Intraoperative electromyography during thoracolumbar spinal surgery

Area of Science:

• Neurosurgery
• Spinal Surgery
• Nerve Monitoring

Background:

• Intraoperative electromyography (EMG) is valuable for assessing lumbosacral nerve root function during thoracolumbar spinal surgery.
• Free-running EMG offers continuous feedback on nerve root location and potential injury.
• Stimulus-evoked EMG verifies correct placement of transpedicular instrumentation.

Purpose of the Study:

• To discuss the limitations of intraoperative EMG in spinal surgery.
• To present improved methods for enhancing the efficacy of intraoperative EMG.
• To guide surgeons in optimizing EMG use for nerve root protection.

Main Methods:

• Review of EMG sensitivity and specificity in detecting nerve root injury.
• Emphasis on appropriate muscle selection for EMG recording based on myotomes.
• Discussion of pharmacologic neuromuscular blockade management for effective EMG.
• Techniques for direct nerve root stimulation as a positive control.
• Adjustments in stimulus parameters for pedicle holes and screws under varying blockade levels.
• Consideration of altered nerve root excitability in chronic compression and axonotmesis.

Main Results:

• EMG is sensitive to blunt nerve root injury but may miss clean transection.
• Accurate EMG requires recording from muscles innervated by the at-risk nerve roots.
• Effective EMG monitoring necessitates careful management of neuromuscular blockade.
• Direct nerve root stimulation is crucial for validating stimulus-evoked EMG findings.
• Adjusting stimulation intensity and comparing thresholds to direct nerve root activation are vital for chronically injured nerves.

Conclusions:

• Intraoperative EMG is a powerful tool but has limitations that must be understood.
• Optimized EMG techniques, including appropriate muscle selection and stimulus control, enhance its utility.
• Comparing stimulus thresholds to direct nerve root activation is essential for diagnosing injury in chronically compressed nerves.