The effect of positive changes during intraoperative monitoring of the functional improvement in patients with cervical compressive myelopathy

Cervical compressive myelopathy (CCM) is a progressive, degenerative spine disease and the most common cause of spinal cord dysfunction in older individuals. Current clinical guidelines for spinal surgery recommend multimodal intraoperative monitoring (IOM) during spinal surgery as a reliable and valid diagnostic adjunct to assess spinal cord integrity. The aim of this study was to evaluate the effect of positive changes during IOM on the functional status in patients with CCM. Patients who underwent spinal surgery with IOM due to CCM were enrolled. During the surgery, patients underwent IOM using motor evoked potential (MEP) and somatosensory evoked potential (SEP). MEP and SEP were checked before and immediately after decompression. A decrease in latency >10% or an increase in amplitude >50% was regarded as a "positive changes". Subjects were divided according to the presence of positive changes. Motor scores of American Spinal Injury Association (ASIA) impairment scale and Korean version of Modified Barthel Index (K-MBI) were evaluated before and after operation. Twenty-nine patients underwent spinal surgery due to CCM. Eleven patients showed positive changes in MEP during IOM. When the two groups were compared, improvement rate in the ASIA motor score and K-MBI were significantly higher in patients with positive changes than in patients without positive changes at 1 month after surgery. However, 6 months after surgery, there were no significance differences between the groups. Regardless of positive change, nearly all patients suffered from neuropathic pain after operation. Positive changes in MEP during IOM may affect functional improvement 1 month after operation and early discharge without significant complications in CCM patients. However, they do not affect the neuropathic pain and long-term functional outcome. Thus, tailored proper management is needed to achieve maximal functional recovery in each patient after cervical spinal decompression surgery.