MRI analysis of sulcation morphology in polymicrogyria

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Polymicrogyria (PMG) is a malformation of cortical development in which the process of normal cortical development is interrupted during the late stages of neuronal migration and during the stages of cortical organization; the result is the abnormal development of the deeper layers of the cerebral cortex and the formation of multiple small gyri. Patients with polymicrogyria may present with developmental delay, focal neurologic signs and symptoms, or epilepsy, depending upon the portion(s) of brain involved. Affected patients may be micro-, normo-, or macrocephalic (Dobyns et al., 2008). Polymicrogyria may be associated with congenital infection (Barkovich and Linden, 1994, Wright et al., 1997), in utero ischemia (Hallervorden, 1949), or chromosomal mutations (Kuzniecky, 1994, Bingham et al., 1998, Leventer et al., 2001, Piao et al., 2002, Villard et al., 2002, Roll et al., 2006, Dobyns et al., 2008). No difference in neurologic manifestations has been detected in patients who have polymicrogyria of different causes (Guerrini et al., 1992, Barkovich and Linden, 1994, Barkovich and Kjos, 1992), but the severity of the clinical presentation depends upon the extent of cortical involvement; bilateral involvement and involvement of more than half of a single hemisphere are poor prognostic indicators, portending moderate to severe developmental delay and significant motor dysfunction (Barkovich and Kjos, 1992). Polymicrogyria has a range of histologic appearances, all having in common a derangement of the normal six-layered lamination of the cortex (Evrard et al., 1989), with an associated derangement of sulcation. Thus, it would seem likely that the gross morphologic appearance of polymicrogyria might vary, as well, perhaps depending upon the underlying cause or the pattern of distribution of the anomalous sulcation within the brain. However, this topic has not heretofore been addressed in the literature. We report the imaging characteristics of a large number of patients with polymicrogyria and attempt to determine specific sulcation patterns and their variability.