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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June 16, 2016
Dural Arteriovenous Fistula (DAVF), with Perimedullary Drainage
- Background:
- DAVF make up 10–15% of all intracranial arteriovenous malformations.
- They may occur as a result of abnormal angiogenesis induced by previously dural venous sinus thrombosis.
- Classification systems include Borden and Cognard. DAVF with perimedullary venous drainage are classified as Cognard type V.
- Clinical Presentation:
- Is highly variable and depends on the location and pattern of venous drainage. DAVF with perimedullary venous drainage can present with progressive myelopathy.
- Key Diagnostic Features:
- MRI can demonstrate dilated vessels and signs of venous hypertension. Dynamic MR angiography can demonstrate early opacification of the involved dural sinus. Further characterization still requires conventional angiography.
- Conventional angiography remains the gold standard for the diagnosis and classification of DAVF, especially for the detection of corticovenous reflux.
- Differential Diagnoses:
- Differential diagnosis of myelopathy and imaging features that help to differentiate: ischemia (restricted diffusion on DWI), demyelination and auto-immune (coexisting cerebral white matter lesions), inflammatory and infectious (co-existing systemic manifestations), traumatic (other spinal traumatic lesions), tumor (contrast enhancement, though this can be seen in venous congestion as well), toxic or metabolic (dorsal column localization).
- The most important differential diagnosis is a difusse infiltrating astrocytoma. Both entities will show high T2 signal and variable medulla/spinal cord expansion, but the cord edema spares the periphery in DAVFs, and diffuse infiltrating tumors will not show dilated flow voids.
- Spinal cord ischemia: Restricted diffusion on DWI, acute onset of symptoms (usually the maximum deficit is seen in less than 4 hours)
- Demyelinating/inflammatory lesions: Patchy or punctate enhancement. May have associated supratentorial brain lesions or optic neuritis. Lumbar puncture will show various degrees of pleocytosis depending on the cause. No dilated flow voids are seen.
- Treatment:
- Conservative (Borden type I and Cognard type I–IIa)
- Endovascular embolization (transvenous or transarterial, depending on the angioarchitecture) is the treatment of choice for Borden type II–III, Cognard type IIb–V fistulas. Surgical resection or stereotaxic radiosurgery is reserved for those in which embolization cannot achieve a complete cure.
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