When you see a patient with a massive stroke, and now knowing that most massive strokes occur in the internal capsule from the middle cerebral artery, what does the information you’ve learned this week tell you about lack of involvement of the face, swallowing, eating, etc.?
The correct answer and explanation is:
Correct Answer:
If a patient has had a massive stroke involving the internal capsule from the middle cerebral artery (MCA) but shows a lack of involvement of the face, swallowing, or eating, this suggests that the stroke may not have affected the corticobulbar tract, or that the lesion was not extensive enough to disrupt the fibers controlling cranial nerves involved in these functions.
Explanation (Approx. 300 words):
The internal capsule is a white matter structure in the brain through which motor and sensory pathways pass. It is supplied primarily by the lenticulostriate branches of the middle cerebral artery (MCA). A “massive stroke” in this area usually affects the posterior limb of the internal capsule, which carries corticospinal and corticobulbar fibers.
The corticospinal tract is responsible for voluntary movement of the limbs and trunk, while the corticobulbar tract transmits motor signals from the brain to the cranial nerves, which control the muscles of the face, tongue, swallowing, and speech. Therefore, damage to the posterior limb often results in contralateral hemiparesis, typically affecting the face, arm, and leg.
However, if a patient presents with weakness in the arm and leg but no facial droop, no difficulty swallowing (dysphagia), and no speech problems (dysarthria or aphasia), it suggests that the corticobulbar tract may be spared. This could mean that the infarct is localized more to the posterior part of the internal capsule, affecting primarily corticospinal fibers and sparing anterior regions where corticobulbar fibers run.
Alternatively, some fibers for face and swallowing muscles have bilateral innervation, meaning both hemispheres contribute input. Therefore, even with a unilateral stroke, there might be sufficient function from the unaffected hemisphere to maintain these functions.
In summary, the absence of facial and swallowing involvement in a massive internal capsule stroke indicates a more selective injury, sparing the corticobulbar tract and/or taking advantage of bilateral cranial nerve innervation. This anatomical and vascular understanding is crucial for accurate neuro-assessment and prognosis.