Extreme microcephaly with agyria-pachygyria, partial agenesis of the corpus callosum, and pontocerebellar dysplasia.

A 1-year-old boy with extreme microcephaly and a complex brain malformation is reported. Magnetic resonance imaging revealed an abnormal gyral pattern with features of the agyria-pachygyria spectrum, partial agenesis of the corpus callosum, severely hypoplastic posterior cerebellar vermis, and an abnormal foliation pattern of the cerebellar hemispheres associated with a flat and wide isthmus and pons. Although this phenotype shares some features with malformations classified as microcephaly with a simplified gyral pattern, microlissencephaly, or lissencephaly with cerebellar hypoplasia, none of the several subgroups of these categories are identical to the cerebral dysgenesis found in this patient.

Magnetic resonance imaging findings and novel mutations in GM1 gangliosidosis.

Two unrelated children and their siblings of Arab origin were diagnosed as having GM1 gangliosidosis on the basis of clinical features and markedly low levels of beta-galactosidase. The T2-weighted magnetic resonance images of the brain revealed certain characteristic features, including delayed myelination and abnormal appearance of the subcortical white matter, internal capsule, and basal ganglia. Their mutation analysis showed two novel mutations, which have not been described in an Arabic population.

Spectrum of malformations of the hindbrain (cerebellum, pons, and medulla) in a cohort of children with high rate of parental consanguinity.

We review 25 patients with a spectrum of hindbrain (cerebellum, pons, and medulla) malformations from a cohort of children with high parental consanguinity rate. Twenty-three of the 25 patients were born to consanguineous parents. The patients were classified in four groups. Eleven patients of 6 families had malformation of the hindbrain and midbrain with molar tooth sign (10 patients of 5 families with typical Joubert syndrome), 5 patients showed severe supratentorial anomalies in addition to the hindbrain malformations, 5 patients had pontocerebellar or cerebellar hypoplasia with anterior horn cell disease in the spinal cord (spinal muscular atrophy), and 4 patients showed malformations affecting predominantly the hindbrain without substantial involvement of other systems. A locus for Joubert syndrome was previously identified on chromosome 9q34.3 in two families, and a second locus on chromosome 11p12-q13.3 in another family. A third Joubert syndrome locus has been mapped at 6q23 and a mutation in the AHI1 gene at this site has been found recently in a further family from this cohort. Delineation of homogeneous subgroups of patients with hindbrain malformations and molecular genetic analysis of these groups may lead to identification of further loci, genes and mutations responsible for the malformations.

Clinical, MRI, and pathological features of polymicrogyria in chromosome 22q11 deletion syndrome.

Polymicrogyria is a brain malformation due to abnormal cortical organization. Two histological types, unlayered or four-layered can be distinguished. Polymicrogyria is a rare manifestation of chromosome 22q11 deletion syndrome. We report two boys with chromosome 22q11 deletion syndrome and polymicrogyria, and describe the neuropathological features of the malformation in one of them. Clinical examinations, EEG, brain MRI, chromosomal analysis with FISH, and neuropathological studies of surgically resected cortical tissue were performed. Both patients showed severe developmental delay with cardiovascular malformations and one of them had drug resistant epilepsy. Polymicrogyria was found in the frontal, parietal, and temporal areas, unilaterally in one patient and bilaterally in the other. Histology revealed four-layered polymicrogyria. The pathogenesis of polymicrogyria in 22q11 deletion syndrome is discussed.