The Utility of SSEP Monitoring During Cervical Spine Surgery: How Often Does it Prompt Intervention and Affect Outcome

Purpose: Intraoperative monitoring during cervical spine surgery is not a universally accepted standard of care. This is due in part to the paucity of literature regarding the impact of monitoring on patient management or outcome. This study sought to evaluate the utility of spinal cord monitoring during cervical spine surgery in a single surgeon’s practice, based on how often it prompted an intraoperative intervention. To our knowledge, this is the largest such series of cervical spine cases with SSEP monitoring data.

Methods: Somatosensory evoked potentials (SSEP) for tibial, median, and ulnar nerves were monitored in 809 consecutive cervical spine operations performed by a single surgeon. The avg pt age was 52 yrs (range, 2 to 88), with 472 males and 332 females. Cases were screened for significant degradation or loss of SSEP data. Specific attention was paid to 1) what interventions were performed in response to the SSEP degradation with subsequent improvement, and 2) whether SSEP changes corresponded with postop neurological deficits.

Results: 17 of 809 pts (2.1%) had SSEP degradation that met warning criteria and therefore prompted intervention. Intraop maneuvers that led to improvement in SSEP data included: shoulder tape release (8), traction release (4), pt repositioning (2), surgical decompression (2), and truncation of surgery (1). In 14 of the 17 cases (82%), the SSEP data improved substantially in response to intraop interventions, and 13 of 14 pts (93%) had no new deficits; 1 pt sustained a CVA. However, in 3 of 17 cases (18%), minimal SSEP improvement was noted, and only 1 of these 3 pts (33%) had no new deficit; 2 pts had new neurological deficits (hemiplegia and brachial plexopathy). All neurological deficits resolved between 6 hrs and 2 mo. Pts with ossification of the posterior longitudinal ligament (OPLL) were at significantly increased risk for intraop SSEP deterioration (5/17 pts, p=0.002).

Conclusions: SSEP monitoring in this surgical population proved sensitive to perioperative factors which may increase the risk of postoperative neurologic deficit. Improvement in data following intervention appears to correlate well with unchanged neurologic status. Experience with intraoperative monitoring in this patient series has led to incorporation of these techniques as a standard of care in cervical spine surgeries performed by this surgeon.