Neuroradiology Case of the Week

Case 38

Francisco Garcia-Morales, MD and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Fifty-year-old male presents with acute onset of seizures.

Radiological Findings: CT scan (Fig. 1) demonstrates a small amount of subarachnoid hemorrhage in the right frontal lobe. T2-weighted image shows slight swelling of the gyri in the corresponding region (Fig. 2). Diffusion-weighted image (Fig. 3) demonstrates a focal area of decreased signal suggestive of magnetization susceptibility artifact. FLAIR image (Fig. 4) is the most sensitive for subarachnoid hemorrhage and demonstrates the area of subarachnoid hemorrhage. Coronal gradient echo image (Fig. 5) demonstrates multiple small cortical areas of decreased signal indicative of hemorrhage. MR angiography (Fig. 6) shows the prominence of vessels in the corresponding area erasing the suspicion of a vascular malformation such as a dural fistula.
   Conventional angiography in AP (Fig. 7A) demonstrates abnormal vessels from the external carotid artery with early draining veins. Lateral conventional digital subtraction angiography (Fig. 7B) again demonstrates the branches of the scalp vessels having abnormal transcranial connections and early intracranial dual draining brains.

Figure 1: Non-enhanced CT scan demonstrates increased density at the convexity consistent with a small amount of subarachnoid hemorrhage in the right frontal lobe.	Figure 2: T2-weighted image shows slight swelling of the frontal gyri in the corresponding region of subarachnoid hemorrhage.
Figure 3: Diffusion-weighted image demonstrate a focal area of signal void suggestive of magnetization susceptibility artifact due to hemorrhage.	Figure 4: FLAIR image is the most sensitive for subarachnoid hemorrhage and demonstrates the area of subarachnoid hemorrhage (arrow).
Figure 5: Coronal gradient echo image demonstrates multiple small cortical areas of decreased signal indicative of hemorrhage.	Figure 6: MR angiography demonstrates the prominence of vessels raising the suspicion of a vascular malformation such as a dural fistula.
Figure 7A&B: Conventional angiography in AP (A) and lateral (B) demonstrates abnormal vessels from the external carotid artery with early draining veins (arrows).

Diagnosis: Dural arteriovenous fistula.

Discussion:
   Dural arteriovenous malformation or fistula is uncommon [1] and account for 10-15% of intracranial arteriovenous malformations [2]. They usually present with pulsatile tinnitus, audible bruit, and headache, depending on where the malformation is located. The venous drainage pattern is important for the clinical presentation. If the venous drainage is unobstructed and drainage occurs directly into the sinus with normal flow direction, collateral venous pathway usually does not develop and hemorrhagic complications are uncommon. If there is reflux into the cortical veins or drainage into the cortical veins directly, subarachnoid intracerebral hemorrhage is much more common [3]. The natural history includes a hemorrhagic incidence of between 2-4% per year. This is cumulative so that the risk of hemorrhage increases over time. On the other end of the spectrum, spontaneous obliteration occurs in a few percent of the cases. The treatment is surgery, radiosurgery, or embolization [4].

References:

1. Berman MF et al. The epidemiology of arteriovenous malformations. Neurosurg 2000;47:389-397.
2. Morris, Pearse. Practical Neuroangiography, Williams & Wilkins, 1997, p339.
3. Pierot L, Chiras J, et al.: Dural Arteriovenous fistulas of the posterior fossa draining into subarachnoid veins. AJNR 13:315-323, 1992.
4. Lewis AI, Rosenblatt SS: Surgical Management of deep-seated dural arteriovenous malformations. J Neurosurg 1997, 87(2):198-206.