Bilateral blindness top of the basilar artery

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Sudden cortical blindness is a rare symptom of TIA or stroke and has been explained by an occlusion of the "top of the basilar artery" at the origin of the posterior cerebral arteries [11]. The visual field defects may be

Top Basilar Artery Stroke

Figure 9.4. "Blind sight". A 65-year-old patient with known Parkinson's disease and vascular risk factors (diabetes mellitus, hypertension, obesity and smoking) suddenly lost muscle tone and consciousness. On admission he was awake, responded to verbalcommands and was partially oriented. Pupils were mid-dilated, response to light was reduced. He reported not seeing anything with either eye. There was no weakness of the limbs. Although without conscious visualperception he was able to unconsciously prevent himself from bumping into objects when walking. When showing him different numbers of fingers he mentioned not seeing the fingers but his performance of rating the number of presented fingers was much above chance. CCT showed a bilateralinfarction in the territory of the posterior cerebralartery with hemorrhage on the right side. The primary visualcortex of each side was damaged.

Figure 9.4. "Blind sight". A 65-year-old patient with known Parkinson's disease and vascular risk factors (diabetes mellitus, hypertension, obesity and smoking) suddenly lost muscle tone and consciousness. On admission he was awake, responded to verbalcommands and was partially oriented. Pupils were mid-dilated, response to light was reduced. He reported not seeing anything with either eye. There was no weakness of the limbs. Although without conscious visualperception he was able to unconsciously prevent himself from bumping into objects when walking. When showing him different numbers of fingers he mentioned not seeing the fingers but his performance of rating the number of presented fingers was much above chance. CCT showed a bilateralinfarction in the territory of the posterior cerebralartery with hemorrhage on the right side. The primary visualcortex of each side was damaged.

quite asymmetric and variable. Symptoms may be transient (TIA) or persisting. Even when severe cortical blindness is present, patients may retain some ability to avoid bumping into objects and may blink to visual threat. This so-called blind sight is probably explained by some sparing of the visual cortex and by preservation of the so-called second visual system, which is composed of the superior colliculi and their projections to peristriate cortex (Figure 9.4). Embolism from the heart or the proximal vertebrobasilar artery is the cause of this sign [12]. Other symptoms of bilateral ischemia in the territory of the PCA may be: memory loss, usually involving both anterograde and retrograde amnesia, and agitated delirium. In cases of persistent amnesia, bilateral infarction of the mesial temporal lobe was described [8].

Bilateral blindness can be due to occlusion of the basilar artery at the bifurcation to the posterior cerebral arteries.

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