A Case of Brainstem Cavernous Hemangioma Showing False Positive Response to Electromyographic Tracheal Tube

Brainstem cavernous hemangioma is a complex lesion associated with hemorrhage and neurological deficit. The damage of the vagus nerve is a devastating surgical complication. Therefore, intraoperative anatomical and functional evaluation of this nerve is crucial. We used electromyographic tracheal tube (EMG tube)to monitor electromyogram from the vocal cord. We report a case of brainstem cavernous hemangioma showing false positive response to EMG tube. A 66-year-old woman underwent resection of cavernous hemangioma in the pontine tegmentum. General anesthesia was induced with remifentanl, propofol, and suxamethonium, and was maintained with oxygen, air, remifentanil and propofol. We monitored somatosensory evoked potentials, motor evoked potentials, and electromyogram of the vocal cord, orbicularis oculi, orbicularis oris and lateral rectus. When the manipulation reached brainstem, slight spontaneous respiration (SR) appeared on capnogram. Simultaneously, an alarm rang. Exposed nerves were stimulated electrically. However, there was no electromyographic response on the vocal cord. We concluded that the cause was SR accompanied by vocal cord movement. Remifentanil was increased up to 1 μg x kg(-1) x min(-1). SR did not disappear. Remifentanil was not increased any more without hindering the operation. Her operative course was uneventful. It is necessary to pay attention to false positive response caused by SR with EMG tube.