Article
Prognostic value of transcranial MEP-Monitoring during minimally invasive dorsal decompression of cervical stenosis
Prognostischer Wert von transkraniellem MEP-Monitoring bei minimal invasiver dorsaler Dekompression bei zervikaler Spinalkanalstenose
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Published: | May 25, 2022 |
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Objective: The value of intraoperative neuromonitoring during degenerative spine surgery is controversial. Data on transcranial motor evoked potentials (MEP) during dorsal decompression of the cervical spine are limited. The aim of this study was to determine the prognostic value of MEP based on changes in threshold level during dorsal decompression for cervical spondylotic myelopathy.
Methods: This is a prospective study including patients operated for cervical spondylotic myelopathy at our institution, between June 2018 and October 2020. A minimally invasive dorsal decompression of the spinal canal through unilateral hemilaminectomy using a cross-over technique was the standard procedure for all patients. Japanese Orthopedic Association (JOA) Score was measured preoperatively and at discharge. For intraoperative monitoring, transcranial electrical stimulation using the combination C3-C4 was applied. MEP were recorded from the upper extremities and threshold levels were determined for each of the representative muscles of the relative cervical nerve root departing the spinal canal at or below the level of the decompression. The percentual change in threshold level was evaluated for each muscle and the differences (DTL) between start and end of the decompression were analyzed and their correlation with JOA score variation was investigated.
Results: We included 31 patients in this study. Surgical decompression was performed at 3 levels or more in 20 patients, at 2 levels in 10 patients and at one level in one. Intraoperative MEP improved at least in one muscle in 23 patients (1- 8 muscles, median 4 muscles). In 21 patients, at least one of the presenting symptoms improved postoperatively. The remaining patients reported either no improvement (n=9) or a transient worsening of their symptoms (n=1). Average threshold level decreased in 23 patients, remained unchanged in one and increased in 7 patients. An independent t-test showed a significant difference when comparing DTL between patients with clinical improvement (n=21) and those without (n=10) (-8.16% ± 8.78% vs 0.38% ± 6.80%, p=0.012). A decrease in average threshold level was significantly associated with a postoperative clinical improvement (OR 5- 95%, 1.53 to 184.9, P= 0.017).
Conclusion: This pilot study shows a significant correlation between intraoperative MEP improvement and early postoperative JOA score variation. Prospective randomized studies may provide stronger evidence as to the prognostic value of MEP in cervical spine surgery.