Case of the Week
Section Editors: Matylda Machnowska1 and Anvita Pauranik2
1University of Toronto, Toronto, Ontario, Canada
2BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
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August 10, 2017
Dural Arteriovenous Fistula (DAVF)
- Background:
- Potentially reversible cause of progressive dementia
- Easily missed without vascular imaging (as in this case)
- Requires surgical disconnection; in this location, conventional ligation is difficult and endovascular embolization is preferred.
- Clinical Presentation:
- Progressive cognitive decline, including memory disturbance; Montreal Cognitive Assessment score of 10/30
- Weight loss and ataxia
- Key Diagnostic Features:
- Symmetrical bithalamic edema on CT confirmed by MRI (FLAIR hyperintensity)
- No diffusion restriction (cytotoxic edema) on DWI/ADC and no venous abnormality
- Abnormal arterial flow signal within tortuous peri-vein of Galen vascular structure demonstrated by MRA
- Formal DSA confirms arteriovenous shunt from left-sided posterior meningeal arteries into distended collateral veins and vein of Galen
- Embolization material fills fistulous connection
- Complete resolution of FLAIR signal abnormality at 12 weeks postembolization
- Differential Diagnoses:
- Vascular: Acute stroke secondary to artery of Percheron occlusion: would demonstrate high DWI and low ADC signals (restricted water diffusion)
- Infection: Viral encephalitis including West Nile and CJD: expect relevant travel history +/- cortical signal abnormality +/- callosal splenium lesion
- Metabolic: Osmotic myelinolysis: bithalamic involvement is unusual; abnormal signal often includes pons and water diffusion can be restricted.
- Inherited metabolic: Fabry disease (lysosomal storage disease) and Leigh syndrome (mitochondrial disease): diffusion restriction expected. May show the T1 hyperintense pulvinar sign.
- Neoplasm: Diffuse low-grade astrocytoma: vascular imaging would be normal; otherwise difficult to differentiate
- Treatment:
- Disconnection of arteriovenous shunt (surgical or endovascular using liquid embolic via transarterial or transvenous approach)
- Increasing endovascular management with improved neurologic outcome
- Follow-up imaging is recommended to review for resolution of bithalamic edema and to exclude any residual or recanalization of fistula. This can be restricted to short-term if complete occlusion is confirmed.
- Clinical improvement can occur within days of definitive treatment. In this case, dementia completely resolved.
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