Traumatic middle meningeal arteriovenous fistula presenting with long delayed-onset facial nerve palsy without temporal bone fracture: illustrative case.

BACKGROUND: Traumatic facial nerve palsy (FNP) without temporal bone fracture (TBF) has a delayed onset in some cases; however, long delayed-onset FNP in this setting has not been reported. The middle meningeal vein (MMV) is one of the venous drainage routes from the facial nerve. Herein, the authors describe a rare case of traumatic middle meningeal arteriovenous fistula (MMAVF) presenting with the long delayed-onset FNP without TBF. OBSERVATIONS: A 42-year-old man with pulsatile tinnitus and left FNP was admitted to our hospital 4 weeks after head trauma without TBF. Cerebral angiography revealed an MMAVF between the middle meningeal artery and the MMV on the left side. Seven days after admission, the FNP showed slight improvement, and preoperative angiography revealed decreased shunt flow of the MMAVF. Transarterial coil embolization was successfully performed. Postoperative angiography showed no residual fistula. Two weeks after the procedure, there was complete resolution of the FNP. This clinical course was correlated with the angiographic findings, suggesting that the long delayed-onset FNP was caused by the traumatic MMAVF without TBF. LESSONS: In patients presenting with long delayed-onset FNP after head trauma without TBF, the vascular lesion must be evaluated to exclude MMAVF.