CLINICAL CASE | Right Side Paralysis, and Global Aphasia
A 57-year-old right-handed man was brought to the emergency department after being discovered by his wife to be unable to move his right arm or leg. On testing, his right upper limb strength was 0/5 and the lower limb, 1/5. The left limbs had normal strength and spontaneous movements. In addition, there was drooping of the right side of the lower face. Pinch of the nail beds—a mildly noxious stimulus that normally elicits a withdrawal response—revealed withdrawal of the left arm but no response for the right arm. The patient was able to look to the left but not the right; there were no saccadic (rapid, conjugate) eye movements to the right. The patient was unable to speak and only followed simple commands.
Figure 3–1A shows a horizontal T1-weighted MRI. The large white territory corresponds to the infarcted region on the left side of the cerebral hemisphere. Figure 3–1B is a magnetic resonance angiogram (MRA), showing the distribution of arteries with flowing blood. The MRA is asymmetric, with an absence of middle cerebral artery perfusion on the left side.
Answer the following questions based on your readings of the case report and this chapter.
1. Occlusion of which cerebral artery produced the lesion, and what were the differential contributions of its deep and superficial branches of the occluded artery?
2. Damage to what single key structure could produce the major limb and facial motor signs?
3. Why is there loss of lower, but not upper, facial muscle control?
4. Why is the patient neither able to follow verbal commands nor to speak?
5. Why can the patient look to the left but not to the right? Does this mean that the right eye is paralyzed?
Conclusion: The patient had an occlusion of the middle cerebral artery, close to where the artery branches from the internal carotid artery. As a consequence, the brain regions supplied by the artery are deprived of their blood supply and the tissues became infarcted. Both the superficial and the deep branches of the artery are affected. This, in turn, affects both cortical areas supplied by the artery and parts of the basal ganglia. However, the thalamus is not affected because it receives blood from the posterior cerebral artery. Key neurological signs and corresponding damaged brain structures Paralyzed right arm and leg
The corticospinal tract is key to moving the contralateral arm and leg voluntarily. Axons of the corticospinal tract descend subcortically and then travel in the posterior limb of the internal capsule (see Figure 2–16). The internal capsule and the more dorsal parts of the posterior limb are supplied by deep branches of the middle cerebral artery. The infarction also would have destroyed part of the lateral precentral gyrus, where the corticospinal tract to the arm segments of the spinal cord originates. This cortical area is supplied by superficial branches of the middle cerebral artery. By contrast, ...