Intraoperative neurophysiologic monitoring and neurologic outcomes in patients with epidural spine tumors.

PURPOSE: Multimodal intraoperative neurophysiologic monitoring (IOM) provides assessment of spinal cord pathways during neurosurgery. Despite widespread use, few data exist regarding sensitivity and specificity of IOM in predicting neurologic outcome during decompression and instrumentation for epidural spine tumors.
METHODS: Retrospective analysis evaluated consecutive spine procedures involving IOM modalities (somatosensory evoked potentials [SSEP], motor evoked potentials [MEP], and electromyography [(EMG]) from 2007 to 2009. Demographic and surgical information, intraoperative neurophysiologic data, and pre- and postoperative neurologic status were collected. All cases involved neoplastic epidural spinal cord compression by a primary or metastatic tumor and included posterolateral decompression and instrumented fusion.
RESULTS: Two-hundred and eight consecutive patients had spine surgery during this time period and one hundred and fifty-two met inclusion criteria. All patients had SSEP monitoring, with 4 having transient changes and 7 persistent changes. One hundred and twenty-two patients had combined SSEP and MEP monitoring, with 3 having transient changes and 4 persistent changes in MEP signals. Two patients had neurophysiologic changes associated with hypotension and correction led to normalization. One developed new neurologic deficits after surgery. Two from the total cohort had new postoperative neurologic deficits. One had a transient decrease in MEP amplitude while the other had no intraoperative changes. DISCUSSION: These cases are often long with significant blood loss, and stability of multiple IOM modalities provides reassurance that spinal cord function remains intact. Signal changes should result in scrutiny of blood pressure, surgical technique and anesthesia. Preserved IOM signals are suggestive of preserved neurologic outcome.