Fall 2007

Dural Fistulas

Dural fistulas are arteriovenous connections typically involving a major dural sinus lying between the skull and the brain. Due to their location, dural fistulas often cause intense and regular headaches.

UCSF Medical Center, which has more than 20 years of experience working with patients with dural fistula, receives roughly 50 new patients per year from around the world. The multidisciplinary team at UCSF includes vascular neurologist Vineeta Singh, M.D., vascular neurosurgeon Michael Lawton, M.D., and interventional neuroradiologist Van Halbach, M.D., who pioneered the minimally invasive endovascular occlusion treatment of dural fistula 19 years ago.

"UCSF is the world's largest center for diagnosis and treatment of dural fistula. We also have the largest literature base, with more than 60 papers on the topic," says Halbach.

Halbach has performed more than 500 endovascular treatments, which often provide a permanent cure with minimal risk. During the procedure, a catheter is inserted through the groin and advanced in the vessel up to the dura with X-ray guidance. The fistula is embolized using ethanol from the arterial side or, more commonly a series of platinum coils is positioned from the venous side, which seals off the shunt.

Patients with a high-risk fistula may require surgery, but these instances are rare, says Halbach. Lawton has developed extensive experience with the surgical management of high-risk dural fistulas, which receive preoperative embolization to reduce the shunt and make surgical interruption possible. Roughly a third of dural fistulas cause subdural, subarachnoid and parenchymal brain hemorrhage and the risk depends on the pathway through which the fistula drains its blood.

There are 10 types of dural fistula, distinguished by location and drainage pathway. The three most common types, and their accompanying symptoms, are:

  • Carotid-cavernous sinus fistula — The fistula is located behind the eye, causing headache and eye problems including swelling, bulging, redness, congestion and decreased vision. Patients typically hear a "swishing" noise.
  • Transverse-sigmoid sinus fistula — Blood drains behind the ear, causing symptoms of pulsatile tinnitus, pain behind the ear, headache and neck pain. Fistulas draining into cortical veins due to obstruction or narrowing of the transverse or sigmoid sinus downstream often present with bleeding.
  • Sagittal sinus and scalp fistula — Blood drains toward the top of the head, causing bruit, headache, prominent blood vessels on the scalp and above the ear, and pain near the top of the head.

"Since these symptoms are so general, recognizing the disorder is a problem," says Singh. "Thirty percent of the population suffers from significant headaches, but that doesn't mean they should be screened for dural fistula because the prevalence is less than one per 100,000. So neurologists and ophthalmologists should be aware of the other associated symptoms to know when to refer."

Diagnosis is another concern because, even with high-quality CT or MRI scans, dural fistulas often escape detection.

"The gold standard for detecting dural fistula is an arteriogram with selective injections of all cerebral arteries, particularly the external carotid arteries, and it must be done by a radiologist experienced with this disorder," says Singh, who maintains constant communication with referring physicians to create a cohesive medical plan.

Causes of dural fistula are not known, but many believe it is an acquired disorder. Head injury can result in development of dural fistula, as there is increased recruitment of blood vessels during the healing phase, increasing the chances of shunting between a dural artery and vein. Cerebral venous sinus thrombosis can lead to increased pressure in the venous sinuses and the opening of shunts that are normally only present during embryonic development. Dural fistula can also develop after craniotomies involving meningioma resection.

Singh is also researching a possible link between carotid-cavernous sinus fistulas and hormonal changes in women. She has observed that dural fistulas tend to arise during pregnancy and menopause.

"Women with these conditions who complain of new headaches and tinnitus should be followed closely for subtle neurologic signs of dural fistula, such as minor cranial neuropathies or cranial bruit," says Singh. "If a dural fistula is not diagnosed and treated, vision loss, hemorrhage and cognitive impairment can occur. We have two patients whose memory has improved after treatment for dural fistula."

For more information, call Vineeta Singh, M.D., at (415) 353-1489 or Van Halbach, M.D., at (415) 353-1863.

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