Usefulness of somatosensory evoked magnetic field dipole measurements by magnetoencephalography for assessing spinal cord function.
OBJECTIVE
Objective assessment of sensory function disorders is difficult. In the present study, the authors investigated the possibility of assessing cervical myelopathy-induced sensory disorders by using magnetoencephalography (MEG) to measure somatosensory evoked magnetic fields (SSEMFs).


METHODS
In 12 patients with cervical myelopathy, SSEMFs were measured before and after surgery by using a 160-channel helmet-type MEG system to stimulate the median nerve, and the intensity and latency of N20m (first response occurring 20 msec after stimulation) were then determined. Additionally, the severity of the sensory disorder was assessed before and after surgery by obtaining sensory scores determined using the Neurosurgical Cervical Spine Scale. Furthermore, in 11 healthy individuals (control group), the intensity and latency of N20m were measured in the same fashion. Analysis of the results showed that the preoperative intensity of N20m in the 12 patients with cervical myelopathy was significantly lower than that demonstrated in the control patients (p < 0.005, Student t-test). In addition, of six patients in whom sensory scores improved postoperatively, there were significant increases in the intensity of N20m (p < 0.005, paired t-test). Furthermore, there was a significant correlation between sensory scores and dipole intensity (p < 0.001, Spearman correlation coefficient by rank test).


CONCLUSIONS
Somatosensory evoked magnetic field measurements determined by MEG are useful in objectively and noninvasively assessing sensory disorders caused by cervical myelopathy.
Goto
Takeo
T
Department of Neurosurgery, Osaka City University Medical School, Osaka, Japan. goto@df6.so-net.ne.jp
Tsuyuguchi
Naohiro
N
Ohata
Kenji
K
Tsutada
Tsuyoshi
T
Hattori
Hideji
H
Shimogawara
Masahiro
M
Matusaka
Yasuhiro
Y
Sakamoto
Sinichi
S
Hara
Mitsuhiro
M
D000328:Adult; D000368:Aged; D004558:Electric Stimulation; D004574:Electromagnetic Fields; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D015225:Magnetoencephalography; D008297:Male; D008875:Middle Aged; D011183:Postoperative Complications / Q000175:diagnosis / Q000503:physiopathology; D011237:Predictive Value of Tests; D011930:Reaction Time / Q000502:physiology; D012016:Reference Values; D013116:Spinal Cord / Q000503:physiopathology / Q000601:surgery; D013118:Spinal Cord Diseases / Q000175:diagnosis* / Q000503:physiopathology / Q000601:surgery; D016896:Treatment Outcome