Dural arteriovenous fistula - Cognard type IV

Case contributed by Richard Flood

Presentation

Previously fit and well. Presented with confusion. The time of onset was unknown as the patient lived alone.

Patient Data

Age: 70 years
Gender: Male

Presentation CT: edema in the right medial thalamus, left thalamus, posterior limb of the left internal capsule, left lentiform nucleus, splenium of the left corpus callousm and left cerebral peduncle. The edema was causing some mass effect, seen as compression of the third ventricle.

MRI was recommended.

The MRI demonstrated edema as identified by the presentation CT with no restricted diffusion. Prominent veins were present over the inferior cortex of the left cerebellar hemisphere, within the left thalamus and along the cerebellar vermis (on both SWI and TI C+ images). There was patchy enhancement in both medial thalami.

CT angiogram confirmed tortuous veins over the inferior cortex of the left cerebellar hemisphere and dilated superior and inferior vermin veins. No definite venous occlusion was identified.

Catheter positioned proximally within the left occipital artery. Angiography demonstrated a branch arising from the occipital artery which passed cranially through the jugular fossa and then posteriorly along the floor of the posterior cranial fossa towards the torcula. At the torcula there was a dural arteriovenous fistula with shunting into the superior and inferior vermin veins.

The branch supplying the fistula was felt to represent the 'jugular division' artery which normally arises from the neuromeningeal trunk but can arise from the occipital artery as an anatomical variant. The jugular division supplies CN IX, X, XI and dura of the posterior cranial fossa.

A microcatheter was navigated along the artery supplying the fistula to a position just proximal to the fistulous point. The fistula was embolized with a liquid embolic agent.

Repeat angiography demonstrated complete occlusion of the fistula with no residual shunting.

Early follow up CT demonstrated a reduction of the edema and reduced mass effect on the 3rd ventricle. Liquid embolic can be seen at the site of fistula.

The patient made gradual cognitive improvement following treatment.

Case Discussion

The initial CT demonstrated deep midline edema; the differential is long but includes deep cerebral vein thrombus, artery of percheron infract and top of basilar syndrome.

MRI did not demonstrate any acute ischemia but did identify tortuous veins overlying the cerebellar hemisphere, suggesting venous hypertension as a cause for the edema. Venous occlusion and retrograde arterial flow into the venous system are two possible causes of venous hypertension.

A CT angiogram was arranged to assess patency of the deep cerebral veins but was inconclusive, DSA was then recommended.

High frame rate DSA demonstrated arterial shunting into the superior/inferior vermin veins and cerebellar cortical veins. The artery supplying the shunt was a vessel which normally supplies the posterior fossa dura, hence dural artery-venous fistula. The vermian veins and cerebellar cortical veins were tortuous and dilated. There was no shunting/arterial flow into the dural venous sinuses. The fistula was therefore graded as a Cognard type IV (direct drainage into cortical veins, venous ecstasies, high annual risk of intracranial hemorrhage).

The fistula was treated via a trans-arterial approach using a liquid embolic agent. On repeat angiography the fistula was completely occluded.

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