A 38-year-old man is brought to the office for evaluation of behavioral changes. His wife says the patient has had frequent outbursts of anger, depressive mood, and insomnia. The patient recently lost his job as a machine operator because of lack of focus and poor memory. Over the past several years, he also has had involuntary, jerky, nonpurposeful movements of the extremities and face that have progressively worsened. These abnormal movements are present while he is awake but not during sleep. His 55-year-old mother has similar abnormal body movements and is at a nursing home with dementia. Which of the following labeled regions of a normal brain is most likely to be affected by this patient's disease process?

Question

A 38-year-old man is brought to the office for evaluation of behavioral changes.  His wife says the patient has had frequent outbursts of anger, depressive mood, and insomnia.  The patient recently lost his job as a machine operator because of lack of focus and poor memory.  Over the past several years, he also has had involuntary, jerky, nonpurposeful movements of the extremities and face that have progressively worsened.  These abnormal movements are present while he is awake but not during sleep.  His 55-year-old mother has similar abnormal body movements and is at a nursing home with dementia.  Which of the following labeled regions of a normal brain is most likely to be affected by this patient's disease process?

Quizplus · Accepted Answer

11ec160b_35b2_46e9_9249_25438455f86d_MD0001_00 This patient's cognitive decline, chorea (jerky, nonpurposeful movements), and family history of similar symptoms are highly suggestive of Huntington disease (HD). This autosomal dominant disease results from an excessive number of CAG trinucleotide repeats in the huntingtin gene, causing a gain-of-function mutation that results in the accumulation of toxic mutant huntingtin protein. The abnormal protein buildup causes loss of inhibitory (GABA) neurons in the caudate nucleus, leading to the characteristic movement abnormalities observed in HD. Although the diagnosis of HD is confirmed by genetic analysis, imaging studies can support the clinical findings and typically show atrophy of the caudate nuclei, causing enlargement of the lateral ventricles. The caudate nucleus is a curved or C-shaped structure in its complete form. The head of the caudate can be identified in the inferolateral walls of the frontal horns of the lateral ventricles. The caudate nucleus and putamen together make up the striatum, which is critical for movement control and coordination along with behavioral regulation. (Choice B) This structure is the internal capsule. The anterior limb of the internal capsule separates the caudate nucleus from the globus pallidus and putamen and carries a portion of the thalamocortical fibers. The posterior limb of the internal capsule separates the globus pallidus and putamen from the thalamus and carries corticospinal motor and somatic sensory fibers as well as visual and auditory fibers. (Choice C) This structure is the insular cortex (insula). The insula plays a role in the limbic system (emotion) as well as in the coordination of some autonomic functions. (Choice D) Although the putamen does atrophy in Huntington disease, this change is not as significant or as specific to Huntington disease as atrophy of the caudate nucleus. (Choice E) Atrophy of the globus pallidus is observed late in the progression of HD when generalized cortical atrophy occurs. Educational objective: The head of the caudate lies in the inferolateral wall of the frontal horn of the lateral ventricle. It is separated from the globus pallidus and putamen by the internal capsule. Atrophy of the caudate nuclei with enlargement of the lateral ventricles is characteristic of Huntington disease and can be observed on neuroimaging.

A 38-Year-Old Man Is Brought to the Office for Evaluation