A Case of an Intraosseous Arteriovenous Fistula at the Squamous Part of the Occipital Bone with Spontaneous Occlusion of Diploic Venous Drainage.

Objective: An intraosseous arteriovenous fistula (AVF) is a rare fistula with an intracranial shunted pouch. A case of an intraosseous AVF at the squamous part of the occipital bone with spontaneous occlusion of diploic venous drainage is described. Case Presentation: The patient, a Japanese woman in her 80s, presented with headaches at the back of the head and a history of multiple unruptured cerebral aneurysms but no recent head trauma. MRA showed abnormal signals in the occipital diploic region, and DSA showed an intraosseous AVF with a shunted pouch in the squamous part of the occipital bone near the inion. This was not seen on MRA 6 months earlier. One month later, follow-up examinations showed spontaneous occlusion of the diploic venous drainage, leading to a change in retrograde drainage into the superior sagittal sinus. Transvenous coil embolization was performed, and the shunted pouch was completely occluded. Postoperatively, the patient's symptoms resolved, and subsequent follow-ups showed no recurrence of the AVF. Conclusion: This case suggested that the vascular architecture of intraosseous AVFs might change over a short period. Transvenous embolization was effective in obliterating the intraosseous shunted pouch.