Nodular heterotopia: a neuropathological study of 24 patients undergoing surgery for drug-resistant epilepsy.
OBJECTIVE
Despite the availability of detailed electroclinical and imaging data, only a few neuropathological studies of nodular heterotopia have been published. The aim of this study was to describe the neuropathological features of various types of nodular heterotopia obtained from patients undergoing surgery for intractable epilepsy.


METHODS
Specimens of heterotopic nodules taken from 24 patients were neuropathologically investigated using routine and immunocytochemical procedures, and the data were compared with magnetic resonance imaging (MRI), electroclinical findings, and surgical outcomes.


RESULTS
The neuropathological data distinguished two groups. Group 1 (14 patients, 78% in Engel class 1) had similar characteristics regardless of the size, number, or location of the nodules, with both projecting and local circuit neurons in the nodules intermingled with glial cells. Thirteen patients had focal cortical dysplasia. The nodules were identified by MRI in all cases. In group 2 (10 patients, 90% in Engel class 1), all of the nodules were within the temporal lobe and associated with hippocampal sclerosis or gangliogliomas. They were very small (undetected by MRI) and mainly formed by projecting neurons with no evidence of glial cells. All of the patients had cortical dysplasia.


CONCLUSIONS
The distinctive neuropathological features of the nodules in the two groups suggest different etiopathogenetic mechanisms. In group 2, the presence of nodular formations in association with cortical dysplasia and either hippocampal sclerosis or ganglioglioma raises a question concerning so-called dual pathology in the temporal lobe.
Meroni
Alessandra
A
Division of Clinical Epileptology and Experimental Neurophysiology, IRCCS Foundation Neurological Institute C Besta, Milan, Italy.
Galli
Carlo
C
Bramerio
Manuela
M
Tassi
Laura
L
Colombo
Nadia
N
Cossu
Massimo
M
Lo Russo
Giorgio
G
Garbelli
Rita
R
Spreafico
Roberto
R
D000293:Adolescent; D001927:Brain Diseases / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D002828:Choristoma / Q000150:complications* / Q000378:metabolism / Q000473:pathology*; D004351:Drug Resistance; D004569:Electroencephalography; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000378:metabolism / Q000601:surgery*; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D008279:Magnetic Resonance Imaging; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000378:metabolism / Q000473:pathology; D009415:Nerve Net / Q000378:metabolism / Q000473:pathology; D013702:Temporal Lobe
D005904:Glial Fibrillary Acidic Protein