A recent study by Staff et al. (2010) looked at the possibility that inflammation after surgery may be the cause of neuropathy. Commonly blamed for this problem are stretch, compression, contusion and transection of the nerve but in fact there are cases when these mechanisms fail to explain the neuropathy due to the time or location in relation to the procedure.
These authors studied a series of patients by clinical picture, imaging, electrophysiology and pathology including nerve biopsy to confirm inflammation. They went on to manage patients who did not improve with immunotherapy.
So what did they find in the 23 patients with post-operative neuropathy? 21 biopsies showed increased inflammation so they used these patients to look at their clinical features along with 12 patients with post-operative neuropathy without nerve trauma (total 33). The neuropathies had all developed within 30 days. Focal and multifocal neuropathies were found, the former demonstrating signs similar to a mechanical cause. The investigations highlighted epineurial perivascular lymphocytic inflammation in 21 patients biopsies, microvasculitis in 15 biopsies, ischaemic nerve injury in 19 biopsies, axonal degeneration in 17 biopsies, axonal damage (electrophysiology) and abnormal T2 nerve signal (MRI of 22 patients’ roots, plexuses and peripheral nerves). 17 of the biopsied patients were given immunotherapy and 13 of these demonstrated improvement in the neuropathy impairment score (30 to 24).
The conclusions were that inflammatory mechanisms can cause post-operative neuropathy that present with pain and weakness in a focal or diffuse manner, identifiable by the features of time and location in relation to the site and date of the operation . There are characteristic MRI changes and biopsy maybe required in those cases that are difficult to determine compared to a mechanical mechanism. Using this mechanism based approach it was possible to identify appropriate patients for immunotherapy.
The call for a pain mechanism based approach is not new. Woolf (2004) wrote about this in pharmacological management of pain (click here) and it seems sensible that this can be applied in physical therapy when assessing a patient. Determining the type of pain(s) is a way of reasoning the best and wisest course of action. Deciding which treatments and interventions are appropriate can be guided by understanding the pain mechanisms, e.g. Inflammatory nociceptive, neuropathic, central mechanisms of sensitisation. It will also guide whether other disciplines are needed for successful management, e.g. referral to a pain specialist for medication. This is the approach that we take at the Specialist Pain Physio Clinics, identifying the pain mechanisms at play that can guide the most effective treatments methods.