Possibilities of endovascular embolization of spinal cord arteriovenous malformations using neurophysiological monitoring and provocative pharmacological tests

The study objective is to evaluate the results of pharmacologic provocative tests with neurophysiological intraoperative monitoring application during spinal cord arteriovenous malformation (AVM) embolization.

Materials and methods. In the period from 2016 to 2018, 38patients with spinal cord AVM of different types (according the J. Anson and R. Spetzler classification) underwent endovascular surgery at the Federal Neurosurgical Center (Novosibirsk, Russia). Fifteen of these patients were operated using pharmacologic provocative tests with neurophysiological intraoperative monitoring of motor (MEP) and somatosensory evoked potentials (SSEP). Aminoff and Logue Disability Scale was used to estimate neurological deficit before and after surgery, additionally Medical Research Council Muscle Scale was used to estimate motor deficit.

Results. In 15 patients, 37provocative samples with propofol and 38 samples with lidocaine with simultaneous registration of MEP and SSEP were performed. In the early postoperative period, a significant improvement in motor function was achieved in 2 patients, 3 showed a noticeable improvement, and 10 patients remained without dynamics. Urinary function improved in 2 patients, and in 13 remained unchanged. In 4 patients, the pharmacological test with propofol was positive, which was manifested by a decrease in the amplitudes of the MEP, and among the samples with lidocaine in 10 cases, a decrease in the amplitudes of the MEP was noted, with a simultaneous decrease in the amplitudes of the SSEP during 3 samples. In all patients, the decrease in the amplitudes of the evoked potentials was transient in nature and disappeared after a change in the place of administration of the pharmacological agent. This did not allow us to determine the sensitivity of the method for predicting persistent postoperative neurological deficit. To predict the development of motor deficiency in the early postoperative period, the specificity of lowering the amplitude of the MEP during the pharmacological test was: 57 % to reduce by 50 %; 87 % for a reduction of 80 % and 93 % for the complete disappearance of MEP. For the prognosis in the distant period (3 months after endovascular treatment), the specificity of decreasing the amplitude of the MEP by 50, 80 and 100 % was 46, 85 and 100 %, respectively.

Conclusion. The use of neurophysiological monitoring and provocative tests is a safe method that allows you to make the optimal tactical decision in the endovascular treatment of spinal cord AVM. As a provocative test, it is recommended to use two pharmacological drugs (propofol and lidocaine). A 80 % decrease in MVP amplitudes or the disappearance of MVPs are more accurate criteria for the clinical outcome of spinal cord AVM embolization. The specificity of MVP in detecting an increase in motor deficiency in the early and long-term postoperative periods was maximum (93 and 100 %, respectively), if the disappearance of MVP was chosen as a criterion of pathology.

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