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Q1: What is a lumbar facet synovialcyst?
Lumbar facet synovial cyst was first described in 1968 by Kao et al.1 It is now being commonly reported with advanced neuroimaging techniques. It can pose serious diagnostic and therapeutic problems. The aetiology of this condition is degenerative including osteoarthritis, rheumatoid arthritis, and spondylolisthesis. It is commonly located at L4/5 in the most mobile part of the spine and is uncommon in cervical and thoracic regions. Repeated microtrauma is blamed for its aetiopathogenesis. It is related to the degenerative facet joint. It might be a very common cause of refractory low back pain with radicular pain; it is very rarely bilateral. It can present, although very rarely, acutely as an emergency and there have been reports of cervical cord compression and cauda equina syndrome after a bleed into this cyst. Elderly patients with low back pain and radiation with a leading symptom of aggravation of pain on standing and walking should be suspected.
Q2: How is it diagnosed?
Blood tests and radiographs are usually unhelpful. MRI is the investigation of choice.2 The differential diagnosis with MRI could be a migrated disc fragment, a perineural cyst, schwannoma, and a extradural space occupying lesion. Pathologists divide these cysts into synovial and ganglion types but they do not have any prognostic significance
Q3: How is lumbar facet synovial cyst treated?
It is treated only if it is symptomatic.3 If it is an incidental finding, analgesia can be given. Spontaneous disappearance has been reported in 10% of these cysts. Aspiration has led to recurrence and steroid injection into the cyst has been reported to increase the severity of pain. Surgery is the treatment of choice with excision of the cyst and associated laminectomy. If there is associated instability then fusion is the treatment of choice.