Case of the Month

Edited by Robert N. Johnson, MD

Case History

A 15 year-old girl was referred for evaluation of a retinal lesion in the right eye. She has had no vision in the right eye since she can remember. She also complained of gradually decreasing vision in her left eye for several years. There was no associated pain or other ocular symptoms. Her past medical history is only significant for asthma. Family and social history were noncontributory.

On examination, best-corrected visual acuity was NLP in the right eye and 20/160 in the left eye. Intraocular pressure and anterior segment examinations were normal in both eyes. Posterior segment examination of the right eye showed a large arteriovenous malformation with massive dilation and tortuosity of the involved vessels (Figure 1A). There was perivascular sheathing in the inferotemporal periphery, as seen on wide-field photography (Figure 1B). The left fundus appeared completely normal (Figure 1C). Wide-field fluorescein angiography (FA) of the right eye revealed direct and rapid transit of dye through the anomalous vessels in early frames along with peripheral nonperfusion temporally (Figure 2A) with scattered areas of vascular leakage from the neighboring microvasculature in late frames (Figure 2B). Wide-field FA of the left eye was normal (Figure 2C). Fundus autofluorescence and indocyanine green angiography were unremarkable in both eyes. Optical coherence tomography (OCT) of the right eye showed intraretinal and subretinal fluid with prominent, dilated vasculature (Figure 3A). OCT of the left eye was normal.

Differential Diagnosis

The differential diagnosis for diffuse retinal arteriovenous malformations is small, as these lesions have a rather characteristic appearance. However, other vasucular anomalies such as congenital retinal macrovessels, retinal capillary hemangiomas, and retinal cavernous hemangiomas can occasionally have similar characteristics and should be excluded. The diagnosis in our case was a retinal arteriovenous malformation of the right eye.

Additional Case History

Magnetic resonance imaging of the brain, face, orbit, and neck and magnetic resonance angiography of the head were performed to evaluate for associated midbrain, mandibular, and orbital arteriovenous malformations. It was also ordered to evaluate for a possible neurological cause of decreased vision in the left eye. All of the neuroimaging was negative. Given that there was only an isolated retinal AVM without systemic involvement, observation was recommended for our patient. The cause of her decreased vision in the left eye is not known.

Discussion

Retinal arteriovenous malformation (AVM) is a rare congenital, non-hereditary, and sporadic vascular anomaly that tends to arise from the optic nerve unilaterally and extend into the macula or periphery.¹ Archer et al subdivided these anomalies into different groups, depending on their severity. Group 1 consists of retinal arteriovenous communication with interposition of an arteriolar or abnormal capillary plexus. Group 2 has single or multiple direct arteriovenous communications without the interposition of capillary or arteriolar elements. Group 3 has extensive and complex arteriovenous communication with large caliber vessels and without the interposition of a capillary plexus. Visual acuity is usually poor with some eyes being blind since birth, and these patients are most likely to have associated periorbital or cerebral arteriovenous malformations.² These associated systemic AVMs, often in the midbrain, mandible, or orbit, occur as part of Wyburn-Mason syndrome.³ Our patient had an isolated group 3 retinal AVM with no light perception vision.

Mild retinal AVMs usually retain good vision. In more severe cases, vision loss may occur secondary to a number of ocular complications, including intraretinal or vitreous hemorrhage, exudation, retinal artery occlusion, retinal vein occlusion, mechanical compression of the optic nerve, or neovascular glaucoma.¹ In most AVMs, fluorescein angiography shows a short dye transit time without extravascular leakage from the AVM itself. However, there may be leakage from the neighboring vasculature as these vessels can be altered by the AVM. While treatment of the AVM is usually not needed, photocoagulation may be helpful in cases that develop exudative maculopathy.¹

One potential complication that our patient may have had was a retinal vein occlusion, as evidenced by the perivascular sheathing in the inferotemporal periphery and temporal nonperfusion as seen on wide-field fluorescein angiography. It is uncertain if a CRVO caused loss of all vision in our patient or rather was an incidental finding. Schatz et al reported 2 cases of retinal AVMs that developed central retinal vein occlusions. They proposed that when the venous portion of AVMs are subjected to turbulent flow, high intravascular volume, and higher arteriolar pressure, vessel wall damage can occur leading to thrombosis and occlusion. In addition, they also suggested that compression of the central retinal vein by the mass effect of the AVM on the optic nerve could lead to turbulence and eventual thrombosis.⁴

In patients with retinal AVMs, neuroimaging with magnetic resonance imaging of the brain and orbit and magnetic resonance angiography should be considered because of the risk of associated systemic AVMs, which are typically in the midbrain, mandible, orbit, or facial skin. Patients with retinal and systemic AVMs are defined as having Wyburn-Mason syndrome. Intracranial AVMs can cause vision loss secondary to strokes or disruption of the anterior visual pathway, as these AVMs tend to be located in the distribution of the optic tracts and optic radiations. These cerebral AVMs have limited neoplastic potential, however, they may change in time due to hemodynamic factors. This may lead to spontaneous thrombosis or hemorrhage with significant morbitiy.⁵

Our patient had a Group 3 retinal arteriovenous malformation with NLP vision in her right eye but without any other associated AVMs. As Archer et al had described, most Group 3 retinal AVMs occur as part of Wyburn-Mason syndrome, unlike our case.² In a large review of patients with retinal AVMs described in the literature, 57 of 121 patients had just isolated retinal AVMs. Of these 57 patients, only 4 (7%) had significant vision loss, with NLP or LP vision.³ Given these trends in the literature, our case’s presentation of having an isolated Group 3 retinal AVM with NLP vision is a rare combination of characteristics. As stated earlier, a number of ocular complications may occur from retinal AVMs, but the cause of NLP vision in patients with severe retinal AVMs is still unclear, as is the case with our patient.

References

1. Agarwal A. Gass’ Atlas of Macular Diseases – 5th ed. Philadelphia: Elsevier, 2012:442-6.
2. Archer DB, Deutman A, Ernest JT, Krill AE. Arteriovenous communications of the retina. Am J Ophthalmol. 1973;75:224-41.
3. Schmidt D, Pache M, Schumacher M. The congenital unilateral retinocephalic vascular malformation syndrome (Bonnet-Dechaume-Blanc syndrome or Wyburn-Mason syndrome): review of the literature. Surv Ophthalmol. 2008;53:227-49.
4. Schatz H, Chang LF, Ober RR, McDonald HR, Johnson RN. Central retinal vein occlusion associated with retinal arteriovenous malformation. Ophthalmology. 1993;100:24-30.
5. Dayani PN, Sadun AA. A case report of Wyburn-Mason syndrome and review of the literature. Neuroradiology. 2007;49:445-56.