CONTINUOUS INTRAOPERATIVE ELECTROMYOGRAPHIC MONITORING OF CRANIAL NERVES DURING RESECTION OF 4TH VENTRICULAR TUMORS IN CHILDREN

The authors reviewed the results of continuous intraoperative electrom yographic (EMG) monitoring of muscles innervated by cranial nerves in 17 children whose preoperative imaging studies showed compression or i nfiltration of the fourth ventricular floor by tumor to determine how intraoperative EMG activity correlated with postoperative cranial nerv e morbidity. Bilateral lateral rectus (sixth) and facial (seventh) ner ve musculatures were monitored in all children. Cranial nerve function was documented immediately postoperatively and at I year. Of the 68 n erves monitored, nine new neuropathies occurred in six children (sixth nerve in four children and seventh nerve in five). In five new neurop athies, intraoperative EMG activity could be correlated in one of four sixth nerve injuries and four of five seventh nerve injuries. Electro myographic activity could not be correlated in four children with new neuropathies. Of 59 cranial nerves monitored that remained unchanged, 47 had no EMG activity. Twelve cranial nerves (three sixth nerves and nine seventh nerves) had EMG activity but no deficit. Of four children with lateral rectus EMG activity, three had new seventh nerve injurie s. Lateral rectus EMG activity did not predict postoperative abducens injury. The absence of lateral rectus EMG activity did not assure pres erved abducens function postoperatively. Likely because of the close a pposition of the intrapontine facial nerve to the abducens nucleus, la teral rectus EMG activity was highly predictive of seventh nerve injur y. Although facial muscle EMG activity was not an absolute predictor o f postoperative facial nerve dysfunction, the presence of facial muscl e EMG activity was associated statistically with postoperative facial paresis. The absence of facial muscle EMG activity was rarely associat ed with facial nerve injury. The authors speculate that EMG activity i n the facial muscles may have provided important intraoperative inform ation to the surgeon so as to avoid facial nerve injury.