Shrinking of a Tarlov cyst

Correspondence to Professor Kieran P Murphy, [email protected]

Background

Tarlov cysts were first described in 1938 by Tarlov as an incidental finding during autopsy.¹ Tarlov cysts are one of many mimics of discogenic radiculopathy with a reported incidence of 4.6% in back pain patients, 20% of which are symptomatic.² A 2013 case report published in the New England Journal of Medicine found that in previous large studies, the prevalence of symptomatic Tarlov cysts found on lumbosacral MRI images ranged from 1.5%–2.1%.³ A more recent study published in 2017 by Kuhn et al assessed 1100 sacral MRIs, finding sacral Tarlov cysts in 132 cases (13.2%). They also found that the prevalence of Tarlov cysts appeared to increase with age.⁴ They are most commonly found in Caucasian women.² Also known as perineural cysts, Tarlov cysts are cerebrospinal-fluid-filled meningeal dilations of nerve roots, most often found in the spinal canal of the S1–S5 region of the spinal cord.¹ They can, however, be found in the cervical, thoracic and lumbar regions.⁵ The aetiology of Tarlov cysts is not well understood, however, several hypotheses have been proposed, which may be either congenital or acquired. Congenital causes include connective tissue disorders such as Loeys Dietz, Ehlers-Danlos and Marfan syndromes^{6 7} while acquired causes include inflammation within the nerve root cysts, arachnoidal proliferation around and along the exiting nerve root, haemorrhagic infiltration of the spinal tissue and breakage of the venous drainage in the perineurium and epineurium secondary to haemosiderin deposition after trauma.⁸ Tarlov cysts can cause backache, sciatica, perineal, buttock and lower extremity pain as well as sexual, urinary and bowel dysfunction but are often ignored on MRI or thought to be of little significance in causing back pain.^9–11 Lumbosacral MRI and CT myelography are the most common methods of diagnosing Tarlov cysts, however, dedicated sacral MRI is more sensitive.¹¹ Treatment options include non-surgical lumbar cerebrospinal fluid drainage and percutaneous cyst drainage, as well as surgical options such as cyst fenestration, cyst wall resection, simple decompressive laminectomy and myofascial flap repair and closure.^{10 12} More recently, less-invasive procedures to treat Tarlov cysts have been described, including the two-needle technique, which has been employed in this case.¹⁰ Prior to...