Special Systems



Figure 12-1
Ophthalmic artery vascular anatomy




  • OA passes into orbit through optic canal where it travels with the optic nerve


  • Gives off central retinal artery (first branch) and posterior ciliary arteries near the orbital apex


  • Central Retinal Artery: main artery supplying the retina; gives off terminal branches (end arteries) that can be visualized by ophthalmoscopy


  • Posterior Ciliary Arteries: pierce the sclera and supply the uvea, optic nerve





      Transient Monocular Blindness (TMB)






      • Transient retinal ischemia



        • Partial/complete dimming or obscuration of vision, lasting seconds to minutes, followed by total recovery


        • Commonly due to carotid disease



          • Retinal emboli



            • Thromboembolism (artery to artery or cardioembolic): pale white platelet plugs


            • Cholesterol (bright Hollenhorst plaques seen in central retinal artery)


          • Hypoperfusion – due to severe stenosis or occlusive disease leading to low retinal arterial pressure



            • Symptom onset is less rapid, and duration is longer than embolic TMB


            • Vision loss induced by situations that increase retinal oxygen demand (exposure to bright light)


            • Contrast acuity altered: bright objects appear brighter; darker objects more difficult to see


            • Symptoms more likely to recur


            • Provoked by systemic hypotension, venous hypertension , extracerebral steal


          • Either mechanism can lead to complete or partial vision loss of the ipsilateral eye


          • Associated with lower risk of future ipsilateral stroke than hemispheric TIA


        • Ophthalmic artery occlusion



          • Similar pathogenesis to ICA occlusion


          • Vision loss severe or permanent, with most patients having only residual trace light perception


          • Proximal OA occlusion may be asymptomatic due to ECA collateral flow


          • Clinical signs: opacified retina, faint or absent cherry red spot due to infarction of choroid, eye pain, pupillary dilation (concurrent ischemia to ciliary ganglion or iris sphincter), with chronic changes of optic atrophy and arterial attenuation


        • Central retinal artery occlusion (Fig. 12-2)

          A330798_1_En_12_Fig2_HTML.gif


          Figure 12-2
          Central retinal artery occlusion (left). Note the pale retina and cherry red spot. Hollenhorst plaque (right) in a patient with acute monocular vision loss and hyperlipidemia




          • Due to occlusion of central retinal artery from embolic obstruction, thrombosis or hemorrhage, inflammatory (GCA, PAN, Buergers), angiospasm, hypotension, glaucoma, APLS


          • Most common emboli are cholesterol, platelet-fibrin, and calcium


          • Clinical signs: nonreactive pupil to direct light, preserved consensual response, cherry red spot on macula, white ground glass appearance of retina, absent temporal artery pulse in GCA


          • Treatment: lie patient flat, digital globe massage +/− anterior paracentesis by ophthalmology, consider tPA , Diamox or mannitol to reduce intraocular pressure


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      Oct 7, 2017 | Posted by in NEUROLOGY | Comments Off on Special Systems

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