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CLINICAL CASE | Middle Cerebral Artery Occlusion, Right Side Paralysis, and Global Aphasia
A 57-year-old male was brought to the emergency room 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 elicits a withdrawal—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 MRI. The large white territory corresponds to the infarcted region on the left side of the cerebral hemisphere. Figure 3–18B is a magnetic resonance angiogram (MRA), showing the distribution of arteries with flowing blood. Note the asymmetry in the MRA, 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. The patient's lesion is large. Occlusion of which cerebral artery produced the lesion, and what was the contribution of its deep and superficial branches?
2. Damage to what single key structure could produce the major limb and facial motor signs?
Key neurological signs and corresponding damaged brain structures Paralyzed right arm and leg The corticospinal tract, which is key to controlling the contralateral arm and leg, descends subcortically and then travels in the posterior limb of the internal capsule (see Figure 2–17). This subcortical white matter and the more dorsal parts of the posterior limb of the internal capsule 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 is supplied by superficial branches of the middle cerebral artery. By contrast, the infarction spares the leg area of motor cortex (see Figure 10–8). Whereas the descending axons are destroyed when they are in the internal capsule, as we shall see in later chapters sparing of the cortex may help during neurorehabilitation.
Right lower facial droop The corticobulbar tract controls facial muscles. This is the component of the descending cortical motor pathway that controls cranial motor nuclei in the brain stem. (Bulb is an archaic term to describe the lower brain stem.) The tract travels subcortically from lateral part of the precentral gyrus (face area of motor cortex) to the genu and posterior limb of the internal capsule, rostral to the corticospinal tract axons. The subcortical white matter and dorsal parts of the internal capsule are largely supplied by the deep branches of the middle cerebral artery. ...