Nerve Root Block in Spasticity

Overview

In this work the investigators propose to briefly apply kilohertz frequency alternating current via PNS device placed next to the isolated nerve in 4 patients undergoing peripheral neurectomy, just before cutting the nerve. The intervention shall be performed utilizing EMG monitoring and mapping. After the muscular branches of the tibial nerve are exposed, proximal stimulation (1Hz) shall be applied to a selected branch with a bipolar electrode to produce muscle contractions. A high frequency (10kHz) blocking current shall be applied by placing a PNS electrode distally to the bipolar electrode and the EMG shall be recorded. The PNS electrode shall be removed from surgical field and further proximal stimulation done to confirm reversal of block (return to baseline) on the EMG. Then the nerve will be severed as a part of standard tibial neurectomy, and further proximal and distal stimulation shall be performed. The results will be compared to see if high frequency conduction block can physiologically mimic peripheral neurectomy; and obtain parameters of stimulation required for that.

Dysregulated neural activity is responsible for many ailments- focal spasticity after stroke or spinal cord injury, reflex incontinence, overactive bladder, etc. Current treatment options for such pathologies are suboptimal and include ablative procedures like neurectomy. Neurectomy inadvertently leads to loss of function. Modulated electrical conduction block can help control this activity without causing additional loss of function and thus has immense potential in treatment of these conditions. Animal experiments have suggested that such a block is feasible. While safety ranges for delivery of current to human peripheral nerves are known and stimulation parameters for activation of nerves well established, further data is needed to assess the parameters for clinically useful conduction block. Currently such data studies are being conducted to block pain from neuroma after amputation and to block vagal nerve for obesity. Peripheral Neurectomy is a procedure used for treating focal spasticity when less invasive options have been unsuccessful. The procedure is performed under full Neurophysiology monitoring. Intra-operatively, the nerve is exposed and motor activity from this is recorded spontaneously and with direct bipolar stimulation with help of EMG electrodes placed in the territory of the nerve. A tetanic response obtained upon such stimulation indicates spasticity. The nerve is cut, and further testing done by stimulating proximal and distal to the cut. Lack of tetanic response after proximal stimulation indicates adequacy of procedure. In this work the investigators propose to briefly apply kilohertz frequency alternating current via PNS device placed next to the isolated nerve in 4 patients undergoing peripheral neurectomy, just before cutting the nerve. The intervention shall be performed utilizing EMG monitoring and mapping. After the muscular branches of the tibial nerve are exposed, proximal stimulation (1Hz) shall be applied to a selected branch with a bipolar electrode to produce muscle contractions. A high frequency (10kHz) blocking current shall be applied by placing a PNS electrode distally to the bipolar electrode and the EMG shall be recorded. The PNS electrode shall be removed from surgical field and further proximal stimulation done to confirm reversal of block (return to baseline) on the EMG. Then the nerve will be severed as a part of standard tibial neurectomy, and further proximal and distal stimulation shall be performed. The results will be compared to see if high frequency conduction block can physiologically mimic peripheral neurectomy; and obtain parameters of stimulation required for that. This will be a proof of concept work assessing feasibility of conduction block for focal spasticity. If successful, further pilot study shall be done to assess efficacy. Apart from brief application of high frequency stimulation, the rest of the procedure will be standard. The stimulation will be within parameters approved by FDA and CE marking. As the nerve will then be cut anyway, there is no additional risk of harm to the nerve or the patient. This study will adhere to the principles outlined in the UK Policy Framework for Health and Social Care Research (v3.2 10th October 2017). It will be conducted in compliance with the protocol, the EU General Data Protection Regulation 2016 and Data Protection Act 2018, and other regulatory requirements as appropriate.