Generators and temporal succession of giant somatosensory evoked potentials in cortical reflex myoclonus: epicortical recording from sensorimotor cortex.
OBJECTIVE
To clarify the generator mechanism of giant somatosensory evoked potentials (giant SEPs) and the hyperexcitability of primary somatosensory and motor cortices (SI and MI).


METHODS
In a patient with intractable focal seizures manifesting cortical reflex myoclonus of the left foot, giant SEPs to left tibial nerve stimulation were epicortically recorded as a part of presurgical evaluation with subdural electrodes.


RESULTS
In the single pulse SEPs, enlarged P1-N1 components were observed at the foot area of the SI and MI (86.5-258.8 microV, respectively), and the peak latencies were always shorter at SI than at MI by 6 ms. Similar findings were obtained for peroneal and sural nerve stimulation. In the paired pulse SEPs, the second response was less suppressed, as compared to other interstimulus intervals (ISIs), with ISIs of 40 and 200 ms both at SI and MI.


CONCLUSIONS
In this particular patient, cortical hyperexcitability to somatosensory stimuli seems to originate from SI but subsequently both SI and MI are responsible for the generation of giant SEPs and cortical reflex myoclonus.


CONCLUSIONS
Somatosensory and primary motor cortices both generated enhanced early cortical components of SEPs, most likely by enhancing the latter by the former.
Hitomi
Takefumi
T
Department of Neurology, Kyoto University Graduate School of Medicine, and Takeda General Hospital, Kyoto, Japan.
Ikeda
Akio
A
Matsumoto
Riki
R
Kinoshita
Masako
M
Taki
Junya
J
Usui
Keiko
K
Mikuni
Nobuhiro
N
Nagamine
Takashi
T
Hashimoto
Nobuo
N
Shibasaki
Hiroshi
H
Takahashi
Ryosuke
R
D000328:Adult; D001931:Brain Mapping; D004558:Electric Stimulation / Q000379:methods; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D007839:Functional Laterality; D006801:Humans; D008297:Male; D009044:Motor Cortex / Q000503:physiopathology; D009207:Myoclonus / Q000503:physiopathology*; D010543:Peroneal Nerve / Q000503:physiopathology / Q000528:radiation effects; D011930:Reaction Time / Q000502:physiology / Q000528:radiation effects; D013003:Somatosensory Cortex / Q000503:physiopathology*; D013979:Tibial Nerve / Q000503:physiopathology / Q000528:radiation effects