Dural arteriovenous fistula (DAVF) are a heterogeneous collection of conditions that share arteriovenous shunts from dural vessels. They make up 10-15% of all cerebral vascular malformations. DAVF, is an abnormal connection of vessels in the tissues around the brain or spinal cord in which one or more arteries are directly connected to one or more veins or venous spaces called sinuses. Arteries carry blood from the heart to the tissues, and veins take blood back from the tissues to the heart. In a DAVF, there is a direct connection between one or more arteries and veins or sinuses which gives rise to many problems. DAVFs differ from arteriovenous malformations (AVMs) in that AVMs are found within the tissue of the brain or spinal cord, but DAVFs are found in the coverings of the brain or spinal cord, such as the dura mater or arachnoid. The most serious problem associated with DAVFs is that they transfer high-pressure arterial blood into the veins or venous sinuses that drain blood from the brain or spinal cord. This results in an increase in the pressure of the venous system around the brain or spinal cord. The symptoms of DAVFs vary depending on the location of DAVF. Headache is one of the non-specific symptoms that could be associated with all types of DAVFs. Although DAVFs can occur in any part of the location where the dura mater exists, DAVFs are commonly found in cavernous sinus (behind the eye) and transverse / sigmoid sinus (behind the ear, back of your head). Patients with DAVFs behind the eye (cavernous DAVFs) usually complain of decreased vision and redness / congestion / swelling of the eye. Patients with DAVFs behind the ear (transverse / sigmoid DAVFs) frequently hear a pulsating noise (tinnitus) due to the fast blood flow going through the fistulas. All types of DAVFs can cause stroke-type symptoms and seizures. Brain hemorrhage is the most serious presentation of DAVFs and can cause permanent disability and death. Some DAVFs do not present any symptoms at all.
Severity of the symptoms is not necessarily associated with the risk of brain hemorrhage. For example, DAVFs without any symptoms can cause brain hemorrhage. Initial symptoms of venous congestion are nonspecific and include difficulty in climbing stairs, gait disturbances, and, more often, sensory symptoms such as paresthesias, diffuse or patchy sensory loss, but also radicular pain that may affect both lower limbs or initially only 1 limb. Lower back pain without radicular distribution is also frequently encountered. These neurologic symptoms are progressive with time and are often ascending. Bowel and bladder incontinence, erectile dysfunction, and urinary retention are more often seen late in the course of the disease. SDAVFs are the most frequent vascular malformation of the spine and account for approximately 70% of all vascular spinal malformations. An estimation based on the retrospective series of the major German referral center for spinal vascular diseases arrived at 5–10/million/year in the general population. This disease seems to be underdiagnosed till now. Usually, SDAVFs become symptomatic in elderly men. A recent meta-analysis of all series larger than 5 patients concluded that men are affected 5 times more often than women and that the mean age at the time of diagnosis is 55–60 years.
Patients younger than 30 years of age constituted less than 1% of patients with a DAVF, whereas, to our knowledge, no patient younger than 20 years of age has ever been reported. Most fistulas are solitary lesions and are found in the thoracolumbar region. Almost >80% of all DAVFs are located between T6 and L2. Sacral lesions occur in approximately 4% of patients, whereas high cervical lesions (at the level of the foramen magnum) occur in 2% of patients. Low cervical DAVFs are extremely rare. In approximately 2% of patients, double spinal DAVFs or an association of a spinal dural with a spinal pial AV shunt may be present, raising the possibility of a potential etiologic connection. The first step of treatment is to obtain an entire picture of a DAVF and characterize it. Cerebral angiography (dye injection into brain arteries through a plastic tube) is the gold-standard and the most accurate way to do so. Based on the finding of cerebral angiography and the symptoms, the following options are offered: • Endovascular embolization • Open surgery • Observation One of the most worrisome finding is so called "cortical venous reflux". This is the sign that blood flow return to the brain is compromised and associated with high risk of brain hemorrhage. Regardless of the symptoms, DAVF's with cortical venous reflux should be treated as soon as practical by either endovascular embolization or open surgery. Recently, most DAVF's can be treated by endovascular embolization. When a patient cannot tolerate the symptom such as pulsating noise, endovascular embolization is considered. Simple observation can be an option for some DAVF's with negligible risk of hemorrhage. The other two treatment methods are: Minimally invasive endovascular embolization- It is sufficient to cure the majority of DAVFs. During this procedure, we pass a catheter through the groin up into the arteries in the brain that lead to the DAVF and inject liquid embolic agents such as NBCA, glue or Onyx into these arteries. This injection shuts off that artery and reduces the flow of blood through the DAVF. Microsurgical resection is a reserved method for DAVFs that cannot be closed with endovascular embolization. During microsurgical resection isolate the DAVF from the tissues around the brain or spinal cord by craniotomy and using an optical microscope.