An elderly hypertensive woman suddenly develops violent, flailing, involuntary movements of her left arm and leg without weakness or sensory loss. CT shows a small hemorrhage in the right diencephalon. Which nucleus is damaged?

• A Subthalamic nucleus ✓
• B Globus pallidus externa
• C Substantia nigra pars reticulata
• D Ventrolateral nucleus of the thalamus

Explanation

Contralateral wild flinging movements, hemiballismus, result from destruction of the contralateral subthalamic nucleus, almost always by a small hypertensive hemorrhage or lacunar infarct. The subthalamic nucleus normally exerts excitatory drive onto the globus pallidus interna within the indirect basal ganglia pathway; losing this disinhibits thalamocortical motor output. Parkinsonism points to the substantia nigra pars compacta rather than pars reticulata, and a pure thalamic ventrolateral lesion produces ataxia or tremor, not ballistic movements.

Reference: Ganong's Review of Medical Physiology, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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