Periventricularlaminar Heterotopia (PLH): Characterization in a Series of 18 Patients (P7.326)

OBJECTIVE: We report a series of eighteen patients with PLH. BACKGROUND: Periventricular grey matter heterotopia is a neuronal migration disorder often associated with epilepsy. Most patients have a nodular type. A laminar variant, divided into linear or ribbon-like (gyriform), was previously described in only 4 unrelated patients; in one case associated with complex subcortical and hippocampal malformations, and in three others with mild gyral abnormalities but severe intellectual disabilities. DESIGN/METHODS: Here we present a detailed review of brain MRIs of 18 patients (2 familial and 16 sporadic) with a diagnosis of PLH; assessment of the location and extension of the lesion, the presence of associated brain malformations and correlation of these with the clinical features. RESULTS: Based on the brain MRI findings of the 18 patients, we defined six major subclasses of PLH. These consisted of diffuse linear PLH (5/18), frontal PLH (4/18), posterior predominant PLH with a mixed linear and ribbon-like aspect (3/18), mixed subcortical and periventricular laminar heterotopia (4/18), diffuse ribbon-like (1/18) and diffuse unilateral (1/18). Associated brain malformations included subtle irregularity of the white matter-PLH border (2/18), diffuse polymicrogyria (3/18), asymmetric hippocampal formation (2/18), hypoplastic cerebellar vermis with mega cisterna magna (1/18), global cerebellar hypoplasia (2/18), and various abnormalities of the lateral ventricles (10/18). The clinical phenotype was variable, with no or some dysmorphic features, normal to low IQ, epilepsy, and psychiatric symptoms. In three patients, standard karyotype, comparative genomic hybridization (CGH) microarray, TUBA1A and FLNA sequencing were normal. CGH microarray showed a 14q deletion in one patient. CONCLUSIONS: PLH represents a rare variant of periventricular heterotopia. It is often discrete and hence can be easily overlooked on routine MRI. It is often associated with other brain malformations and a variable phenotype. We have identified six major subclasses according to the topography and extension of the lesion, and to its linear or ribbon-like aspect. The underlying etiology is not clear and likely heterogeneous. Disclosure: