years, and the lobar and middle interhemispheric variant types would be more difficult to detect prenatally, because associated brain anomalies may be subtle or even absent. The majority of patients with holoprosencephaly can be detected via ultrasonography and magnetic resonance imaging during pregnancy. This prenatal diagnosis often results in the termination of pregnancy, depending on the severity of disease.
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Table 3. Craniofacial abnormalities associated with holoprosencephaly
Total (n = 111) n %
Associated Craniofacial Abnormalities Hypotelorism Cyclopia Microphthalmia Cleft lip Cleft palate Proboscis Single nostril Micrognathia Low-set ears Microstomia
20 15 4 20 15 15 8 7 5 2
18.0 13.5 3.6 18.0 13.5 13.5 7.2 6.3 4.5 1.8
The higher incidence of holoprosencephaly among females was previously reported [19,21], and our results also yielded consistent findings, although phenotypic sex was not mentioned in seven cases. The female predominance may be explained by the higher likelihood of males to abort spontaneously [21]. We identified chromosomal aberrations in 18 (45.0%) of 40 karyotyped cases, and trisomy 13 and triploidy comprised the most frequent abnormalities. Estimates of holoprosencephaly associated with karyotype abnormalities range between 38-55% of the cases reported in the literature. Trisomy 13, trisomy 18, and triploidy are the most frequently observed chromosomal aberrations in holoprosencephaly [20,22]. Moreover, 12 candidate regions on 11 chromosomes and 7qter contiguous genes were identified that may be involved in holoprosencephaly [23]. If a numeric chromosomal abnormality is detected in the proband, the risk of recurrence is not increased significantly. However, if holoprosencephaly is associated with structural chromosomal aberrations, the risk of recurrence depends on whether or not one of the parents is a balanced chromosomal rearrangement carrier. This finding was evident in one of the present patients. In approximately 25% of cases, holopro-
Prenatally Diagnosed Patients (n)
Postnatally Diagnosed Patients (n)
9 10 1 10 8 10 6 5 1 1
11 5 3 10 7 5 2 2 4 1
sencephaly can be associated with several multiple malformation syndromes with a normal karyotype, and may be an isolated manifestation without a chromosomal or syndromic etiology [24]. Although we were unable to conduct a molecular analysis in this study, more than seven genes are positively implicated in holoprosencephaly thus far: SHH, ZIC2, SIX3, TGIF, PTCH, GLI2, and TDGF1. However, only 20-30% of isolated cases of holoprosencephaly can be explained by searching for alterations in the four main holoprosencephaly genes, including SHH, ZIC2, SIX3, and TGIF, and subtelomeric regions [9,10]. More than 65% of isolated cases of holoprosencephaly remain unexplained, thus suggesting the involvement of many other unidentified genes in holoprosencephaly. Children with holoprosencephaly experience a variety of medical and neurologic problems, including developmental delays, epilepsy, weakness, spasticity, dystonia, choreoathetosis, and endocrinologic disorders [25]. The care of children with holoprosencephaly requires multidisciplinary management. The results of our study indicate that global developmental delays affect virtually all patients with holoprosencephaly. The degree of delay and of neurologic problems was generally correlated with the severity of the brain
Table 4. Chromosomal aberrations observed in 18 patients with holoprosencephaly
Total (n = 18) Chromosomal Aberration
n
%
Trisomy 13 46,XY,t(13;18) 46,XY,rec(13) dup(13q)(p13;q21.3) Triploidy 46,XX, del(7)(q32) 46,XX,der(7)t(3;7)(p24;q36) 46,XX,der(7)t(5;7)(p15.3;q32) 46,XX,i(18)(q10)t(15;18)(p12;p11) 45,XX,der(15;21)(q10;q10) 47,XY,+21p 45,XY, 21 47,XXX 46,XX [25]/hypodiploidy [5]
4 1 1 3 1 1 1 1 1 1 1 1 1
22.2 5.6 5.6 16.7 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6
250 PEDIATRIC NEUROLOGY Vol. 43 No. 4
Prenatally Diagnosed Patients (n)
Postnatally Diagnosed Patients (n)
3 0 1 2 1 1 1 1 0 0 0 0 0
1 1 0 1 0 0 0 0 1 1 1 1 1
malformation, and poor rates of survival and performance were previously observed [25]. Approximately 50% of children with holoprosencephaly manifested at least one episode of seizure, and one half of those seizures were difficult to control [4,26]. However, routine prophylactic treatment with antiepileptic drugs is not recommended, because more than 50% of children with holoprosencephaly do not develop seizures. Three (50%) of the six surviving patients in the present study were diagnosed with epilepsy and were treated with antiepileptic drugs, regardless of their type of holoprosencephaly. Their seizure types comprised neonatalonset generalized tonic seizure in one patient with the alobar type, and complex partial seizures in the other two patients. Approximately 30% of holoprosencephaly patients with epilepsy manifested complex partial seizures, 9% manifested generalized tonic-clonic seizures, 12% manifested other generalized seizures, and 20% manifested mixed seizures [6]. Electroencephalogram studies also revealed various abnormalities, including slow waves, focal epileptiform discharges, slow spike-and-wave complexes, hypsarrhythmia, frontal fast activity, fronto-occipital gradient, and lack of photic driving [6,27]. In the present study, slow background activities and focal spikes were evident in all three patients with epilepsy, frontal fast activities were evident in the patient with neonatal-onset generalized tonic seizure, and slow spike-and-wave complexes were evident in the patients with complex partial seizures. Although our study population was too small to correlate types of holoprosencephaly with the severity of epilepsy, some reports state that the severity of cortical malformation is not correlated with the presence or absence of seizures [4,27]. Two lobar patients and one patient with the middle interhemispheric variant without seizures in our study also produced normal electroencephalogram findings. Children with holoprosencephaly are also at risk for endocrine disorders, because the midline brain malformation can influence the development of the hypothalamus and pituitary gland. Endocrinopathies contribute importantly to the morbidity and mortality of holoprosencephaly. Anterior pituitary dysfunctions such as growth hormone deficiency, central hypothyroidism, and hypocortisolism were previously observed, and diabetes insipidus was also identified as a common problem. Endocrinopathies were evident in 28.6% of the surviving patients in this study, which is lower than in the results of a study that reported a prevalence of 59% [28]. This finding may be attributable to the relatively shorter period of observation and higher ratio of milder holoprosencephaly types than was described in the study mentioned above [28]. All of our surviving patients exhibited microcephaly, and none of them manifested hydrocephalus or a dorsal cyst, even those with alobar holoprosencephaly. Microcephaly was present in a greater proportion of patients with semilobar and lobar holoprosencephaly, whereas in other studies, hydrocephalus was more frequently detected in alobar holoprosencephaly [4,25]. The presence of a dorsal cyst was strongly correlated with the nonseparation of the thalami
and hydrocephalus. The less severely the thalami are separated, the higher the rate of dorsal cyst and hydrocephalus tends to be [4]. Our results could therefore be explained in this context. Because the midbrain is often involved in holoprosencephaly, aqueductal stenosis or even atresia, resulting in obstructive hydrocephalus, can be superimposed on the basic malformation of the forebrain. In addition, posterior fossa abnormalities such as rhombencephalosynapsis, in which abnormal nonseparation of the cerebellar hemispheres occurs, are also occasionally observed in holoprosencephaly [29-31]. Although some correlation exists between the severity of holoprosencephaly and the prognosis, and because early mortality is common in severe forms of holoprosencephaly, the spectrum of outcomes is extremely broad, and caution should be exercised in anticipatory counseling, because many children with mild to moderate holoprosencephaly can survive past infancy [6]. Moreover, in the present study, three of 13 patients who survived more than 1 month after birth manifested alobar holoprosencephaly, and one of them was followed for 6.9 years. In conclusion, the results of this study underline the heterogeneity of holoprosencephaly, with clinical features and different etiologies. Although the majority of cases of holoprosencephaly are present prenatally or at birth, the diagnosis of holoprosencephaly may be delayed in patients with milder types of holoprosencephaly or without any craniofacial malformations. By virtue of recent advances in neuroimaging and methods of molecular analysis, the understanding and recognition of the broad clinical spectrum of holoprosencephaly should allow for more accurate diagnoses and prognoses. Despite the poor outcomes of prenatally diagnosed holoprosencephaly and the likely decision by parents to opt for a termination of pregnancy, karyotyping or genetic studies for associated genes should be performed to predict the risk of recurrence, and to facilitate counseling.
References [1] Edison R, Muenke M. The interplay of genetic and environmental factors in craniofacial morphogenesis: Holoprosencephaly and the role of cholesterol. Congenit Anom (Kyoto) 2003;43:1-21. [2] Orioli IM, Castilla EE, Ming JE, et al. Identification of novel mutations in SHH and ZIC2 in a South American (ECLAMC) population with holoprosencephaly. Hum Genet 2001;109:1-6. [3] Simon EM, Hevner RF, Pinter JD, et al. The middle interhemispheric variant of holoprosencephaly. AJNR 2002;23:151-6. [4] Plawner LL, Delgado MR, Miller VS, et al. Neuroanatomy of holoprosencephaly as predictor of function: Beyond the face predicting the brain. Neurology 2002;59:1058-66. [5] Hahn JS. Holoprosencephaly. Edinburgh: Elsevier, 2008. [6] Hahn JS, Plawner LL. Evaluation and management of children with holoprosencephaly. Pediatr Neurol 2004;31:79-88. [7] Stashinko EE, Clegg NJ, Kammann HA, et al. A retrospective survey of perinatal risk factors of 104 living children with holoprosencephaly. Am J Med Genet [A] 2004;128A:114-9. [8] Olsen CL, Hughes JP, Youngblood LG, Sharpe-Stimac M. Epidemiology of holoprosencephaly and phenotypic characteristics of affected children: New York State, 1984-1989. Am J Med Genet 1997; 73:217-26.
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[9] Dubourg C, Bendavid C, Pasquier L, Henry C, Odent S, David V. Holoprosencephaly. Orphanet J Rare Dis 2007;2:8. [10] Dubourg C, Lazaro L, Pasquier L, et al. Molecular screening of SHH, ZIC2, SIX3, and TGIF genes in patients with features of holoprosencephaly spectrum: Mutation review and genotype-phenotype correlations. Hum Mutat 2004;24:43-51. [11] Ming JE, Kaupas ME, Roessler E, et al. Mutations in PATCHED-1, the receptor for SONIC HEDGEHOG, are associated with holoprosencephaly. Hum Genet 2002;110:297-301. [12] Roessler E, Du YZ, Mullor JL, et al. Loss-of-function mutations in the human GLI2 gene are associated with pituitary anomalies and holoprosencephaly-like features. Proc Natl Acad Sci USA 2003;100:13424-9. [13] de la Cruz JM, Bamford RN, Burdine RD, et al. A loss-offunction mutation in the CFC domain of TDGF1 is associated with human forebrain defects. Hum Genet 2002;110:422-8. [14] Demyer W. Holoprocencephaly (cyclopia-arhinencephaly). Amsterdam: North-Holland Publishing Co., 1977. [15] Barkovich AJ, Quint DJ. Middle interhemispheric fusion: An unusual variant of holoprosencephaly. AJNR 1993;14:431-40. [16] KAMJE. Korean Association of Medical Journal Editors. Available at: http://www.koreamed.org/1997. Last updated January 18, 2010. [17] Richieri-Costa A, Ribeiro LA. Holoprosencephaly and holoprosencephaly-like phenotypes: Review of facial and molecular findings in patients from a craniofacial hospital in Brazil. Am J Med Genet [C] Semin Med Genet 2010;154C:149-57. [18] Sarnat HB, Flores-Sarnat L. Neuropathologic research strategies in holoprosencephaly. J Child Neurol 2001;16:918-31. [19] Croen LA, Shaw GM, Lammer EJ. Risk factors for cytogenetically normal holoprosencephaly in California: A population-based casecontrol study. Am J Med Genet 2000;90:320-5. [20] Bullen PJ, Rankin JM, Robson SC. Investigation of the epidemiology and prenatal diagnosis of holoprosencephaly in the north of England. Am J Obstet Gynecol 2001;184:1256-62.
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[21] Rasmussen SA, Moore CA, Khoury MJ, Cordero JF. Descriptive epidemiology of holoprosencephaly and arrhinencephaly in metropolitan Atlanta, 1968-1992. Am J Med Genet 1996;66:320-33. [22] Ming PM, Goodner DM, Park TS. Cytogenetic variants in holoprosencephaly. Report of a case and review of the literature. Am J Dis Child 1976;130:864-7. [23] Roessler E, Muenke M. Holoprosencephaly: A paradigm for the complex genetics of brain development. J Inherit Metab Dis 1998;21: 481-97. [24] Kelley RL, Roessler E, Hennekam RC, et al. Holoprosencephaly in RSH/Smith-Lemli-Opitz syndrome: Does abnormal cholesterol metabolism affect the function of Sonic Hedgehog? Am J Med Genet 1996;66: 478-84. [25] Barr M Jr, Cohen MM Jr. Holoprosencephaly survival and performance. Am J Med Genet 1999;89:116-20. [26] Lewis AJ, Simon EM, Barkovich AJ, et al. Middle interhemispheric variant of holoprosencephaly: A distinct cliniconeuroradiologic subtype. Neurology 2002;59:1860-5. [27] Yang MT, Lee WT, Peng SS, et al. The roles of electroencephalography and neuroimaging in children with holoprosencephaly. Epileptic Disord 2004;6:173-80. [28] Cameron FJ, Khadilkar VV, Stanhope R. Pituitary dysfunction, morbidity and mortality with congenital midline malformation of the cerebrum. Eur J Pediatr 1999;158:97-102. [29] Vogel H, Gessaga EC, Horoupian DS, Urich H. Aqueductal atresia as a feature of arhinencephalic syndromes. Clin Neuropathol 1990;9: 191-5. [30] Pasquier L, Marcorelles P, Loget P, et al. Rhombencephalosynapsis and related anomalies: A neuropathological study of 40 fetal cases. Acta Neuropathol (Berl) 2009;117:185-200. [31] Hahn JS, Barnes PD. Neuroimaging advances in holoprosencephaly: Refining the spectrum of the midline malformation. Am J Med Genet [C] Semin Med Genet 2010;154C:120-32.
Introduction Holoprosencephaly is a structural anomaly of the brain in which the developing forebrain fails to divide into two sep-
From the *Department of Medical Genetics, and †Division of Pediatric Neurology, Department of Pediatrics, Ajou University School of Medicine, Suwon, South Korea.
Ó 2010 by Elsevier Inc. All rights reserved. doi:10.1016/j.pediatrneurol.2010.05.001 0887-8994/$—see front matter
arate hemispheres and ventricles. It occurs between days 18 and 28 of gestation, and affects both the forebrain and the face. This condition is estimated to occur in 1:250 embryos [1] and in 1:10,000 to 1:20,000 births [2]. Three ranges of increasing severity have been characterized: lobar, semilobar, and alobar holoprosencephaly. Another milder subtype of holoprosencephaly, referred to as the middle interhemispheric variant or syntelencephaly, is also reported [3-5]. A spectrum of craniofacial anomalies accompanies holoprosencephaly in approximately 80% of affected individuals, including cyclopia, proboscis, median or bilateral cleft lip and palate, ocular hypotelorism, and single central incisor. Developmental delays are evident in virtually all individuals with holoprosencephaly, and chronic seizures were associated in 40% as a complication [6]. The outcome of the disease is principally dependent on its severity and the associated medical and neurologic complications. Almost without exception, severely affected children do not survive beyond early infancy [6], but a significant proportion of more mildly affected children survive longer than 1 year [7]. Approximately 25-50% of individuals with holoprosencephaly also manifest a numeric or structural chromosomal abnormality [8]. Eighteen percent to 25% of individuals with monogenic holoprosencephaly manifest a recognizable syndrome, and the remainder exhibit nonsyndromic holoprosencephaly [9]. Thus far, more than seven genes have been positively implicated in nonsyndromic holoprosencephaly: SHH, ZIC2, SIX3, TGIF, PTCH, GLI2, and TDGF1 [10-13]. Nevertheless, in approximately 70% of patients, the molecular basis of the disease remains unknown, possibly suggesting the existence of several other candidate genes or environmental factors, such as maternal diabetes, drugs, or infection. In this study, we describe 12 cases of postnatally diagnosed holoprosencephaly in a single Korean institution
Communications should be addressed to: Dr. Kim; Division of Pediatric Neurology, Department of Pediatrics; Ajou University School of Medicine; San 5, Woncheon-dong; Youngtong-gu, Suwon 443-721, South Korea. E-mail: [email protected] Received January 17, 2010; accepted May 3, 2010.
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Table 1. Clinical characteristics in 12 cases of holoprosencephaly
Patient
Sex
GA (wk)
Birth Weight (kg)
Age at Diagnosis
Diagnostic Method
Holoprosencephaly Type
1 2 3 4 5 6 7 8 9 10 11 12
M F M M F M M F F F M F
37.5 38 41 34 36 43 38 37.5 36 32 37 38
3.44 1.87 3.1 1.5 3.8 2.5 3.1 2.72 2 2.36 2.4 3.06
1 day 1 day 1 day 1 day 1 day 15 days 1.4 years 6 months 1 day 4 years 4.5 years 1 year
Magnetic resonance imaging US US Autopsy Autopsy Autopsy Magnetic resonance imaging Magnetic resonance imaging Autopsy Magnetic resonance imaging Magnetic resonance imaging Magnetic resonance imaging
A A A A A S S S S L M M
Abbreviations: A = Alobar CL = Cleft lip CP = Cleft palate GA = Gestational age GDD = Global developmental delay HP = Hypopituitarism, including growth hormone deficiency HT = Hypotelorism L = Lobar M = Middle interhemispheric variant
Lissencephaly Dorsal cyst Dorsal cyst Dorsal cyst, Lissencephaly Pachygyria Schizencephaly Dorsal cyst Cortical dysplasia
MC = Microcephaly MO = Microphthalmia ONH = Optic nerve hypoplasia PP = Precocious puberty S = Semilobar SN = Single nostril SNHL = Sensorineural hearing loss SZ = Seizure US = Ultrasonography
between the years 1990 and 2009, along with a brief review of other Korean literature on this subject. Patients and Methods Study Population AJOU UNIVERSITY HOSPITAL CASES Between January 1990 and September 2009, 12 patients with holoprosencephaly were diagnosed at the Department of Pediatrics at Ajou University Hospital. All patients were evaluated and followed by one pediatric neurologist. Clinical data (including gestational age, birth weight, maternal age at delivery, age at diagnosis, method of diagnosis, type of holoprosencephaly, associated brain anomalies, associated facial anomalies, karyotype, family history, prognoses, and follow-up period) were collected via retrospective reviews of medical records. This study was approved by the Institutional Review Board at Ajou University Hospital, and informed consent was obtained from all parents before enrollment. Types of holoprosencephaly were classified into four grades of severity, according to the classification of Demyer [14] and the findings of neuroimaging studies [3,15]: alobar, semilobar, lobar, and middle interhemispheric variant. In alobar holoprosencephaly, the most severe form of this condition, only a single ventricle is evident, and the cerebral hemispheres are not separated. In semilobar holoprosencephaly, the left and right frontal and parietal lobes are fused, and the interhemispheric fissure is only present posteriorly. In lobar holoprosencephaly, the right and left cerebral hemispheres and lateral ventricles are largely separate, but the most rostral aspect of the telencephalon and the frontal lobes are fused, especially ventrally. The middle interhemispheric variant involves a failure of separation in the posterior frontal and parietal lobes, with a varying lack of cleavage of the basal ganglia and thalami, and absence of the body portion of the corpus callosum [3,15]. CASES FROM THE REVIEWED LITERATURE Forty-three prenatally or postnatally diagnosed cases of holoprosencephaly were identified in Korea via online database searches (KoreaMed) [16]. Inclusion criteria
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Associated Brain Anomaly
for this database study entailed cases of holoprosencephaly that were confirmed via neuroimaging (magnetic resonance imaging or high-quality computed tomography) reviews of postnatally diagnosed patients, and by typical sonographic findings such as abnormalities of the falx cerebri and face or other associated central nervous system malformations for prenatally diagnosed patients. In each prenatally diagnosed patient, an autopsy confirmed the initial sonographic diagnosis. The clinical variables examined in the 12 patients at Ajou University Hospital were also collected and analyzed.
Methods In total, 55 Korean patients (12 from Ajou University Hospital, and 43 from the reviewed literature) were divided into two groups: (1) 27 postnatally diagnosed, and (2) 28 prenatally diagnosed using sonography and confirmed by autopsy. Clinical characteristics were compared between the two groups. Moreover, in the postnatally diagnosed group, we compared variables between the subgroup that survived more than 1 month and the subgroup that died before age 1 month.
Statistical Analysis Statistical analyses were performed using SPSS for Windows, version 11.5 (SPSS, Inc., Chicago, IL). A Student t test was conducted to assess the possible relationships between maternal age and the group according to age at diagnosis, and the Mann-Whitney U test was used to compare gestational age, birth weight, and maternal age between the two postnatally diagnosed subgroups, according to duration of survival after birth. The frequencies of categorical variables such as sex ratio, type of holoprosencephaly, presence of craniofacial malformations, and family history were compared between the prenatally and postnatally diagnosed groups, using the Fisher exact test.
Craniofacial Anomalies HT, CL, CP HT, CL, CP, MO CL, CP, MO Cyclopia, Proboscis
HT, CP, SN, MO
Karyotype
Prognosis
46,XY 69,XXY 46,XY 46,XY 46,XX/hypdiploid 46,XY 46,XY 46,XX 46,XX 47,XXX 46,XY 46,XX
Survived Died (age 1 day) Died (age 1 day) Died (age 1 day) Died (age 1 day) Died (age 15 days) Survived Survived Died (age 1 day) Survived Survived Survived
Results Clinical Characteristics of 12 Patients With Holoprosencephaly From Ajou University Hospital All 12 patients (6 boys and 6 girls) included in this study were diagnosed postnatally, and their mean age at diagnosis was 1.6 years (range, 1 day to 4.5 years). Among these patients, six (50%) were referred because of severe facial dysmorphism, and were diagnosed on the day of birth. One patient who exhibited no facial anomalies was diagnosed by autopsy at age 16 days. Among five (41.7%) patients diagnosed after the neonatal period, none evidenced any facial dysmorphism. The mean age of mothers at time of delivery was 27.9 years (range, 22-34 years). One mother had become pregnant by in vitro fertilization, and none of the mothers had any history of chronic diseases (including diabetes mellitus) before or during the pregnancy. The mean gestational age at delivery was 37.3 weeks (range, 32-43 weeks). Four patients were delivered before 37 weeks of gestation, and one patient was delivered after 42 weeks of gestation. The mean birth weight was 2.7 kg (range, 1.5-3.8 kg). Seven (58.3%) patients were diagnosed via magnetic resonance imaging or high-quality computed tomography scans, and autopsies were conducted as a diagnostic tool in the other five patients, all of whom died during the neonatal period. The cerebral and facial features of patients are listed in Table 1. With regard to type of holoprosencephaly, five alobar (41.7%), four semilobar (33.3%), one lobar (8.3%), and
Complications in Survivors MC, GDD, HP, ONH
Epilepsy
Follow-Up (yr)
Generalized tonic seizures
6.9
MC, GDD MC, GDD, hypertonia, SNHL MC, GDD, PP, SNHL MC, GDD, HP MC, GDD
0.1 3.5 Complex partial seizures Complex partial seizures
5.9 0.1 0.1
two middle interhemispheric variant (16.7%) cases were identified. Associated cerebral anomalies were identified in eight (66.7%) patients. In those with alobar holoprosencephaly, variably sized dorsal sacs were detected in three patients, and lissencephaly was detected in one patient. Pachygyria and schizencephaly were detected in two patients with semilobar holoprosencephaly, respectively. Cortical dysplasia was detected in one patient with the middle interhemispheric variant. Four of five patients with alobar holoprosencephaly exhibited facial anomalies. The most severe facial phenotype, which involved cyclopia and proboscis, was present in one patient with alobar holoprosencephaly, and cebocephaly was evident in one semilobar patient. Midline cleft palate was detected in four patients (three alobar and one semilobar), and three also manifested cleft lip. Microphthalmia with distinct orbits were detected in two patients (one alobar and one semilobar). Karyotype analysis was performed in all 12 cases, and three (25%) demonstrated abnormal karyotypes such as 69,XXY, mosaicism of 46,XX and hypodiploidy, and 47,XXX. The first two karyotypes were discovered in the patients with alobar holoprosencephaly, and the third was detected in one of the lobar cases. The male/female sex ratio for all cases was 1.0:1.0. Although one patient who died 1 hour after birth manifested indistinguishable genitalia, chromosome analysis confirmed the 46,XX karyotype. Among our 12 patients, one (8.3%) was a familial case. The parents had a preterm delivery history of an anencephalic infant 2 years previously. No additional affected individuals were present on either side of the family, and the
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karyotype of this case was normal. Thus, an autosomal recessive inheritance of holoprosencephaly was suggested in this familial case. Although all 12 patients were born alive, four of the alobar cases and one of the semilobar cases died 24 hours after birth. One semilobar patient, who died at age 16 days because of respiratory difficulty and sepsis, was diagnosed at autopsy as manifesting holoprosencephaly. Neuropathologic examination at the microscopic level could not be performed in six autopsies. Six patients survived for more than 1 year. Five of these patients were diagnosed more than 1 month after birth and manifested no facial dysmorphism, and the sixth was the alobar patient who demonstrated hypotelorism coupled with cleft lip and palate. The mean duration of follow-up for these patients living with holoprosencephaly was 2.8 years (range, 1 month to 6.9 years). All six patients who survived for longer than 1 year have survived to date. Microcephaly (below the third percentile) and global developmental delay were identified in all six, and symptomatic seizures, controlled with antiepileptic drugs, developed in three (50%) patients. Their seizure types were neonatal-onset generalized tonic seizure in one patient of the alobar type, and complex partial seizures in the other two patients. Their electroencephalogram findings revealed slow background activities and focal spikes in all three patients with epilepsy, frontal fast activities in one patient with neonatal-onset generalized tonic seizure, and slow spike-and-wave complexes in two patients with complex partial seizures. The other three (50%) patients who had not previously experienced any seizures exhibited normal sleep and waking patterns according to electroencephalograms. Short stature with hypopituitarism and bilateral sensorineural hearing loss were each detected in two patients. Optic nerve hypoplasia in the spectrum of septo-optic dysplasia and central precocious puberty were each evident in one patient. Clinical Characteristics of 43 Holoprosencephaly Patients From Online Koreamed Database Among the 43 reported Korean patients with holoprosencephaly, 13 (30.2%) were male, and 20 (46.5%) were female. Phenotypic sex was not mentioned in the reports on the other seven (16.3%) patients, and the other three (7.0%) patients exhibited ambiguous genitalia. The mean gestational age at diagnosis was 26.6 6.6 weeks for 28 (50.9%) patients who were prenatally diagnosed, and 1.0 2.8 years for the 27 (49.1%) patients who were postnatally diagnosed. Mean maternal age at birth was 28.7 4.9 years, and mean gestational age at birth and birth weight were 39.0 1.7 weeks and 2.6 0.5 kg for postnatally diagnosed patients, respectively. One mother had a history of diabetes mellitus during her pregnancy. The tools used initially for diagnosis included ultrasonography in 29 (67.4%) patients (including all 28 diagnosed prenatally), magnetic resonance imaging in 10 (23.3%) patients, and autopsy in
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four (9.3%) cases, without any imaging studies. The type of holoprosencephaly was classified as alobar in 32 (74.4%) patients, semilobar in four (9.3%) patients, and lobar in seven (16.3%) patients. Brain anomalies associated with holoprosencephaly were evident in 15 (34.9%) patients. Among them, dorsal sac (20.9%), hydrocephalus (16.3%), and lissencephaly (9.3%) were the most frequently detected anomalies. Craniofacial malformations were present in 36 (83.7%) patients, whereas in seven (16.3%) patients, isolated holoprosencephaly without any craniofacial malformation was evident. The eyes, the oral cavity and palate, and the nose were the most commonly affected organ systems, at frequencies of 69.8%, 41.9%, and 46.5%, respectively. Hypotelorism and cyclopia, as well as anophthalmia, provided the majority of ocular malformations, and cleft lip and/or palate proved to be the most frequent malformations. Proboscis and single nostril were the most frequently detected nasal malformations. Karyotyping was performed in 28 (65.1%) of 43 patients. Chromosomal aberrations that appeared to be a cause of holoprosencephaly were detected in 15 (53.6%) of 28 patients. Trisomy 13, which was detected in four patients, was the most frequently observed chromosomal aberration, and structural abnormalities of chromosome 13 were also evident in two other patients. The mother of one patient with 46,XY,rec(13)dup(13q)(p13;q21.3) was a carrier of a balanced chromosomal rearrangement. Structural abnormalities of chromosome 7 and triploidy were evident in three and two patients, respectively. Six patients with normal karyotypes had a positive family history of holoprosencephaly in their siblings, and the pattern of inheritance in these families appeared to be autosomal recessive. In 25 of 28 prenatally diagnosed patients, the pregnancy was terminated by missed abortion (7.1%) or induced preterm labor (82.1%). Three (10.7%) patients were delivered at full term, and one of them died on postnatal day 1. In the 15 postnatally diagnosed cases, seven (46.7%) died during postnatal month 1, and the other eight patients survived for a mean follow-up duration of 1.2 0.8 years. The principal causes of neonatal death comprised central apnea or respiratory difficulty. Frequently observed signs in survivors included microcephaly (100%), psychomotor developmental delay (62.5%), and epilepsy (50.0%). Other associated signs were also identified, including growth hormone deficiency or other pituitary hormone deficiencies (12.5%), hypertonia (12.5%), sensorineural hearing loss (12.5%), optic nerve hypoplasia (12.5%), and hypotonia (12.5%). Comparisons Between Two Groups According to Time of Diagnosis The 55 patients in total were classified into two groups: prenatally diagnosed, and the postnatally diagnosed. We then compared each clinical variable to identify differences between the two groups (Table 2). Differences in types of
Table 2. Types of holoprosencephaly observed in 55 patients
Type Alobar Semilobar Lobar MIH
Total (n = 55) n % 37 8 8 2
67.3 14.5 14.5 3.6
Prenatally Diagnosed Patients n
Total
23 3 2 0
14 5 6 2
Postnatally Diagnosed Patients Death <1 mo Survival $1 mo 11 2 1 0
3 3 5 2
Abbreviation: MIH = Middle interhemispheric variant
holoprosencephaly and the presence of craniofacial malformations were demonstrated to be statistically significant (Table 3). More severe types of holoprosencephaly were evident in the prenatally diagnosed group than in the postnatally diagnosed group, and this association proved meaningful, with a P value of 0.018. In addition, more craniofacial malformations were detected in prenatally diagnosed patients at a significantly greater frequency than in postnatally diagnosed patients (P = 0.026). We were unable to detect any differences in regard to maternal age at birth, the incidence of associated brain anomalies and chromosomal aberrations (Table 4), and the presence of a positive family history. Comparison Between Two Subgroups According to Duration of Survival After Birth in Postnatally Diagnosed Patients Among 55 patients in total, 27 with postnatal diagnoses were classified into two subgroups according to duration of survival after birth. In 14 patients, death occurred less than 1 month after birth, and 13 patients survived more than 1 month after birth. Differences in types of holoprosencephaly and the presence of craniofacial malformations were statistically significant. More severe types of holoprosencephaly were evident in the subgroup which survived more than 1 month after birth, and this association proved meaningful, with a P value of 0.022. Furthermore, significantly more craniofacial malformations were detected in the subgroup that died less than 1 month after birth than in the subgroup that survived (P = 0.041). None of the patients with cyclopia or proboscis survived more than 1 month after birth. Although birth weight tended to increase in the surviving subgroup (2.83 0.45 kg in the surviving subgroup vs 2.42 0.65 kg in the subgroup that died; P = 0.08), no differences between the two subgroups were evident in terms of sex ratio, gestational age, maternal age, the incidence of associated brain anomalies and chromosomal aberrations, and the presence of a positive family history. Discussion Holoprosencephaly is a genetically heterogeneous anomaly, and its phenotype is implicated in a variety of syndromes and chromosomal anomalies. Although
holoprosencephaly is divided into four types according to severity of the disease, these types should be envisioned as nodes on a continuous spectrum of abnormal hemispheric separation, rather than as clear and distinct divisions [9]. The most severe type of holoprosencephaly is alobar, and children with this type can present with severe craniofacial malformations, such as cyclopia or proboscis. The lobar or middle interhemispheric variant types are associated with milder facial dysmorphisms, including single central incisor and cleft lip and/or palate. The severity of facial malformation was demonstrated to correlate with brain anomalies [6,9,17], and our results indicated a similar tendency. However, many exceptions occur. The reason for facial dysmorphism does not involve a forebrain malformation, but rather the rostrocaudal gradient of the longitudinal axis. If the gradient reaches as far as the midbrain, a facial dysmorphism occurs because of defective mesencephalic neural crest migration, and if the gradient reaches only to the diencephalon or is confined to the telencephalon, facial dysmorphism may not occur [4,18]. The proportion of patients with the alobar type of holoprosencephaly in our study was 67.3%, and this finding does not differ from those in other reports [19]. However, less severe forms (e.g., middle interhemispheric variant or lobar) can now be readily identified because of rapid advances in neuroimaging, and the prevalence of each type will be altered. Although these morphologic categories are attractive because they are easy to identify on neuroimaging, they do not denote an etiology, and do not provide clues to specific genetic defects, because various genes and environmental factors are associated with the development of holoprosencephaly. In this study, 50.9% of patients were diagnosed prenatally with holoprosencephaly, and this rate of detection was somewhat lower than in previous studies [20], in which prenatal diagnoses were achieved in more than 70% via routine ultrasonography scans. Our data were collected over 20 years, and the lobar and middle interhemispheric variant types would be more difficult to detect prenatally, because associated brain anomalies may be subtle or even absent. The majority of patients with holoprosencephaly can be detected via ultrasonography and magnetic resonance imaging during pregnancy. This prenatal diagnosis often results in the termination of pregnancy, depending on the severity of disease.
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Table 3. Craniofacial abnormalities associated with holoprosencephaly
Total (n = 111) n %
Associated Craniofacial Abnormalities Hypotelorism Cyclopia Microphthalmia Cleft lip Cleft palate Proboscis Single nostril Micrognathia Low-set ears Microstomia
20 15 4 20 15 15 8 7 5 2
18.0 13.5 3.6 18.0 13.5 13.5 7.2 6.3 4.5 1.8
The higher incidence of holoprosencephaly among females was previously reported [19,21], and our results also yielded consistent findings, although phenotypic sex was not mentioned in seven cases. The female predominance may be explained by the higher likelihood of males to abort spontaneously [21]. We identified chromosomal aberrations in 18 (45.0%) of 40 karyotyped cases, and trisomy 13 and triploidy comprised the most frequent abnormalities. Estimates of holoprosencephaly associated with karyotype abnormalities range between 38-55% of the cases reported in the literature. Trisomy 13, trisomy 18, and triploidy are the most frequently observed chromosomal aberrations in holoprosencephaly [20,22]. Moreover, 12 candidate regions on 11 chromosomes and 7qter contiguous genes were identified that may be involved in holoprosencephaly [23]. If a numeric chromosomal abnormality is detected in the proband, the risk of recurrence is not increased significantly. However, if holoprosencephaly is associated with structural chromosomal aberrations, the risk of recurrence depends on whether or not one of the parents is a balanced chromosomal rearrangement carrier. This finding was evident in one of the present patients. In approximately 25% of cases, holopro-
Prenatally Diagnosed Patients (n)
Postnatally Diagnosed Patients (n)
9 10 1 10 8 10 6 5 1 1
11 5 3 10 7 5 2 2 4 1
sencephaly can be associated with several multiple malformation syndromes with a normal karyotype, and may be an isolated manifestation without a chromosomal or syndromic etiology [24]. Although we were unable to conduct a molecular analysis in this study, more than seven genes are positively implicated in holoprosencephaly thus far: SHH, ZIC2, SIX3, TGIF, PTCH, GLI2, and TDGF1. However, only 20-30% of isolated cases of holoprosencephaly can be explained by searching for alterations in the four main holoprosencephaly genes, including SHH, ZIC2, SIX3, and TGIF, and subtelomeric regions [9,10]. More than 65% of isolated cases of holoprosencephaly remain unexplained, thus suggesting the involvement of many other unidentified genes in holoprosencephaly. Children with holoprosencephaly experience a variety of medical and neurologic problems, including developmental delays, epilepsy, weakness, spasticity, dystonia, choreoathetosis, and endocrinologic disorders [25]. The care of children with holoprosencephaly requires multidisciplinary management. The results of our study indicate that global developmental delays affect virtually all patients with holoprosencephaly. The degree of delay and of neurologic problems was generally correlated with the severity of the brain
Table 4. Chromosomal aberrations observed in 18 patients with holoprosencephaly
Total (n = 18) Chromosomal Aberration
n
%
Trisomy 13 46,XY,t(13;18) 46,XY,rec(13) dup(13q)(p13;q21.3) Triploidy 46,XX, del(7)(q32) 46,XX,der(7)t(3;7)(p24;q36) 46,XX,der(7)t(5;7)(p15.3;q32) 46,XX,i(18)(q10)t(15;18)(p12;p11) 45,XX,der(15;21)(q10;q10) 47,XY,+21p 45,XY, 21 47,XXX 46,XX [25]/hypodiploidy [5]
4 1 1 3 1 1 1 1 1 1 1 1 1
22.2 5.6 5.6 16.7 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6
250 PEDIATRIC NEUROLOGY Vol. 43 No. 4
Prenatally Diagnosed Patients (n)
Postnatally Diagnosed Patients (n)
3 0 1 2 1 1 1 1 0 0 0 0 0
1 1 0 1 0 0 0 0 1 1 1 1 1
malformation, and poor rates of survival and performance were previously observed [25]. Approximately 50% of children with holoprosencephaly manifested at least one episode of seizure, and one half of those seizures were difficult to control [4,26]. However, routine prophylactic treatment with antiepileptic drugs is not recommended, because more than 50% of children with holoprosencephaly do not develop seizures. Three (50%) of the six surviving patients in the present study were diagnosed with epilepsy and were treated with antiepileptic drugs, regardless of their type of holoprosencephaly. Their seizure types comprised neonatalonset generalized tonic seizure in one patient with the alobar type, and complex partial seizures in the other two patients. Approximately 30% of holoprosencephaly patients with epilepsy manifested complex partial seizures, 9% manifested generalized tonic-clonic seizures, 12% manifested other generalized seizures, and 20% manifested mixed seizures [6]. Electroencephalogram studies also revealed various abnormalities, including slow waves, focal epileptiform discharges, slow spike-and-wave complexes, hypsarrhythmia, frontal fast activity, fronto-occipital gradient, and lack of photic driving [6,27]. In the present study, slow background activities and focal spikes were evident in all three patients with epilepsy, frontal fast activities were evident in the patient with neonatal-onset generalized tonic seizure, and slow spike-and-wave complexes were evident in the patients with complex partial seizures. Although our study population was too small to correlate types of holoprosencephaly with the severity of epilepsy, some reports state that the severity of cortical malformation is not correlated with the presence or absence of seizures [4,27]. Two lobar patients and one patient with the middle interhemispheric variant without seizures in our study also produced normal electroencephalogram findings. Children with holoprosencephaly are also at risk for endocrine disorders, because the midline brain malformation can influence the development of the hypothalamus and pituitary gland. Endocrinopathies contribute importantly to the morbidity and mortality of holoprosencephaly. Anterior pituitary dysfunctions such as growth hormone deficiency, central hypothyroidism, and hypocortisolism were previously observed, and diabetes insipidus was also identified as a common problem. Endocrinopathies were evident in 28.6% of the surviving patients in this study, which is lower than in the results of a study that reported a prevalence of 59% [28]. This finding may be attributable to the relatively shorter period of observation and higher ratio of milder holoprosencephaly types than was described in the study mentioned above [28]. All of our surviving patients exhibited microcephaly, and none of them manifested hydrocephalus or a dorsal cyst, even those with alobar holoprosencephaly. Microcephaly was present in a greater proportion of patients with semilobar and lobar holoprosencephaly, whereas in other studies, hydrocephalus was more frequently detected in alobar holoprosencephaly [4,25]. The presence of a dorsal cyst was strongly correlated with the nonseparation of the thalami
and hydrocephalus. The less severely the thalami are separated, the higher the rate of dorsal cyst and hydrocephalus tends to be [4]. Our results could therefore be explained in this context. Because the midbrain is often involved in holoprosencephaly, aqueductal stenosis or even atresia, resulting in obstructive hydrocephalus, can be superimposed on the basic malformation of the forebrain. In addition, posterior fossa abnormalities such as rhombencephalosynapsis, in which abnormal nonseparation of the cerebellar hemispheres occurs, are also occasionally observed in holoprosencephaly [29-31]. Although some correlation exists between the severity of holoprosencephaly and the prognosis, and because early mortality is common in severe forms of holoprosencephaly, the spectrum of outcomes is extremely broad, and caution should be exercised in anticipatory counseling, because many children with mild to moderate holoprosencephaly can survive past infancy [6]. Moreover, in the present study, three of 13 patients who survived more than 1 month after birth manifested alobar holoprosencephaly, and one of them was followed for 6.9 years. In conclusion, the results of this study underline the heterogeneity of holoprosencephaly, with clinical features and different etiologies. Although the majority of cases of holoprosencephaly are present prenatally or at birth, the diagnosis of holoprosencephaly may be delayed in patients with milder types of holoprosencephaly or without any craniofacial malformations. By virtue of recent advances in neuroimaging and methods of molecular analysis, the understanding and recognition of the broad clinical spectrum of holoprosencephaly should allow for more accurate diagnoses and prognoses. Despite the poor outcomes of prenatally diagnosed holoprosencephaly and the likely decision by parents to opt for a termination of pregnancy, karyotyping or genetic studies for associated genes should be performed to predict the risk of recurrence, and to facilitate counseling.
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