Deep Gluteal Syndrome
Prof. Kevork Hopayian
University of Nicosia, Cyprus
These pages have been written to support a long term project on causes of back pain and sciatica arising in the pelvis. The current focus is on the clinical features and in particular the many clinical tests that have been suggested to be diagnostic.
When the word sciatica is used, most clinicians will think of one pathology, compression of the nerve roots by a bulging or prolapsed intervertebral disc. Those with a special interest in musculoskeletal conditions will also know pressure can also arise from narrowing of the spinal canal by osteophytes, lumbar canal stenosis. In the UK at least, very few will think of compression of the nerve trunk, the sciatic nerve, outside the spine. As many as 47% of patients investigated for sciatica with conventional MRI in secondary care do not have disc herniation or lumbar canal stenosis. Could compression of the sciatic nerve explain some of these cases? After all, syndromes for compression of other nerves as they pass through confined spaces are well described. The two commonest are carpal tunnel syndrome (median nerve at the wrist) and cubital tunnel syndrome (ulnar nerve at the elbow).
The deep gluteal space lies in the buttock (anatomy described here). Cases of sciatic nerve compression in the deep gluteal space, either by space occupying lesions or by musculoskeletal structures, have been reported over many years. The piriformis muscle is the musculoskeletal structure that was first implicated and the one for which there has consequently been most research. Indeed, the term piriformis syndrome was previously used to cover all DGS. It would be better if it were restricted to cases where the piriformis muscle is proven to be the cause. The sciatic nerve passes under the piriformis muscle. This close relation makes the nerve prone to conditions afflicting the muscle. Other muscles such as the obturators and gemelli have more recently been implicated and fibrous bands have been discovered at operation to compress the nerve hence the term Deep Gluteal Syndrome is now preferred by many. DGS is best used to describe musculoskeletal causes of pelvic sciatica (i.e. sciatica caused by conditions in the pelvis as opposed to the spine) and other causes, such as space occupying lesions, better seen as part of the differential diagnosis.