Characterizing magnetoencephalographic spike sources in children with tuberous sclerosis complex.
OBJECTIVE
Tuberous sclerosis complex (TSC) often causes medically intractable seizures. Magnetoencephalography (MEG) localizes epileptiform discharges. To evaluate the use of MEG spike sources (MEGSSs) for localizing epileptic zones in TSC patients, we characterized MEGSSs and correlated them to EEG and magnetic resonance imaging (MRI) results.


METHODS
We analyzed data from seven children who underwent prolonged video-EEG, MEG, and MRI. We classified MEGSSs as clusters (six or more spike sources, <or=1 cm between sources) and scatters (fewer than six spike sources regardless of distance between sources; sources with >1 cm between sources regardless of number of sources).


RESULTS
A single, unilateral cluster with additional scatters occurred in two patients; these predominantly lateralized dipoles correlated to prominent tubers on MRI and ictal/interictal EEG zones. Bilateral clusters with scatters existed in two patients; cluster locations partly overlapped multiple prominent tubers. These patients also had bilateral or diffuse interictal discharges, bilateral or generalized seizures, and changing seizure types and EEG findings. Only bilateral scatters occurred in three patients; scatters partly overlapped EEG interictal/ictal-onset regions; one patient had coexisting generalized seizures. In one patient with equally bilateral scatters, scatters overlapped a prominent tuber and interictal/ictal-onset zones in the right frontal region.


CONCLUSIONS
MEG contributes to information from EEG and MRI for localizing epileptogenic zones in children with TSC. A single cluster with scatters in a unilateral hemisphere predicts a primary epileptogenic zone or hemisphere; bilateral or multiple clusters indicate bilateral primary or potential epileptogenic zones; and bilateral scatters without clusters may indicate epileptogenic zones that are hidden within extensive areas of scattered MEGSSs.
Iida
Koji
K
Division of Neurology, Department of Pediatrics, The Hospital for Sick Children and University of Toronto, Toronto, Ontario, Canada.
Otsubo
Hiroshi
H
Mohamed
Ismail S
IS
Okuda
Chiyuki
C
Ochi
Ayako
A
Weiss
Shelly K
SK
Chuang
Sylvester H
SH
Snead
O Carter
OC
D001931:Brain Mapping / Q000379:methods*; D002540:Cerebral Cortex / Q000503:physiopathology*; D002648:Child; D004569:Electroencephalography / Q000706:statistics & numerical data; D004827:Epilepsy / Q000175:diagnosis* / Q000503:physiopathology; D005260:Female; D007839:Functional Laterality / Q000145:classification; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000706:statistics & numerical data; D015225:Magnetoencephalography / Q000706:statistics & numerical data*; D008297:Male; D014402:Tuberous Sclerosis / Q000175:diagnosis* / Q000503:physiopathology; D014743:Videotape Recording