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

Abstract

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.

Independent component analysis reveals dynamic ictal BOLD responses in EEG-fMRI data from focal epilepsy patients

“…SEEG studies in patients with nodular heterotopia have shown that the nodules may be epileptogenic (Kothare et al, 1998), but almost never exclusively. Seizures usually start in the mesial temporal structures or in the cortex overlying the nodules, with only occasional involvement of the nodules themselves Battaglia et al, 2006;Tassi et al, 2005). Abnormalities in the overlying cortex are an indicator of epileptogenicity Porter et al, 2002), as seen in patients #1 and 5.…”

Periventricular Heterotopia: New Insights into Ehlers-Danlos Syndrome

“…26 Resection of the epileptogenic zones from patients with unilateral rather than bilateral PH also faired better. 27 …”

Tuber or Not Tuber: The Question of Epileptogenic Lesions in Tuberous Sclerosis Complex (TSC)

“…In some of these other conditions, there is growing evidence to support the notion that development of aberrant connectivity-which may lead to hyperexcitable neuronal circuits-is a critical substrate of epileptogenesis (4), and successful surgery may require resections that extend beyond mere lesionectomies (5).…”