Radicular Somatosensory Evoked Potentials Recording During Foraminotomy

Summary

Among the various cerebral and myeloradicular pathologies in which we use a BASIS EPM for somatosensory evoked potential (SEP) recording, we have given much attention to the study of the cervical radicular compressions.

The motor and sensory alterations are evidenced by means of the electromyographic (EMG) and electroneurographic (ENG) methods, allowing a fine analysis of the function of these systems at distal and proximal parts of the nerve, including the metameric spinal cord.

SEPs offer the advantage of verifying the transmission of the sensory stimulus leading to the cortex.

The use of SEPs in the pre- and postsurgical phases, associated with EMG and ENG, has allowed us to demonstrate the amplitude, morphology and latency of the evoked responses at various levels, supplying the necessary data on the functional status of the sensory systems near the lesion. Together with the clinical and neuroradiological findings, the SEP has allowed us to follow the evolution of the disease and to verify and determine the degree of the effectiveness of the surgical intervention.

We recently initiated intraoperative recording of the SEP to immediately verify the restoration of radicular conduction at the intervertebral foramen level with special flexible metal hooked electrodes that are directly inserted on the nerve root and needle electrodes placed at Erb’s point and on other recording points.

If the sensory conduction at the intervertebral foramen level, which has been widened by means of foraminotomy, is well restored, an evoked response obtained by means of peripheral electric stimulation shows a far greater amplitude than all other responses.

By analyzing the latency, amplitude, morphology and timing of this response, and comparing these parameters with others, we obtain an immediate verification of the effectiveness of the operation.