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Value of computerized tomography scanning in syndromes associated with mental retardation: Preliminary report
VALUE OF COMPUTERIZED TOMOGRAPHY SCANNING IN SYNDROMES ASSOCIATED WITH MENTAL RETARDATION: PRELIMINARY REPORT MOHAMMAD H. NAHEEDY Department of Radiology, Division of Neuroradiology, and Peter Bent Brigham
Hospital.
and JAMES A. SCHNUR Harvard Medical School, Cambridge, Mass., U.S.A.
25 Shattuck
St., Boston,
6 June 1978: received for puhlicurim
(Recrirrrl
MA 02115, U.S.A.
13 Svptrrnher
1978)
Abstract-The In in In is
application of CT scanning in the evaluation of mental retardation syndromes is reviewed. a representative sample of 35 institutionalized patients, the CT scan showed gross anatomic abnormality most. However, these findings were diagnostic in only a small minority. Implications of this are discussed. addition, the potential role of CT in the diagnosis of intercurrent diseases in the mentally retarded considered.
Computerized
tomography
Mental
retardation
INTRODUCTION
Defined as a condition characterized by faulty neurologic development, mental retardation (MR) impairs an individual’s ability to learn or to adapt to the demands of society [l]. The neurologic (and somatic) impairments of MR become manifest before adulthood. In contrast, the intellectual disorders that develop during adulthood are ordinarily classified as dementia syndromes [2], Reliable sources estimate that 3% of the population of the United States is mentally retarded. although no precise figures are available [3]. The causes of MR are both mysterious and numerous. Perhaps the most common MR syndrome is borderline to minimal retardation with subtle behavior abnormalities. Another frequent picture of MR is typified by children with minimal to moderate retardation (IQ 50-70) of unknown etiology. In contrast, a smaller, but not significant, number of MR patients exhibit severe retardation, and require institutionalization. Regarding the neuropathologic basis of MR, it has been generally held that a significant majority of patients demonstrate neither gross nor microscopic lesions of the brain. CLASSIFICATION An admittedly simplistic but practical way to classify MR is on clinical grounds. Using this approach, Holmes et al. [2] were able to assign 60.7% of the 1378 mentally retarded residents of the Walter E. Fernald State School in Waltham, Massachusetts, to various etiologic categories (Table 1). Table
Disease
I. Clinical
evaluation
of 1378 individuals
at Walter
E. Fernald
State School,
Number of patients IQ < 50 IQ > 50
category
38 5 278 247 49 64 4
Metabolic and endocrine diseases Progressive diseases of the nervous system Acquired conditions Chromosomal abnormalities Central nervous system abnormalities Multiple congenital deformities Neurocutaneous diseases Psychosis Mentally retarded, cause unknown Not mentally retarded Total See Ref. [Z] 1
3x5 0
79 10 16 16 0 6 156 6
1077
301
Waltham.
Mass.
“, of surveyed population 3.1 0.9 25.9 18.7 4.7 5.8 0.3 0.9 39.3 0.4
IOO.0
MOHAMMAD H. NAHEEDY and JAMES A. SCHNUR
2
DIAGNOSTIC
APPROACHES
Despite the obscure etiology and neuropathology of most cases of MR, it is often possible to define certain distinctive characteristics of these syndromes. For example, some cases manifest a particular clinical picture while others are associated with specific chemical, serological or other laboratory abnormalities. In-uivo imaging of gross brain morphology is also helpful. Available techniques include skull X-rays, pneumoencephalography, angiography, radionuclide scanning and computerized tomography. Imaging studies are important for a number of reasons. In Huntington’s chorea for example, a firm diagnosis can usually be made by pneumoencephalography. While limited in therapeutic value, this information can help considerably in the management of such patients. Furthermore, imaging studies are of obvious utility in the detection of intercurrent problems such as subdural hematomas. Prior to 1973, imaging options were limited because of the unavailability of the necessary equipment, an unacceptably high level of risk to the patient, or unjustifiable expense. The advent of computerized tomography (CT) changed this situation dramatically. For the first time, it became possible to image the brain directly at a modest cost and with little risk.
MATERIALS
AND
METHODS
The study population comprised 35 residents of the Walter E. Fernald State School, Waltham, Massachusetts, who were referred for CT scans from 1975 through 1977.* While not random, this patients sample nevertheless represents a typical group of institutionalized retarded patients (Table 2). The CT scan findings were first judged to be either normal or abnormal. If abnormal, classification was based on the major finding. Four categories were defined in this manner (Table 3). Included were CT scans judged to be normal as well as those demonstrating diffuse enlargement of the lateral ventricles with or without prominent sulci, focal brain lesions and a number of miscellaneous abnormalities. CT scans were then juxtaposed against etiology of MR syndromes (Table 4).
Table
2. Etiology
of MR No. of patients
Etiology Idiopathic Metabolic Acquired Chromosomal abnormality Multiple congenital malformations Central nervous system malformations
18 7 4 4
Total
35
Table
1 1
51.3 20 11.5 11.5 2.85 2.85 100
3. CT scan findings
Finding
No. of patients
Normal Enlarged ventricles Unassociated with prominent sulci Associated with prominent sulci Focal lesions Encephalomalacia Pathologic calcification Miscellaneous
* All scans were performed
at the Sidney
Farber
Cancer
Institute,
Boston.
Massachusetts
on an EMI Mark-l
unit.
CT in syndromes
Table
associated
4. Etiology
with mental
3
retardation
vs CT scan findings
CT scan findings Enlarged Etiology Idiopathic Metabolic Acquired Chromosomal Multiple tong. malformations CNS mal. Total
Normal I 2
Unassociated with wide sulci 4
Focal
ventricles Associated with wide sulci
Path.
Cal.
Misc.
1
4 3
1
10
Encephalomalacia
lesions
18 7 4 4
1 1
3
I
14
1
1
Total
1 1 2
I
1 35
RESULTS In 18 patients with idiopathic MR, the CT scan demonstrated enlargement of the lateral ventricles without prominent sulci in 4, enlargement with prominent sulci in 7 and normal ventricular development in 7 instances. In 7 patients with metabolic MR, the CT scan revealed enlarged lateral ventricles with prominent sulci in 4, demonstrated pathologic calcification in 1, and normal development in 2 instances. In 4 patients with acquired MR, the CT scan showed enlarged lateral ventricles with prominent sulci in 3. Porencephaly in the territory of the left middle cerebral artery was noted in the remaining patient in the acquired MR subgroup. In 4 patients with MR associated with chromosomal abnormalities the CT scan revealed large lateral ventricles with prominent sulci in 3, while the remaining patient proved normal. In the single patient with Crouzon’s disease, the most striking CT scan abnormality was agenesis of the corpus callosum. Finally, a sole case of central nervous system malformation with MR showed cerebral herniatrophy. DISCUSSION When all etiologic types of MR were correlated with CT scan findings, 10 of the 35 patients (28.6”/,) had normal CT scans. This finding suggests that marked changes in intellectual function are not always mirrored by corresponding gross morphologic changes. In contrast. 14 patients (40?;,) showed prominent lateral ventricles and sulci, probably reflecting various degrees and comof the lateral ventricles binations of gray and white matter loss (Figs. 1 and 2). An enlargement together with an essentially normal cortex was seen in 7 patients (209J perhaps reflecting prcdominantly white matter loss or obstructive hydrocephalus (Figs. 3a and b). Thus, in well over 50”,, of the sample population, the CT scan showed gross pathologic changes. Despite this seemingly high incidence of abnormalities, the morphologic changes may not necessarily be specific to the etiology of MR. In a small minority of cases exemplified by pathologic intracerebral calcification, central nervous system malformation or focal encephalomalacia, the CT scan would seem to be more specific with respect to the etiology of MR syndromes (Figs. 4a and b). Confirmation of a fixed brain disease such as gross dysplasia also provides important practical data concerning prognosis and long term management. CT scans can demonstrate intercurrent processes such as subdural hematomas or obstructive hydrocephalus. findings of essentially comparable utility in the management of both retarded and normal patients. CONCLUSION Although CT appears quite specific in defining the etiology of MR in a small minority of cases, the technique is unfortunately equivocal in the majority. Nonetheless, the CT scan does play a number of clinically important roles in MR, notably defining anatomic normality or elucidating structural abnormality. In the first instance, the question of “functional” etiology might then arise
MOHAMMAD H. NAHEEDV and JAMES A. SCHNUR
Fig. 1. CT scan without contrast in 3f-year old male with proven Tay--Sachs disease. (a) CT scan shows moderate dilatation of both lateral ventricles with some prominence of the Sylvian fissures, (b) Cut at higher level demonstrates abnormal widening of sulci in fronto-partial convexity. CT scan diagnosis: Nonspecific loss of gray and white matter.
CT in syndromes
associated
with mental
retardation
Fig. 2. CT scan without contrast in 60-year old male with mental retardation and proven Down’s syndrome. (a) CT scan shows prominence of the third ventricle, trigones and Sylvian fissure. (b) CT scan at a higher level shows moderate enlarged lateral ventricles as well as widened sulci in mid-upper convexity. CT scan diagnosis: Nonspecific loss of gray and white matter.
6
MOHAMMAD H. NAHEEDY
Fig. 3. CT scan without contrast of 29-year old male, blastoma at age 1 year with mental retardation since. significantly dilatated lateral and third ventricles and tive hydrocephalus,
and
JAMES A. SCHNUR
status post-surgery and radiation therapy for neuro(a and b) CT scan reveals striking disparity bletween relatively normal sulci. CT scan diagnosis: 0 sbstrucprobably arrested.
CT in syndromes
associated
with mental
retardation
Fig. 4. CT scan without contrast in 33 year-old male with mental retardation and spastic right hemiparesis. fluid absorption value in the territory (a and b) CT scans show a large cavitary lesion of cerebrospinal communication with the left lateral ventricle. CT scan of the left t@ddle cerebral artery with probable probably due to infarction resulting from occlusion of the left middle cerebral diagnc )sis: Encephalomalacia artery.
8
MOHAMMAD H. NAHEEDY and JAMES A. SCHNUR
while in the latter, prognosis and mangement may be altered. The value of CT in detecting intercurrent disease in MR should be obvious. Considering the more than 6 million retarded pkople in the United States alone, these implications are substantial. Clearly the role of brain imaging, particularly that of CT scanning, in the retarded patient requires more study. The place of CT scanning in the diagnostic and therapeutic strategy in the mentally retarded must eventually be based on solid scientific data. An even more important yet elusive goal is to employ the CT scan in furthering our understanding of MR. REFERENCES I. M. Best, Public Prouisionfbr the Mentally Retarded in the United States. pp. 3-5. Thomas Crowell, New York (1965). 2. L. Holmes, H. Moser, S. Halldorsson, C. Mack, S. S. Pant and B. Matzilevich, Mental Retardation, an Atlas qf Disease with Associated Physical Abnormalities. pp. 1, 2, 4, 62, 69, 100. Macmillan, New York (1971). 3. A. M. Freedman, H. 1. Kaplan and B. J. Sadock, Modern Synopsis of Psychiatry. pp. 313-314. Williams & Wilkins, Baltimore (1971). About the Author-MOHAMMAD H. NAHEEDY was born in Rezaiyeh, Iran on 21 March 1946. He attended the Tehran Medical School from 1964 to 1971 and received his M.D. degree from that University. He finished his internship in St. Luke’s Hospital of Philadelphia in June, 1974. He had three years of residency in diagnostic radiology at Episcopal Hospital of Philadelphia which is part of Temple Medical School. He was Board Certified in diagnostic radiology in December, 1977. He started his clinical Fellowship in Harvard Medical School Hospitals in July. 1977 and is currently a second year Fellow in Neuradiology on that program. About the Author-JAMES SCHNUR was born in New York City on 19 July, 1940. He received his A.B. degree from New York University in 1961 and attended Harvard Medical School from which he received his M.D. degree in 1965. He had training in Neurology, Radiology and Neuroradiology at the Harvard Medical School Hospitals. He was certified by the Diplomate American Board of Psychiatry and Neurology in 1974 and by the American Board of Radiology in 1978. Since 1975 he has been Assistant Professor of Radiology at Harvard Medical School-Peter Bent Brigham Hospital. In July, 1978 he left that department and currently he is Neurocardiologist in the Department of Radiology, Nyack Hospital, Nyack, New York. He has been engaged in research regarding CT scanning and has published a number of articles in this field.
Hospital.
and JAMES A. SCHNUR Harvard Medical School, Cambridge, Mass., U.S.A.
25 Shattuck
St., Boston,
6 June 1978: received for puhlicurim
(Recrirrrl
MA 02115, U.S.A.
13 Svptrrnher
1978)
Abstract-The In in In is
application of CT scanning in the evaluation of mental retardation syndromes is reviewed. a representative sample of 35 institutionalized patients, the CT scan showed gross anatomic abnormality most. However, these findings were diagnostic in only a small minority. Implications of this are discussed. addition, the potential role of CT in the diagnosis of intercurrent diseases in the mentally retarded considered.
Computerized
tomography
Mental
retardation
INTRODUCTION
Defined as a condition characterized by faulty neurologic development, mental retardation (MR) impairs an individual’s ability to learn or to adapt to the demands of society [l]. The neurologic (and somatic) impairments of MR become manifest before adulthood. In contrast, the intellectual disorders that develop during adulthood are ordinarily classified as dementia syndromes [2], Reliable sources estimate that 3% of the population of the United States is mentally retarded. although no precise figures are available [3]. The causes of MR are both mysterious and numerous. Perhaps the most common MR syndrome is borderline to minimal retardation with subtle behavior abnormalities. Another frequent picture of MR is typified by children with minimal to moderate retardation (IQ 50-70) of unknown etiology. In contrast, a smaller, but not significant, number of MR patients exhibit severe retardation, and require institutionalization. Regarding the neuropathologic basis of MR, it has been generally held that a significant majority of patients demonstrate neither gross nor microscopic lesions of the brain. CLASSIFICATION An admittedly simplistic but practical way to classify MR is on clinical grounds. Using this approach, Holmes et al. [2] were able to assign 60.7% of the 1378 mentally retarded residents of the Walter E. Fernald State School in Waltham, Massachusetts, to various etiologic categories (Table 1). Table
Disease
I. Clinical
evaluation
of 1378 individuals
at Walter
E. Fernald
State School,
Number of patients IQ < 50 IQ > 50
category
38 5 278 247 49 64 4
Metabolic and endocrine diseases Progressive diseases of the nervous system Acquired conditions Chromosomal abnormalities Central nervous system abnormalities Multiple congenital deformities Neurocutaneous diseases Psychosis Mentally retarded, cause unknown Not mentally retarded Total See Ref. [Z] 1
3x5 0
79 10 16 16 0 6 156 6
1077
301
Waltham.
Mass.
“, of surveyed population 3.1 0.9 25.9 18.7 4.7 5.8 0.3 0.9 39.3 0.4
IOO.0
MOHAMMAD H. NAHEEDY and JAMES A. SCHNUR
2
DIAGNOSTIC
APPROACHES
Despite the obscure etiology and neuropathology of most cases of MR, it is often possible to define certain distinctive characteristics of these syndromes. For example, some cases manifest a particular clinical picture while others are associated with specific chemical, serological or other laboratory abnormalities. In-uivo imaging of gross brain morphology is also helpful. Available techniques include skull X-rays, pneumoencephalography, angiography, radionuclide scanning and computerized tomography. Imaging studies are important for a number of reasons. In Huntington’s chorea for example, a firm diagnosis can usually be made by pneumoencephalography. While limited in therapeutic value, this information can help considerably in the management of such patients. Furthermore, imaging studies are of obvious utility in the detection of intercurrent problems such as subdural hematomas. Prior to 1973, imaging options were limited because of the unavailability of the necessary equipment, an unacceptably high level of risk to the patient, or unjustifiable expense. The advent of computerized tomography (CT) changed this situation dramatically. For the first time, it became possible to image the brain directly at a modest cost and with little risk.
MATERIALS
AND
METHODS
The study population comprised 35 residents of the Walter E. Fernald State School, Waltham, Massachusetts, who were referred for CT scans from 1975 through 1977.* While not random, this patients sample nevertheless represents a typical group of institutionalized retarded patients (Table 2). The CT scan findings were first judged to be either normal or abnormal. If abnormal, classification was based on the major finding. Four categories were defined in this manner (Table 3). Included were CT scans judged to be normal as well as those demonstrating diffuse enlargement of the lateral ventricles with or without prominent sulci, focal brain lesions and a number of miscellaneous abnormalities. CT scans were then juxtaposed against etiology of MR syndromes (Table 4).
Table
2. Etiology
of MR No. of patients
Etiology Idiopathic Metabolic Acquired Chromosomal abnormality Multiple congenital malformations Central nervous system malformations
18 7 4 4
Total
35
Table
1 1
51.3 20 11.5 11.5 2.85 2.85 100
3. CT scan findings
Finding
No. of patients
Normal Enlarged ventricles Unassociated with prominent sulci Associated with prominent sulci Focal lesions Encephalomalacia Pathologic calcification Miscellaneous
* All scans were performed
at the Sidney
Farber
Cancer
Institute,
Boston.
Massachusetts
on an EMI Mark-l
unit.
CT in syndromes
Table
associated
4. Etiology
with mental
3
retardation
vs CT scan findings
CT scan findings Enlarged Etiology Idiopathic Metabolic Acquired Chromosomal Multiple tong. malformations CNS mal. Total
Normal I 2
Unassociated with wide sulci 4
Focal
ventricles Associated with wide sulci
Path.
Cal.
Misc.
1
4 3
1
10
Encephalomalacia
lesions
18 7 4 4
1 1
3
I
14
1
1
Total
1 1 2
I
1 35
RESULTS In 18 patients with idiopathic MR, the CT scan demonstrated enlargement of the lateral ventricles without prominent sulci in 4, enlargement with prominent sulci in 7 and normal ventricular development in 7 instances. In 7 patients with metabolic MR, the CT scan revealed enlarged lateral ventricles with prominent sulci in 4, demonstrated pathologic calcification in 1, and normal development in 2 instances. In 4 patients with acquired MR, the CT scan showed enlarged lateral ventricles with prominent sulci in 3. Porencephaly in the territory of the left middle cerebral artery was noted in the remaining patient in the acquired MR subgroup. In 4 patients with MR associated with chromosomal abnormalities the CT scan revealed large lateral ventricles with prominent sulci in 3, while the remaining patient proved normal. In the single patient with Crouzon’s disease, the most striking CT scan abnormality was agenesis of the corpus callosum. Finally, a sole case of central nervous system malformation with MR showed cerebral herniatrophy. DISCUSSION When all etiologic types of MR were correlated with CT scan findings, 10 of the 35 patients (28.6”/,) had normal CT scans. This finding suggests that marked changes in intellectual function are not always mirrored by corresponding gross morphologic changes. In contrast. 14 patients (40?;,) showed prominent lateral ventricles and sulci, probably reflecting various degrees and comof the lateral ventricles binations of gray and white matter loss (Figs. 1 and 2). An enlargement together with an essentially normal cortex was seen in 7 patients (209J perhaps reflecting prcdominantly white matter loss or obstructive hydrocephalus (Figs. 3a and b). Thus, in well over 50”,, of the sample population, the CT scan showed gross pathologic changes. Despite this seemingly high incidence of abnormalities, the morphologic changes may not necessarily be specific to the etiology of MR. In a small minority of cases exemplified by pathologic intracerebral calcification, central nervous system malformation or focal encephalomalacia, the CT scan would seem to be more specific with respect to the etiology of MR syndromes (Figs. 4a and b). Confirmation of a fixed brain disease such as gross dysplasia also provides important practical data concerning prognosis and long term management. CT scans can demonstrate intercurrent processes such as subdural hematomas or obstructive hydrocephalus. findings of essentially comparable utility in the management of both retarded and normal patients. CONCLUSION Although CT appears quite specific in defining the etiology of MR in a small minority of cases, the technique is unfortunately equivocal in the majority. Nonetheless, the CT scan does play a number of clinically important roles in MR, notably defining anatomic normality or elucidating structural abnormality. In the first instance, the question of “functional” etiology might then arise
MOHAMMAD H. NAHEEDV and JAMES A. SCHNUR
Fig. 1. CT scan without contrast in 3f-year old male with proven Tay--Sachs disease. (a) CT scan shows moderate dilatation of both lateral ventricles with some prominence of the Sylvian fissures, (b) Cut at higher level demonstrates abnormal widening of sulci in fronto-partial convexity. CT scan diagnosis: Nonspecific loss of gray and white matter.
CT in syndromes
associated
with mental
retardation
Fig. 2. CT scan without contrast in 60-year old male with mental retardation and proven Down’s syndrome. (a) CT scan shows prominence of the third ventricle, trigones and Sylvian fissure. (b) CT scan at a higher level shows moderate enlarged lateral ventricles as well as widened sulci in mid-upper convexity. CT scan diagnosis: Nonspecific loss of gray and white matter.
6
MOHAMMAD H. NAHEEDY
Fig. 3. CT scan without contrast of 29-year old male, blastoma at age 1 year with mental retardation since. significantly dilatated lateral and third ventricles and tive hydrocephalus,
and
JAMES A. SCHNUR
status post-surgery and radiation therapy for neuro(a and b) CT scan reveals striking disparity bletween relatively normal sulci. CT scan diagnosis: 0 sbstrucprobably arrested.
CT in syndromes
associated
with mental
retardation
Fig. 4. CT scan without contrast in 33 year-old male with mental retardation and spastic right hemiparesis. fluid absorption value in the territory (a and b) CT scans show a large cavitary lesion of cerebrospinal communication with the left lateral ventricle. CT scan of the left t@ddle cerebral artery with probable probably due to infarction resulting from occlusion of the left middle cerebral diagnc )sis: Encephalomalacia artery.
8
MOHAMMAD H. NAHEEDY and JAMES A. SCHNUR
while in the latter, prognosis and mangement may be altered. The value of CT in detecting intercurrent disease in MR should be obvious. Considering the more than 6 million retarded pkople in the United States alone, these implications are substantial. Clearly the role of brain imaging, particularly that of CT scanning, in the retarded patient requires more study. The place of CT scanning in the diagnostic and therapeutic strategy in the mentally retarded must eventually be based on solid scientific data. An even more important yet elusive goal is to employ the CT scan in furthering our understanding of MR. REFERENCES I. M. Best, Public Prouisionfbr the Mentally Retarded in the United States. pp. 3-5. Thomas Crowell, New York (1965). 2. L. Holmes, H. Moser, S. Halldorsson, C. Mack, S. S. Pant and B. Matzilevich, Mental Retardation, an Atlas qf Disease with Associated Physical Abnormalities. pp. 1, 2, 4, 62, 69, 100. Macmillan, New York (1971). 3. A. M. Freedman, H. 1. Kaplan and B. J. Sadock, Modern Synopsis of Psychiatry. pp. 313-314. Williams & Wilkins, Baltimore (1971). About the Author-MOHAMMAD H. NAHEEDY was born in Rezaiyeh, Iran on 21 March 1946. He attended the Tehran Medical School from 1964 to 1971 and received his M.D. degree from that University. He finished his internship in St. Luke’s Hospital of Philadelphia in June, 1974. He had three years of residency in diagnostic radiology at Episcopal Hospital of Philadelphia which is part of Temple Medical School. He was Board Certified in diagnostic radiology in December, 1977. He started his clinical Fellowship in Harvard Medical School Hospitals in July. 1977 and is currently a second year Fellow in Neuradiology on that program. About the Author-JAMES SCHNUR was born in New York City on 19 July, 1940. He received his A.B. degree from New York University in 1961 and attended Harvard Medical School from which he received his M.D. degree in 1965. He had training in Neurology, Radiology and Neuroradiology at the Harvard Medical School Hospitals. He was certified by the Diplomate American Board of Psychiatry and Neurology in 1974 and by the American Board of Radiology in 1978. Since 1975 he has been Assistant Professor of Radiology at Harvard Medical School-Peter Bent Brigham Hospital. In July, 1978 he left that department and currently he is Neurocardiologist in the Department of Radiology, Nyack Hospital, Nyack, New York. He has been engaged in research regarding CT scanning and has published a number of articles in this field.