Megalencephaly and polymicrogyria with polydactyly syndrome.

We report the clinical manifestations of a 26-month-old Japanese girl with megalencephaly-polymicrogyria-polydactyly-hydrocephalus syndrome. She was born to healthy, nonconsanguineous parents at 37 weeks by caesarian section after prenatal ultrasonography suggested hydrocephalus. Macrocephaly and polydactyly of both lower extremities were noted at birth. At 3 months of age, epileptic seizures developed. The patient displayed impaired vision and profound global developmental delay. Magnetic resonance imaging of the brain revealed dilatation of the lateral and third ventricles with cavum septi pellucidi et vergae and generalized polymicrogyria, most prominent in both perisylvian regions and the right frontal region. Despite ventriculomegaly, radionuclide cisternography indicated normal cerebrospinal circulation, suggesting that pathogenesis of the megalencephaly was unrelated to obstructive hydrocephalus. Decreased white matter volume and abnormal signal intensity in the occipital lobes were also noted. Visual disturbance due to white matter abnormality appears to represent a significant characteristic of this syndrome. The genetic background of the syndrome remains unclear.