1. Is there evidence of peripheral nervous system involvement in this case, and, if so, what is the level of that involvement?
No
2. Is the patient’s left upper limb weakness of the upper motor neuron or lower motor neuron type?
This is difficult to determine. The decrease in muscle tone suggests a lower motor neuron (LMN) process. However, the deep tendon reflexes are brisker in the left upper limb, suggesting an upper motor neuron (UMN) process.
3. Is there evidence of spinal cord involvement in this case and, if so, at what level?
Unlikely. A spinal cord lesion would have to be located in the left lateral funiculus of the cervical cord, involving the lateral corticospinal tract but sparing the spinothalamic tract. These two structures are both in the vascular territory of the anterior spinal artery; so it is unlikely that one would be involved and not the other.
If this were a subacute or chronic process, cervical spondylosis or a mass lesion might cause a LMN or mixed process in the LUE and an UMN process in the LLE. Could this be an acute demyelinating process involving mainly the LUE fibers in the lateral corticospinal tract? Maybe.
4. Could this patient’s signs and symptoms be localized to any other place in the central nervous system? If so, what is the precise localization of his neurologic lesion, including the side of involvement? Indicate the specific structure(s) involved by this lesion.
Yes. A relatively isolated left upper limb weakness could be caused by a lesion involving the hand and upper limb part of the right precentral gyrus. Such a lesion would interrupt the origin of the corticospinal fibers to the contralateral upper limb (review the “motor homunculus” on the primary motor cortex [area 4]).
5. In general, what type of pathologic process is involved in this case? If vascular, what vessel is involved?
Vascular – This patient sustained a “watershed infarct” in primarily the hand and upper limb region of the right precentral gyrus and adjacent premotor area (area 6). This region of the cerebral cortex derives its arterial supply from the terminal cortical branches of the anterior cerebral artery and the middle cerebral artery. In this case, the cause of the “watershed infarct” was an occlusion of the right internal carotid artery. The etiology of the stroke was not immediately apparent, since the patient had no vascular risk factors.
6. What diagnostic procedure(s) would you undertake at this point?
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