The clinical presentation and possible mode of inheritance of familial perisylvian polymicrogyria (FPP) are described in twelve affected kindreds presenting at 10 medical centers. Among 42 patients, clinical and radiological findings were variable in families and within members of the same family, except for abnormal tongue movements and/or dysarthria correlating with bilateral MRI findings. The main clinical features, pseudobulbar palsy, cognitive deficits, epilepsy, and perisylvian abnormalities, were not present uniformly, and varied in severity. The syndrome showed an X-linked transmission, except for 2 families with autosomal dominant inheritance and decreased penetrance. 
COMMENT. A new X-linked syndrome, named familial perisylvian polymicrogyria, is characterized by pseudobulbar palsy, cognitive deficits, epilepsy, and cortical maldevelopment. The syndrome is genetically heterogeneous, and the clinical presentation is variable.