Case Study

Case Study A 77-year-old woman was cooking in the kitchen when she collapsed onto the floor.
Her daughter called an ambulance and the woman was taken to the emergency room. She had suffered a stroke, and slowly regained consciousness over the next two days. However, when she woke up, she had the following signs and symptoms:
- paralysis of the right face and arm - loss of sensation to touch on the skin of the right face and arm - inability to answer questions but ability to understand what was said to her - ability to write down her thoughts more easily than to speak them Based upon the patient's symptoms, which cerebral artery was blocked? (Be Specific
Answer: The loss of all sensation on the right face and arm, coupled with the paralysis of muscles in these regions suggests that this woman suffered damage to the lateral portions of her left frontal and parietal lobes. Specifically, damage to the face and arm regions of the left somatosensory and primary motor cortices would cause these deficits. Damage on the left side of her brain causes right-sided symptoms since the motor and sensory tracts cross the mid-line as they travel between the cerebrum and the spinal cord. The language disorder that this patient has is called Broca's (expressive) aphasia, and it may result from damage to the dominant Broca's motor speech area, a control center that sits just anterior to the face portion of the primary motor cortex in the left frontal lobe. The artery that supplies blood to these regions is the superior division of the left middle cerebral artery. Blockage of this artery by a thrombus or embolism could cause all of this patient's signs and symptoms.
Damage to other areas of the patient's nervous system would not create this specific collection of signs and symptoms. For example, damage to the underlying left internal capsule and thalamus, or to the left brainstem, may cause sensory and motor loss, but the loss is usually more diffusely spread throughout the body in such cases and is not usually associated with Broca's aphasia. Damage further down in the spinal cord would preserve sensory and motor function in the head. Thus, the single most likely event causing her illness is blockage of the superior division of the left middle cerebral artery.
Why was she paralyzed in the right face and arm?
The patient's inability to voluntarily move her right face and arm is due to the damage to the face and arm portion of her left primary motor cortex, an area that lies just anterior to the central sulcus in the posterior portion of the frontal lobe. The primary motor cortex normally controls voluntary movements of skeletal muscles by virtue of its large neurons (or Betz cells) whose axons project down through the corticospinal tract (pyramidal tract) to interneurons and lower motor neurons in the spinal cord. The type of paralysis that typically results from cerebral cortex damage is a spastic paralysis. Interestingly, lower mammals who have had just the primary motor cortex destroyed end up with flaccid paralysis, while those whose neighboring cortical areas are damaged as well end up with spastic paralysis.
It is believed that, in humans, damage to the primary cortex's neighboring, non-pyramidal, cortical areas removes their normally inhibitory influence on reticular and vestibular nuclei in the brainstem, which, in turn, causes these brainstem nuclei to fire off inappropriately excessive excitatory signals through the reticulo- and vestibulospinal tracts to lower motor control centers in the spinal cord. This presumably causes excessive facilitation of lower motor neurons and a spastic paralysis.
Was this woman's dominant or nondominant hemisphere damaged? While most functional regions of the cerebral cortex are found in both the right and left cerebrum, there is some division of labor between the cerebral hemispheres. For example, the dominant hemisphere, which is the left hemisphere in over 90% of individuals, controls the fine dexterity of the dominant hand, which is why over 90% of the population is right-handed (recall that the descending motor tracts cross in the mid-line on their way to the spinal cord). The dominant area is also where the Wernicke's and Broca's language centers are located. The non-dominant cerebral hemisphere seems to play a role in 3dimensional, spatial orientation tasks. Since this patient suffered from Broca's aphasia, we can assume that her dominant cerebral hemisphere was damaged.

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Case Study A 77-year-old woman was cooking in the kitchen when she collapsed onto the floor.

Why was she paralyzed in the right face and arm?

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