The impact of surgery to relieve leg pain on cortical control of trunk and leg muscles
File(s)
Author(s)
Buisson, Yoann
Type
Thesis
Abstract
All current chronic low back pain (LBP) treatments have variable long-term efficacy. Changes in the central nervous system pathways controlling trunk and leg muscles (T&L) in LBP have been reported, and this thesis investigated whether surgery (n=24) or conservative management (spinal injections [SIs;n=12] or no treatment [NT;n=18]), impact upon these changes in the long term.
19 healthy controls and 54 LBP patients were recruited. 45 of the LBP patients also had leg pain distal to the knee (LBPLP), 12 of which had radicular pain/radiculopathy at L5 and 12 at S1. Transcranial magnetic stimulation (TMS) was used to evoke a number of outcome measures in electromyographic activity. The first long term TMS T&L reliability study established suitable parameters to assess corticomotor excitability (CE) (i.e. motor evoked potential (MEP) threshold (MTh)) and intracortical inhibition (ICI: i.e. the cortical silent period (cSP)) on 4 occasions, prior and up to 1 year following treatment.
LBPLP patients had pain-lateralised and markedly prolonged leg cSPs, which, unlike in SI patients, were gradually normalised in high functional responders to surgery. Significant reductions in leg MThs occurred in high functional responders to surgery at 6 weeks, whilst further reductions occurred in those with excellent leg pain outcome. Tibialis anterior was exclusively sensitive to L5 group ICI&CE changes. By contrast, back muscles in LBP had markedly elevated MTh and altered MEP recruitment; with longer MEPs and more moderate bilaterally prolonged cSPs. Patients who improved had more abnormal baseline CE and ICI.
These studies establish patho-anatomically specific (side, root level and likely pathway-specific) cortical changes in leg pain/radiculopathy, which are reversible by successful surgery. More significantly, the distinct ICI and CE profiles found in back and leg muscles may eventually be useful in determining which patients are likely to benefit from surgical intervention.
19 healthy controls and 54 LBP patients were recruited. 45 of the LBP patients also had leg pain distal to the knee (LBPLP), 12 of which had radicular pain/radiculopathy at L5 and 12 at S1. Transcranial magnetic stimulation (TMS) was used to evoke a number of outcome measures in electromyographic activity. The first long term TMS T&L reliability study established suitable parameters to assess corticomotor excitability (CE) (i.e. motor evoked potential (MEP) threshold (MTh)) and intracortical inhibition (ICI: i.e. the cortical silent period (cSP)) on 4 occasions, prior and up to 1 year following treatment.
LBPLP patients had pain-lateralised and markedly prolonged leg cSPs, which, unlike in SI patients, were gradually normalised in high functional responders to surgery. Significant reductions in leg MThs occurred in high functional responders to surgery at 6 weeks, whilst further reductions occurred in those with excellent leg pain outcome. Tibialis anterior was exclusively sensitive to L5 group ICI&CE changes. By contrast, back muscles in LBP had markedly elevated MTh and altered MEP recruitment; with longer MEPs and more moderate bilaterally prolonged cSPs. Patients who improved had more abnormal baseline CE and ICI.
These studies establish patho-anatomically specific (side, root level and likely pathway-specific) cortical changes in leg pain/radiculopathy, which are reversible by successful surgery. More significantly, the distinct ICI and CE profiles found in back and leg muscles may eventually be useful in determining which patients are likely to benefit from surgical intervention.
Version
Open Access
Date Issued
2013-09
Date Awarded
2014-03
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Strutton, Paul
McGregor, Alison
Sponsor
The DISCS Foudation
Grant Number
DSB_P06568
Publisher Department
Department of Surgery & Cancer
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)