Agenesis/Dysgenesis

Agenesis/dysgenesis of the corpus callosum is among the xvii. Opitz G syndrome most common developmental malformation with a wide xviii. Peters plus syndrome spectrum of associated clinical and pathologic abnormalities. a) Peters anomaly The prevalence and clinical significance are uncertain. It is esti- b) Short-limb dwarfism mated to be 0.3–0.7% in the general population and 2–3% in xix. Shapiro syndrome (recurrent hypothermia) the developmentally disabled. xx. Smith-Lemli-Opitz syndrome xxi. Toriello-Carey syndrome /BASIC DEFECTS a) Agenesis/dysgenesis of the corpus callosum 1. Markedly heterogeneous etiology of agenesis/dysgenesis b) Facial anomalies of the corpus callosum c) Robin sequence a. Sporadic in most cases xxii. Vici syndrome b. Environmental factors a) Agenesis/dysgenesis of the corpus callosum i. Alcoholism b) ii. Maternal rubella c) Cleft lip/palate iii. Maternal diabetes d) c. A multifactorial trait e) Hypopigmentation d. As a part of autosomal dominant syndrome xxiii. Walker-Warburg syndrome i. Agenesis/dysgenesis of the corpus callosum a) ii. b) Agyria iii. Basal cell nevus syndrome c) Retinal dysplasia iv. Miller-Dieker syndrome xxiv. Warburg micro syndrome v. Rubinstein-Taybi syndrome a) vi. Tuberous sclerosis b) Microphthalmia e. As a part of autosomal recessive syndrome c) Cerebral malformations i. Agenesis/dysgenesis of the corpus callosum d) Other anomalies ii. Agenesis/dysgenesis of the corpus callosum with f. As a part of X-linked syndrome thrombocytopenia i. Agenesis/dysgenesis of the corpus callosum iii. ii. Agenesis/dysgenesis of the corpus callosum with iv. Andermann syndrome Hirschsprung disease a) Agenesis/dysgenesis of the corpus callosum iii. Agenesis/dysgenesis of the corpus callosum with with peripheral neuropathy hypohidrotic ectodermal dysplasia b) Mapping of the gene to a 5-cm region in iv. (retinovertebral anomalies in chromosome 15q13-15 females) v. Cerebro-oculo-facio-skeletal (COFS) syndrome v. ATR-X syndrome (X-linked alpha thalassemia vi. Cogan syndrome (ocular motor apraxia) mental retardation syndrome) vii. Craniotelencephalic dysplasia vi. Craniofrontonasal syndrome viii. Dincsoy syndrome vii. Curatolo syndrome a) Multiple midline malformations a) Agenesis/dysgenesis of the corpus callosum b) Limb abnormalities b) Chorioretinal abnormality c) Hypopituitarism viii. FG syndrome ix. Fukuyama congenital a) Mental retardation x. Hydrolethalis syndrome b) Large head xi. (cerebellar vermis agenesis) c) Imperforate anus xii. Leprechaunism d) Congenital xiii. Lowry-Wood syndrome e) Partial agenesis/dysgenesis of the corpus a) Epiphyseal dysplasia callosum b) Microcephaly ix. HSAS syndrome (hydrocephalus due to congen- c) ital stenosis of aqueduct of Sylvius) xiv. Meckel-Gruber syndrome x. Lenz dysplasia xv. Microcephalic osteodysplastic primordial a) Microphthalmia/anophthalmia dwarfism type I/III b) Associated anomalies xvi. Neu-Laxova syndrome xi. Lujan-

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a) X-linked mental retardation c. Essential for efficient cognitive function b) Marfanoid habitus d. Failure of development of the commissural fibers xii. MASA syndrome connecting the cerebral hemispheres produces dysge- a) Mental retardation nesis or agenesis of the corpus callosum b) e. Diagnosis of agenesis: a challenge even for expert c) Shuffling gait sonologists, particularly prior to 20 weeks of gestation d) Adducted thumbs 3. Types of agenesis xiii. MLS syndrome a. Complete agenesis: commonly regarded as a malfor- a) Microphthalmia mation deriving from faulty embryogenesis b) Linear skin defects b. Type I agenesis xiv. Opitz G syndrome i. Not associated with other disorder xv. OFD I ii. Usually absent or associated with mild neurologic xvi. Proud syndrome manifestations a) X-linked syndrome c. Type II agenesis b) i. Associated with other migrational, genetic, and c) Acquired micrencephaly chromosomal disorders d) Agenesis/dysgenesis of the corpus callosum ii. Usually associated with severe neurologic mani- xvii. XLIS syndrome (X-linked ) festations g. As a part of unknown-genesis syndrome d. Partial agenesis i. Calloso-genital dysplasia i. Referred to as dysgenesis ii. Delleman (oculocerebrocutaneous) syndrome ii. Either a true malformation or a disruptive event iii. Frontonasal dysplasia occurring at any time during pregnancy iv. Opitz C trigonocephaly syndrome iii. Missing caudad portion (splenium and body) to v. Sebaceous nevus syndrome varying degrees h. As a part of metabolic disorders 4. Agenesis/dysgenesis of the corpus callosum i. Adenylosuccinase deficiency a. Without other associated brain anomalies ii. Adipsic hypernatremia b. Frequently associated with other brain anomalies iii. β-hydroxyisobutyryl coenzyme A deacyclase i. Defects of septum pellucidum and fornix deficiency ii. Hydrocephalus iv. Glutaric aciduria type II iii. Dandy-Walker malformation v. Histidinemia iv. Interhemispheric cyst vi. Hurler syndrome v. vii. Leigh syndrome vi. viii. Menkes syndrome vii. ix. Neonatal viii. Macrogyria x. Nonketotic hyperglycinemia ix. Cortical heterotopia and atrophy xi. Pyruvate dehydrogenase deficiency x. xii. Zellweger syndrome xi. i. Associated chromosome abnormalities xii. Hypoplasia of cerebellum i. Trisomy 18 c. Frequently associated other anatomical anomalies ii. Trisomy 8 i. Congenital heart defects iii. Trisomy 21 ii. Costovertebral defects iv. Trisomy 22 iii. Gastrointestinal anomalies v. Other trisomies iv. Genitourinary anomalies vi. Deletions vii. Translocations viii. Duplications CLINICAL FEATURES j. Agenesis of the corpus callosum with interhemispheric 1. Craniofacial abnormalities cyst: a heterogeneous group of disorders that have in a. Microcephaly common callosal agenesis and extraparenchymal b. cysts, both of which are among the commonest CNS 2. Developmental anomalies malformations a. Nonspecific mental retardation k. Incidental finding in normal individuals (isolated dys- b. Developmental delay genesis of the corpus callosum) c. Learning disabilities 2. Embryogenesis of the corpus callosum d. Behavioral disorder a. Development of the corpus callosum e. Mental retardation i. A late event in cerebral ontogenesis f. ii. Taking place between 12–18 weeks of gestation 3. Infantile spasms/seizures b. An important brain commissure connecting the cere- 4. Signs and symptoms related to type I and type II agenesis bral hemispheres a. Type I CORPUS CALLOSUM AGENESIS/DYSGENESIS 249

i. Variable intelligence: normal to mild or moder- b) Affected father (all brothers normal, all sis- ate mental retardation ters carriers) ii. disorder vi. X-linked dominant inheritance iii. Impaired visual, motor, and/or bimanual coordi- a) Affected mother (50% of brothers and sis- nation ters affected) iv. Mild impairment of crossed tactile localization b) Affected father (all brothers normal; all sis- and skills requiring matching of visual patterns ters affected) b. Type II vii. Chromosomal disorder: recurrence risk increased, i. Mental retardation especially if a parent carries a balanced translo- ii. Seizures cation iii. Hydrocephaly b. Patient’s offspring iv. Microcephaly i. Environmental factor: recurrence risk not v. Hemiparesis increased by avoiding the environmental factor vi. Diplegia ii. Autosomal recessive inheritance: recurrence risk vii. not increased unless the spouse is also a carrier viii. Failure to thrive in which case the recurrence risk is 50% iii. Autosomal dominant inheritance: 50% DIAGNOSTIC INVESTIGATIONS iv. X-linked recessive inheritance a) Carrier female (50% of sons affected, 50% 1. Psychometric tests of daughters carriers) a. Difficulties in motor coordination b) Affected male (all sons normal, all daugh- b. Difficulties in inter-hemispheric transfer of tactile ters carriers) information v. X-linked dominant inheritance c. Difficulties in some areas of memory a) Affected female (50% of sons and daughters d. A marked difference in verbal IQ and performance IQ affected) in children b) Affected male (all sons normal, all daugh- 2. EEG for seizure activities ters affected) 3. CT and/or ultrasound of the brain vi. Chromosomal disorder: recurrence risk increased, a. Absence of the corpus callosum especially if a parent carries a balanced translo- b. Absence of septum pellucidum cation c. Increased separation of the lateral ventricles 2. Prenatal diagnosis d. Marked separation of the slit-like anterior horns of the a. Ultrasonography lateral ventricles and dilatation of the occipital horns i. Prenatal detection of the agenesis of the corpus creating the typical ‘rabbit’s ear’ or ‘tear drop’ callosum usually not possible before 22 weeks of appearance gestations e. Upward displacement of the third ventricle ii. Direct demonstration of the absence or partial f. Evidence of other migration disorders absence of the corpus callosum 4. Coronal radiographs showing a pathognomonic bat-wing iii. Failure to visualize the cavum septum pellu- ventricular pattern cidum 5. Karyotyping for underlying chromosomal disorder iv. Third ventricle lying between widely separated 6. Metabolic studies for underlying inborn error of metab- lateral ventricles due to absent corpus callosum olism v. Lateral ventricles more parallel to the midline than usual vi. A cyst arising from the superior aspect of the 1. Recurrence risk third ventricle communicating with the lateral a. Patient’s sib: depending on the etiology and the mode ventricles of inheritance vii. Vertical orientation of the gyri with agenesis i. Isolated Agenesis/dysgenesis of the corpus callo- instead of normal horizontal alignment sum: recurrence risk not increased viii. (locally dilated occipital horns of ii. Environmental factor: recurrence risk not the lateral ventricle) forming an appearance on increased by avoiding the environmental factor axial views similar to bulls’ horns iii. Autosomal recessive inheritance: 25% of sib- ix. Absence of pericallosal artery lings affected, 50% siblings carriers, and 25% of x. Up to 50% of cases with other associated siblings normal anatomic defects iv. Autosomal dominant inheritance: recurrence xi. Variable developmental outcome on prenatal risk not increased unless a parent is affected in detection of an isolated agenesis of the corpus which case the recurrence risk is 50% callosum v. X-linked recessive inheritance b. MRI a) Carrier mother (50% of brothers affected; i. Allows more detailed visualization of the fetal 50% of sisters carriers) brain than ultrasonography 250 CORPUS CALLOSUM AGENESIS/DYSGENESIS

ii. Constitutes a useful additional procedure after Barkovich AJ, Simon EM, Walsh CA: Callosal agenesis with cyst. A bet- ultrasonographic diagnosis or suspicion of cor- ter understanding and new classification. 56:220–227, 2001. pus callosum agenesis Bennett GL, Bromley B, Benacerraf BR: Agenesis of the corpus callosum: pre- c. Amniocentesis recommended for karyotyping as natal detection usually is not possible before 22 weeks of gestation. there is 10–20% risk of aneuploidy associated with Radiology 199:447–450, 1996. the agenesis of the corpus callosum Casaubon LK, Melanson M, Lopes-Cendes I, et al.: The gene responsible d. Prenatal counselling for ultrasonically diagnosed fetal for a severe form of peripheral neuropathy and agenesis of the corpus callosum maps to chromosome 15q. Am J Hum Genet 58:28–34, agenesis of the corpus callosum remains very diffi- 1996. cult, as giving precise information on outcome is da-Silva EO: Callosal defect, microcephaly, severe mental retardation, and impossible. The following observation, however, may other anomalies in three sibs. Am J Med Genet 29:837–843, 1988. be of help in prenatal counseling: D’Ercole C, Girard N, Cravello L, et al.: Prenatal diagnosis of fetal corpus cal- i. Isolated agenesis/dysgenesis of the corpus callo- losum agenesis by ultrasonography and magnetic resonance imaging. Prenat Diagn 18:247–253, 1998. sum (in the absence of other sonographically Dobyns WB: Absence makes the search grow longer. (Editorial) Am J Hum detectable anomalies) carrying apparent excel- Genet 58:7–16, 1996. lent prognosis Finlay DC, Peto T, Payling J, et al.: A study of three cases of familial related a) 85% chance of a normal developmental out- agenesis of the corpus callosum. J Clin Exp Neuropsychol 22:731–742, come 2000. Gupta JK, Lilford RJ: Assessment and management of fetal agenesis of the cor- b) 15% risk of handicap pus callosum. Prenat Diagn 15:301–312, 1995. ii. Agenesis/dysgenesis of the corpus callosum with Lacey, DJ: Agenesis of the corpus callosum. Clinical features in 40 children. other associated anomalies: poor outcome Am J Dis Child 139:953–955, 1985. 3. Management Loeser JD, Alvord EC: Agenesis of the corpus callosum. Brain 91:553–570, 1968. Moutard M-L, Kieffer V, Feingold J, et al.: Agenesis of corpus callosum: pre- a. Identification of actual deficits resulting from the natal diagnosis and prognosis. Child Nerv Syst 19:471–476, 2003. absence of such a major structure (corpus callosum): Pilu G, Hobbins JC: Sonography of fetal cerebrospinal anomalies. Prenat clearly an issue Diagn 22:321–330, 2002. b. Multidisciplinary team approach to intervention pro- Pilu GL, Sandri F, Perolo A, et al.: Sonography of fetal agenesis of the corpus grams callosum: a survey of 35 cases. Ultrasound Obstet Gynecol 3:318–329, 1993. c. Anticonvulsants for seizures Probst FP: Agenesis of the corpus callosum. Acta Radiol 331 (Suppl):1–150, d. Management based on the underlying etiology 1973. Serur D, Jeret JS, Wisniewski K, et al.: Agenesis of the corpus callosum: clin- ical, neuroradiological and cytogenetic studies. Neuropediatrics 19: REFERENCES 87–91, 1988. Achiron R, Achiron A: Development of the human fetal corpus callosum: a Vergani P, Ghidini A, Strobelt N, et al.: Prognostic indicators in the prenatal high-resolution, cross-sectional sonographic study. Ultrasound Obstet diagnosis of agenesis of the corpus callosum. Am J Obstet Gynecol Gynecol 18:343–347, 2001. 170:753–758, 1994. CORPUS CALLOSUM AGENESIS/DYSGENESIS 251

Fig. 1. An infant (ages 3 months and 16 months) with agenesis of the corpus callosum and interhemispheric cyst, illustrated by MRI.