Changes in central nervous system (CNS) pathways controlling trunk and leg muscles in patients with low back pain(LBP) and lumbar radiculopathy have been observed and this study investigated whether surgery impacts upon these changes in the long term. 80 participants were recruited into the following groups: 25 surgery(S), 20 chronic LBP(CH), 14 spinal injection(SI), and 21 controls(C). Parameters of corticospinal control were examined before, at 6, 26 and 52 weeks following lumbar decompression surgery and equivalent intervals. Electromyographic(EMG) activity was recorded from tibialis anterior(TA), soleus(SOL), rectus abdominis(RA), external oblique(EO) and erector spinae(ES) muscles at the T12&L4 levels in response to transcranial magnetic stimulation of the motor cortex. Motor evoked potentials (MEP) and cortical silent periods(cSP) recruitment curves(RC) were analysed.Introduction
Methods
Alterations in the neural drive to trunk muscles have been implicated in low back pain (LBP). This is supported by evidence of reduced corticospinal excitability, delayed muscle activation, reduced endurance and enhanced fatigability of these muscles; whether these changes persist during pain free periods remain unclear. Neural drive (or voluntary activation-VA) can be measured using twitch interpolation and the aim of this study is to investigate if subjects with a history of LBP show reduced VA. Twenty five subjects participated (13 with a history of LBP, 12 controls). Back extensor torque was measured using a dynamometer and bilateral electromyographic (EMG) activity was recorded from erector spinae and rectus abdominis. Transcranial magnetic stimulation of the motor cortex was applied while the subject, lying prone, performed graded voluntary back extensions. VA was calculated from the size of the twitches evoked by the TMS and EMG data were analysed for evidence of altered neural drive.Background
Methods
