A 72-year-old man is brought to the emergency department due to involuntary movements of his right arm that started several hours ago. He was watching television when his arm "threw the remote control across the room." His past medical history is significant for long-standing hypertension and diabetes mellitus. The patient does not use alcohol, tobacco, or illicit drugs. Physical examination shows wild, large-amplitude, flinging movements affecting the proximal muscles of his right arm. Which of the following areas of the brain is most likely injured in this patient?

Question

A 72-year-old man is brought to the emergency department due to involuntary movements of his right arm that started several hours ago.  He was watching television when his arm "threw the remote control across the room."  His past medical history is significant for long-standing hypertension and diabetes mellitus.  The patient does not use alcohol, tobacco, or illicit drugs.  Physical examination shows wild, large-amplitude, flinging movements affecting the proximal muscles of his right arm.  Which of the following areas of the brain is most likely injured in this patient?

Quizplus · Accepted Answer

11ec160b_35af_d5e3_9249_4f5c15dcaff4_MD0001_00 The subthalamic nucleus is a lens-shaped structure located ventral (inferior) to the thalamus, dorsal (superior) to the substantia nigra, and medial to the internal capsule. It is a component of the basal ganglia and plays an important role in the modulation of basal ganglia output. Damage to the subthalamic nucleus can decrease excitation of the globus pallidus internus, thereby reducing inhibition of the thalamus. This may result in contralateral hemiballism, a movement disorder characterized by wild, involuntary, large-amplitude, flinging movements involving the proximal limbs (eg, arm and/or leg) on one side of the body. This most commonly occurs in the setting of lacunar stroke, which is often a consequence of long-standing hypertension and diabetes mellitus. (Choice A) Atrophy of the caudate nucleus occurs in Huntington disease, which is characterized by the insidious onset of chorea (involuntary, low-amplitude movements involving the distal limbs), dementia, and behavioral abnormalities. (Choice B) Damage to the internal capsule may occur with lacunar infarcts, but patients typically have contralateral pure motor or combined sensorimotor deficits. (Choice C) Atrophy of the lentiform nucleus (eg, globus pallidus and putamen) occurs in Wilson disease (hepatolenticular degeneration), which is characterized by liver (eg, hepatitis, cirrhosis), psychiatric (eg, depression, personality changes), and neurologic (eg, dysarthria, movement disorder) abnormalities. (Choice D) Degeneration of the substantia nigra occurs in Parkinson disease, which is characterized by bradykinesia, rigidity, and resting tremor. (Choice F) Lacunar stroke involving the ventral posterior lateral nucleus and ventral posterior medial nucleus of the thalamus typically results in complete contralateral sensory loss. Damage to the thalamus may also cause thalamic syndrome, characterized by contralateral burning or stabbing pain over one side of the body. Educational objective: The subthalamic nucleus plays an important role in the modulation of basal ganglia output. Damage to this structure (eg, due to lacunar stroke) may result in contralateral hemiballism, characterized by wild, involuntary, large-amplitude, flinging movements of the proximal limbs (eg, arm and/or leg) on one side of the body. __________ References: Hemiballismus: current concepts and review. (http://www.ncbi.nlm.nih.gov/pubmed/21930415) The subthalamic nucleus in the context of movement disorders. (http://www.ncbi.nlm.nih.gov/pubmed/14607789)

A 72-Year-Old Man Is Brought to the Emergency Department Due