Clinical History
A 26-year-old woman presented with intellectual disability and refractory epilepsy.
Imaging Findings
A brain MRI was performed. There were bilateral symmetrical cortical surface irregularity, multiple small folds, scalloped appearance of the gray matter-white matter junction and abnormally thick cortex in both frontal lobes and parasagittal parieto-occipital regions. A focal hyperintense area in the right centrum semiovale was also noted. Diffusion weighted MRI findings were completely normal.
Discussion
Polymicrogyria (PMG) is a malformation of cortical development characterized by excessive small and prominent convolutions separated by shallow sulci, giving the cortical surface and cortical–white matter junction an irregular appearance. PMG is believed to result from a developmental disorder or injury that occurs between 17 and 25 or 26 weeks’ gestation. Several syndromes have been described in which patients have rather specific clinical manifestations associated with imaging of bilateral symmetrical PMG [1]. Bilateral symmetrical PMG seems to develop in specific topological locations within the brain (frontal, perisylvian, medial parieto-occipital, and lateral parietal) and in combinations of those regions. Affected patients seem to manifest reasonably well-defined symptom complexes that correlate with the regions of the cortex that are involved [2]. Bilateral frontal PMG is usually associated with cognitive and motor delay, spastic quadriparesis and epilepsy. Partial seizures, some with intellectual disability, are seen in bilateral parasagittal parieto-occipital PMG [3]. Our patient presented with intellectual disability and epilepsy without an evidence of spastic manifestations.
PMG is usually isolated but can also be seen in association with other brain malformations. In certain malformations, such as schizencephaly, PMG is almost invariably present. The association of PMG with gray matter heterotopia, agenesis of the corpus callosum, and other developmental brain anomalies have been reported [3].
The diagnosis is typically made by MRI. The combination of three characteristics on MRI has been used to identify PMG: abnormal gyral pattern, increased cortical thickness, and irregularity of the cortical–white matter junction due to packing of microgyri [1]. The location and topological extent of the PMG are often better determined on the sagittal images than on the axial or coronal images. The different angulations of the axial images sometimes give misleading impressions as to the actual site of the PMG [2].
PMG needs to be distinguished from pachygyria, a distinct brain malformation in which the surface folds are excessively broad and sparse. The irregular, scalloped, or corrugated appearance of the gray matter-white matter junction that characterizes PMG and that is particularly evident on T1-weighted inversion recovery sequences usually distinguishes the two malformations [4].
Recommended treatment of manifestations of PMG are: physical therapy, pharmacologic management, orthotic devices, and surgery for those with spastic motor impairment; speech therapy for language impairment; occupational therapy for fine motor difficulties; antiepileptic drugs for seizures; assessment of educational needs and evaluations for speech, vision, and hearing difficulties in infancy and preschool years [3].
Differential Diagnosis List
Bifrontal and bilateral parasagittal parieto-occipital polymicrogyria
Pachygyria
Diffuse bihemispheric polymicrogyria
Final Diagnosis
Bifrontal and bilateral parasagittal parieto-occipital polymicrogyria
