Neurophysiological detection of iatrogenic C-5 nerve deficit during anterior cervical spinal surgery

Object. The incidence of postoperative C-5 spinal nerve root palsy following decompressive cervical spinal surgery has been reported to be as high as 12% for anterior procedures and 30% for posterior procedures. The present study was conducted to document the prevalence of iatrogenic C-5 nerve root deficit during anterior cervical spinal Surgery, as well as to evaluate the sensitivity and specificity of intraoperative transcranial electrical stimulation (TES)-induced motor evoked potentials (MEPs) and spontaneous electromyographic (EMG) activity for identifying evolving C-5 nerve root impairment. Methods. The authors conducted a retrospective study of 238 consecutive anterior cervical spinal procedures performed by a single surgeon at Christiana Care Hospital within a 48-month period. Techniques used to monitor spinal nerve root function included TES-induced MEPs and spontaneous EMG activity from deltoid, biceps, triceps, wrist extensor, and hand intrinsic muscles innervated by the C5-T1 spinal nerve roots. Spinal cord function was monitored by recording TES-induced MEPs from upper- and lower-extremity muscles as well as somatosensory evoked potentials from stimulation of the ulnar and posterior tibial nerves. Conclusions. Transcranial electrical stimulation-induced MEPs and spontaneous EMG activity offer complementary information about evolving iatrogenic C-5 spinal nerve root impairment during anterior cervical spinal surgery. The TES-induced MEPs provide prognostic information and show increased sensitivity to C-5 deficit compared with spontaneous EMG activity alone. Monitoring of spinal nerve root function using only EMG activity carries a risk of false-negative findings; without timely warning of impending neurological impairment, timely intervention to prevent permanent deficit cannot occur.