J Korean Orthop Assoc.  2008 Aug;43(4):420-427. 10.4055/jkoa.2008.43.4.420.

Motor Evoked Potential and Continuous Electromyography Monitoring during Spinal Surgery

• Yang JY
• Lee JK
• Song HS

• KMID: 1480400
• DOI: http://doi.org/10.4055/jkoa.2008.43.4.420

Abstract

PURPOSE: A prospective study to determine the usefulness of the spinal cord monitoring (SCM) for predicting and preventing iatrogenic nerve injury during spinal surgery.
MATERIALS AND METHODS
We studied 27 cases with adolescent idiopathic scoliosis (AIS, 7), degenerative spinal deformity (DSD, 13), and spinal stenosis (7) who received decompression and SCM including MEP and EMG. Intravenous anesthesia was performed using propofol. We initially could not measure SCM because of the presence of muscle relaxants. But later could check SCM in 24 cases. We evaluated the success rate of SCM, the degree of electrical stimulus, and abnormal signals.
RESULTS
The success rate of SCM was 88.9%. MEP showed an increased stimulus indicating a normal neurologic response in: AIS (26.6%), DSD (24.3%), and spinal stenosis (15.7%). EMG showed abnormal signals in 4 cases. but 3 cases had no significant nerve damage. In one case, we reinserted the pedicle screw because we found nerve irritation by the probe. None of theses cases had neural deficits after the operation.
CONCLUSION
MEP and EMG allow for correction and decompression without spinal cord or nerve root injury with appropriate anesthesia technique and interpretation of abnormal signals required for SCM.

Keyword

Spinal surgery; Motor evoked potential; Electromyography

MeSH Terms

Adolescent
Anesthesia
Anesthesia, Intravenous
Congenital Abnormalities
Decompression
Electromyography
Evoked Potentials, Motor
Humans
Muscles
Propofol
Prospective Studies
Scoliosis
Spinal Cord
Spinal Stenosis
Propofol

Figure

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  Fig. 1 (A) Normal muscular response by motor evoked potential (MEP) stimulus at 70 mA before pedicle screw placement. (B) Similar muscular response by MEP stimulus at 90 mA after pedicle screw placement.

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  Fig. 2 Channel 3 and 6 show abnormal signals below the event threshold, indicating proximity of the pedicle screw to the nerve root.

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  Fig. 3 (A) Channel 1 shows the severe train warning wave of the L1 nerve root, indicating reversible nerve root injury. (B) Normal signals after replacement of the pedicle screw.

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