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HIGHER FUNCTIONS

A 67-year-old man suffers an infarct of the geniculothalamic branch of the posterior cerebral artery. In particular, there is involvement of nuclei of the posterior thalamus. Which of the following is the most likely effect of such an infarct?

a. Emotional volatility in response to an innocuous statement

b. Short-term memory loss that occurs about 1 week following the infarct

c. Long-term memory loss that occurs about 1 month following the infarct

d. Severe pain triggered by cutaneous stimuli applied to the patient

e. Spastic paralysis of the contralateral limbs

The answer is D. (Afifi, pp 163-168. Ropper, pp 138, 159-160. Siegel and Sapru, pp 265-266, 471-472.) The infarct caused damage to posterior thalamic nuclei, which may also include VPL and VPM (Dejerine Roussy disease). When these structures are damaged, a disorder referred to as thalamic pain can ensue. In this condition, light cutaneous stimulation is sufficient to produce severe pain. The nuclei situated in this region project principally to the parietal and occipital lobes and play a role in the regulation of pain (although the precise mechanisms remain unknown). The projections to the occipital cortex relate to visual functions of the neurons of the posterior thalamus that are unrelated to pain. The other processes offered as alternate choices have not been shown to be related to functions of the posterior thalamus.

A 67-year-old man suffers an infarct of the geniculothalamic branch of the posterior cerebral artery. In particular, there is involvement of nuclei of the posterior thalamus. Which of the following regions would the neurons affected by this infarction normally project?

a. Hypothalamus and midbrain

b. Parietal and occipital cortices

c. Precentral and postcentral gyri

d. Basal ganglia and premotor cortex

e. Prefrontal cortex and medial aspect of the frontal lobe

The answer is B. (Afifi, pp 163-168. Ropper, pp 138, 159-160. Siegel and Sapru, pp 265-266, 471-472.) The infarct caused damage to posterior thalamic nuclei, which may also include VPL and VPM (Dejerine Roussy disease). When these structures are damaged, a disorder referred to as thalamic pain can ensue. In this condition, light cutaneous stimulation is sufficient to produce severe pain. The nuclei situated in this region project principally to the parietal and occipital lobes and play a role in the regulation of pain (although the precise mechanisms remain unknown). The projections to the occipital cortex relate to visual functions of the neurons of the posterior thalamus that ...

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