Table 1.

Principles of combined MEP data interpretation and corrective measures (from ref. [45])

D-wave	Muscle MEPs	Corrective measures	Predicted outcome
Unchanged	Present	None	Unchanged
Unchanged or above 50%	Present with minor changes (decreased amplitude or increased threshold)	Transiently move surgical manipulation to a different area; warm irrigation; correct hypotension	Unchanged
Unchanged or above 50%	Lost uni- or bilaterally	All the above, then transiently stop surgery and/or improve spinal cord blood flow (local irrigation with papaverine). If mMEPs do not re-appear, abandon surgery in selective cases; as a rule surgery can proceed	Transient motor deficit (affecting the involved extremity)
Decreased >50%	Lost bilaterally	Stop surgery immediately. If D-wave does not recover, abandon surgery	Permanent motor deficit
Unmonitorable	Lost bilaterally	All the above. If mMEPs do not recover, abandon surgery	Cannot differentiate between transient and permanent motor deficit

mMEPs muscle motor evoked potentials