Motor Threshold and Motor Cortex Stimulation

The Relationship Between Motor Threshold and Effective Stimulation Threshold During Motor Cortex Stimulation

Motor cortex stimulation (MCS) is a form of brain stimulation for patients with neuropathic pain not responsive to medication. An electrode is placed on the surface of the brain and connected to a programmable battery in the chest.

The strength of stimulation can be individually adjusted by changing the voltage of stimulation. A too high voltage will produce side effects (e.g. seizures) while a too low voltage will not provide pain control. The aim of this study is to analyze the optimal stimulation parameters in patients already implanted with a motor cortex stimulation who have received good pain relief. The actual voltage may vary widely between patients but the investigators feel that there may be an "ideal" voltage if it is measured as a percentage of motor threshold (PMT). If motor threshold is the stimulation voltage that can evoke a muscle contraction then a PMT = 80% would be a voltage that was eighty percent of that value. Although the actual voltage may be widely different between patients, the percentage needed may be very similar. The investigators therefore plan to measure the effect of different percentages of PMT in patients already being treated with motor cortex stimulation.

Systematic analysis of the findings of this study might help the individual participant and future patients to better programming and less side effects.

Study Overview

• Status: Completed
• Conditions: Neuropathic Pain
• Intervention / Treatment: Device: Change of PMT setting

Detailed Description

Motor cortex stimulation (MCS) is a form of brain stimulation for patients with medically refractory neuropathic pain. The strength of stimulation can be individually adjusted by changing the voltage of stimulation. Too high voltage will produce side effects (e.g. seizures) while too low voltage will not provide pain control. The aim of this study is to analyze the optimal stimulation parameters in patients already implanted with a motor cortex stimulation who have received good pain relief. The actual voltage may vary widely between patients (because of the individual variations in tissue resistance) but the investigators feel that there may be an "ideal" voltage if it is measured as a percentage of motor threshold (PMT).

If motor threshold is the voltage that can evoke a muscle contraction then a PMT = 80% would be a voltage that was eighty percent of that value. Although the actual voltage may be different between patients, the effective PMT may be similar since it represents a more physiologic measure of stimulation.

Systematic analysis of the findings of this study might help the individual participant and future patients by reducing voltage to the lowest effective setting and reducing the chance of seizures.

Motor cortex stimulation is used in the treatment of neuropathic pain since 1991 but still no guidelines for programming exist and programming is therefore mainly bases on trial and error. This is mostly due to many variables influencing the choice of stimulation parameters and significant individual differences in susceptibility to stimulation. Routinely the motor threshold is determined during programming to identify the superior limit of voltage at which twitching is induced. No stimulation above the motor threshold should be performed as this is known to cause seizures. The voltage of simulation that will be effective for an individual is unknown at the beginning of the treatment.

The investigators try to find the lowest effective voltage because that will reduce the risk of stimulation-induced seizures and prolong the life of the pacemaker.

• Study Type: Interventional
• Enrollment (Actual): 7
• Phase: Not Applicable

Contacts and Locations

Study Locations

• Canada
  • British Columbia
    • Vancouver, British Columbia, Canada, V5Z 4E3
      • Vancouver General Hospital

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No
• Genders Eligible for Study: All

Description

Inclusion Criteria:

• Adult patient more than 18 years of age
• Chronic neuropathic pain effectively treated with motor cortex stimulation
• Stable medication during the trial
• Willing and able to comply with the study protocol and to return per the follow-up visit schedule and able to provide informed consent.

Exclusion Criteria:

• Evidence of an active disruptive psychiatric disorder or other known condition significant enough to impact the perception of pain, compliance to intervention and/or ability to evaluate treatment outcome as determined by the investigator
• Technical malfunction of the MCS device
• History of seizures
• Unable to provide informed consent

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Crossover Assignment
• Masking: Single

Number of Arms

3

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Experimental: -10% of effective PMT; Patients are set to a voltage 10% less than their original PMT at start of study, Changes in PMT settings	Device: Change of PMT setting; The patients current motor threshold is determined and the patient is set to a new PMT (= new treatment arm)
Active Comparator: former setting (+/- 0% of PMT); Patients are set to their original PMT at start of study, Changes in PMT settings	Device: Change of PMT setting; The patients current motor threshold is determined and the patient is set to a new PMT (= new treatment arm)
Experimental: +10% of effective PMT; Patients are set to a voltage 10% more than their original PMT at start of study, Changes in PMT settings	Device: Change of PMT setting; The patients current motor threshold is determined and the patient is set to a new PMT (= new treatment arm)

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Time Frame
Change in Pain measured on the Visual Analogue Scale with different PMT Settings	at the End of each trial period, typically 14 days after changes in PMT Settings

Secondary Outcome Measures

Outcome Measure	Time Frame
Quality of Life assessment with the SF-36 questionnaire	at the end of each trial period, typically at 14 days

Other Outcome Measures

Outcome Measure	Time Frame
Pain assessment with the McGill pain questionnaire to record impact of pain	at the end of each trial period, typically 14 days

Collaborators and Investigators

• Sponsor: University of British Columbia

Publications and helpful links

General Publications

• Tsubokawa T, Katayama Y, Yamamoto T, Hirayama T, Koyama S. Chronic motor cortex stimulation for the treatment of central pain. Acta Neurochir Suppl (Wien). 1991;52:137-9. doi: 10.1007/978-3-7091-9160-6_37.
• Tsubokawa T, Katayama Y, Yamamoto T, Hirayama T, Koyama S. Treatment of thalamic pain by chronic motor cortex stimulation. Pacing Clin Electrophysiol. 1991 Jan;14(1):131-4. doi: 10.1111/j.1540-8159.1991.tb04058.x.
• Peyron R, Garcia-Larrea L, Deiber MP, Cinotti L, Convers P, Sindou M, Mauguiere F, Laurent B. Electrical stimulation of precentral cortical area in the treatment of central pain: electrophysiological and PET study. Pain. 1995 Sep;62(3):275-286. doi: 10.1016/0304-3959(94)00211-V.
• Lima MC, Fregni F. Motor cortex stimulation for chronic pain: systematic review and meta-analysis of the literature. Neurology. 2008 Jun 10;70(24):2329-37. doi: 10.1212/01.wnl.0000314649.38527.93.

Study record dates

Study Major Dates

• Study Start: October 1, 2014
• Primary Completion (Actual): November 1, 2014
• Study Completion (Actual): December 1, 2014

Study Registration Dates

• First Submitted: September 25, 2014
• First Submitted That Met QC Criteria: September 29, 2014
• First Posted (Estimate): October 2, 2014

Study Record Updates

• Last Update Posted (Estimate): December 18, 2014
• Last Update Submitted That Met QC Criteria: December 16, 2014
• Last Verified: December 1, 2014

More Information

Terms related to this study

• Keywords: chronic neuropathic pain; motor cortex stimulation
• Additional Relevant MeSH Terms: Nervous System Diseases; Pain; Neurologic Manifestations; Neuromuscular Diseases; Peripheral Nervous System Diseases; Neuralgia
• Other Study ID Numbers: H14-01258