REFERENCE VALUES FOR AMPLITUDE OF MOTOR EVOKED POTENTIAL ELICITED BY TRANSCRANIAL ELECTRICAL STIMULATION IN PATIENTS UNDERGOING SPINE CORRECTIVE SURGERIES

A. Bansal¹, N. Shah², G. Patel¹

Background: Intraoperative Neurophysiological Monitoring is considered to be a valuable technique to monitor spinal cord function and reduced the risk of neurological damage during spinal surgery. Motor evoked potential (MEPs) is one of the various techniques used to monitor motor function of spinal cord. MEPs are considered to have better correlation with good postoperative outcome and are advocated by many surgeons to be used in spine surgeries.

Purpose: The purpose of this study was to determine the reference values of amplitudes for motor evoked potential by transcranial electrical stimulation intraoperatively and to find whether there was a significant difference in the values of evoked potential for both sides of the body.

Methods: A retrospective data of 75 patients with spinal deformity who underwent corrective surgeries from July 2015 to July 2019 were collected. Transcranial electrical stimulation was used to stimulate motor cortex and MEPs were recorded bilaterally from Abductor digiti minimi in hand and abductor hallucis in foot by needle electrodes. Amplitudes were measured from peak to peak of waveform of the potential.

Results: Reference values for amplitudes of motor evoked potential were calculated by mean and standard deviation for left and right Abductor digiti minimi(ADM) and abductor hallucis (AH). Mean amplitude for LT ADM was 1.732mv with SD +/-1.94mv.Mean amplitude for RT ADM was 1.824mv with SD+/-1.59mv. Mean amplitude for LT AH was 1.349mv with SD +/-0.985mv.Mean amplitude for RT AH was 1.436mv with SD+/-1.65mv. There was no statistical significant difference for left and right side for both ADM and AH muscles with P value 0.545 and 0.180 respectively.

Conclusion(s): The reference value presented provides a standard to consider the baseline values of motor evoked potential for Abductor digiti minimi and abductor hallucis for a patient with spinal deformity corrective surgery.

Implications: The reference values should be considered as baseline values for motor evoked potentials. Reference values should be correlated with depth of anaesthesia age and height of the patient.

Funding, acknowledgements: This work received no funding. 
We would like to thank Dr. Amit Jhala and Chirayu Orthopaedic and Spine Hospital, Ahmedabad, India
 
 

Keywords: Motor Evoked potential, Transcranial electrical stimulation, Spine surgery

Topic: Musculoskeletal: spine

Did this work require ethics approval? No

Institution: N/A

Committee: N/A

Reason: This was a retrospective study and data was extracted from previously performed surgeries