The purpose of this study was to determine the frequency and severity of peripheral nerve lesions occurring in patients with traumatic brain injury. A prospective study of 132 patients was conducted. Patients fulfilling research criteria (flaccidity, areflexia, abnormal motor patterns) underwent neurodiagnostic examination. Fifteen electromyograph/NCV studies were performed, yielding positive findings in 13 patients (10%); 3 patients were found to have preventable lesions. Many patients had permanent impairment or attendant complications from the peripheral nerve injury that adversely affected eventual recovery.