Abnormal auditory cortex with giant N100m signal in patients with autosomal dominant lateral temporal lobe epilepsy.
OBJECTIVE
Lateralization of functionally abnormal cortical area in autosomal dominant lateral temporal lobe epilepsy (ADLTE).


METHODS
A sound pulse of pure tone was delivered monaurally to the ears alternately. Auditory evoked magnetic fields (AEF) were measured by using whole-head magnetoencephalography (MEG) system.


RESULTS
Significantly large N100m signals (a magnetic counterpart of N1/N100 in EEG) were detected in three out of five patients, either in the left or in the right hemisphere, contralateral to the auditory stimulation. The peak latency, location and orientation of distinct N100m exhibited no clear difference from those of normal controls.


CONCLUSIONS
Unilateral cortical abnormality exists in some of the patients in ADLTE. Patients with abnormally large N100m had seizures apparently provoked by auditory stimuli, suggesting that the appearance of significantly large N100m is associated with the epileptogenicity. Based on the detailed examination using MRI and FDG-PET for two of the patients, the authors hypothesize hyperexcitability caused by the decreased inhibitory functions, larger number of synchronously activated neurons, or the elongation of neuronal firing in the pathological temporal cortex in ADLTE.


CONCLUSIONS
The present study revealed clear abnormalities in the auditory cortex that have not been well detected by conventional EEG in patients with ADLTE.
Usui
Keiko
K
Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan; National Epilepsy Center, Shizuoka Institute of Epilepsy and Neurological Disorders, Shizuoka, Japan.
Ikeda
Akio
A
Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan. Electronic address: akio@kuhp.kyoto-u.ac.jp.
Nagamine
Takashi
T
Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Matsubayashi
Jun
J
Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Matsumoto
Riki
R
Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Hiraumi
Harukazu
H
Department of Otolaryngology, Head and Neck Surgery, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Kawamata
Jun
J
Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Matsuhashi
Masao
M
Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Takahashi
Ryosuke
R
Department of Neurology, Kyoto University Graduate School of Medicine, Kyoto, Japan.
Fukuyama
Hidenao
H
Human Brain Research Center, Kyoto University Graduate School of Medicine, Kyoto, Japan.
D000328:Adult; D001303:Auditory Cortex / Q000503:physiopathology*; D004569:Electroencephalography / Q000379:methods* / Q000592:standards; D004833:Epilepsy, Temporal Lobe / Q000175:diagnosis* / Q000235:genetics / Q000503:physiopathology*; D005072:Evoked Potentials, Auditory / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography / Q000379:methods* / Q000592:standards; D008297:Male; D008875:Middle Aged; D055815:Young Adult