Dural defect in Tarlov cyst instead of cerebrospinal fluid-venous fistula as the cause of spontaneous intracranial hypotension: illustrative case.

BACKGROUND: Spontaneous intracranial hypotension results from CSF loss due to a dural defect or meningeal diverticulum. Precise localization of the leak is challenging, especially when multiple levels present abnormalities. OBSERVATIONS: A 58-year-old woman presented with progressive orthostatic headache, with no history of trauma. MRI of the brain showed signs of CSF hypotension, while MRI of the spine revealed Tarlov cysts in the left T12 and L1 roots. CT myelography suggested a CSF-venous fistula leak at the right T7 level. Three thoracic epidural blood patches were performed with no improvement. As the patient's condition progressed and she developed right abducens nerve paresis, surgical exploration was indicated. The level of the presumed CSF-venous leak (T7) was explored, and no anomalous drainage was found. Then the Tarlov cysts at T12 and L1 were addressed. A dural defect with spontaneous CSF leakage was found on the dorsal surface of the nerve root of the L1 cyst, which ceased with suturing. Postoperatively, there was significant improvement of the patient's headache and right abducens paresis. LESSONS: Even in a presumed diagnosis of CSF-venous fistula, exploration of Tarlov cysts may reveal a dural defect and CSF leakage. Therefore, surgical decision-making should include a critical analysis of Tarlov cysts for definitive repair. https://thejns.org/doi/10.3171/CASE25871.