What predicts transient motor deficits during intramedullary spinal cord tumor resection?

The presence of lost motor evoked potentials (MEPs) in conjunction with preserved D-waves is a strong indicator of potential transient motor deficits during intramedullary spinal cord tumor resection. MEPs are recorded to provide information about the integrity of the corticospinal tract, which is responsible for voluntary motor function. When MEPs are lost, it typically signifies disruption or compromise to these pathways, thereby predicting potential difficulty in motor function post-surgery.

D-waves (descending waves), on the other hand, reflect preserved motor pathways but do not always correlate directly with muscle function. If D-waves remain intact while MEPs are lost, it suggests that while some spinal cord circuits are still conducting information, the primary motor output pathways might be compromised, leading to a possibility of transient motor deficits despite the preservation of some neuronal pathways.

This distinction emphasizes why the loss of MEPs, coupled with stable D-wave responses, can be particularly concerning during surgical interventions on the spinal cord, allowing clinicians to prepare for potential motor deficits in the patient after resection.