Can a dural arteriovenous fistula (dAVF) cause a relative afferent pupillary defect (RAPD)?

From the Guidelines

Yes, a dural arteriovenous fistula (dAVF) can cause a relative afferent pupillary defect (RAPD). This occurs when the dAVF affects the blood supply to the optic nerve or causes increased pressure within the eye. A dAVF is an abnormal connection between arteries and veins within the dura mater covering the brain, which can lead to altered blood flow patterns. When a dAVF occurs near the optic pathways, it can compromise blood flow to the optic nerve through various mechanisms including venous hypertension, arterial steal phenomenon, or direct compression. The resulting optic nerve dysfunction manifests as a RAPD, where the affected pupil constricts less vigorously when light is shined into it compared to the unaffected eye. This pupillary response abnormality indicates asymmetric optic nerve function and is an important clinical sign that may help localize the pathology. Patients with dAVF-related RAPD may also experience other visual symptoms such as decreased visual acuity, visual field defects, or pulsatile tinnitus. Prompt neuroimaging with MRI/MRA or cerebral angiography is essential for diagnosis, as early intervention through endovascular embolization or surgical treatment of the dAVF can prevent permanent visual loss, as noted in studies such as 1.

Key Points to Consider

• A dAVF can cause RAPD by affecting the blood supply to the optic nerve or increasing pressure within the eye.
• The presence of a large RAPD should warrant a search for compressive optic neuropathy or other etiologies of visual impairment, as stated in 1.
• Pupillary evaluation in infants and children may be challenging due to frequent shifts in the patient’s fixation and focusing, as mentioned in 1.
• Early intervention through endovascular embolization or surgical treatment of the dAVF can prevent permanent visual loss, highlighting the importance of prompt diagnosis and treatment.

Diagnostic Approach

• Neuroimaging with MRI/MRA or cerebral angiography is essential for diagnosis.
• A comprehensive eye examination, including assessment of pupillary responses, visual acuity, and visual fields, is crucial in evaluating patients with suspected dAVF-related RAPD, as outlined in 1.

Treatment Options

• Endovascular embolization or surgical treatment of the dAVF can prevent permanent visual loss.
• The choice of treatment depends on the location and characteristics of the dAVF, as well as the patient's overall health status, as discussed in 1.

From the Research

Dural Arteriovenous Fistula and Relative Afferent Pupillary Defect (RAPD)

• A dural arteriovenous fistula (dAVF) is a vascular lesion with arteriovenous shunting that may cause various symptoms, including ocular symptoms such as proptosis and chemosis 2.
• The clinical characteristics of dAVFs can vary depending on the location and venous drainage pattern, with some patients experiencing more aggressive symptoms, including intracranial hemorrhage 2.
• While the studies reviewed do not directly address the relationship between dAVF and RAPD, they do suggest that dAVFs can cause a range of ocular symptoms, including vision loss and blindness 3, 2.
• In particular, one study noted that two patients with cavernous dAVFs became blind in one eye, demonstrating that the clinical course of dAVFs can be aggressive 2.
• Another study reported a minor complication of blurry vision attributed to posterior ischemic optic neuropathy after trans-ophthalmic artery embolization of a dAVF 3.
• These findings suggest that dAVFs can potentially cause RAPD, although the exact relationship between the two conditions is not explicitly stated in the reviewed studies 3, 2, 4.

Mechanism of RAPD in dAVF

• The mechanism of RAPD in dAVF is not clearly understood, but it may be related to the abnormal blood flow and venous drainage patterns associated with dAVFs 5, 6.
• The presence of cortical venous drainage and venous ectasia can contribute to the aggressiveness of the clinical course in dAVFs, and may potentially lead to RAPD 5, 2.
• Further studies are needed to fully understand the relationship between dAVF and RAPD, and to determine the optimal treatment approaches for patients with these conditions 3, 4.