What is the role of motor evoked potentials (MEPs) in the assessment of spinal cord ischemia?

Updated: Aug 20, 2019
  • Author: Jasvinder Chawla, MD, MBA; Chief Editor: Selim R Benbadis, MD  more...
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Answer

Monitoring MEPs is a significantly reliable technique to assess spinal cord ischemia during thoracoabdominal aortic aneurysm repair. [12, 13]

The prognostic value of MEP studies in spinal cord injury (SCI) is limited, probably because of the spinal shock in the acute phase. In one study, among 10 patients who presented within 2 weeks after injury, MEPs were absent below the level of the lesion in 7 patients with complete paraplegia; MEPs remained absent 6 months later. In 3 patients with incomplete quadriplegia and subsequent recovery, MEPs were recordable in 2 subjects and absent in 1 subject.

Among 25 patients studied within 6 hours after onset and monitored over 6 weeks, MEPs were not obtained in patients without preceding clinical evidence of voluntary contraction.

MEPs recorded from the lower extremities can fail to provide rapid detection of spinal cord ischemia in the upper thoracic level after cross clamping of the descending thoracic aorta.

Currently utilized MEP and SSEPs are unable to differentiate between central and peripheral paraplegia in patients with acute spinal cord ischemia during thoracoabdominal aortic replacement. Researchers have proposed combining MEP and peripheral compound muscle action potential induced by posterior tibialis nerve stimulation, enabling the surgeon to quickly distinguish between central and peripheral neurologic injury. [14]


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