[Intraoperative electrophysiological monitoring for functional preservation of the cauda equina during lumbosacral surgery].
Adequate electrophysiological techniques to monitor function of the cauda equina have been proposed for surgery in patients with lumbosacral lipoma or myeloschisis. Motor fibers were identified by electrical stimulation in the operating field with bipolar rectangular impulses of 200 mu sec duration at 2 Hz under 5 mA and compound muscle action potentials (CMAPs) recorded from the leg and anal muscles. By recording CMAPs from the tibialis anterior, the biceps femoris, the gastrocnemius, and the external anal sphincter muscles, all of the roots from the fourth lumbar to the fourth sacral segment were continuously monitored. To spare recording channels, recordings were obtained from the right versus the left side. In our institute, 5 patients have undergone lumbosacral surgery while using this monitoring system, and the results indicated that there was no postoperative neurological exacerbation in any of the cases. According to a combination of the CMAPs produced by stimulation, the segment of the stimulated motor root could be identified electrophysiologically. Monitoring of somatosensory evoked potentials was not performed because this would have required too much time and would have prolonged surgery. However, some sensory fibers, which appeared to be posterior roots of the cauda equina on intraoperative inspection, could be identified indirectly with CMAPs recording because of current spreading from the stimulation to motor fibers.
Hatayama
T
T
Department of Neurosurgery, Hirosaki University School of Medicine, Japan.
Sekiya
T
T
Ohkuma
H
H
Shimamura
N
N
Suzuki
S
S
Yotsuyanagi
T
T
Osari
S
S
D000200:Action Potentials; D002420:Cauda Equina / Q000502:physiology*; D002648:Child; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008067:Lipoma / Q000601:surgery; D008161:Lumbosacral Region / Q000601:surgery*; D008591:Meningomyelocele / Q000601:surgery; D016343:Monitoring, Intraoperative / Q000379:methods*; D018482:Muscle, Skeletal / Q000502:physiology