Bilateral posterior parietal polymicrogyria: a mild form of congenital bilateral perisylvian syndrome?

Purpose: The main features of congenital bilateral perisylvian syndrome (CBPS) are pseudobulbar palsy, cognitive deficits, epilepsy, and perisylvian abnormalities on imaging studies, however, the clinical spectrum of this syndrome is much wider than previously believed and may vary from minor speech difficulties to severely disabled patients. The objective of this study was to present the different imaging and clinical findings of 17 patients with CBPS, their genetic background, and the occurrence of prenatal injury during their pregnancies.
Methods: We evaluated 17 consecutive patients with CBPS and divided them into two groups according to the imaging findings: (a) diffuse polymicrogyria around the sylvian fissure and (b) posterior polymicrogyria at the posterior parietal regions. They were systematically interviewed regarding history of prenatal events during their pregnancies, family history of speech difficulties, epilepsy, or other neurologic abnormality.
Results: There were seven women, ages ranging from 3 to 41 years (mean, 11.5; median, 7 years). Seven patients had bilateral posterior parietal polymicrogyria (BPPP), and 10 had diffuse bilateral perisylvian polymicrogyria. All seven patients with BPPP had only minor speech difficulties, none had epilepsy, and all but one had a family history of epilepsy or cortical dysgenesis. In contrast, 10 patients with diffuse bilateral perisylvian polymicrogyria had pseudobulbar palsy, four had epilepsy, eight had a history of a major prenatal event, and only four had a family history of epilepsy or developmental delay.
Conclusions: These findings suggest that diffuse bilateral perisylvian polymicrogyria appears to be more related to injuries caused by environmental factors, whereas BPPP has a stronger genetic predisposition. In addition, BPPP appears to have a wider clinical spectrum than previously believed, and may represent a milder extreme within the spectrum of CBPS.