Neuronal migration disorders: clinical, neuroimaging and neurophysiologic studies

Impaired neuronal migration is the basis of many cerebral malformations presenting with mental retardation, epilepsy and motor impairment. We aimed at correlating clinico-radiological presentations and findings of neuro-physiological studies in neuronal migration disorders. This study included 13 child, with mean age 22.6 months, from 12 families presented mainly with developmental delay and diagnosed by CT and MRI as neuronal migration disorders. Neurophysiologic studies including EEG and multi-modality evoked potentials, namely VEP and BAEP were performed. According to neuroimaging findings, lissencephaly was the commonest diagnosis [n=9], followed by unilateral open lip schizencephaly [n=2], periventricular heterotopia [n=1] and hemimegalencephaly [n=1]. Positive family history of similar cases was recorded in 3 families, all had lissencephaly. Abnormal EEG changes were observed in 12 patients [92.3%]; only 10 patients had epilepsy. EEG records were normal in a single patient with periventricular heterotopia. VEP was abnormal in 10 patients [76%] and BAEP was abnormal in 12 patients [92.3%]. Both VEP and BAEP were in the form of ill defined waves in patients with microlissencephaly. Asymmetry of BAEP between right and left side was detected in 3 cases; two of them had' unilateral disorders: hemimegalencephaly [n=1], and unilateral open lip schizencephaly [n=1] and the third had bilateral asymmetric periventricular nodular heterotopia. In conclusion, this study documented the frequent association of cortical and brain stem dysfunction with neuronal migration disorders. It also implied that the type of neuronal migration defect might influence the severity or symmetry of neurophysiologic studies results. Proper assessment of these cases clinically and by neuroimaging and neurophysiologic studies, advances our understanding thus genetic counseling of neuronal migration disorders