WHAT IS THE DISTRIBUTION OF PAIN ATTRIBUTABLE TO LUMBO-SACRAL NERVE ROOT COMPRESSION?

Aim: To determine the distribution of pain which can be most reliably attributed to individual lumbo-sacral nerve root compression. Introduction: Patients are selected for nerve root decompression based on a correlation between symptoms, signs and imaging findings. However, the belief that a given pain may be attributable to a specific nerve root varies widely between surgeons. Some will only consider decompressing a nerve root in the presence of pain radiating in a classical dermatomal distribution whilst others consider nerve root compression to be a cause of back, buttock or thigh pain. We sought to determine the distribution of pain which significantly improves following decompression of lumbo-sacral nerve roots. Methods: Data from consecutive patients undergoing lumbo-sacral nerve root decompression between 2002 and 2005 was prospectively analysed. Inclusion criteria were: uni- or bilateral single level nerve root decompression Three month post-operative visual analogue pain scores of less than 2 (0 = no pain, 10 = worst pain). For individual nerve roots the distribution of pain described on post-operative pain drawings was sub-tracted from that described on pre-operative pain drawings. This produced a composite pain drawing demonstrating the distribution of pain most reliably improved by decompressing a particular nerve root. Results: 52 cases fulfilled the inclusion criteria. There were 6 L4, 36 L5 and 17 S1 nerve root decompressions. The distribution of dramatically improved pain following nerve root decompression did not follow the classic dermatomal patterns described in standard text books. Conclusions: Pain as a consequence of lumbo-sacral nerve root compression does not appear to be restricted to classical dermatomal distributions. Lumbo-sacral nerve root compression may be a significant cause of back pain. In order to decide who is likely to benefit from lumbo-sacral nerve root decompression further characterisation of the pain distribution attributable to lumbosacral nerve root compression is required.