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Congenital hydrocephalus in clinical practice: A genetic diagnostic approach
European Journal of Medical Genetics 54 (2011) e542ee547
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Original article
Congenital hydrocephalus in clinical practice: A genetic diagnostic approach J.M.A. Verhagen a, b, C.T.R.M. Schrander-Stumpel b, c, I.P.C. Krapels b, c, C.E.M. de Die-Smulders b, c, F.H.M. van Lint b, C. Willekes b, d, J.W. Weber b, e, A.W.D. Gavilanes f, M.V.E. Macville b, c, A.P.A. Stegmann b, c, J.J.M. Engelen b, c, J. Bakker b, c, Y.J. Vos g, S.G.M. Frints b, c, * a
Department of Clinical Genetics, Erasmus Medical Center Rotterdam, The Netherlands GROW, School for Oncology and Developmental Biology, Maastricht University, The Netherlands c Department of Clinical Genetics, Maastricht University Medical Center, The Netherlands d Department of Obstetrics and Gynecology, Maastricht University Medical Center, The Netherlands e Department of Child Neurology, Maastricht University Medical Center, The Netherlands f Department of Pediatrics, Maastricht University Medical Center, The Netherlands g Department of Clinical Genetics, University Medical Center Groningen, The Netherlands b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 February 2011 Accepted 29 June 2011 Available online 30 July 2011
Congenital hydrocephalus is a common and often disabling disorder. The etiology is very heterogeneous. Little is known about the genetic causes of congenital hydrocephalus. A retrospective survey was performed including patients with primary congenital hydrocephalus referred to the Department of Clinical Genetics between 1985 and 2010 by perinatologists, (child) neurologists or pediatricians. Patients with hydrocephalus secondary to other pathology were excluded from this survey. We classified patients with primary congenital hydrocephalus into two main groups: non-syndromic hydrocephalus (NSH) and syndromic hydrocephalus (SH). Seventy-five individuals met the inclusion criteria, comprising 36% (27/75) NSH and 64% (48/75) SH. In 11% (8/75) hydrocephalus was familial. The cause of hydrocephalus was unknown in 81% (61/75), including all patients with NSH. The maleefemale ratio in this subgroup was 2.6:1, indicating an X-linked factor other than the L1CAM gene. In the group of SH patients, 29% (14/48) had a known cause of hydrocephalus including chromosomal abnormalities, L1 syndrome, MardeneWalker syndrome, WalkereWarburg syndrome and hemifacial microsomia. We performed this survey in order to evaluate current knowledge on the genetic etiology of primary congenital hydrocephalus and to identify new candidate genes or regulatory pathways for congenital hydrocephalus. Recommendations were made concerning the evaluation and genetic workup of patients with primary congenital hydrocephalus. We conclude that further molecular and functional analysis is needed to identify new genetic forms of congenital hydrocephalus. Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords: Congenital Etiology Genetic Hydrocephalus L1CAM
1. Introduction Hydrocephalus is defined as an increase in the cerebral ventricular size and/or subarachnoid space [1]. It is caused by an imbalance between the production, circulation and resorption of cerebrospinal fluid (CSF). This excludes ventriculomegaly caused by primary cerebral atrophy. Most forms of hydrocephalus are caused by obstruction of the flow of CSF. In non-communicating
* Corresponding author. Department of Clinical Genetics, Prenatal Diagnostics and Therapy, Maastricht University Medical Centerþ, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands. Tel.: þ31 43 3877855; fax: þ31 43 3875800. E-mail addresses: [email protected], [email protected] (S.G.M. Frints). 1769-7212/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ejmg.2011.06.005
hydrocephalus, the obstruction site lies within the ventricles (e.g. aqueduct stenosis) or at the junction between the ventricular and subarachnoid space. Communicating hydrocephalus results from an obstruction within the subarachnoid space (e.g. venous sinus occlusion). Non-obstructive hydrocephalus is caused by overproduction of CSF (e.g. choroid plexus papillomata) [2]. Fetal cerebral ventriculomegaly is evident in most of the patients with congenital hydrocephalus [3]. Clinical features in newborns and children up to two years are characterized by macrocephaly, frontal bossing, bulging anterior fontanel, prominent scalp veins, sunset phenomenon and increased muscle tone. Parents may report poor feeding, irritability and vomiting. In older children, head size may be normal if fontanels are closed. Symptoms include vomiting, headaches, vision loss secondary to
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papilledema and optic nerve atrophy, disturbances of consciousness, abnormal hypothalamic functions and difficulty in walking secondary to spastic lower limbs. Congenital hydrocephalus accounts for approximately 50% of all forms of hydrocephalus [4]. The etiology of congenital hydrocephalus is very heterogeneous. The majority consists of secondary forms, caused by intra-uterine infections, intracranial hemorrhages, trauma, teratogens and tumors (Table 1). Congenital hydrocephalus may also result from neural tube defects and is found in association with other central nervous system malformations. Primary congenital hydrocephalus occurs in 0.2e0.8 per 1000 live births [5]. A possible genetic etiology is present in about 40% of patients with congenital hydrocephalus. This includes cytogenetic abnormalities, monogenic or complex inherited conditions and multifactorial disorders. However, in the majority of cases the cause of primary congenital hydrocephalus is still unknown.
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as hydrocephalus accompanied by at least one major congenital abnormality (other than major brain malformations) or three minor congenital anomalies. Classification of phenotypic findings as “minor” or “major” was adapted from Merks et al. (2003) [6]. 3. Results Using the definitions for non-syndromic (NSH) and syndromic hydrocephalus (SH) in these 75 patients, 36% (27/75) had NSH and 64% (48/75) SH. Hydrocephalus was familial in 11% (8/75) of the included patients. In 81% (61/75) the cause of hydrocephalus was unknown. The maleefemale ratio in this subgroup was 2.6:1. In 75% (56/75) patients conventional or molecular karyotyping was performed. L1CAM gene mutations analysis was carried out in 18 males. Pregnancy outcome was lethal in 27% (20/75) cases, consisting of 2 miscarriages, 10 induced abortions and 8 stillbirths. 3.1. Phenotype in non-syndromic hydrocephalus (NSH)
2. Materials and methods The local Medical Ethical Committee of the Maastricht University Medical Centerþ approved this retrospective survey. The selected individuals included patients referred for genetic counseling and diagnostics on congenital hydrocephalus at the Department of Clinical Genetics of the South-East part of the Netherlands between 1985 and 2010. These patients were clinically re-evaluated for primary versus secondary and dysgenetic forms of hydrocephalus using inclusion and exclusion criteria (Table 2). In six patients with congenital hydrocephalus radiological examination and/or autopsy of the brain was not performed or too much data were lost. They could therefore not be included in this survey. The majority of the patients was excluded because hydrocephalus had a secondary cause, mainly neural tube defects. Patients with dysgenetic hydrocephalus resulting from disturbances in early embryonic development (e.g. holoprosencephaly, hydrancephaly and lissencephaly) were also excluded. In addition, patients with known classical cytogenetic abnormalities (e.g. trisomies 13, 18, 21 and triploidy) at referral were removed from this survey. Finally, 75 patients were included in this survey. In these patients pre- or postnatal conventional karyotyping and, since its introduction at our department in 2009, genome-wide single nucleotide polymorphism (SNP) and copy number variation (CNV) analysis was offered to screen for small chromosomal imbalances. In males L1CAM gene mutation analysis was performed. We clinically subdivided patients with congenital hydrocephalus into two main categories: non-syndromic hydrocephalus and syndromic hydrocephalus. Non-syndromic hydrocephalus (NSH) was defined as congenital hydrocephalus without other major congenital abnormalities and with a maximum of two minor congenital anomalies. Syndromic hydrocephalus (SH) was defined
Table 1 Causes of congenital hydrocephalus. Cause
%
Reference
Neural tube defects Trauma Infectionsa Intracranial hemorrhages CNS malformations Tumors Cytogenetic abnormalities Genetic disorders
25e30% 29% 9e21%b 16%b 11%b 5% 0.5e25%b 3%b
[4] [29] [30,31] [30,31] [30,31] [29] [4,30e33] [30,31]
CNS ¼ central nervous system. a Intra-uterine and perinatal infections including TORCH (TOxoplasma, Rubella, Cytomegalovirus, Herpes simplex virus). b Patients with neural tube defects and tumors were excluded from these studies.
In all 27 patients with NSH the cause was unknown. One patient had affected male family members, suggestive of an X-linked form of NSH. L1CAM gene mutation analysis did not reveal any mutation. In general, outcome was not favorable: death occurred in 30% (8/27) before the age of one year. Ages in the survivors ranged from 6 to 37 years. Remarkably, in 14/27 patients with NSH radiological examination of the brain showed additional abnormalities including aqueduct stenosis (8/27), corpus callosum agenesis (2/27), septum pellucidum aplasia (1/27), secondary cerebral atrophy (2/27) and cerebellar hypoplasia (1/27). A small number of patients displayed additional neurological features such as general or axial hypotonia (3/27), spastic diplegia (1/27) or seizures (2/27). Developmental delay and/or mental retardation was present in 2 of 4 individuals with complete clinical follow-up until the age of 18 years. In some patients minor features were present involving the eye, skin, hair and kidney (Table 3). 3.2. Phenotype in syndromic hydrocephalus (SH) The SH group consisted of 48 patients, of which 29% (14/48) had a known cause of hydrocephalus (Table 4). Five SH patients had a chromosomal abnormality: two de novo trisomy 9 (Fig. 1A), one familial partial trisomy 9p21.3, one de novo unbalanced translocation 46,XY,der(6)t(6;13)(p25;q34) (Fig. 1B) and one familial unbalanced translocation 46,XY,der(6)t(6;18)(q26;p11.2). Six patients had mutations in the L1CAM gene (c.76þ5G>A; c.78T>A; c.778_785del8; c.938T>C; c.1124-1G>C; c.1267C>T) (Fig. 1C and see: http://www.l1cammutationdatabase.info). One family had MardeneWalker syndrome (Fig. 1D), one patient had WalkereWarburg syndrome (Fig. 1E) with proven defective O-glycosylation of alpha-dystroglycan and one patient had hemifacial microsomia (Fig. 1F). Two other patients with SH had affected family members. In one family, a male and his maternal uncle presented with hydrocephalus indicating a possible X-linked form of SH. L1CAM gene mutation analysis was normal. In another family an X-linked dominant skeletal phenotype was present in carrier women with a lethal form of hydrocephalus in affected males (Fig. 1G). Carrier women showed 100% non-random X-inactivation in their blood lymphocytes. X-exome sequencing, segregation analysis and functional analysis is still pending to identify the underlying gene defect for this new syndromic form of congenital hydrocephalus. General prognosis in the 34 patients with SH of unknown cause was poor. Death occurred in 32% (11/34) before the age of one year. Ages in the survivors ranged from 2 to 53 years. In 50% (17/34) patients radiological examination of the brain showed additional
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Table 2 Inclusion and exclusion criteria. Primary congenital hydrocephalus (inclusion)
Congenital hydrocephalus secondary to other pathology (exclusion)
Diagnosis of hydrocephalus within the first year of life Congenital hydrocephalus confirmed by ultrasound examination, magnetic resonance imaging (MRI) or computed tomography (CT) scan and/or autopsy of the brain
Insufficient clinical or radiographic evidence for hydrocephalus Hydrocephalus secondary to infections, trauma, intracranial hemorrhages, tumors, neural tube defects, ArnoldeChiari malformation and teratogens Hydrocephalus secondary to major brain abnormalities e.g. holoprosencephaly, hydranencephaly, lissencephaly and primary cerebral atrophy
Clinical features of cerebral ventricular enlargement and/or increased intracranial pressure at history or physical examination with or without positive family history
abnormalities including aqueduct stenosis (6/34), corpus callosum agenesis (8/34), septum pellucidum aplasia (3/34), corticospinal tract abnormalities (1/34), secondary cerebral atrophy (3/34) and cerebellar hypoplasia (1/34). About one third of the patients displayed additional neurological features such as general or axial hypotonia (3/34), spastic hemiplegia (2/34) or seizures (5/34). Developmental delay and/or mental retardation was present in seven of nine individuals with complete clinical follow-up until the age of 18 years. A large number of patients (18/34) had ocular abnormalities, including eye movements disorders and visual disturbances. Skeletal and digital abnormalities were present in 41% (14/34) patients. Nine patients had genitourinary abnormalities, such as renal agenesis (3/34), hydronephrosis (2/34) and micropenis (2/34). Congenital heart defects were present in five
Table 3 Summary of clinical findings in patients with unknown causes of primary congenital hydrocephalus.
Total Male gender Death before age 1 year Developmental delay/mental retardation Ocular abnormalities Skin or hair abnormality Central nervous system features Aqueduct stenosis Corpus callosum agenesis Septum pellucidum abnormality Cerebral atrophy or hypoplasiab Cerebellar hypoplasia Corticospinal tract abnormality Neurologic features General or axial hypotonia Spasticity Seizures/epilepsy Skeletal features Adducted thumb Other thumb abnormality Polydactyly Radial defect Vertebral anomaly Genitourinary features Renal agenesis Hydronephrosis Renal cysts Genital abnormality Cardiac features Septal defects Cardiac valve defects Gastrointestinal features Diaphragmatic hernia Inguinal hernia Esophageal fistula or atresia Hirschsprung
NSH
SH
Total
27/27 19 8 2/4a 4 3
34/48 25 11 7/9a 18 8
61/75 44 19 9/13a 22 11
8 2 1 2 1
6 8 3 3 1 1
14 10 4 5 2 1
3 1 2
3 2 5
6 3 7
3
1 4 2 2 5
4 4 2 2 5
3 2 1 3
3 2 2 4
4 1
4 1
1 1
3 3 2 1
3 3 2 1
NSH ¼ non-syndromic hydrocephalus, SH ¼ syndromic hydrocephalus. a Value is based on the patients from whom data was available. b Cerebral atrophy or hypoplasia developed during follow-up, secondary to hydrocephalus.
patients, including septal defects and supravalvular pulmonary stenosis. Congenital diaphragmatic hernia was present in three patients. Three other patients had inguinal hernias (Table 3). Furthermore, two patients had anemia. In one patient a T-cell immunodeficiency was confirmed and presented with severe complications. 4. Discussion 4.1. Definition and classification of hydrocephalus Providing an accurate definition and classification on hydrocephalus is challenging. It has been part of an ongoing debate since many years. The discussion mainly focuses on the in- or exclusion of cerebral atrophy and the distinction between primary and dysgenetic forms of congenital hydrocephalus in the presence of other major central nervous system malformations [7]. Completely excluding cerebral atrophy from the definition is controversial as hydrocephalus and cerebral atrophy sometimes coexist independently within the same clinical entity. The same problem is encountered if other central nervous system malformations are present next to congenital hydrocephalus. A clear distinction between primary en dysgenetic forms of congenital hydrocephalus is not always possible in these cases. For example, cilia disorders that affect cerebellar development can lead to hydrocephalus at the same time. Another example is the nosologic discussion on MardeneWalker syndrome, which will probably continue until the underlying gene defect is known. The DandyeWalker malformation with hydrocephalus in this syndrome can lead to cerebral and cerebellar atrophy, but the reverse can also be true. Thus, these brain malformations can be either primary, secondary or associated with each other. Further discussion is needed to reach consensus at these critical points. The lack of a final definition and classification on hydrocephalus is an important limitation to this survey. It makes our in- and exclusion criteria disputable and carries the potential risk of selection bias. 4.2. General diagnostic approach to congenital hydrocephalus Genetic evaluation of congenital hydrocephalus starts with a detailed medical history, physical examination and brain imaging
Table 4 Patients with known causes of syndromic hydrocephalus. No. of patients Cytogenetic abnormalities (Partial) trisomy 9 46,XY,der(6)t(6;13)(p25;q34) 46,XY,der(6)t(6;18)(q26;p11.2) Genetic disorders L1 syndrome MardeneWalker syndrome WalkereWarburg syndrome Hemifacial microsomia
5/48 (10%) 3 1 1 9/48 (19%) 6 1 1 1
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Fig. 1. Patients with congenital SH. A. trisomy 9, B. 6p25 terminal deletion due to de novo unbalanced translocation 46,XY,der(6)t(6;13)(p25;q34), C. MRI scan of the brain in patient with pathogenic L1CAM gene mutation, D. CT scan of the brain in patient with MardeneWalker syndrome, E. MRI scan of the brain in patient with WalkereWarburg syndrome, F. hemifacial microsomia, G. unknown lethal X-linked form of congenital hydrocephalus.
with close involvement of child neurologists, pediatricians and clinical geneticists (Fig. 2). The first step is to make a clinical distinction between primary, secondary and dysgenetic forms of congenital hydrocephalus (Table 2) and a proper differential diagnosis (Supplemental Tables 1e3). This survey focused exclusively on the primary forms of (N)SH. Depending on the presence of additional clinical features, one should decide whether the hydrocephalus is non-syndromic (no major and 2 minor anomalies) or syndromic (1 major and >2 minor anomalies). The genetic diagnostic approach differs substantially between both groups.
4.3. Genetic evaluation of non-syndromic hydrocephalus So far, L1 syndrome is the most common genetic cause of congenital hydrocephalus. It accounts for about 5e10% of males with congenital hydrocephalus [4]. The L1 syndrome is caused by mutations in the neural cell adhesion molecule L1 (L1CAM) gene at Xq28. The phenotypic spectrum is variable and comprises both NSH and SH: X-linked hydrocephalus with stenosis of the aqueduct of Sylvius (HSAS), MASA syndrome (Mental retardation, Aphasia, Spastic paraplegia and Adducted thumbs), X-linked complicated
Congenital hydrocephalus
Corpus callosum agenesis or otherwise normal brain structures
Other major brain malformation(s)
Other major or at least three minor congenital malformation(s)
Use primary brain malformation for genetic diagnostic work-up
Non-syndromic hydrocephalus (NSH)
Syndromic hydrocephalus (SH)
Unknown
Genome-wide SNP/CNV analysis L1CAM gene mutation analysis
Empirical recurrence risk NSH: Sporadic: male 4%, female 2% Familial: XL: males 50%, females 50% chance of being carrier and <5% being affected AD: male and female 50% AR: male and female 25%
Genome-wide SNP/CNV analysis L1CAM gene mutation analysis Metabolic investigation On indication: Conventional karyotyping Chromosome breakage studies
Recognized syndrome (Supplemental table 1−3)
Specific/targeted genetic testing
Empirical recurrence risk SH: Sporadic: male or female 5% Familial: XL: males 50%, females 50% chance of being carrier and <5% being affected. AD: male and female 50% AR: male and female 25%
Fig. 2. Flowchart on clinical genetic and molecular diagnostics, and recurrence risks in patients with primary congenital hydrocephalus. AD ¼ autosomal dominant, AR ¼ autosomal recessive, CNV ¼ copy number variation, NSH ¼ non-syndromic hydrocephalus, SH ¼ syndromic hydrocephalus, SNP ¼ single nucleotide polymorphism, XL ¼ X-linked.
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hereditary spastic paraplegia type 1 and X-linked complicated corpus callosum agenesis [8]. Mutation analysis of the L1CAM gene should be performed in all males with NSH. As hydrocephalus is described in w5% of female carriers, mutation analysis of the L1CAM gene should also be considered in (mildly) affected females, especially if there is a positive family history of congenital hydrocephalus or in the presence of aqueduct stenosis of Sylvius, corpus callosum agenesis or adducted thumbs. In patients with NSH array-based comparative genomic hybridization (CGH) or single nucleotide polymorphism (SNP) array CNV analysis can be considered to screen for small chromosomal imbalances. However, the prevalence of pathogenic copy number variants in NSH patients is thus far unknown and needs further investigation. 4.4. Genetic evaluation of syndromic hydrocephalus The most frequent cytogenetic abnormalities in SH include (mosaic) trisomy 9, 9p, 13 and 18 and (mosaic) triploidy [9]. Since the introduction of genome-wide CNV analysis using microarray platforms several other small chromosomal aberrations have been reported in SH patients (Supplementary Table 1). In particular, partial 6p terminal deletions are reported rather frequently [10]. The 6p terminal deletion has a recognizable phenotype. Clinical features include Axenfeld-Rieger anomaly, hearing loss, congenital heart disease, dental anomalies, developmental delay and a characteristic facial appearance (Fig. 1B). Maclean et al. (2005) reported a child with a 6pter microdeletion arising from a de novo translocation (6;18)(p25.1;p11.2) including the FOXC1, FOXF2 and FOXQ1 forkhead gene cluster at 6p25. Central nervous system anomalies included hydrocephalus and hypoplasia of the cerebellum, brainstem and corpus callosum with mild to moderate developmental delay [11]. The most interesting candidate gene for this form of congenital hydrocephalus is FOXC1: mice with homozygous nonsense mutations of the Foxc1 gene die at birth because of progressive hydrocephalus [12]. Mutations in the FOXC1 gene have been identified in patients with Axenfeld-Rieger syndrome and more recently, also in DandyeWalker syndrome [13]. The latter is defined by partial or complete absence of the cerebellar vermis and cystic dilatation of the fourth ventricle, often accompanied by congenital hydrocephalus. In SH patients without a directly recognized syndrome, array platforms combining SNP and CNV analysis allow for the detection of (partial) uniparental disomy or regions of homozygosity (ROH). We prefer to use both techniques, especially in patients with presumed autosomal recessive congenital hydrocephalus (e.g. consanguineous parents or affected sib pairs). This sometimes leads to identification of a disease-causing gene. Multiplex Ligation-dependent Probe Amplification (MLPA) analysis remains a valuable, inexpensive tool to directly confirm clinically suspected (subtelomeric) microdeletions or -duplications. Conventional karyotyping can still be useful to investigate mosaic (<30%) chromosome abnormalities and possible (de novo) inversions or balanced translocations in which the breakpoints can potentially disrupt genes or have a position effect on neighboring genes. The L1 syndrome should be excluded in every male with SH. Vos et al. (2010) screened 60 patients suspected of having L1 syndrome without L1CAM gene mutation using a high density X-chromosome specific array-based CGH. Eleven CNVs were identified containing candidate genes expressed in brain (including e.g. the GDI1 gene) (thesis Y. Vos: Genetics of L1 syndrome, Chapter 8, 2010). Further research is needed to determine the potential role of these genes in X-linked congenital SH. Few other families with X-linked SH have been described. The high maleefemale ratio observed in our cohort
(2.6:1) indicates possible involvement of X-linked disease-causing genes other than L1CAM. Candidate genes for lethal forms of congenital hydrocephalus in males include OFD1, AP1S2 and HDAC6 involved in respectively orofaciodigital syndrome type I [14], X-linked mental retardation [15] and X-linked dominant chondrodysplasia [16]. SH is otherwise mainly inherited in an autosomal recessive manner. Congenital hydrocephalus has occasionally been described in numerous other genetic disorders [17]. A nonexhaustive list is available in Supplementary Table 3. In 21% (7/34) of our patients with unresolved SH clinical features of the VACTERL-H association were identified. The phenotypic spectrum of the VACTERL-H association is wide and poorly understood [18]. Hemifacial microsomia and Fanconi anemia show many overlapping features including vertebral, gastrointestinal, cardiac and limb defects. Convincing relationships between these conditions and VACTERL-H have been described in literature [19e21]. As suggested earlier by Faivre [22], chromosome breakage studies should be considered in patients with congenital hydrocephalus and additional features of VACTERL-H association. Metabolic disorders should not be disregarded as a possible cause of hydrocephalus. Given the mainly autosomal recessive inheritance, it should especially be considered in affected sib pairs. Metabolic disorders are more likely to cause postnatal hydrocephalus. Congenital hydrocephalus is a common feature in disorders with glycosylation defects such as muscular dystrophydystroglycanopathies, including WalkereWarburg syndrome (Supplementary Table 2). Other metabolic disorders associated with congenital hydrocephalus include for example mucopolysaccharidoses, alpha-mannosidosis and Smith-Lemli-Opitz syndrome (Supplementary Table 3). Metabolic investigation in SH should at least include assessment of blood creatine kinase (CK) and lactate, plasma cholesterol metabolites, urinary mucopolysaccharides and isoelectric focusing for sialotransferrine. 4.5. Future perspectives Upcoming next generation sequencing technologies are rapidly changing the field of genetic diagnostics. At present, whole exome and/or genome sequencing are still too expensive for widespread use. Analysis of the large amount of data generated, e.g. interpreting the numerous unclassified genetic variants, will become a major challenge. Targeted X-exome sequencing can be a more readily available option in males with congenital hydrocephalus, especially in case of a positive family history. Growing evidence from literature indicates that cilia disorders may play an important role in congenital hydrocephalus. Cilia are microtubule-based organelles that extend from the surface of almost every cell in the human body (e.g. in the ependyma of the cerebral ventricles) and are able to propel fluid [23, 24]. As ciliated ependymal cells play a crucial role in the control of cerebrospinal fluid homeostasis in the brain, cilia defects can lead to the formation of hydrocephalus [25]. Two cilia-related disease mechanisms have been identified in hydrocephalus formation: A. defects in the transport of proteins across the ciliary compartment border leading to the formation of aberrant cilia with overproduction of CSF, and B. ependymal ciliary dysmotility leading to an impaired circulation and obstruction of CSF. The phenotypic spectrum of cilia disorders includes cerebellar hypoplasia, retinopathy, polycystic kidneys, liver cysts, polydactyly, obesity, leftright asymmetry, situs inversus, infertility and (sometimes) hydrocephalus. To date, more than 100 human cilia genes are detected. The genetic heterogeneity of cilia disorders complicates current diagnostics. Implementation of genome-wide exome sequencing in the near future will enable us to generate data on the various known cilia genes in a single experiment. The Ciliary
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Proteome Database can then be a helpful instrument for interpreting this data [26]. 4.6. Prognosis The prognosis of a child with congenital hydrocephalus is highly variable and mainly depends on the underlying cause of hydrocephalus, associated malformations and the timing and success of surgical treatment [27]. General mortality rate varies from 5% to 15%. About 40% of the children with congenital hydrocephalus is cognitively impaired, ranging from mild to severe retardation. The degree of cognitive impairment does not necessarily correlate with head circumference or severity of hydrocephalus [8]. Motor problems are seen in 30% of the children with congenital hydrocephalus, of which half is wheelchair dependent [28]. Delay of treatment is an important risk factor for poor outcome [2]. 4.7. Recurrence risk The recurrence risk in sporadic patients with NSH is low: approximately 4% in males and 2% in females [4]. However, when NSH is familial the recurrence risk increases dramatically, depending on the mode of inheritance. Familial forms of NSH are often X-linked with a 50% recurrence risk for the male offspring of female carriers. Daughters have a 50% chance of being a carrier with a low risk (<5%) of manifesting clinical features of congenital hydrocephalus [4]. In sporadic patients with SH the recurrence risk depends on the inheritance pattern of the suspected syndrome. In SH patients with hydrocephalus of unknown origin the estimated recurrence risk, after extensive clinical and molecular investigations, is 5%. In familial forms of SH the recurrence risk depends on the inheritance pattern suspected from pedigree data (Fig. 2). 5. Conclusion We have to conclude that genetic causes of congenital hydrocephalus are still largely unknown. This retrospective survey provides evidence for new genetically determined forms of congenital hydrocephalus. Candidate gene and functional analysis is ongoing. We recommend L1CAM gene mutation analysis and genome-wide SNP/CNV analysis in every patient with congenital hydrocephalus. In addition, metabolic investigation, conventional karyotyping and chromosomal breakage studies should be considered in patients with unknown forms of SH. Further research is needed in order to identify the underlying gene defects in hitherto unknown, possibly genetic forms of (non-) syndromic congenital hydrocephalus. Appendix. Supplementary material Supplementary material related to this article can be found at doi:10.1016/j.ejmg.2011.06.005 References [1] J.L. Tolmie, Clinical genetics of neural tube defects and other congenital central nervous system malformations. in: D.L. Rimoin, J.M. Connor, R.E. Pyeritz, B.R. Korf (Eds.), Emery and Rimoin’s Principles and Practice of Medical Genetics. Churchill Livingstone, London, 2002, pp. 2975e3011. [2] K. Mori, J. Shimada, M. Kurisaka, et al., Classification of hydrocephalus and outcome of treatment, Brain Dev. 17 (5) (1995) 338e348. [3] G.H. Davis, Fetal hydrocephalus, Clin. Perinatol. 30 (3) (2003) 531e539. [4] C. Schrander Stumpel, J.P. Fryns, Congenital hydrocephalus: nosology and guidelines for clinical approach and genetic counselling, Eur. J. Pediatr. 157 (5) (1998) 355e362.
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[5] J.H. Chi, H.J. Fullerton, N. Gupta, Time trends and demographics of deaths from congenital hydrocephalus in children in the United States: National Center for Health Statistics data, 1979e1998, J. Neurosurg. 103 (Suppl. 2) (2005) 113e118. [6] J.H. Merks, C.D. van Karnebeek, H.N. Caron, et al., Phenotypic abnormalities: terminology and classification, Am. J. Med. Genet. A 123 (3) (2003) 211e230. [7] H.L. Rekate, The definition and classification of hydrocephalus: a personal recommendation to stimulate debate, Cerebrospinal Fluid Res. 5 (2008) 2. [8] C.T.R.M. Schrander Stumpel, Y. Vos, L1 syndrome, in: GeneReviews at GeneTests: Medical Genetics Information Resource (Database Online). University of Washington, Seattle, 2006 Available from. http://www.genetests.org. [9] R.J. Gorlin, M.M. Cohen, R.C.M. Hennekam, in: A.G. Motulsky, M. Bobrow, P.S. Harper, C. Scriver (Eds.), Syndromes of the Head and Neck, fourth ed. Oxford University Press, New York, 2001. [10] R.J. Lin, A.M. Cherry, K.C. Chen, et al., Terminal deletion of 6p results in a recognizable phenotype, Am. J. Med. Genet. A 136 (2) (2005) 162e168. [11] K. Maclean, J. Smith, L. St Heaps, et al., Axenfeld-Rieger malformation and distinctive facial features: clues to a recognizable 6p25 microdeletion syndrome, Am. J. Med. Genet. A 132 (4) (2005) 381e385. [12] T. Kume, K.Y. Deng, V. Winfrey, et al., The forkhead/winged helix gene Mf1 is disrupted in the pleiotropic mouse mutation congenital hydrocephalus, Cell 93 (6) (1998) 985e996. [13] K.A. Aldinger, O.J. Lehmann, L. Hudgins, et al., FOXC1 is required for normal cerebellar development and is a major contributor to chromosome 6p25.3 DandyeWalker malformation, Nat. Genet. 41 (9) (2009) 1037e1042. [14] M.I. Ferrante, G. Giorgio, S.A. Feather, et al., Identification of the gene for oralefacialedigital type I syndrome, Am. J. Hum. Genet. 68 (3) (2001) 569e576. [15] Y. Saillour, G. Zanni, V. Des Portes, et al., Mutations in the AP1S2 gene encoding the sigma 2 subunit of the adaptor protein 1 complex are associated with syndromic X-linked mental retardation with hydrocephalus and calcifications in basal ganglia, J. Med. Genet. 44 (11) (2007) 739e744. [16] D. Simon, B. Laloo, M. Barillot, et al., A mutation in the 30 -UTR of the HDAC6 gene abolishing the post-transcriptional regulation mediated by hsa-miR-433 is linked to a new form of dominant X-linked chondrodysplasia, Hum. Mol. Genet. 19 (10) (2010) 2015e2027. [17] R.S. Lachman, Taybi and Lachman’s Radiology of Syndromes, Metabolic Disorders and Skeletal Dysplasias, fifth ed. Mosby Elsevier, , Philadelphia, 2007. [18] J.A. Evans, L.C. Stranc, P. Kaplan, et al., VACTERL with hydrocephalus: further delineation of the syndrome(s), Am. J. Med. Genet. 34 (2) (1989) 177e182. [19] P.A. Duncan, L.R. Shapiro, Interrelationships of the hemifacial microsomiaVATER, VATER, and sirenomelia phenotypes, Am. J. Med. Genet. 47 (1) (1993) 75e84. [20] S.T. Holden, J.J. Cox, I. Kesterton, et al., Fanconi anaemia complementation group B presenting as X linked VACTERL with hydrocephalus syndrome, J. Med. Genet. 43 (9) (2006) 750e754. [21] L.J. Russell, D.D. Weaver, M.J. Bull, The axial mesodermal dysplasia spectrum, Pediatrics 67 (2) (1981) 176e182. [22] L. Faivre, M.F. Portnoi, G. Pals, et al., Should chromosome breakage studies be performed in patients with VACTERL association? Am. J. Med. Genet. A 137 (1) (2005) 55e58. [23] J. Pan, Q. Wang, W.J. Snell, Cilium-generated signaling and cilia-related disorders, Lab. Invest. 85 (4) (2005) 452e463. [24] M. Fliegauf, T. Benzing, H. Omran, When cilia go bad: cilia defects and ciliopathies, Nat. Rev. Mol. Cell Biol. 8 (11) (2007) 880e893. [25] B.A. Afzelius, Cilia-related diseases, J. Pathol. 204 (4) (2004) 470e477. [26] A. Gherman, E.E. Davis, N. Katsanis, The ciliary proteome database: an integrated community resource for the genetic and functional dissection of cilia, Nat. Genet. 38 (9) (2006) 961e962. [27] A.V. Kulkarni, I. Shams, Quality of life in children with hydrocephalus: results from the Hospital for Sick Children, Toronto, J. Neurosurg. 107 (5) (2007) 358e364. [28] M. Platenkamp, P.W. Hanlo, K. Fischer, et al., Outcome in pediatric hydrocephalus: a comparison between previously used outcome measures and the hydrocephalus outcome questionnaire, J. Neurosurg. 107 (Suppl. 1) (2007) 26e31. [29] J. Jansen, Etiology and prognosis in hydrocephalus, Childs Nerv. Syst. 4 (5) (1988) 263e267. [30] E. Fernell, B. Hagberg, G. Hagberg, et al., Epidemiology of infantile hydrocephalus in Sweden. III. Origin in preterm infants, Acta Paediatr. Scand. 76 (3) (1987) 418e423. [31] E. Fernell, B. Hagberg, G. Hagberg, et al., Epidemiology of infantile hydrocephalus in Sweden. II. Origin in infants born at term, Acta Paediatr. Scand. 76 (3) (1987) 411e417. [32] V. D’Addario, V. Pinto, L. Di Cagno, et al., Sonographic diagnosis of fetal cerebral ventriculomegaly: an update, J. Matern. Fetal Neonatal. Med. 20 (1) (2007) 7e14. [33] C. Stoll, Y. Alembik, B. Dott, et al., An epidemiologic survey of environmental and genetic factors in congenital hydrocephalus, Eur. J. Epidemiol. 8 (6) (1992) 797e803.
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European Journal of Medical Genetics journal homepage: http://www.elsevier.com/locate/ejmg
Original article
Congenital hydrocephalus in clinical practice: A genetic diagnostic approach J.M.A. Verhagen a, b, C.T.R.M. Schrander-Stumpel b, c, I.P.C. Krapels b, c, C.E.M. de Die-Smulders b, c, F.H.M. van Lint b, C. Willekes b, d, J.W. Weber b, e, A.W.D. Gavilanes f, M.V.E. Macville b, c, A.P.A. Stegmann b, c, J.J.M. Engelen b, c, J. Bakker b, c, Y.J. Vos g, S.G.M. Frints b, c, * a
Department of Clinical Genetics, Erasmus Medical Center Rotterdam, The Netherlands GROW, School for Oncology and Developmental Biology, Maastricht University, The Netherlands c Department of Clinical Genetics, Maastricht University Medical Center, The Netherlands d Department of Obstetrics and Gynecology, Maastricht University Medical Center, The Netherlands e Department of Child Neurology, Maastricht University Medical Center, The Netherlands f Department of Pediatrics, Maastricht University Medical Center, The Netherlands g Department of Clinical Genetics, University Medical Center Groningen, The Netherlands b
a r t i c l e i n f o
a b s t r a c t
Article history: Received 12 February 2011 Accepted 29 June 2011 Available online 30 July 2011
Congenital hydrocephalus is a common and often disabling disorder. The etiology is very heterogeneous. Little is known about the genetic causes of congenital hydrocephalus. A retrospective survey was performed including patients with primary congenital hydrocephalus referred to the Department of Clinical Genetics between 1985 and 2010 by perinatologists, (child) neurologists or pediatricians. Patients with hydrocephalus secondary to other pathology were excluded from this survey. We classified patients with primary congenital hydrocephalus into two main groups: non-syndromic hydrocephalus (NSH) and syndromic hydrocephalus (SH). Seventy-five individuals met the inclusion criteria, comprising 36% (27/75) NSH and 64% (48/75) SH. In 11% (8/75) hydrocephalus was familial. The cause of hydrocephalus was unknown in 81% (61/75), including all patients with NSH. The maleefemale ratio in this subgroup was 2.6:1, indicating an X-linked factor other than the L1CAM gene. In the group of SH patients, 29% (14/48) had a known cause of hydrocephalus including chromosomal abnormalities, L1 syndrome, MardeneWalker syndrome, WalkereWarburg syndrome and hemifacial microsomia. We performed this survey in order to evaluate current knowledge on the genetic etiology of primary congenital hydrocephalus and to identify new candidate genes or regulatory pathways for congenital hydrocephalus. Recommendations were made concerning the evaluation and genetic workup of patients with primary congenital hydrocephalus. We conclude that further molecular and functional analysis is needed to identify new genetic forms of congenital hydrocephalus. Ó 2011 Elsevier Masson SAS. All rights reserved.
Keywords: Congenital Etiology Genetic Hydrocephalus L1CAM
1. Introduction Hydrocephalus is defined as an increase in the cerebral ventricular size and/or subarachnoid space [1]. It is caused by an imbalance between the production, circulation and resorption of cerebrospinal fluid (CSF). This excludes ventriculomegaly caused by primary cerebral atrophy. Most forms of hydrocephalus are caused by obstruction of the flow of CSF. In non-communicating
* Corresponding author. Department of Clinical Genetics, Prenatal Diagnostics and Therapy, Maastricht University Medical Centerþ, P.O. Box 5800, 6202 AZ Maastricht, The Netherlands. Tel.: þ31 43 3877855; fax: þ31 43 3875800. E-mail addresses: [email protected], [email protected] (S.G.M. Frints). 1769-7212/$ e see front matter Ó 2011 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.ejmg.2011.06.005
hydrocephalus, the obstruction site lies within the ventricles (e.g. aqueduct stenosis) or at the junction between the ventricular and subarachnoid space. Communicating hydrocephalus results from an obstruction within the subarachnoid space (e.g. venous sinus occlusion). Non-obstructive hydrocephalus is caused by overproduction of CSF (e.g. choroid plexus papillomata) [2]. Fetal cerebral ventriculomegaly is evident in most of the patients with congenital hydrocephalus [3]. Clinical features in newborns and children up to two years are characterized by macrocephaly, frontal bossing, bulging anterior fontanel, prominent scalp veins, sunset phenomenon and increased muscle tone. Parents may report poor feeding, irritability and vomiting. In older children, head size may be normal if fontanels are closed. Symptoms include vomiting, headaches, vision loss secondary to
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papilledema and optic nerve atrophy, disturbances of consciousness, abnormal hypothalamic functions and difficulty in walking secondary to spastic lower limbs. Congenital hydrocephalus accounts for approximately 50% of all forms of hydrocephalus [4]. The etiology of congenital hydrocephalus is very heterogeneous. The majority consists of secondary forms, caused by intra-uterine infections, intracranial hemorrhages, trauma, teratogens and tumors (Table 1). Congenital hydrocephalus may also result from neural tube defects and is found in association with other central nervous system malformations. Primary congenital hydrocephalus occurs in 0.2e0.8 per 1000 live births [5]. A possible genetic etiology is present in about 40% of patients with congenital hydrocephalus. This includes cytogenetic abnormalities, monogenic or complex inherited conditions and multifactorial disorders. However, in the majority of cases the cause of primary congenital hydrocephalus is still unknown.
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as hydrocephalus accompanied by at least one major congenital abnormality (other than major brain malformations) or three minor congenital anomalies. Classification of phenotypic findings as “minor” or “major” was adapted from Merks et al. (2003) [6]. 3. Results Using the definitions for non-syndromic (NSH) and syndromic hydrocephalus (SH) in these 75 patients, 36% (27/75) had NSH and 64% (48/75) SH. Hydrocephalus was familial in 11% (8/75) of the included patients. In 81% (61/75) the cause of hydrocephalus was unknown. The maleefemale ratio in this subgroup was 2.6:1. In 75% (56/75) patients conventional or molecular karyotyping was performed. L1CAM gene mutations analysis was carried out in 18 males. Pregnancy outcome was lethal in 27% (20/75) cases, consisting of 2 miscarriages, 10 induced abortions and 8 stillbirths. 3.1. Phenotype in non-syndromic hydrocephalus (NSH)
2. Materials and methods The local Medical Ethical Committee of the Maastricht University Medical Centerþ approved this retrospective survey. The selected individuals included patients referred for genetic counseling and diagnostics on congenital hydrocephalus at the Department of Clinical Genetics of the South-East part of the Netherlands between 1985 and 2010. These patients were clinically re-evaluated for primary versus secondary and dysgenetic forms of hydrocephalus using inclusion and exclusion criteria (Table 2). In six patients with congenital hydrocephalus radiological examination and/or autopsy of the brain was not performed or too much data were lost. They could therefore not be included in this survey. The majority of the patients was excluded because hydrocephalus had a secondary cause, mainly neural tube defects. Patients with dysgenetic hydrocephalus resulting from disturbances in early embryonic development (e.g. holoprosencephaly, hydrancephaly and lissencephaly) were also excluded. In addition, patients with known classical cytogenetic abnormalities (e.g. trisomies 13, 18, 21 and triploidy) at referral were removed from this survey. Finally, 75 patients were included in this survey. In these patients pre- or postnatal conventional karyotyping and, since its introduction at our department in 2009, genome-wide single nucleotide polymorphism (SNP) and copy number variation (CNV) analysis was offered to screen for small chromosomal imbalances. In males L1CAM gene mutation analysis was performed. We clinically subdivided patients with congenital hydrocephalus into two main categories: non-syndromic hydrocephalus and syndromic hydrocephalus. Non-syndromic hydrocephalus (NSH) was defined as congenital hydrocephalus without other major congenital abnormalities and with a maximum of two minor congenital anomalies. Syndromic hydrocephalus (SH) was defined
Table 1 Causes of congenital hydrocephalus. Cause
%
Reference
Neural tube defects Trauma Infectionsa Intracranial hemorrhages CNS malformations Tumors Cytogenetic abnormalities Genetic disorders
25e30% 29% 9e21%b 16%b 11%b 5% 0.5e25%b 3%b
[4] [29] [30,31] [30,31] [30,31] [29] [4,30e33] [30,31]
CNS ¼ central nervous system. a Intra-uterine and perinatal infections including TORCH (TOxoplasma, Rubella, Cytomegalovirus, Herpes simplex virus). b Patients with neural tube defects and tumors were excluded from these studies.
In all 27 patients with NSH the cause was unknown. One patient had affected male family members, suggestive of an X-linked form of NSH. L1CAM gene mutation analysis did not reveal any mutation. In general, outcome was not favorable: death occurred in 30% (8/27) before the age of one year. Ages in the survivors ranged from 6 to 37 years. Remarkably, in 14/27 patients with NSH radiological examination of the brain showed additional abnormalities including aqueduct stenosis (8/27), corpus callosum agenesis (2/27), septum pellucidum aplasia (1/27), secondary cerebral atrophy (2/27) and cerebellar hypoplasia (1/27). A small number of patients displayed additional neurological features such as general or axial hypotonia (3/27), spastic diplegia (1/27) or seizures (2/27). Developmental delay and/or mental retardation was present in 2 of 4 individuals with complete clinical follow-up until the age of 18 years. In some patients minor features were present involving the eye, skin, hair and kidney (Table 3). 3.2. Phenotype in syndromic hydrocephalus (SH) The SH group consisted of 48 patients, of which 29% (14/48) had a known cause of hydrocephalus (Table 4). Five SH patients had a chromosomal abnormality: two de novo trisomy 9 (Fig. 1A), one familial partial trisomy 9p21.3, one de novo unbalanced translocation 46,XY,der(6)t(6;13)(p25;q34) (Fig. 1B) and one familial unbalanced translocation 46,XY,der(6)t(6;18)(q26;p11.2). Six patients had mutations in the L1CAM gene (c.76þ5G>A; c.78T>A; c.778_785del8; c.938T>C; c.1124-1G>C; c.1267C>T) (Fig. 1C and see: http://www.l1cammutationdatabase.info). One family had MardeneWalker syndrome (Fig. 1D), one patient had WalkereWarburg syndrome (Fig. 1E) with proven defective O-glycosylation of alpha-dystroglycan and one patient had hemifacial microsomia (Fig. 1F). Two other patients with SH had affected family members. In one family, a male and his maternal uncle presented with hydrocephalus indicating a possible X-linked form of SH. L1CAM gene mutation analysis was normal. In another family an X-linked dominant skeletal phenotype was present in carrier women with a lethal form of hydrocephalus in affected males (Fig. 1G). Carrier women showed 100% non-random X-inactivation in their blood lymphocytes. X-exome sequencing, segregation analysis and functional analysis is still pending to identify the underlying gene defect for this new syndromic form of congenital hydrocephalus. General prognosis in the 34 patients with SH of unknown cause was poor. Death occurred in 32% (11/34) before the age of one year. Ages in the survivors ranged from 2 to 53 years. In 50% (17/34) patients radiological examination of the brain showed additional
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Table 2 Inclusion and exclusion criteria. Primary congenital hydrocephalus (inclusion)
Congenital hydrocephalus secondary to other pathology (exclusion)
Diagnosis of hydrocephalus within the first year of life Congenital hydrocephalus confirmed by ultrasound examination, magnetic resonance imaging (MRI) or computed tomography (CT) scan and/or autopsy of the brain
Insufficient clinical or radiographic evidence for hydrocephalus Hydrocephalus secondary to infections, trauma, intracranial hemorrhages, tumors, neural tube defects, ArnoldeChiari malformation and teratogens Hydrocephalus secondary to major brain abnormalities e.g. holoprosencephaly, hydranencephaly, lissencephaly and primary cerebral atrophy
Clinical features of cerebral ventricular enlargement and/or increased intracranial pressure at history or physical examination with or without positive family history
abnormalities including aqueduct stenosis (6/34), corpus callosum agenesis (8/34), septum pellucidum aplasia (3/34), corticospinal tract abnormalities (1/34), secondary cerebral atrophy (3/34) and cerebellar hypoplasia (1/34). About one third of the patients displayed additional neurological features such as general or axial hypotonia (3/34), spastic hemiplegia (2/34) or seizures (5/34). Developmental delay and/or mental retardation was present in seven of nine individuals with complete clinical follow-up until the age of 18 years. A large number of patients (18/34) had ocular abnormalities, including eye movements disorders and visual disturbances. Skeletal and digital abnormalities were present in 41% (14/34) patients. Nine patients had genitourinary abnormalities, such as renal agenesis (3/34), hydronephrosis (2/34) and micropenis (2/34). Congenital heart defects were present in five
Table 3 Summary of clinical findings in patients with unknown causes of primary congenital hydrocephalus.
Total Male gender Death before age 1 year Developmental delay/mental retardation Ocular abnormalities Skin or hair abnormality Central nervous system features Aqueduct stenosis Corpus callosum agenesis Septum pellucidum abnormality Cerebral atrophy or hypoplasiab Cerebellar hypoplasia Corticospinal tract abnormality Neurologic features General or axial hypotonia Spasticity Seizures/epilepsy Skeletal features Adducted thumb Other thumb abnormality Polydactyly Radial defect Vertebral anomaly Genitourinary features Renal agenesis Hydronephrosis Renal cysts Genital abnormality Cardiac features Septal defects Cardiac valve defects Gastrointestinal features Diaphragmatic hernia Inguinal hernia Esophageal fistula or atresia Hirschsprung
NSH
SH
Total
27/27 19 8 2/4a 4 3
34/48 25 11 7/9a 18 8
61/75 44 19 9/13a 22 11
8 2 1 2 1
6 8 3 3 1 1
14 10 4 5 2 1
3 1 2
3 2 5
6 3 7
3
1 4 2 2 5
4 4 2 2 5
3 2 1 3
3 2 2 4
4 1
4 1
1 1
3 3 2 1
3 3 2 1
NSH ¼ non-syndromic hydrocephalus, SH ¼ syndromic hydrocephalus. a Value is based on the patients from whom data was available. b Cerebral atrophy or hypoplasia developed during follow-up, secondary to hydrocephalus.
patients, including septal defects and supravalvular pulmonary stenosis. Congenital diaphragmatic hernia was present in three patients. Three other patients had inguinal hernias (Table 3). Furthermore, two patients had anemia. In one patient a T-cell immunodeficiency was confirmed and presented with severe complications. 4. Discussion 4.1. Definition and classification of hydrocephalus Providing an accurate definition and classification on hydrocephalus is challenging. It has been part of an ongoing debate since many years. The discussion mainly focuses on the in- or exclusion of cerebral atrophy and the distinction between primary and dysgenetic forms of congenital hydrocephalus in the presence of other major central nervous system malformations [7]. Completely excluding cerebral atrophy from the definition is controversial as hydrocephalus and cerebral atrophy sometimes coexist independently within the same clinical entity. The same problem is encountered if other central nervous system malformations are present next to congenital hydrocephalus. A clear distinction between primary en dysgenetic forms of congenital hydrocephalus is not always possible in these cases. For example, cilia disorders that affect cerebellar development can lead to hydrocephalus at the same time. Another example is the nosologic discussion on MardeneWalker syndrome, which will probably continue until the underlying gene defect is known. The DandyeWalker malformation with hydrocephalus in this syndrome can lead to cerebral and cerebellar atrophy, but the reverse can also be true. Thus, these brain malformations can be either primary, secondary or associated with each other. Further discussion is needed to reach consensus at these critical points. The lack of a final definition and classification on hydrocephalus is an important limitation to this survey. It makes our in- and exclusion criteria disputable and carries the potential risk of selection bias. 4.2. General diagnostic approach to congenital hydrocephalus Genetic evaluation of congenital hydrocephalus starts with a detailed medical history, physical examination and brain imaging
Table 4 Patients with known causes of syndromic hydrocephalus. No. of patients Cytogenetic abnormalities (Partial) trisomy 9 46,XY,der(6)t(6;13)(p25;q34) 46,XY,der(6)t(6;18)(q26;p11.2) Genetic disorders L1 syndrome MardeneWalker syndrome WalkereWarburg syndrome Hemifacial microsomia
5/48 (10%) 3 1 1 9/48 (19%) 6 1 1 1
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Fig. 1. Patients with congenital SH. A. trisomy 9, B. 6p25 terminal deletion due to de novo unbalanced translocation 46,XY,der(6)t(6;13)(p25;q34), C. MRI scan of the brain in patient with pathogenic L1CAM gene mutation, D. CT scan of the brain in patient with MardeneWalker syndrome, E. MRI scan of the brain in patient with WalkereWarburg syndrome, F. hemifacial microsomia, G. unknown lethal X-linked form of congenital hydrocephalus.
with close involvement of child neurologists, pediatricians and clinical geneticists (Fig. 2). The first step is to make a clinical distinction between primary, secondary and dysgenetic forms of congenital hydrocephalus (Table 2) and a proper differential diagnosis (Supplemental Tables 1e3). This survey focused exclusively on the primary forms of (N)SH. Depending on the presence of additional clinical features, one should decide whether the hydrocephalus is non-syndromic (no major and 2 minor anomalies) or syndromic (1 major and >2 minor anomalies). The genetic diagnostic approach differs substantially between both groups.
4.3. Genetic evaluation of non-syndromic hydrocephalus So far, L1 syndrome is the most common genetic cause of congenital hydrocephalus. It accounts for about 5e10% of males with congenital hydrocephalus [4]. The L1 syndrome is caused by mutations in the neural cell adhesion molecule L1 (L1CAM) gene at Xq28. The phenotypic spectrum is variable and comprises both NSH and SH: X-linked hydrocephalus with stenosis of the aqueduct of Sylvius (HSAS), MASA syndrome (Mental retardation, Aphasia, Spastic paraplegia and Adducted thumbs), X-linked complicated
Congenital hydrocephalus
Corpus callosum agenesis or otherwise normal brain structures
Other major brain malformation(s)
Other major or at least three minor congenital malformation(s)
Use primary brain malformation for genetic diagnostic work-up
Non-syndromic hydrocephalus (NSH)
Syndromic hydrocephalus (SH)
Unknown
Genome-wide SNP/CNV analysis L1CAM gene mutation analysis
Empirical recurrence risk NSH: Sporadic: male 4%, female 2% Familial: XL: males 50%, females 50% chance of being carrier and <5% being affected AD: male and female 50% AR: male and female 25%
Genome-wide SNP/CNV analysis L1CAM gene mutation analysis Metabolic investigation On indication: Conventional karyotyping Chromosome breakage studies
Recognized syndrome (Supplemental table 1−3)
Specific/targeted genetic testing
Empirical recurrence risk SH: Sporadic: male or female 5% Familial: XL: males 50%, females 50% chance of being carrier and <5% being affected. AD: male and female 50% AR: male and female 25%
Fig. 2. Flowchart on clinical genetic and molecular diagnostics, and recurrence risks in patients with primary congenital hydrocephalus. AD ¼ autosomal dominant, AR ¼ autosomal recessive, CNV ¼ copy number variation, NSH ¼ non-syndromic hydrocephalus, SH ¼ syndromic hydrocephalus, SNP ¼ single nucleotide polymorphism, XL ¼ X-linked.
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hereditary spastic paraplegia type 1 and X-linked complicated corpus callosum agenesis [8]. Mutation analysis of the L1CAM gene should be performed in all males with NSH. As hydrocephalus is described in w5% of female carriers, mutation analysis of the L1CAM gene should also be considered in (mildly) affected females, especially if there is a positive family history of congenital hydrocephalus or in the presence of aqueduct stenosis of Sylvius, corpus callosum agenesis or adducted thumbs. In patients with NSH array-based comparative genomic hybridization (CGH) or single nucleotide polymorphism (SNP) array CNV analysis can be considered to screen for small chromosomal imbalances. However, the prevalence of pathogenic copy number variants in NSH patients is thus far unknown and needs further investigation. 4.4. Genetic evaluation of syndromic hydrocephalus The most frequent cytogenetic abnormalities in SH include (mosaic) trisomy 9, 9p, 13 and 18 and (mosaic) triploidy [9]. Since the introduction of genome-wide CNV analysis using microarray platforms several other small chromosomal aberrations have been reported in SH patients (Supplementary Table 1). In particular, partial 6p terminal deletions are reported rather frequently [10]. The 6p terminal deletion has a recognizable phenotype. Clinical features include Axenfeld-Rieger anomaly, hearing loss, congenital heart disease, dental anomalies, developmental delay and a characteristic facial appearance (Fig. 1B). Maclean et al. (2005) reported a child with a 6pter microdeletion arising from a de novo translocation (6;18)(p25.1;p11.2) including the FOXC1, FOXF2 and FOXQ1 forkhead gene cluster at 6p25. Central nervous system anomalies included hydrocephalus and hypoplasia of the cerebellum, brainstem and corpus callosum with mild to moderate developmental delay [11]. The most interesting candidate gene for this form of congenital hydrocephalus is FOXC1: mice with homozygous nonsense mutations of the Foxc1 gene die at birth because of progressive hydrocephalus [12]. Mutations in the FOXC1 gene have been identified in patients with Axenfeld-Rieger syndrome and more recently, also in DandyeWalker syndrome [13]. The latter is defined by partial or complete absence of the cerebellar vermis and cystic dilatation of the fourth ventricle, often accompanied by congenital hydrocephalus. In SH patients without a directly recognized syndrome, array platforms combining SNP and CNV analysis allow for the detection of (partial) uniparental disomy or regions of homozygosity (ROH). We prefer to use both techniques, especially in patients with presumed autosomal recessive congenital hydrocephalus (e.g. consanguineous parents or affected sib pairs). This sometimes leads to identification of a disease-causing gene. Multiplex Ligation-dependent Probe Amplification (MLPA) analysis remains a valuable, inexpensive tool to directly confirm clinically suspected (subtelomeric) microdeletions or -duplications. Conventional karyotyping can still be useful to investigate mosaic (<30%) chromosome abnormalities and possible (de novo) inversions or balanced translocations in which the breakpoints can potentially disrupt genes or have a position effect on neighboring genes. The L1 syndrome should be excluded in every male with SH. Vos et al. (2010) screened 60 patients suspected of having L1 syndrome without L1CAM gene mutation using a high density X-chromosome specific array-based CGH. Eleven CNVs were identified containing candidate genes expressed in brain (including e.g. the GDI1 gene) (thesis Y. Vos: Genetics of L1 syndrome, Chapter 8, 2010). Further research is needed to determine the potential role of these genes in X-linked congenital SH. Few other families with X-linked SH have been described. The high maleefemale ratio observed in our cohort
(2.6:1) indicates possible involvement of X-linked disease-causing genes other than L1CAM. Candidate genes for lethal forms of congenital hydrocephalus in males include OFD1, AP1S2 and HDAC6 involved in respectively orofaciodigital syndrome type I [14], X-linked mental retardation [15] and X-linked dominant chondrodysplasia [16]. SH is otherwise mainly inherited in an autosomal recessive manner. Congenital hydrocephalus has occasionally been described in numerous other genetic disorders [17]. A nonexhaustive list is available in Supplementary Table 3. In 21% (7/34) of our patients with unresolved SH clinical features of the VACTERL-H association were identified. The phenotypic spectrum of the VACTERL-H association is wide and poorly understood [18]. Hemifacial microsomia and Fanconi anemia show many overlapping features including vertebral, gastrointestinal, cardiac and limb defects. Convincing relationships between these conditions and VACTERL-H have been described in literature [19e21]. As suggested earlier by Faivre [22], chromosome breakage studies should be considered in patients with congenital hydrocephalus and additional features of VACTERL-H association. Metabolic disorders should not be disregarded as a possible cause of hydrocephalus. Given the mainly autosomal recessive inheritance, it should especially be considered in affected sib pairs. Metabolic disorders are more likely to cause postnatal hydrocephalus. Congenital hydrocephalus is a common feature in disorders with glycosylation defects such as muscular dystrophydystroglycanopathies, including WalkereWarburg syndrome (Supplementary Table 2). Other metabolic disorders associated with congenital hydrocephalus include for example mucopolysaccharidoses, alpha-mannosidosis and Smith-Lemli-Opitz syndrome (Supplementary Table 3). Metabolic investigation in SH should at least include assessment of blood creatine kinase (CK) and lactate, plasma cholesterol metabolites, urinary mucopolysaccharides and isoelectric focusing for sialotransferrine. 4.5. Future perspectives Upcoming next generation sequencing technologies are rapidly changing the field of genetic diagnostics. At present, whole exome and/or genome sequencing are still too expensive for widespread use. Analysis of the large amount of data generated, e.g. interpreting the numerous unclassified genetic variants, will become a major challenge. Targeted X-exome sequencing can be a more readily available option in males with congenital hydrocephalus, especially in case of a positive family history. Growing evidence from literature indicates that cilia disorders may play an important role in congenital hydrocephalus. Cilia are microtubule-based organelles that extend from the surface of almost every cell in the human body (e.g. in the ependyma of the cerebral ventricles) and are able to propel fluid [23, 24]. As ciliated ependymal cells play a crucial role in the control of cerebrospinal fluid homeostasis in the brain, cilia defects can lead to the formation of hydrocephalus [25]. Two cilia-related disease mechanisms have been identified in hydrocephalus formation: A. defects in the transport of proteins across the ciliary compartment border leading to the formation of aberrant cilia with overproduction of CSF, and B. ependymal ciliary dysmotility leading to an impaired circulation and obstruction of CSF. The phenotypic spectrum of cilia disorders includes cerebellar hypoplasia, retinopathy, polycystic kidneys, liver cysts, polydactyly, obesity, leftright asymmetry, situs inversus, infertility and (sometimes) hydrocephalus. To date, more than 100 human cilia genes are detected. The genetic heterogeneity of cilia disorders complicates current diagnostics. Implementation of genome-wide exome sequencing in the near future will enable us to generate data on the various known cilia genes in a single experiment. The Ciliary
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Proteome Database can then be a helpful instrument for interpreting this data [26]. 4.6. Prognosis The prognosis of a child with congenital hydrocephalus is highly variable and mainly depends on the underlying cause of hydrocephalus, associated malformations and the timing and success of surgical treatment [27]. General mortality rate varies from 5% to 15%. About 40% of the children with congenital hydrocephalus is cognitively impaired, ranging from mild to severe retardation. The degree of cognitive impairment does not necessarily correlate with head circumference or severity of hydrocephalus [8]. Motor problems are seen in 30% of the children with congenital hydrocephalus, of which half is wheelchair dependent [28]. Delay of treatment is an important risk factor for poor outcome [2]. 4.7. Recurrence risk The recurrence risk in sporadic patients with NSH is low: approximately 4% in males and 2% in females [4]. However, when NSH is familial the recurrence risk increases dramatically, depending on the mode of inheritance. Familial forms of NSH are often X-linked with a 50% recurrence risk for the male offspring of female carriers. Daughters have a 50% chance of being a carrier with a low risk (<5%) of manifesting clinical features of congenital hydrocephalus [4]. In sporadic patients with SH the recurrence risk depends on the inheritance pattern of the suspected syndrome. In SH patients with hydrocephalus of unknown origin the estimated recurrence risk, after extensive clinical and molecular investigations, is 5%. In familial forms of SH the recurrence risk depends on the inheritance pattern suspected from pedigree data (Fig. 2). 5. Conclusion We have to conclude that genetic causes of congenital hydrocephalus are still largely unknown. This retrospective survey provides evidence for new genetically determined forms of congenital hydrocephalus. Candidate gene and functional analysis is ongoing. We recommend L1CAM gene mutation analysis and genome-wide SNP/CNV analysis in every patient with congenital hydrocephalus. In addition, metabolic investigation, conventional karyotyping and chromosomal breakage studies should be considered in patients with unknown forms of SH. Further research is needed in order to identify the underlying gene defects in hitherto unknown, possibly genetic forms of (non-) syndromic congenital hydrocephalus. Appendix. Supplementary material Supplementary material related to this article can be found at doi:10.1016/j.ejmg.2011.06.005 References [1] J.L. Tolmie, Clinical genetics of neural tube defects and other congenital central nervous system malformations. in: D.L. Rimoin, J.M. Connor, R.E. Pyeritz, B.R. Korf (Eds.), Emery and Rimoin’s Principles and Practice of Medical Genetics. Churchill Livingstone, London, 2002, pp. 2975e3011. [2] K. Mori, J. Shimada, M. Kurisaka, et al., Classification of hydrocephalus and outcome of treatment, Brain Dev. 17 (5) (1995) 338e348. [3] G.H. Davis, Fetal hydrocephalus, Clin. Perinatol. 30 (3) (2003) 531e539. [4] C. Schrander Stumpel, J.P. Fryns, Congenital hydrocephalus: nosology and guidelines for clinical approach and genetic counselling, Eur. J. Pediatr. 157 (5) (1998) 355e362.
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