An 80-year-old lady develops CVA. She describes unrelenting pain on right side of the body as if somebody poured acid on her. Where is the lesion located?
First, I need to recall the different types of stroke and their effects. A stroke can be ischemic or hemorrhagic, but the key here is the symptom: burning pain on the right side. The description of the pain as "acid-like" suggests a sensory disturbance, possibly involving the thalamus or spinal pathways.
The thalamus is a major relay center for sensory information. The ventral posterolateral (VPL) nucleus of the thalamus is responsible for relaying sensory information from the body (except the face) to the sensory cortex. A lesion in the VPL nucleus would disrupt this pathway, leading to sensory deficits. Since the pain is on the right side, the lesion would be in the contralateral thalamus. So, a left thalamic lesion would cause right-sided sensory loss or pain.
Wait, but the question mentions a CVA. Strokes in the posterior cerebral artery (PCA) territory can affect the thalamus. The PCA supplies the thalamus, and a stroke here could lead to a thalamic lesion. The VPL nucleus is in the thalamus, so a lesion there would cause contralateral sensory loss. But the patient is experiencing pain, which is a part of the sensory system. Thalamic lesions can cause thalamic pain syndrome, characterized by burning, aching, or electric-like pain.
The other options might be related to different areas. For example, a lesion in the spinal cord would cause a different pattern. If the lesion were in the spinal cord's dorsal columns, it would affect proprioception and vibration sense, but the pain is more likely from spinothalamic tract damage. However, a spinal lesion would present with sensory loss below the level of the lesion, not the entire right side. If it's a peripheral nerve or dermatomal issue, the pattern would be more localized. But since the question is about a CVA, the lesion is in the CNS.
Another possibility is the sensory cortex. A lesion in the primary sensory cortex (postcentral gyrus) would cause contralateral sensory loss, but typically it's a loss rather than a specific type of pain. The thalamus is more involved in processing sensory signals, so a thalamic lesion could lead to the described pain.
So the correct answer is likely a left thalamic lesion, specifically in the VPL nucleus. The options would include other areas like the sensory cortex, spinal cord, or brainstem. The key differentiator here is the type of pain and the contralateral distribution, pointing to the thalamus.
**Core Concept**
This question tests the localization of CNS lesions causing sensory deficits after a cerebrovascular accident (CVA). The thalamus, particularly the **ventral posterolateral (VPL) nucleus**, is the key relay center for somatosensory information from the body to the cerebral cortex. Lesions here disrupt sensory processing, leading to contralateral sensory loss or dysaesthesia.
**Why the Correct Answer is Right**
The patient's **burning, acid