Monitoring of anterior cervical spinal cord function

Anterior surgery is frequently chosen for treatment of cervical myelopathy. However, intraoperative spinal cord recording has rarely been used to monitor the function of the ventral columns. We report a method of monitoring evoked spinal cord potentials useful for detection of minor injury of the anterior spinal cord. Evoked spinal cord potentials elicited in cats by thoracic spinal cord and labyrinth stimulation were studied. Evoked intraspinal field potentials recorded after labyrinth stimulation were confirmed to originate from the vestibulospinal tract in the ventral columns. Low-amplitude potentials were recorded from the posterior epidural space. However, this method has not been used clinically because of difficulty in obtaining selective stimulation in humans. Spinal cord potentials evoked by thoracic stimulation were recorded from the anterior and posterior epidural spaces. The amplitude of the potentials was large enough to permit quantitation of neural function. We confirmed that anterior recording was more sensitive in detecting ventral column injury than posterior recording was. Based on these findings, we used anterior recording from the disc clinically for anterior spinal cord monitoring during anterior cervical surgery.