Facet joint cyst haematoma: a rare cause of cauda equina syndrome.

Facet joint cysts are a feature of lumbar spondylosis and are an uncommon cause of radiculopathy. Facet joint cyst haematoma is a very rare entity and has previously been reported as a subacute cause of leg pain, back pain, sensory deficit and lower limb weakness. We present the unique case of facet joint cyst haematoma presenting as cauda equina syndrome. An 81 year old lady presented with a 7 day history of back pain and left foot drop, a 1 day history of perineal numbness and urinary retention with absent rectal tone, perianal anaesthesia and left leg hypoaesthesia. Emergency MRI scan demonstrated spinal canal stenosis as the aetiology of her cauda equina syndrome. She was taken to theatre for emergency lumbar decompression. At operation a facet joint haematoma compressing the cauda equina was found and extirpated with complete resolution of symptoms. In this case, the aetiology of cauda equina compression was not demonstrated effectively on pre-operative MRI scanning.