Large tumefactive lesion in the right cerebellar hemisphere

A 47-year-old man with two weeks history of headache and vomiting.

A brain MRI obtained few days later (Figure 3) depicts on axial T2-FLAIR and coronal T2-weighted images (A, B) a hyperintense lesion affecting the white matter of the right cerebellar hemisphere that shows also high signal intensity on the apparent diffusion coefficient map (C) indicative of vasogenic edema. Axial T2*-weighted image demonstrated multiple hipointense foci suggestive of underlying micro and macrobleeds (D). The lesion is isointense on the unenhanced T1-weighted image (E), but shows peripheral enhancement associated with enlarged cortical vessels (F), also seen as flow-void signal on the coronal T2-weighted image.

Background

Intracranial dural arteriovenous fistulas (DAVFs) consists of pathological shunts connecting dural arteries with dural or cortical veins. DAVFs account for 10% to 15% of cerebrovascular malformations. They typically develop in the region of the transverse and sigmoid sinuses, although they may affect the dura in any part of the central nervous system. The lesions are thought to arise as a consequence of increased pressure within the dural sinuses, possibly as a sequela of sinus thrombosis [1].

Clinical Perspective

Most patients present in the fifth and sixth decades of life. The clinical symptoms, which include pulsatile tinnitus, intracranial hemorrhage and in some cases, dementia are variable and related to the location of the lesion and pattern of venous drainage. In some cases, intracranial DAVFs may induce cervical myelopathy by interruption of cervical spinal venous drainage [2].

Imaging Perspective

In some cases, increased pressure develops within the venous sinus, and the flow increase through the DAVF causes retrograde transmission of pressure leading to enlargement of cortical veins and impairment of parenchymal venous drainage. As a result of this venous congestion, cerebral parenchyma changes occur, including, vasogenic edema, and petechial hemorrhage, adjacent to or distant from the site of the fistula [3]. Enlarged blood vessels surrounding the affected parenchyma can be seen on T2-weighted images or even more clearly on contrast-enhanced T1-weighted images, being this finding a useful marker for the diagnosis.

Outcome

The symptoms, prognosis, and management are related to the type of venous drainage (to a dural venous sinus or cortical venous drainage) and the direction of flow (Borden classification, type I-III; Cognard classification, type I-V). The definitive treatment of DAVF requires occlusion of the arteriovenous shunt. Currently, the first treatment option is endovascular embolization, with open neurosurgery as a second option. A small percentage of patients can be treated with radiosurgery [4].

Take Home Message / Teaching Points

DAVFs should be considered in adult patients with radiological findings suggestive of diffuse congestive edema involving the cerebellum. The identification of vascular signal voids associated to this diffuse edema further supports the diagnosis of a DAVF, and additional MR angiography or digital subtraction angiography should be performed to confirm the diagnosis. In this particular patient, a digital subtraction angiography confirmed the presence of a DAVF with multiple abnormal vessels in the surface of the right cerebellar hemisphere originating from the posterior meningeal artery and with direct drainage into cerebellar cortical veins.