Neurophysiological monitoring of the spinal sensory and motor pathways during embolization of spinal arteriovenous malformations--propofol: a safe alternative.

Introduction: Embolization of a spinal cord arteriovenous malformation (AVM) is considered a high-risk procedure due to the potential risk of spinal cord injury. We present two cases illustrating the benefits of utilizing pharmacologic provocative testing under general anesthesia with continuous neurophysiologic monitoring of somatosensory evoked potentials (SSEPs) and transcranial electrical motor evoked potentials (TCeMEPs) to identify the functional territory of the catheterized vessels prior to embolization.

Clinical Presentation: Case #1: A 28-year-old male presented with a progressive right lower leg numbness followed by weakness with impaired sphincter control. The MRI and angiogram of the spine showed an arteriovenous malformation (type 4) (subtype 2). Case #2: A 31-year-old male presented with sudden occipital, neck, right shoulder and back pain. He was neurologically intact. MRI and angiogram showed a predominantly right sided arteriovenous malformation. INTERVENTIONAL PROCEDURE: After intubation, bilateral posterior tibial and median nerve SSEPs were recorded. TCeMEP and electromyogram (EMG) were monitored from upper and lower extremity muscles bilaterally. Total intravenous anesthesia was used with propofol and remifentanil infusion. Neuromuscular blockade was used only for initial intubation. A train of four was maintained during the procedure. Pre-incision baselines were obtained with good morphology of waveforms. Selective spinal Wada tests were performed prior to embolization with lidocaine and propofol. Neurophysiological monitoring was performed for any changes.

Results: Complete occlusion of the AVM was achieved. As no changes occurred during provocative testing, all branches were treated with Onyx embolization. At six-month post-operative follow-up, both patients had total relief of symptoms.

Conclusion: Multimodality IONM with continuous SSEP, TCeMEP, and EMG monitoring was utilized effectively during provocative testing with lidocaine and propofol. IONM helped in predicting and preventing post-operative neurological deficits due to ischemia to the spinal cord.