Journal Article

Electroclinical, MRI and neuropathological study of 10 patients with nodular heterotopia, with surgical outcomes

L. Tassi, N. Colombo, M. Cossu, R. Mai, S. Francione, G. Lo Russo, C. Galli, M. Bramerio, G. Battaglia, R. Garbelli, A. Meroni and R. Spreafico

in Brain

Published on behalf of The Guarantors of Brain

Volume 128, issue 2, pages 321-337
Published in print February 2005 | ISSN: 0006-8950
Published online December 2004 | e-ISSN: 1460-2156 | DOI: http://dx.doi.org/10.1093/brain/awh357
Electroclinical, MRI and neuropathological study of 10 patients with nodular heterotopia, with surgical outcomes

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We present the results of a retrospective study on 10 patients operated on for intractable epilepsy associated with nodular heterotopia as identified by high resolution MRI. Seven patients had unilateral heterotopia, one patient had symmetric bilateral heterotopia and two patients had asymmetric bilateral heterotopia. By stereo-electroencephalogram (SEEG) (nine patients) interictal activity within nodules was similar in all cases, and ictal activity never started from nodules alone but from the overlying cortex or simultaneously in nodules and cortex. Excellent outcomes (Engel class Ia, 1987) were achieved in the seven patients with unilateral heterotopia, showing that surgery can be highly beneficial in such cases when the epileptogenic zone is carefully located prior to surgery by MRI and particularly SEEG. For the bilateral cases surgical outcomes were Engel IIa (one patient) or Engel IIIa (two patients). Histological/immunohistochemical studies of resected specimens showed that all nodules had similar microscopic organization, even though their extent and location varied markedly. The overlying cortex was dysplastic in nine patients, but of normal thickness. We suggest that nodule formation may be the result of a dual mechanism: (i) failure of a stop signal in the germinal periventricular region leading to cell overproduction; and (ii) early transformation of radial glial cells into astrocytes resulting in defective neuronal migration. The intrinsic interictal epileptiform activity of nodules may be due to an impaired intranodular GABAergic system.

Keywords: epilepsy surgery; immunocytochemistry; periventricular heterotopia; stereo-EEG; AD = architectural dysplasia; CB = calbindin; CD = cytoarchitectural dysplasia; CR = calretinin; EEG = electroencephalogram; FLAIR = fluid-attenuated inversion recovery; GFAP = glial fibrillary acidic protein; IR = inversion recovery; MAP2 = microtubule-associated protein 2; MCD = malformations of cortical development; PV = parvalbumin; SEEG = stereo-electroencephalogram; SCH = subcortical heterotopia; SE = spin echo; SEH = subependymal heterotopia; TSE = turbo spin-echo

Journal Article.  9054 words.  Illustrated.

Subjects: Neurology ; Neuroscience

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