Incomplete cauda equina syndrome secondary to haemorrhage within a Tarlov cyst

Sacral perineural (Tarlov) cysts are benign, cerebrospinal fluid containing lesions of the spinal nerve root sheath. They are usually asymptomatic; however, a small proportion have the potential to cause compression of nerve roots and/or the cauda equina.We report a case of a 61-year-old man who presented with acute onset back pain associated with bilateral radiculopathy. Between referral and consultation, the patient developed urinary dysfunction which resolved spontaneously.MRI revealed haemorrhage within a Tarlov cyst, resulting in compression of the cauda equina. Due to the considerable clinical improvement at the time of consultation, surgical decompression of the cyst was not considered to be indicated.An interval MRI scan 8 weeks later demonstrated that the haemorrhage within the perineural cyst had spontaneously resolved and the patient remained asymptomatic at 5-year follow-up.