術前に片麻痺を有した破裂脳動脈瘤症例におけるMEP所見と機能予後

抄録

Objective: Intraoperative monitoring of motor evoked potentials (MEPs) is useful for preventing postoperative motor dysfunction during microsurgical clipping of cerebral aneurysms. However, it is uncertain whether MEP is useful for surgery in patients with preoperative hemiparesis. Furthermore, when the MEP disappears, we are not able to anticipate the degree of motor dysfunction. We examined the correlation between MEP findings and functional prognosis in patients with rup- tured cerebral aneurysms with preoperative hemiparesis.

Methods: Among the 127 cases of ruptured cerebral aneurysms, 12 patients with preoperative hemiparesis were included. Five of the 12 patients had subarachnoid hemorrhage (SAH) alone, 2 had temporal hematoma, 2 had Sylvian hematoma, and 3 had putaminal hematoma. Transcranial stimulation MEPs (Tc-MEPs) were recorded on the affected and healthy sides with stimulation intensity up to 200 mA. Cortical stimulation MEP (C-MEP) was recorded only on the affected side, and the stimulation intensity was up to 25 mA. We examined the correlation between the stimulation thresholds of TcMEP and C-MEP, and the degree of postoperative hemiparesis (manual muscle test [MMT] ). In TcMEP, the affected side threshold/healthy side threshold (A/H) ratio was also evaluated. MMT was defined as 5/5 without paralysis, 5-/5 and 4/5 as mild paralysis, and 3/5 to 1/5 as severe paralysis.

Results: There were five cases without paralysis, none of which were accompanied by an intracranial hematoma. There were 3 cases of mild paralysis and 4 of severe paralysis, all of which were accompanied by intracranial hematoma. C-MEP could be recorded in cases with or without mild paralysis; however, it could not be recorded in cases of severe paralysis. A/H ratios were 1.0-1.3 (mean 1.1), 1.0-1.4 (mean 1.2), and 1.5-3.2 (mean 2.5) in the groups without paralysis, with mild hemiparesis, and with severe paralysis, respectively. The thresholds on the affected side of Tc-MEP were significantly higher than those on the healthy side in patients with severe paresis (p＜0.05).

Conclusions: Even though the patients presented with severe preoperative paralysis, there was a possibility that the functional prognosis might be good in cases where C-MEP could be recorded and where there were small A/H ratios in Tc-MEP. It was suggested that the severity of paralysis could be predicted by examining the A/H ratio of Tc-MEP, if MEP disappears during surgery. The number of cases is still small, and further studies are necessary.