Newswise — For patients undergoing complex operations on the spine, combining two forms of monitoring may offer the best approach to early detection of neurological injuries during surgery, reports a study in the March 15 issue of Spine.
Dr. Michael G. Fehlings' team at the Krembil Neuroscience Center, Toronto Western Hospital and the University of Toronto used two monitoring techniques simultaneously in 213 patients undergoing thoracolumbar spinal surgery. One method was electromyography (EMG), which recorded electrical activity of the leg muscles throughout the procedure. The other was somatosensory evoked potentials (SSEP) monitoring, which measured electrical signals running between the nerves of the lower leg and the brain, via the spinal cord. The two techniques, alone and together, were evaluated for their ability to predict neurological complications of surgery.
Electromyography showed significant "activation" during surgery, suggesting possible neurologic damage, in 77.5 percent of patients. In contrast, just 6.6 percent of patients had abnormal signals suggesting possible damage on SSEP monitoring.
The overall rate of new neurological symptoms after spinal surgery was 6.6 percent. Of these 14 patients, all had abnormal results on EMG monitoring, compared with just four on SSEP monitoring.
This meant that EMG monitoring was 100 percent sensitive—it detected all patients with neurological damage. However, it was only about 24 percent specific—less than one-fourth of patients with abnormal EMG activation actually had neurological damage.
In contrast, SSEP monitoring had low sensitivity, detecting only about 29 percent of patients with neurological damage. However, it was highly specific: patients with no evidence of damage on SSEP monitoring were free of neurological damage 95 percent of the time.
Several monitoring techniques have been studied as aids to preventing neurological complications during complex spinal operations. The goal is to give the surgeon early warning of possible damage to spinal or nerve tissue, providing a chance to minimize the resulting neurological deficits. Combining techniques that address different pathways or parts of the nervous system may provide a more powerful approach to identifying potential injury.
The new results suggest that EMG plus SSEP monitoring could be a particularly useful combination. Activation of EMG is very common during spinal operations, and is positive in every patient who suffers neurological damage. Although SSEP changes are less common, patients without abnormal SSEP signals are highly likely to be free of damage. The combined monitoring techniques may be helpful in predicting—and possibly preventing—neurologic damage during complex spinal operations.
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