A patient is brought to the emergency depament following a road traffic accident. MRI shows injury to corpus striatum. This patient is MOST likely to suffer from:
## **Core Concept**
The corpus striatum, a part of the **basal ganglia**, plays a crucial role in movement control and cognition. It receives inputs from the cerebral cortex and sends outputs to the thalamus and brainstem, thereby influencing motor function. Damage to this area can lead to disorders of movement.
## **Why the Correct Answer is Right**
The correct answer, **Hemiballismus**, is a movement disorder characterized by involuntary, violent movements of the limbs, often resulting from damage to the **subthalamic nucleus** or its connections with the **corpus striatum**. Injury to the corpus striatum disrupts the normal functioning of the basal ganglia-thalamocortical motor loop, leading to abnormal movements. Hemiballismus is a classic consequence of lesions in this area, making it the most likely diagnosis.
## **Why Each Wrong Option is Incorrect**
* **Option A: Parkinson's disease** - This is a neurodegenerative disorder primarily affecting the **substantia nigra**, leading to bradykinesia, rigidity, and tremors. While it involves the basal ganglia circuitry, it's not directly caused by acute injury to the corpus striatum.
* **Option B: Huntington's disease** - A genetic disorder causing progressive damage to the **caudate nucleus** (part of the corpus striatum), leading to chorea and dementia. However, it's a chronic condition, not an acute consequence of injury.
* **Option D: Cortical stroke** - This would involve damage to the cerebral cortex, not the corpus striatum, and typically presents with symptoms such as weakness, sensory deficits, or aphasia, depending on the area affected.
## **Clinical Pearl / High-Yield Fact**
A key point to remember is that lesions affecting the basal ganglia, including the corpus striatum, can lead to a variety of movement disorders. **Hemiballismus** is particularly associated with lesions in the subthalamic nucleus or its connections with the corpus striatum. This condition is a medical emergency and may require prompt treatment to manage symptoms.
## **Correct Answer: C. Hemiballismus**