Abstracts

Rationale: Periventricular grey matter heterotopia is a neuronal migration disorder often associated with epilepsy. Most cases are of the nodular type (PNH). A Linear variant (PLH) was rarely acknowledged and described in only 4 unrelated patients; one case with complex structural anomalies (Epilepsia, 00;41:352), and three with mild gyral abnormalities but severe intellectual disabilities (Brain, 06;129:1892). We report a series of three new unrelated patients with PLH and epilepsy.Methods: In addition to the description of PLH, we looked for the presence of anomalies in the cerebral cortex, midline structures, hippocampal formation and posterior fossa. We correlated the findings with clinical, EEG and functional imaging results. Genetic tests were performed in all patients.Results: Patient1 A 42 yo female (French-Canadian and Lebanese ancestry) without pre/perinatal antecedents, risk factors or family history of neurological disorder. Seizures started at 16 yo and semiology was consistent of both focal and generalized epilepsy. EEG showed bilateral temporal spikes with normal background. She has low-average intellectual function and borderline personality disorder. She has no dysmorphism, the neurological exam was unremarkable except for congenital nystagmus. Brain MRI shows symmetrical PLH extending from the frontal horn to atrium and temporal horns of the lateral ventricles (Fig. 1-1) without other structural abnormalities. Patient2 A 49 yo male (French-Canadian ancestry) without pre/perinatal antecedents. A brother had febrile convulsions and there is a family history of ADHD. After initial normal development, at the age of 3 he developed a progressive epileptic encephalopathy with myoclonic absences, drop attacks, intellectual loss and psychiatric problems. Between 13 and 18 yo, seizure control and intellectual functions improved. However, after 18 yo, seizures recurred with further deterioration in behavior and intellect. There is no dysmorphism and neurological examination is normal. EEGs suggest a secondary generalized epileptic process. Brain MRI shows PLH extending along the anterior half of the lateral ventricles, L>R (Fig. 1-2), with cavum septum pellucidum, mega cisterna magna and atrophic cerebellar vermis. Patient3 A 30 yo female (French-Canadian ancestry) without pre/perinatal antecedents or risk factors. A paternal uncle had epilepsy. Seizures started at 14 yo with temporal lobe semiology. Examination revealed no dysmorphism, average intelligence and normal neurological exam. EEGs showed left temporal spikes and a normal background. MRI shows PLH confined to the frontal horns, R>L (fig. 1-3) without other structural anomalies.Conclusions: PLH represents a rare variant of PH. Our cases along with the ones previously described, suggest that this malformation can be associated with variable phenotypic presentations. This heterogeneity might be explained by the extent of the lesion or by different genotypes. Genetic testing is ongoing and might provide some explanations. We also found that PLH appears micronodular on high magnification, is often discreet and, hence, can be easily overlooked on routine MRI.