NBME 21 Left thalamus (NBME Answers)

Retired NBME 21 Answers

nbme21/Block 4/Question#49 (reveal difficulty score)
A 76-year-old man comes to the physician ...
Left thalamus 🔍 / 📺 / 🌳 / 📖
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submitted by ∗tinydoc(276)

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Neuropathic Pain after stroke is central Post stroke pain Syndrome

caused by contralateral thalamic lesions

Pg. 504 FA19

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chandlerbas agreed! more specifically damage to the VPL +6

docshrek Pg. 403 FA 19. +

baja_blast Both commenters above got the page wrong; it's FA 2019 p. 503. +5

teepot123 looooool ^ what were the odd of both being wrong +

mumenrider4ever Pg. 515 FA 2020 +

bbr 503 in 2019 Interesting that its seen in 10% of strokes. Starts with allodynia ---> neuropathic pain. +

skonys Underlying Mech From Wiki: The thalamus is generally believed to relay sensory information between a variety of subcortical areas and the cerebral cortex. It is known that sensory information from environmental stimuli travels to the thalamus for processing and then to the somatosensory cortex for interpretation. The final product of this communication is the ability to see, hear or feel something as interpreted by the brain. Dejerine–Roussy syndrome (Thalamic Pain Syndrome) most often compromises tactile sensation. Therefore, the damage in the thalamus causes miscommunication between the afferent pathway and the cortex of the brain, changing what or how one feels +1

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submitted by ∗neonem(630)

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I think you can know that this is a thalamic stroke rather than cortical because a cortical stroke occurring only in the postcentral gyrus (primary sensory cortex) and involving the entire homunculus without affecting the nearby precentral gyrus (primary motor cortex) is very unlikely.

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sahusema Ya I think this question is trying to test your knowledge between a cortical lesion and a subcortical lesion. +1

cienfuegos Central Stroke Syndrome: Neuropathic pain due to thalamic lesions. Initial paresthesias followed in weeks to months by allodynia (ordinarily painless stimuli cause pain) and dysesthesia on the contralateral side. Occurs in 10% of stroke patients. FA 2018 499 +4

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submitted by ∗an1(114)

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I had no idea this was central Stroke Syndrome. But got it right with this logic. Vibration (Posterior column) and pain (spinothalamic) both ultimately synapse in the VPL thalamus. Symptoms on the right side means that the lesion is contralateral in the brain due to decussation rules. so Left thalamus was the origin. Discussed in table FA'18 page 493

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