Syndromes of bilateral symmetrical polymicrogyria

Abstract

Background and purpose: A number of anatomicoclinical syndromes have been described in which bilateral symmetrical polymicrogyria is the underlying morphologic abnormality. We retrospectively reviewed the clinical, epileptic, and morphologic manifestations of bilateral symmetrical polymicrogyria in 21 patients to determine whether certain areas are at particular risk for these syndromes.

Methods: Clinical records and brain MR studies of 21 patients with bilateral symmetrical polymicrogyria were reviewed to confirm the presence and determine the location of polymicrogyria and to qualitatively correlate location with developmental, neurologic, and epileptic histories. The locations we found were compared with published reports of bilateral symmetrical polymicrogyria to determine whether these locations were random or whether predilections exist for certain areas.

Results: Analysis revealed six patients with bilateral frontal polymicrogyria, nine with bilateral perisylvian polymicrogyria, one with bilateral parietal polymicrogyria, one with bilateral parasagittal parieto-occipital polymicrogyria, two with bilateral frontal polymicrogyria and bilateral perisylvian polymicrogyria, one with bilateral perisylvian and bilateral parasagittal parieto-occipital polymicrogyria, and one with bilateral perisylvian, bilateral parieto-occipital, and bilateral parasagittal parieto-occipital polymicrogyria. Symptom complexes were non-specific, but seemed additive according to the regions of brain involved.

Conclusion: Bilateral symmetrical polymicrogyria has a propensity to develop in specific regions of the cerebral cortex. When the regions are extensive, the areas involved often appear to be simple topological additions of those regions. These locations and the identification of several familial cases raise the possibility that genetic mechanisms influence the development of these malformations in some patients.

fig 1.

Case 1: 3-year-old girl with bifrontal polymicrogyria. Axial spin-echo (SE) (600/20) MR image shows shallow sulci with irregularity or the cortical–white matter junction, consistent with polymicrogyria, involving the entire frontal cortex posteriorly to the central sulcus. fig 2. Case 15: 10-month-old girl with bilateral holosylvian polymicrogyria. A, Axial reformation from 3D Fourier transformation (3DFT) gradient-echo (GRE) (35/7) image shows thickened, irregular cortex involving the entirety of the cortex surrounding the sylvian fissures and widening of the fissures. B, Sagittal reformation from 3DFT GRE (35/7) image shows that the entire perisylvian cortex (arrows) is abnormal.

fig 3.

Case 12: 31-year-old man with bilateral posterior sylvian polymicrogyria. A, Axial SE (2500/80) image shows normal anterior perisylvian cortex, with thickening of the cortex (arrows) posteriorly. B, Sagittal SE (600/20) image shows that the abnormal posterior perisylvian cortex extends superiorly (arrows) to the parietal convexity.

fig 4.

Case 19: 14-month-old boy with bilateral frontal and sylvian polymicrogyria. Axial SE (3000/120) image, obtained at age 3 months, shows polymicrogyria involving the orbital and medial surfaces of the frontal lobes and along the insular cortex. The opercula are too wide. fig 5. Case 16: 10-month-old girl with bilateral lateral parietal polymicrogyria. Axial SE (3000/120) image shows polymicrogyria over the parietal convexities (arrows) bilaterally. fig 6. Case 17: 6-year-old boy with bilateral parasagittal parieto-occipital polymicrogyria. Axial inversion-recovery (1600/16, IR = 400) image shows the irregular cortex (arrows) in a parasagittal location involving the parietal and occipital lobes.

fig 7.

Case 20: 6-year-old boy with bilateral perisylvian and parasagittal parieto-occipital polymicrogyria. A, Axial SE (2800/80) image shows polymicrogyria (arrows) involving the posterior perisylvian cortex and extending posteriorly and medially into the parietal parasagittal region. B, Sagittal SE (550/11) image shows polymicrogyria continuing from the posterior sylvian area (white arrows) into the parieto-occipital area (black arrows).

fig 8.

Case 21: 7-year-old girl with bilateral perisylvian, lateral parietal, and parieto-occipital polymicrogyria. A, Axial SE (2000/40) image shows polymicrogyria (arrows) involving the parasagittal parieto-occipital cortex and the lateral parietal cortex. B, Sagittal SE (600/20) image shows the polymicrogyria involving the entire perisylvian cortex (solid white arrows) and extending posteriorly into the parietal (open black arrows) and occipital (open white arrows) lobes.