Importance of source images of time-of-flight magnetic resonance angiography in the diagnosis of low-flow dural arteriovenous fistulae after traumatic brain injury.

Three-dimensional time-of-flight (TOF) magnetic resonance angiography (MRA) can reliably detect dural arteriovenous fistula (dAVF); however, TOF source images should be checked in cases with low-flow dAVFs. A 69-year-old woman reported intractable pulsatile tinnitus after head trauma. It was difficult to diagnose dAVF using conventional MRA, but it was confirmed using a TOF source image. Cerebral angiography revealed a dAVF with a small shunted pouch draining into the sigmoid sinus, accompanying the arterial jet flow. Transarterial embolisation of the shunted pouch completely obliterated the dAVF. The patient's tinnitus immediately disappeared after embolisation. This case suggests that a low-flow Borden type I dAVF is undetectable using conventional MRA, and we emphasise the importance of evaluating TOF source images. Transarterial embolisation of the shunted pouch while preserving the normal sinus flow was safe and effective.