Facet joint cysts causing cauda equina compression.

Facet joint cysts are commonest at the L4-L5 level and are associated with facet joint degeneration and type III (degenerative) spondylolisthesis. It is extremely rare for facet joint cysts to cause symptomatic cauda equina compression. Three elderly patients presented to us with significant cauda equina compression caused by facet joint cysts. One presented with classic symptoms and signs of a cauda equina syndrome, a second with bilateral lower limb neurologic loss associated with uncontrolled epilepsy, and the third with bilateral leg symptoms as well as an upper limb tremor and fasciculation. The diagnosis was easily made after magnetic resonance scanning in two patients, although in one patient, it was significantly delayed because of his confounding neurologic picture. Lumbar spine surgery (decompression and cyst resection) was successful in resolving symptoms in all three, even though two patients had significant neurologic compromise before surgery. The occurrence of facet joint cysts in older patients can be associated with other degenerative neurologic conditions, and the diagnosis might not be apparent early. We suggest that in older patients who have a mixed picture of central and peripheral neurologic compromise, this diagnosis should be considered and investigation of the whole of the spine, not just the brain and spinal cord, should be undertaken.