The authors report a case of intracranial epidural hemorrhage (ICEH) during spinal surgery. We could not find ICEH, though we recorded transcranial electrical stimulation motor evoked potentials (TcMEPs). A 35-year-old man was referred for left anterior thigh pain and low back pain that hindered sleep. Sagittal T2-weighted magnetic resonance imaging revealed an intradural tumor at L3-L4 vertebral level. We performed osteoplastic laminectomy and en bloc tumor resection. TcMEPs were intraoperatively recorded at the bilateral abductor digiti minimi (ADM), quadriceps, tibialis anterior and abductor hallucis. When we closed a surgical incision, we were able to record normal TcMEPs in all muscles. The patient did not fully wake up from the anesthesia. He had right-sided unilateral positive ankle clonus 15 min after surgery in spite of bilateral negative of ankle clonus preoperatively. Emergent brain computed tomography scans revealed left epidural hemorrhage. The hematoma was evacuated immediately via a partial craniotomy. There was no restriction of the patient's daily activities 22 months postoperatively. We should pay attention to clinical signs such as headache and neurological findgings such as DTR and ankle clonus for patients with durotomy and cerebrospinal fluid (CSF) leakage. Spine surgeons should know that it was difficult to detect ICEH by monitoring with TcMEPs.
Keywords: Evoked potentials; Risk factors.