Subependymal heterotopia: a distinct neuronal migration disorder associated with epilepsy.

Abstract

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...

Bilateral Posterior Periventricular Nodular Heterotopia: A Recognizable Cortical Malformation with a Spectrum of Associated Brain Abnormalities

“…Although the recognized association of callosal and hippocampal abnormalities was seen in our patients, we did not see this combination as a separate subgroup. 1,3,[29][30][31] The arrested hippocampal rotation is likely to be due to secondary effects of abnormal development, though we acknowledge it could be part of the same genetic defect that arrests the migration of neural progenitor cells. 32 Four patients had callosal hypertrophy with dysplastic splenia, hippocampal dysplasia, and abnormal Sylvian fissures.…”

“…[1][2][3][4][5] It may be more often associated with other malformations than commonly appreciated. 5 PNH is a collection of subependymal nodules of gray matter found along the walls of the lateral ventricles.…”

Cortical Malformations and Epilepsy: New Insights from Animal Models

“…These early-onset seizure syndromes are often medically intractable, associated with dramatic mental retardation and a shortened life span. By contrast, nodular heterotopias usually cause seizures only in the second decade of life, can be controlled with standard anticonvulsant medications (AEDs), and are often associated with normal intelligence (76)(77)(78). This suggests that, to some extent, more severe disruptions of brain structure result in more severe forms of epilepsy, whereas milder forms are less epileptogenic.…”

Ring-shaped Lateral Ventricular Nodules Detected with Brain MR Imaging

“…2,3 DiŠerential diagnoses of other lateral ventricular mass lesions include astrocytoma, meningioma, choroid plexus tumor, central neurocytoma, subependymal heterotopia, subependymal nodule, ependymoma, lymphoma, and metastasis. [4][5][6][7] Because subependymomas, subependymal heterotopias, and subependymal nodules are small lesions in the lateral ventricle, it is important to distinguish them from RSLVNs. Subependymal heterotopia and subependymal nodule can be diagnosed based on clinical history and radiologicalˆndings.…”

“…Subependymal heterotopia and subependymal nodule can be diagnosed based on clinical history and radiologicalˆndings. Subependymal heterotopia has been observed either a solitary nodules (nodular subependymal heterotopia) projecting into the ventricles or as diŠuse broad bands (diŠuse subependymal heterotopia) lining the ventricles; nodules are either round or ovoid, 7 and the lesions appear isointense to normal gray matter on all sequences. Subependymal nodules are found in patients with tuberous sclerosis and exhibit a one-to 12-mm diameter, variable signal intensity on MR imaging, and often calciˆca-tion; most demonstrate some enhancement.…”