Central Retinal Artery Occlusion in a Young Female with Fibromuscular Dysplasia

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Figure 2. Right Inferior altitudinal defect

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Figure 3. Right FFA: Early filling of vessels which were expected to be occluded

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Figure 4. Right FFA Contd

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There was no orbitocranial bruits, no lymphadenopathy. The oropharynx was normal, the carotids were pulsatile, non tender and there was no radio-popliteal delay. The fundi were examined under mydriasis. The upper temporal retina appeared pale and ischemic due to nerve fibre layer edema in the right eye (Figure 1). This corresponds to the inferior altitudinal Right field defect (Figure 2).

However, the Fundus Fluorescein angiography results were surprising. The vessels which were expected to be occluded, filled in first. Further, the break up of the dye appearance time in the early, mid and late venous phases was the earliest in the vessels involving the affected area. (Figure 3-Figure 8). This patient had a RIGHT Incomplete CRAO which could either be embolic or non embolic.

Looking at the clinical picture in our case the findings were attributed to embolus reorientation which occured while the artery possibly underwent a spasm (Figure 9). It is known in FMD there is involvement of vasa vasorum and the arteries could undergo spasm ^[1].

Figure 5. Right FFA Contd

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Figure 6. Right FFA Contd

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Figure 7. Right FFA Contd

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Figure 8. Comparison of the dye appearance on FFA: Early/ Mid / Late venous

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Magnetic resonance angiography of the carotids showed the typical “ String of beads sign”, bilaterally.

Other investigations including Transthoracic and Transoesophageal Echocardiogram were normal.

4. Discussion

FMD is a nonatherosclerotic, noninflammatory vascular disease that primarily affects women in the age group 20 to 60 years, however men and older individuals may also be affected ^[4].

Commonly known to occur in the renal and carotid arteries, it has been found to involve almost every artery in the body. There are, however, data to suggest that FMD is much more common than previously thought. It is estimated that the incidence in the general population is 2% to 3% ^[5].

The etiology is multifactorial including vessel wall ischemia, smoking, estrogens, environmental as well as genetic factors.The female to male ratio is 9:1 ^{[6, 7]}.

Histologically FMD may involve the tunica intima,tunica media, and adventitia. Involvement of the media is further classified into medial fibroplasia, perimedial fibroplasia,and medial hyperplasia. The commonest of these is Medial fibroplasia which occurs in 70% to 95% of cases. ^[8] It shows the classic “string-of-beads” appearance on angiography. Adventitial (periarterial) fibroplasia (<5 %) is the least common characterized by replacement of adventitial fibrous tissue by dense collagen ^[9].

Figure 9. Magnetic Resonance Angiography showing bilateral ‘ String of Beads’ sign

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Figure 10. Embolus reorientation

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