Spontaneous Closure of a Traumatic Middle Meningeal Arteriovenous Fistula Accompanied by a Sagittal Epidural Hematoma

Abstract

A 41-year-old woman with a traumatic arteriovenous fistula of the middle meningeal artery and a sagittal epidural hematoma was reported with a review of the literature. The arteriovenous fistula was confirmed by angiography 7 and 24 days after trauma and was no longer demonstrable in a follow-up examination after 5 months. Forty-two traumatic middle meningeal arteriovenous fistulas including the author's case have already been reported throughout the world. Twenty-five of them (60%) were accompanied by epidural hematoma and seven of them(17%) closed spontaneously. It is sometimes difficult to locate extravasated contrast material in connection with the middle meningeal vein. Characteristic features of the fistulas were classified into the following five groups from operative and histological findings: 1) middle meningeal artery—middle meningeal vein fistula; 2) middle meningeal artery—diploic vein fistula; 3) pseudoaneurysm, concomitant with fistula; 4) torn dura, concomitant with fistula; and 5) organized epidural hematoma or thick dura with abnormal vessels.
The high percentage of accompanying epidural hematoma, rapid granulation of epidural hematoma with early formation of vessels, pseudoaneurysms and tunnels in some epidural hematoma, intradural hemorrhage, and cases of late appearance of the fistula indicate that not only simultaneous injury of the middle meningeal artery and vein or diploic vein but also epidural hematoma and dural injury seem to be important in the formation of traumatic middle meningeal arteriovenous fistulas. Spontaneous closure of the fistula found in seven of the 42 cases is thought to be caused by thrombosis in abnormal vessels of the dura. The mechanism of spontaneous closure of the fistula in the author's case is thought to be as follows: sagittal epidural hematoma forced shunted venous blood to flow to the sphenoparietal sinus, but this retrograde flow resumed its original direction to the superior sagittal sinus after spontaneous reduction of the hematoma. A thrombus was formed in the stagnant middle meningeal vein inferior to the fistula and extended into the fistula orifice.