The possible dual occurrence of hippocampal sclerosis (HS) and other structural lesions (especially cortical dysgenesis [CD]) is well established in patients with chronic partial epilepsy. We describe the frequency of additional CD in a series of 100 patients with evidence of HS, using volumetric MRI. Additional, often subtle, CD was present in 15 patients: subependymal heterotopia (six), forme fruste of tuberous sclerosis (two), focal macrogyria (two), focal cortical dysplasia (one), laminar heterotopia (one), bilateral schizencephaly (one), and simplified gyral patterns (two). In contrast, in 46 healthy volunteers, only one had possible CD (p < 0.05). Only 2 of 15 patients had a history of childhood febrile convulsions. HS is a heterogeneous condition; patients being evaluated for temporal lobe surgery should be carefully screened for additional CD using appropriate MR techniques.

Periventricular nodular heterotopia caused by FLN1 mutations in men has a wide clinical spectrum and is caused by different genetic mechanisms, including somatic mosaicism. Mutation analysis of FLN1 should support genetic counseling in men with periventricular nodular heterotopia.

In patients with idiopathic generalized epilepsy (IGE), visual inspection of routine MRI is normal. However, pathological studies have shown microdysgenesis in grey and white matter in a large percentage of autopsies from cases of IGE. Recently, widespread structural changes not evident on visual inspection of high resolution MRI have been shown using quantitative MRI in patients with apparently focal cerebral dysgenesis. We sought to determine whether similar quantitative changes might be present in patients with IGE, reflecting possible underlying structural abnormalities. Twenty patients with juvenile myoclonic epilepsy, 10 patients each with childhood absence epilepsy and juvenile absence epilepsy, five patients with tonic-clonic seizures on awakening and 30 control subjects had T1-weighted volume acquisition MRI scans on a 1.5T GE scanner. The cerebral hemispheres were segmented semi-automatically, allowing the comparison of normalized cortical and subcortical matter volumes between groups, and investigation of the regional distribution of cortical and subcortical matter in individual subjects. Patients with IGE had significantly larger cortical grey matter volumes than control subjects. Significant abnormalities of the regional distribution of cerebral grey and subcortical matter were found in eight out of 20 patients with juvenile myoclonic epilepsy, one out of 10 patients with childhood absence epilepsy, four out of 10 patients with juvenile absence epilepsy and two out of five patients with tonic-clonic seizures on awakening, but in none of the 30 control subjects. Using MRI-segmentation, we identified widespread cerebral structural changes in patients with various IGE syndromes. Quantitative MRI supports the existence of structural abnormalities in patients with IGE.

Subependymal heterotopia has recently been recognised as a cause of epilepsy, but the clinical and investigational features have not been fully described. The clinical, psychometric, imaging, and electroencephalographic features of 13 adult patients with subependymal heterotopia and epilepsy have been reviewed. Age at seizure onset ranged from 18 months to 20 years (median 13 years). There were significantly more female (12) than male (1) patients (p < 0.01). Diagnosis of subependymal heterotopia was made by MRI in 11 patients and CT in two. The heterotopic grey matter was nodular in 11 patients and diffuse in two; bilateral in eight and unilateral in five. There were significantly more patients with predominant right than left cerebral hemisphere involvement (p < 0.01). The most commonly involved site was the occipital horn of the lateral ventricles (10 of 13 patients). Eleven patients presented with partial epilepsy, 10 ofwhom also had secondarily generalised seizures. The clinical description of the seizures often suggested either an occipital (four patients) or temporal (five patients) onset. Two patients presented with absence attacks without clear focal features. Patients demonstrated normal early milestones (12 of 13 patients), including normal motor development (all patients) and average or above average intelligence (10 of 13 patients). An EEG examination showed normal background activity in all but two patients, one of whom had large intracranial haematomas. Epileptiform activity was usually widespread (10 of 13 patients) and in three patients, there was generalised 3-Hz spike and wave activity that had previously led to an erroneous diagnosis of concomitant primary generalised epilepsy. Onset of epilepsy in the second decade of life, normal developmental milestones and intelligence, and the finding of an overwhelming female preponderance differentiates subependymal heterotopia from other cortical dysgeneses. The female preponderance supports the importance of the X chromosome and sex steroids in the maturation and development of the cerebral cortex. (J Neurol Neurosurg Psychiatry 1994;57: 1195-1202 Migration of neuroblasts from the periventricular germinal centres occurs maximally between the 7th and 16th gestational weeks, although it is known to continue for several months postnatally.' Neuroblasts migrate centrifugally along radial glial fibres towards the pial surface. They come to rest in the cortical plate after detaching themselves from the fibres, in an inside out fashion, with more recent arrivals lying more superficial to earlier ones:2' More recently, there is evidence that there is also lateral dispersion of neuroblasts during migration.4The causes of neuronal migration disorders may be both genetic and maternal/environmental.5 A defect in the radial glial fibres has been proposed to be the underlying mechanism for migrational arrest in many of the neuronal migration disorders.6 Morphologically, the disorders appear either as collections of neurons in abnormal locations (grey matte...

Quantitative MRI combining HCT2 and HCVR is a reliable method for diagnosing hippocampal sclerosis noninvasively. End-folium sclerosis and amygdala sclerosis should be considered in patients with intractable TLE and negative findings on MRI studies, including quantitative measures of the hippocampus.