Clinical Pathways in Neuro-ophthalmology : An ... - E-Lib FK UWKS

172 Clinical Pathways in Neuro-Ophthalmology, second edition
of transient visual loss, but more often attacks of TVL with carotid disease last 2 to 15
minutes (see below).
Patients with transient visual obscurations first require ophthalmologic examination.
If papilledema is evident (Chapter 7), these patients must have an MRI scan of the brain.
If this study is normal, a spinal tap is indicated to investigate the possibility of infection
or pseudotumor cerebri (idiopathic intracranial hypertension). Patients with drusen or
other optic disc anomalies causing monocular TVL may require no further evaluation. If
there are signs of an optic neuropathy on the side of the TVL (e.g., relative afferent
pupillary defect, ipsilateral swollen or atrophic optic nerve, etc.), then MRI with
attention to the orbit is warranted to evaluate a compressive lesion. Patients without
apparent disc abnormalities should be screened for carotid atherosclerotic disease or
other sources of emboli (see below). In selected cases, MRI should be performed to
investigate the possibility of a structural brain lesion such as optic nerve sheath
meningioma.
Do the Episodes of Monocular TVL Last
Minutes?
Monocular TVL lasting 5 to 60 minutes (usually 2 to 30 minutes) is strongly suggestive
of thromboembolic disease. Retinal emboli may arise from the aorta (Romano, 1998), the
carotid artery, or the heart. Patients often describe the TVL as a veil or shade descending
or ascending over a portion of their visual field. Other patients complain of patchy
visual loss (‘‘Swiss cheese’’ pattern) or peripheral constriction with central visual
sparing (Bruno, 1990). Some episodes of monocular TVL are accompanied by a
sensation of color or other photopsias. These may superficially be similar to migraine,
consisting of showers of stationary flecks of light that disperse quickly (Bruno, 1990;
Goodwin, 1987; Pessin, 1977). Most episodes of embolic monocular TVL last 2 to 30
minutes. Marshall and Meadows found that in 51 of 67 patients (76%) episodes lasted 30
minutes or less, with 29 patients (43%) experiencing episodes lasting 5 minutes or less
(Marshall, 1968). Pessin et al noted that attacks lasted less than 15 minutes in 30 of 33
patients, and in 14 patients (42%) the episodes lasted 5 minutes or less (Pessin, 1977).
Among 35 patients evaluated by Goodwin et al, 22 patients (63%) had attacks lasting 5
minutes or less, 8 (23%) had episodes lasting 6 to 15 minutes, and 6 patients (17%) had
episodes lasting more than 15 minutes (Goodwin, 1987). Episodes of monocular TVL
due to thromboembolic disease rarely last several hours.
Patients with thromboembolic disease may demonstrate emboli within the retinal
vessels. Emboli may be composed of clotted blood, fibrin, platelets, atheromatous tissue,
white cells, calcium, infectious organisms (septic emboli), air, fat, tumor cells, amniotic
fluid, or foreign materials (e.g., talc, artificial valve material, catheters, silicone,
cornstarch, mercury, corticosteroids). The most common types of emboli seen in
atherosclerotic disease of the aorta=carotid arteries or cardiac disease include the
following:
1. Cholesterol emboli (Hollenhorst plaques) are bright, glistening, yellow or coppercolored
fragments, most often seen in peripheral arterioles in the temporal fundus.
These emboli most often arise from atheromatous plaques in the aorta or carotid
bifurcation.