Electromyography detects mechanically-induced suprasegmental spinal motor tract injury: Review of decompression at spinal cord level

ObjectiveHerein, we report use of electromyography (EMG) to anticipate corticospinal conduction block, as defined by muscle-derived transcranial electrical motor evoked potential (TCE MEP) loss, during extradural spinal cord decompression.MethodsOne hundred and eighty-four patients underwent cervical (173) or thoracic (11) decompression. The same derivations were recorded for EMG and TCE MEP neuromonitoring. When highly repetitive, complex, and prolonged EMG discharges were identified in myotomes below the operated level (severe suprasegmentally-generated EMG discharges = severe SEDs), a report of possible spinal cord impact was made and a TCE MEP obtained. TCE MEP loss (with or without antecedent SEDs) was defined as >90% amplitude reduction compared to baseline recordings.ResultsSevere SEDs, seen in 15 cases, anticipated TCE MEP loss in 7/15. In 13/15 severe SED cases, manipulations near dura were the proximate cause. Interventions after TCE MEP loss included changed instrumentation, re-positioning, increased blood pressure, wake-up test, and surgical pause.ConclusionsSEDs can be identified during extradural spinal cord decompression. Severe SED occurrence is associated with a ∼50% risk of subsequent corticospinal conduction block.SignificanceAlthough SED occurrence does not provide specific information for lesions of the fast neurons of the corticospinal tract, SED surveillance during decompression at spinal cord level can supplement TCE MEP recording.