The hyperkinetic features of the Huntington’s disease are due to the loss of
**Core Concept**
Huntington's disease is a neurodegenerative disorder characterized by progressive damage to the basal ganglia, leading to motor dysfunction, cognitive decline, and psychiatric symptoms. The hyperkinetic features of the disease are primarily due to the disruption of normal motor control pathways.
**Why the Correct Answer is Right**
The hyperkinetic features of Huntington's disease are thought to result from the loss of **medium spiny neurons** in the striatum, particularly those expressing **enkephalin** and **dynorphin**. These neurons play a crucial role in regulating the activity of the **subthalamic nucleus**, a key component of the basal ganglia circuit. Damage to these neurons leads to an imbalance in the excitatory and inhibitory inputs to the subthalamic nucleus, resulting in excessive activity and hyperkinetic symptoms. The loss of these neurons is also associated with the formation of **abnormal protein aggregates**, including **mHTT** (mutant huntingtin protein).
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the hyperkinetic features of Huntington's disease are not primarily due to the loss of **dopamine-producing neurons** in the substantia nigra. While dopamine depletion is a hallmark of Parkinson's disease, it is not a key factor in the pathophysiology of Huntington's disease.
**Option B:** This option is incorrect because the hyperkinetic features of Huntington's disease are not primarily due to the loss of **cortical neurons**. While cortical atrophy is a feature of Huntington's disease, it is not directly responsible for the hyperkinetic symptoms.
**Option C:** This option is incorrect because the hyperkinetic features of Huntington's disease are not primarily due to the loss of **cholinergic neurons**. Cholinergic dysfunction is a feature of Alzheimer's disease, but it is not a key factor in the pathophysiology of Huntington's disease.
**Clinical Pearl / High-Yield Fact**
The hyperkinetic features of Huntington's disease are often accompanied by choreiform movements, which are characterized by brief, irregular movements that are typically more pronounced in the face and limbs. These movements are often described as "dance-like" and can be quite distressing for patients.
**Correct Answer:** C.