Introduction: Changes in the central nervous system (CNS) pathways controlling trunk and leg muscles in patients with low back pain and sciatica have been demonstrated. The aim of this study is to investigate whether these changes are altered by surgery.

Methods: Corticospinal excitability was examined on 2 occasions in 15 patients prior to and 6 weeks following lumbar decompression surgery and 7 control subjects – at the same time intervals. This was achieved by recording electromyographic (EMG) activity 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 (TMS) of the motor cortex.

Results: A significant asymmetry in the cortical silent period (cSP) between the side ipsilateral to the pain and the contralateral side was found pre- but not post surgery in ES at L4 (P=0.012) and SOL (P=0.039). An asymmetry in the size of motor evoked potentials (MEPs) was also found in TA (P=0.009) which was no longer significant post surgery. Abdominal responses could be recorded in 10 subjects, where significant decreases in contralateral cSP in EO (P=0.021) and RA (P=0.033) were found. In controls no significant differences or changes were found.

Discussion: These results show significant asymmetries in the CNS control of trunk and leg muscles in patients prior to surgery to relieve pain which are resolved by the surgery. The degree of change in asymmetry may reflect the variability in surgical outcome. This work is currently ongoing.

Conflicts of Interest: None

Funded by: the DISCS foundation