We illustrate an unusual case of cavernous sinus dural arteriovenous fistula (DAVF) presented by brainstem dysfunction as the only symptoms, making the diagnosis difficult.
DAVF is a unique subtype of vascular malformations along the central nervous system, which is characterized by abnormal connections between meningeal/pial arteries and dural venous sinuses, meningeal veins, or cortical veins [1].
Brainstem venous congestion may develop in patients with DAVF of the posterior fossa as a rare but serious complication [2].
The Cognard classification correlates venous drainage patterns on angiography to neurological course, identifying five DAVF types with increasing rates of symptomatic presentation. Although Cognard Types I–IV DAVF involve only dural sinus or cortical venous drainage [3], type V fistula is defined by its drainage into veins around the brainstem and further caudally into the perimedullary veins [4].
Symptoms are very diverse [5], including pulsatile tinnitus, acute subarachnoid hemorrhage, brainstem dysfunction, myelopathy, radiculopathy, neuralgia, cranial palsy, and seizure [6].
Prominent perimedullary flow voids on T2WI, a feature suggestive of an underlying vascular malformation, are present in only 37% of cases. With contrast-enhanced imaging, the detection rate of atypical perimedullary vessels increases to 76% but is often subtle. Use of MRA increases the detection rate to 85% [4].
The high signal intensity observed on T2WI is attributed to oedema and venous congestion resulting from venous hypertension, whereas the contrast enhancement on Gd-T1WI is attributed to venous congestion and blood–brain barrier breakdown [7].
Our patient had a history of four days admission into another facility, ten days prior to his presentation at our hospital, at that time he was complaining of nausea, vomiting and headache. Contrast-enhanced MRI was done there and revealed T2 hyperintense signal within the brainstem with mild patchy enhancement and no diffusion restriction. He was diagnosed as having a brainstem glioma.
After admission into our hospital; CT, CTA, MRI and MRA were obtained with findings as described in the figures section. Conventional angiography confirmed the presence of a slow flow fistula identified along the posterolateral wall of the right cavernous sinus with arterial feeders from multiple meningeal arteries originating from the right external carotid artery and bilateral internal carotid arteries. Venous outflow was into a posterior vein drains into the superior petrosal sinus and into the right ambient cistern to join a perimedullary vein which runs inferiorly into the anterior spinal vein.
The goal of treatment is closure of the draining vein proximally as it exits the fistula [4].
There is general agreement that embolization should be attempted first, and surgery reserved for lesions that are incompletely occluded or recur after embolization [8].
In our case, the fistula was difficult for endovascular embolization given the slow flow and multiple tiny feeders contributing to the fistula with no large feeder that can be accessed.
Our patient has undergone surgical clipping of the fistula. He showed gradual improvement of communication and engagement after surgery. Two weeks postoperative MRI and conventional angiography revealed significant reduction in the brainstem oedema and obliteration of the posterior draining veins, respectively. He was discharged home and advised to continue neuro-rehabilitation in the outpatient clinics.
Brainstem congestion secondary to cavernous DAVF is a rare but critical complication. Its clinical presentation can mimic infectious, neoplastic, demyelinating or ischemic process. The radiologists and the referring physicians should be aware of this rare entity to avoid delayed diagnosis and improper management.
Written informed patient consent for publication has been obtained.
