Symptoms to Diagnosis

Acute monocular vision loss: Don’t lose sight of the differential

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CENTRAL RETINAL ARTERY OCCLUSION: NONARTERITIC VS ARTERITIC CAUSES

3. Which of the following is least useful to differentiate arteritic from nonarteritic causes of central retinal artery occlusion?

  • Finding emboli in the retinal vasculature on funduscopy
  • Temporal artery biopsy
  • Measuring the C-reactive protein level and the erythrocyte sedimentation rate
  • Echocardiography
  • Positron-emission tomography (PET)
  • Retinal fluorescein angiography

In patients diagnosed with central retinal artery occlusion, the next step is to differentiate between nonarteritic and arteritic causes, since separating them has therapeutic relevance.

The carotid artery is the main culprit for embolic disease affecting the central retinal artery, leading to the nonarteritic subtype. Thus, evaluation of acute retinal ischemia secondary to nonarteritic central retinal artery occlusion is similar to the evaluation of patients with an acute cerebral stroke.4 Studies have shown that 25% of patients diagnosed with central retinal artery occlusion have an additional ischemic insult in the cerebrovascular system, and these patients are at high risk of recurrent ocular or cerebral infarction. Workup includes diffusion-weighted MRI, angiography, echocardiography, and telemetry.5

Arteritic central retinal artery occlusion is most often caused by giant cell arteritis. The American College of Rheumatology classification criteria for giant cell arteritis include 3 of the following 5:

  • Age 50 or older
  • New onset of localized headache
  • Temporal artery tenderness or decreased temporal artery pulse
  • Erythrocyte sedimentation rate 50 mm/hour or greater
  • Positive biopsy findings.6

Temporal artery biopsy is the gold standard for the diagnosis of giant cell arteritis and should be done whenever the disease is suspected.7,8 However, the test is invasive and imperfect, as a negative result does not completely rule out giant cell arteritis.9

Although a unilateral temporal artery biopsy can be falsely negative, several studies evaluating the efficacy of bilateral biopsies did not show significant improvement in the diagnostic yield.10,11

Ophthalmic fluorescein angiography is another helpful test for distinguishing nonarteritic from arteritic central retinal artery occlusion.12 Involvement of the posterior ciliary arteries usually occurs in giant cell arteritis, and this leads to choroidal malperfusion with or without retinal involvement. The optic nerve may also be infarcted by closure of the paraoptic vessels fed by the posterior ciliary vessels.12,13 Such involvement of multiple vessels would not be typical with nonarteritic central retinal artery occlusion. Thus, this finding is helpful in making the final diagnosis along with supplying possible prognostic information.13

PET-CT is emerging as a test for early inflammation in extracranial disease, but its utility for diagnosing intracranial disease is limited by high uptake of the tracer fluoro­deoxyglucose by the brain and low resolution.14 Currently, it has no established role in the evaluation of patients with central retinal artery occlusion and would have no utility in differentiating arteritic vs nonarteritic causes of central retinal artery occlusion.

If giant cell arteritis is suspected, it is essential to start intravenous pulse-dose methyl­prednisolone early to prevent further vision loss in the contralateral eye. Treatment should not be delayed for invasive testing or temporal artery biopsy. Improvement in headache, jaw claudication, or scalp tenderness once steroids are initiated also helps support the diagnosis of giant cell arteritis.7

Unfortunately, visual symptoms may be irreversible despite treatment.

Our patient’s central retinal artery occlusion

This case highlights how difficult it is in practice to distinguish nonarteritic from arteritic central retinal artery occlusion.

Our patient had numerous cardiovascular risk factors, including known carotid and coronary artery disease, favoring a nonarteritic diagnosis.

On the other hand, his elevated inflammatory markers suggested an underlying inflammatory response. He lacked the characteristic headache and other systemic signs of giant cell arteritis, but this has been described in about 25% of patients.15 If emboli are seen on funduscopy, further workup for arteritic central retinal artery occlusion is not warranted, but emboli are not always present. Then again, absence of posterior ciliary artery involvement on fluorescein angiography pointed away from giant cell arteritis.

CASE CONTINUED: FINAL DIAGNOSIS

Biopsy of the left temporal artery showed intimal thickening with focal destruction of the internal elastic lamina by dystrophic calcification with no evidence of inflammatory infiltrates, giant cells, or granulomata in the adventitia, media, or intima. Based on the results of biopsy study and fluorescein angiography, we concluded that this was nonarteritic central retinal artery occlusion related to atherosclerotic disease.

Methylprednisolone was discontinued. The patient was discharged on aspirin, losartan, furosemide, amlodipine, and high-dose atorvastatin for standard stroke prevention. He was followed by the medical team and the ophthalmology department. At 6 weeks, there was only marginal improvement in the visual acuity of the left eye.

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