schermata-2017-01-21-alle-10-11-15

AMAUROSIS FUGAX

Amaurosis fugax (AF) is de ned as a transient monocular visual loss (TMVL) that lasts from seconds to minutes. Sometimes, but uncommonly, the episode may last for several hours. 1 The symptom is caused by ischemia in the retina, the choroid or the optic nerve.

2 The most common underlying mechanism

is an embolus from the ipsilateral carotid artery.3 It is not uncommon for patients suffering from TMVL, presumably caused by retinal ischemia, to show signs of acute brain infarcts using neuroimaging.4 Patients with AF are therefore at risk of having a cerebral transient ischemic attack, retinal artery occlusion or stroke.2 AF is considered a form of transient ischemic attack.5

Carotid disease is one of the major causes of stroke in the world, and stroke itself is one of the most common causes of mortality and severe disability in adults.6 Giant cell arteritis (GCA) is another cause of AF, and it is hence important to analyze in am- matory parameters such as sedimentation rate (SR) and C-reactive protein (CRP) to minimize the risk of permanent visual loss.3

Ultrasound (US) of the carotid arteries is usually performed to detect possible stenoses of the carotids. If the patient has a signi cant carotid stenosis, he or she may be eligible for carotid endarterectomy, which is the most effective stroke prevention method in symptomatic patients.7

The prevalence of significant carotid stenosis reported in this study was 18.9%. Little is known on the prevalence of carotid stenosis in patients with AF. However, compared to studies investigating the prevalence of carotid stenosis in patients with ischemic cerebral stroke, in which numbers of 5%–12% have been reported,9,10 this is a fairly high number. The most common etiology behind AF is an embolus from the ipsilateral carotid artery, ie, a vascular disorder.11 It is thus not surprising that the present study found an association between carotid stenosis and male sex, smoking and diabetes, which are known risk factors for cardiovascular disease.12 In addi- tion, of the ve patients with a history of vasculitis, three had a signi cant carotid stenosis. Large cell vasculitis, including GCA, is a chronic in ammatory disease that results in luminal

stenosis and/or vessel occlusion in the aorta and its primary branches.13 It is hence not surprising to nd carotid stenosis in patients with vasculitis, and the relative contribution of atherosclerosis and arteritis in these patients may be dif- cult to distinguish. Since GCA is a disease that may lead to permanent visual loss, it is recommended to determine in ammatory parameters (SR and/or CRP) in all patients seeking care for AF symptoms.3 In the present study, a blood test for SR and/or CRP was done only in 69.0% of the cases. The low number may be due to underreporting, a negative consequence of the retrospective design of the study.

The duration of the AF episode did not differ between patients with and without carotid stenosis. Median time of the AF symptoms was between 1 and 9 minutes in both the groups, which is similar to what has previously been reported by Biousse and Trobe.2 It is known that visual loss can be either complete or partial, as seen in the present study. It has also been described that if the choroidal circulation is affected, the visual eld loss may be patchy.14 In this study, six of the patients had persistent partial or complete visual eld loss still after 24 hours. Of these patients, one was shown to have a cerebral aneurysm. One had hemianopsia due to a stroke and two were later diagnosed as having central retinal artery occlusion. The symptoms of one patient were eventually considered to be caused by vitreous detachment and for one patient no explanation was found to the persistent visual loss. We included these patients in the study despite the permanent/long duration of the visual loss since they were initially registered as AF with the ICD-10 code G45.3.

A majority of the patients (81.4%) were examined by an ophthalmologist prior to the US. Most ophthalmolo- gists are thus regularly exposed to this category of patients. It has been shown that the number of patients who consult an ophthalmologist because of symptoms related to carotid artery stenosis has increased in recent years.15 However, findings during an eye examination are usually rare, providing poor guidance in diagnostic decision-making. In the present study, only 1.7% of the patients exhibited visible retinal artery emboli at examination and there was no sig- ni cant difference between patients with or without carotid stenosis. This low number may suggest that the patients need not see an ophthalmologist as the primary consultant. A limitation of the study, which is related to the retrospective design, is the lack of information on the number of patients contacting a doctor for TMVL who were not diagnosed as AF. It is probable that ophthalmologists are better than other specialists at nding alternative causes of transient visual disturbances such as migraine and vitreous detachment.

Consulting an ophthalmologist as the rst medical contact could thus avoid unnecessary further examinations and/or admission to hospital.

Conclusion

In summary, the present study shows a high prevalence of carotid stenosis in patients diagnosed with AF. An association with known vascular risk factors is con rmed as well as with previous/current vasculitis.

 

 

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