Presentation
Gradually progressive parieto-occipital headache with intermittent blurring of vision.
Patient Data
Non contrast CT demonstrates a hyperdense tubular structure representing a dilated vessel in the parafalcine right occipital lobe, best seen on sagittal reformation. No intracranial hemorrhage.
Underlying vascular malformation, such as, arteriovenous malformation (AVM) or dural arteriovenous fistula (AVF) is suspected. Patient is subsequently recalled for CT angiography study.
There is interval development of a small focus of intraparenchymal hemorrhage within right occipital lobe in close proximity to tortuous vessels. There is a large draining vein connecting to the transverse sinus with an ectatic segment. No feeding vessel or intervening nidus is identified. Findings are suspicious for an AVF.
The superior sagittal and transverse sinuses are patent. Major intracranial arteries are patent with no evidence of aneurysms.
Selective injection of the left vertebral artery demonstrates a tentorial based dural AVF. Arterial supply is from left posterior meningeal artery with connection to a cortical vein. There is evidence of cortical venous reflux involving the right occipital region associated with venous ectasia. The fistula is draining into superior sagittal sinus and right transverse sinus through cortical venous drainage.
Left vertebral artery angiogram shows no residual AV shunting or dural AVF.
This case is submitted by Dr. Minu Agarwal and Dr. Milita Ramonas.
Case Discussion
Intracranial dural arteriovenous fistulas (DAVFs) are arteriovenous (AV) shunts across the dura with arterial supply from the dural arteries, most commonly from meningeal vessels. The venous drainage involves the dural venous sinuses, meningeal veins or cortical veins. DAVFs are predominantly idiopathic but can be secondary to dural sinus thrombosis, intracranial hypertension, prior craniotomy, and trauma.
Symptoms depend on lesion location and pattern of venous drainage. Common presentations include pulsatile tinnitus, orbital symptoms (typically caroticocavernous fistula) and neurological deficits (secondary to intracranial hemorrhage (ICH) and intracranial hypertension).
Posterior fossa is the most common location of intracranial DAVFs with involvement of transverse and sigmoid sinuses as in this case presenting with headache and visual blurring. Initial suspicion of DAVF was raised on NCCT due to presence of a dilated cortical vessel. In the absence of hemorrhage, non invasive CTA was the preferred next step which demonstrated Cognard type IV/ Borden type III DAVF with interval development of ICH. This prompted emergency DSA and embolization.
The diagnosis is dependent on a high level of clinical suspicion and high-resolution imaging. Atypical location of intracranial hemorrhage, dilated cortical veins and tortuous flow voids adjacent to dural venous sinuses are potential clues on cross-sectional imaging including CT and MR. Noninvasive imaging evaluation by CTA and MRA can provide useful information for diagnosis, classification, and treatment planning. However, conventional angiography remains the most accurate method for assessment of DAVFs.
These are classified based on the pattern of venous drainage as it correlates with the severity of symptoms and the risk of hemorrhage. Cognard and Borden classifications are most commonly used for risk stratification.
Endovascular treatment including trans-arterial or trans-venous embolization is the first line of management for symptomatic and high risk DAVFs. Surgical options are reserved for cases where endovascular treatment fails or is not feasible.
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