Rapid reversal of coma due to brainstem herniation after endovascular treatment of a high-flow cerebrospinal fluid-venous fistula: illustrative case.

BACKGROUND: Spontaneous intracranial hypotension secondary to a CSF leak is a rare phenomenon that is often misdiagnosed and mismanaged. The authors present the case of a patient who presented with rapidly progressive symptoms leading to cerebral herniation, which was rapidly reversed with transvenous embolization of a high-flow CSF-venous fistula. OBSERVATIONS: A 57-year-old male presented with complaints of postural headaches that progressively worsened over 2 months. Imaging demonstrated bilateral subdural hygromas with effacement of the basal cisterns concerning for brainstem sag and impending brainstem herniation. While hospitalized, his neurological examination rapidly deteriorated, and he became comatose and required intubation. Digital subtraction myelography (DSM) demonstrated a high-flow CSF-venous fistula at the right side of T3-4, which was embolized transvenously. Following embolization, the patient awoke without significant neurological deficits. Postprocedure imaging showed a decrease in subdural hygromas and improved effacement of the basal cisterns and preprocedure brain sag. Three weeks postprocedure, he noted significant improvement in symptoms. LESSONS: The authors present the case of a patient who became acutely comatose due to brain herniation caused by a high-flow CSF-venous fistula. The patient was diagnosed and treated using DSM and transvenous CSF-venous fistula embolization with significant improvement of clinical symptoms and radiographic findings posttreatment. https://thejns.org/doi/10.3171/CASE26338.