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World Neurosurg. 2020 Jan 10. pii: S1878-8750(19)33195-X. doi: 10.1016/j.wneu.2019.12.163. [Epub ahead of print]

Myelographic CT, a check-valve mechanism, and microsurgical treatment of sacral perineural Tarlov cysts.

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Department of Neurosurgery, Tokyo Metropolitan Neurological Hospital, 2-6-1, Musashidai, Fuchu, Tokyo, Japan.
Department of Neurosurgery, Tokyo Metropolitan Neurological Hospital, 2-6-1, Musashidai, Fuchu, Tokyo, Japan. Electronic address:



There is currently no consensus regarding surgical indications for symptomatic sacral perineural cysts.


Nine patients with symptomatic sacral perineural cysts underwent microsurgery. All patients fulfilled the following criteria: (1) cyst sizes are larger than 15 mm; (2) cysts show the "delayed inflow" and/or "delayed outflow" of contrast on myelographic CT, and (3) neurological symptoms correlate with the primary cyst.


On myelographic CT, all primary cysts showed the "delayed inflow" of contrast; the average cyst/thecal sac Hounsfield units (HU) ratio was 0.17. In 7 patients, the primary cyst showed "delayed outflow"; the average cyst/thecal sac HU ratio increased to 3.12 on images obtained 24 hours after contrast injection. Regarding modified Rankin Scale, 67% of patients reported that their overall symptoms improved to normal activities after surgery. The most improved symptom was coccydynia (75% improvement, p=0.017), followed by leg radiation pain (67% improvement, p=0.027) and buttock pain (50% improvement, p=0.068). Bowel/bladder dysfunction improved in 100% of patients, but newly developed in 1 patient (p=0.32). Perineal pain only decreased in 33% (p=0.41).


To the best of our knowledge, this is the first study to have performed a quantitative analysis of the dynamics of CSF in sacral perineural cysts using myelographic CT. Sixty-seven percent of patients benefited from surgery; however, our criteria may not be a necessary and sufficient condition for patient selection because 33% did not respond to surgery despite the successful elimination of the check-valve.


CT myelography; Tarlov cyst; diagnosis; meningeal cyst; meningeal diverticulum; outcome; surgical treatment


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