Arteriovenous malformation with unique drainage through the emissary vein of the foramen ovale: illustrative case.

backgroundAs part of the laterotrigeminal venous system (LTVS), the emissary vein of the foramen ovale (EVFO) is an underrecognized venous structure communicating between the cavernous sinus and pterygoid plexus. The sphenobasal sinus is an anatomical variation of the sphenoparietal sinus that drains directly into the EVFO. The authors present the case of a ruptured arteriovenous malformation (AVM) with a unique drainage pattern through the sphenobasal sinus and EVFO. OBSERVATIONS: A 9-year-old female initially presented with loss of consciousness and was subsequently found to have a ruptured AVM in the left basal frontal area. She underwent an immediate decompressive hemicraniectomy, with a computed tomography angiogram demonstrating a unique anatomical variation in which the sphenobasal sinus communicated with the EVFO and LTVS. The final venous drainage returned to the pterygoid plexus and external jugular vein. Postoperatively, the patient made a substantial recovery, with generalized right-sided weakness remaining as the sole deficit. LESSONS: The authors present the case of a ruptured AVM with unique venous drainage into the sphenobasal sinus and EVFO, for which the current literature remains limited. As exemplified by this illustrative case, technique modification may be warranted in the setting of this unique anatomical variation to avoid venous sinus injury.