Citations
The hypoglossal nerve (CN XII) may be placed at risk during posterior fossa surgeries. The use of intraoperative monitoring (IOM), including the utilization of spontaneous and triggered electromyography (EMG), from tongue muscles innervated by CN XII has been used to reduce these risks. However, there were few reports regarding the intraoperative transcranial motor evoked potential (MEP) of hypoglossal nerve from the tongue muscles. For this reason, we report here two cases of intraoperative hypoglossal MEP monitoring in brain surgery as an indicator of hypoglossal deficits. Although the amplitude of the MEP was reduced in both patients, only in the case 1 whose MEP was disappeared demonstrated the neurological deficits of the hypoglossal nerve. Therefore, the disappearance of the hypoglossal MEP recorded from the tongue, could be considered a predictor of the postoperative hypoglossal nerve deficits.
Citations
Tethered cord syndrome is a type of spinal dysraphism with a low-lying conus, which is frequently associated with an intraspinal lipoma, diastematomyelia, or fibrous band. The clinical manifestations include spine abnormalities such as the spina bifida or various neurological symptoms involving lower extremities and sphincters. However, the spinal roots are often injured during the detethering procedures which clinically results in a neurological deficit. The continuity of spinal roots should be monitored during detethering surgery for the tethered spinal cord because neural elements are embedded in lipoma or anomalous tissues. Evoked muscle action potentials indicate only motor function, therefore, it is more appropriate to record somatosensory evoked potentials across the operative field at the same time.
We used a combined technique of tibial nerve somatosensory evoked potential and compound muscle action potentials stimulated in the spinal roots directly for an intraoperative monitoring during the untethering procedure. We reported good results from three patients with tethered cord syndrome who had taken the intraoperative monitoring during the untethering surgery. We suggest that intraoperative monitoring can prevent the unwanted injury to the neural tissue in the level of the tethering during the detethering surgery.
Objective: Intraoperative monitoring using somatosensory evoked potential (SEP) study has been used increasingly to monitor neurological function during scoliosis surgery and other high-risk spinal surgeries. However, there are few studies related to this intraoperative monitoring, particularly in severe spinal deformity surgery, in Korea. So we evaluated the clinical efficacy of intraoperative SEP monitoring and considered the risk factors related to spinal surgery.
Method: We performed a posterior tibial nerve somatosensory evoked potential study for intraoperative monitoring during surgical procedures in 101 patients (male 46, female 55).
Results: Neurologic damage occurred in 16 patients (10 congenital scoliosis cases, 5 tuberculous kyphosis cases, and 1 degenerative spondylosis case) after surgical procedures. Delayed postoperative neurologic damage occurred in 4 patients (2 mild damage cases, 2 severe damage cases) among 85 cases which showed normal responses during surgical procedures. Sensitivity of this study was 75%, and specificity was 95.3%.
Conclusion: Somatosensory evoked potential study for intraoperaive monitoring is a sensitive and very useful method to detect iatrogenic lesions during spinal deformity surgery with satisfactory specificity. However, to improve the sensitivity and specificity of the intraoperative monitoring, combination of motor evoked potentials is recommended.
Electrophysiologic monitoring during surgery for the spinal cord tumor is necessary for identification of the nerve root, prevention of the nerve injury, and prediction of postoperative prognosis. In other countries, intraoperative electrophysiologic monitorings are commonly done in various cases such as selective posterior rhizotomy, scoliosis, sponlylolisthesis, lipomeningocele, and spinal cord tumor, but it is not a common procedure in Korea except for the selective posterior rhizotomy.
We report 3 cases of electrophysiologic monitoring during sugery for the spinal cord tumor at lower thoracic level. Using multichannel EMG machine, we recorded free-run EMG, somatosensory evoked potential(SSEP) of tibial nerve, and compound motor unit action potential (CMAP) of various regions such as abdomen, lower extremity, and anus, stimulating nerve roots at the lower thoracic level.
We identified CMAP from rectus abdominis muscles only in the first case, but in the second case, we identified CMAP from tibialis anterior and gastrocnemius muscles which avoided the injury to lumbosacral roots. In the third case, SSEP improved immediately after we removed the mass at lower thoracic level.
We concluded that intraoperative electrophysiologic monitoring combined with recording CMAP is a useful procedure to minimize neural tissue damage during surgery for the spinal cord tumor at lower thoracic level.
Objective: Intraoperative somatosensory evoked potentials (SEPs) are widely used for the early detections of cerebral ischemia during temporary occlusive procedures of the parent vessels in aneurysm surgery. This study intended to evaluate the usefulness of median nerve SEPs during intracranial aneurysm surgery.
Method: Between September 1995 and June 1997, we monitored 42 aneurysm patients in Uijongbu St. Mary's hospital. Median nerve SEPs were detected on scalp and cervical spine during surgery. We measured latencies, amplitudes of N20 and N13 waveforms and central conduction time (CCT, N20-N13). We analyzed pre- and post-surgical radiologic findings and changes of neurologic signs.
Results: The delayed latencies, CCT, and reduced amplitudes of median nerve SEPs during intraoperative monitoring were closely related to neurological deficits after surgery.
Conclusion: Intraoperative SEPs are useful in preventing clinical neurological injury during surgery of intracranial aneurysm and in predicting which patients will have unfavourable outcomes.
Objective: The purpose of this study is to evaluate the searching stimulus intensity at each pedicle and to identify the most vulnerable roots in transpedicular screw fixation of lumbosacral spine.
Method: Thirty-two patients with unstable lumbosacral vertebra were treated with intrapedicular screw fixation. Small holes were made by an air drill on the pedicle from L2 to S1 for screw fixation. Constant current stimulation pulses(0.2 msec duration) were delivered through a ball-tipped nasopharyngeal probe used to palpate the walls of each pedicle, and observation was made of electromyogram(EMG) evoked lower extremity muscles. The probes were placed in each pedicular wall manually, and evaluated for searching stimulus intensity, the current necessary to evoked EMG.
Results: The cases that the searching stimulus intensity was above 5 mA were 99 cases(97%), above 10 mA were 61 cases(59.8%) and below 5 mA were 3 cases(2.9%). The vastus medialis muscle is most sensitive in L2(100%) and L3(78.9%), tibialis anterior is in L4(81.8%), Peroneus longus is in L5(50.5%) and gastrocnemius is in S1(87.5%).
Conclusion: We can regard the searching stimulus intensity as 5 mA and the root located at Infero-medial side of pedicle is most vulnerable in transpedicular screw fixation. Furthermore, stimulus-evoked EMG monitoring during transpedicular spine instrumentation is helpful to avoid neural tissue injury.
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