Neuroradiology Case of the Month

August 2002

Manoj Ketkar, MD, Henry Wang, MD, PhD,
and P.L. Westesson, MD, PhD, DDS

Clinical Presentation: A 61-year-old woman was referred with symptoms of left eye pain, progressive diplopia, and progressive left sixth nerve palsy.

She had an MRI examination of the head that revealed prominent cavernous sinuses bilaterally. There were extra flow voids noted adjacent to the cavernous portion of the bilateral internal carotid arteries (Figs. 1A&B).

The patient was referred to us for cerebral angiography for possible evaluation of carotid cavernous fistula (CCF). We started with the left side as the patient’s symptoms were mainly left-sided.

Angiogram Findings: The selective left internal carotid artery angiogram revealed multiple small arterial feeders from the cavernous portion of the internal carotid artery, seen as a vascular blush adjacent to it. No single large arterial feeder was identified on this selective angiogram (Fig. 2A).

The left external carotid artery injection revealed a blush in the region of the cavernous sinus with multiple small arterial feeders. Again, no single arterial feeder was identified. There was an early opacification of inferior petrosal sinus draining into the internal jugular vein (Fig. 2B).

We then went ahead and did selective catheterization of the right internal carotid artery and the right external carotid artery. Similar findings were observed on these angiograms with no single arterial feeder identified. There was a blush of contrast in the region of the cavernous sinus with multiple small arterial feeders arising from the right internal and external carotid arteries (Figs. 3A&B).

Diagnosis: Dural AV Malformation (DAVM).

Figure 1 (A&B): Post-Gadolinium axial and coronal T1 weighted MRI of the head demonstrates prominent cavernous sinuses bilaterally with extra flow voids noted adjacent to the ICAs (arrows).

Figure 2 (A&B): The left selective internal and external carotid artery angiograms reveal multiple small arterial feeders, seen as a vascular blush in the region of the cavernous sinus. Note the early filling of the inferior petrosal sinus (arrow).
Figure 3 (A&B): The right selective internal and external carotid angiograms revealed similar findings with multiple small arterial feeders (arrows).

Discussion: Dural AV malformations (DAVM) usually affect people between the ages of 40-60 years. They usually present with bruit, proptosis, and cranial nerve palsies. Posterior fossa and skull base are common sites for the DAVMs, sigmoid and transverse sinus being the commonest (1).

Cavernous sinus is the second most common location (12%). Hemorrhage is thought to be uncommon in DAVM.

Two different theories are suggested for the origin of DAVM. One theory postulates that DAVMs follow sinus thrombosis/occlusion. Whereas, the other says that they start as a single AV fistula (1). The final result is a network of micro fistulae with thickened dual arteries and dilated draining veins.

Barrow’s classification divides DAVMs into four types (1).

• Type A is a fistula between intracavernous segment of ICA and cavernous sinus.
• Type B is a shunt between the dural branch of the ICA and cavernous sinus.
• Type C is a shunt between the meningeal branch of ECA and cavernous sinus.
• Type D is a shunt between branches of ICA and ECA and cavernous sinus.

The case just described represents Type D, which is a shunt between branches of ICA as well as ECA and the cavernous sinus.

Dural AVMs can be approached for embolotherapy from either the arterial aspect or the venous aspect or a combination of both. Transvenous embolization is most often performed with coils or detachable balloons (2).

Transarterial embolization of dural fistulas has been reported to produce complete cure in up to 60% of patients, with venous approach having results of up to 90% complete cure (2).

Our patient was only mildly symptomatic without clinical evidence of venous congestion, i.e. no headache or confusion. The angiograms showed antegrade venous drainage. Hence the chance of hemorrhage was quite low.

She underwent a trial of radiation therapy. If her symptoms worsen, the treatment of choice would be embolization of the cavernous sinuses from a venous approach using coils.

Acknowledgements: Authors wish to thank Belinda De Libero and Margaret Kowaluk for their continued support in preparing the Neuroradiology Case of the Month.

References:

1. Scott W. Atlas, Magnetic Resonance Imaging of the Brain and Spine, third edition, 879-891. Lippincott Williams & Wilkins, Philadelphia, PA.
2. Tony P. Smith, Endovascular Management of Cerebral and Spinal Arteriovenous Malformations. http://www.miit.com/smith2.htm.