The value of non-invasive spinal cord monitoring during spinal surgery and interventional angiography.

The study describes 51 patients, aged 10 to 57 years, who underwent spinal surgery (47) or interventional angiography (4). Multi-channel somatosensory evoked potential (SEP) monitoring was used to measure the functional integrity of the spinal cord. Alternating unilateral tibial SEPs permitted the detection of lateralised and milder abnormality. A combination of recording sites enhanced the certainty of detecting spinal cord dysfunction. Monitoring the ascending peripheral nerve volley below the operative site ensured adequate stimulation. Above the level of surgery, recordings outside the operative field were the simplest to make and did not require the direct assistance of the surgeon. Rapid and reliable recording of spinal cord and subcortical responses was possible in all surgical cases. Even though cortical SEPs could not be relied on as the sole monitor, their reproducibility was improved with the use of different electrode derivations. It is concluded that non-invasive methods of spinal SEP monitoring are a safe, reliable and easily performed alternative to more invasive methods.