A ventrolateral cordotomy is performed to produce relief of pain from the right leg. It is effective because effective because it interrupts the
**Core Concept**
A ventrolateral cordotomy is a surgical procedure performed to alleviate pain by interrupting the transmission of pain signals from the body to the brain. This procedure targets the spinothalamic tract, a pathway responsible for transmitting pain and temperature sensations from the body to the thalamus.
**Why the Correct Answer is Right**
The spinothalamic tract is a crucial component of the anterolateral system, which carries pain and temperature information from the body to the thalamus. The tract is divided into lateral and medial components, with the lateral spinothalamic tract transmitting pain and temperature information from the body to the thalamus. A ventrolateral cordotomy effectively interrupts the transmission of pain signals by damaging the lateral spinothalamic tract, thereby providing relief from pain.
**Why Each Wrong Option is Incorrect**
**Option A:** The substantia nigra is a region of the midbrain involved in motor control and movement disorders, such as Parkinson's disease. It is not directly involved in the transmission of pain signals.
**Option B:** The dorsal columns of the spinal cord transmit vibration, proprioception, and fine touch information to the brain, but are not responsible for pain transmission.
**Option C:** The anterior spinothalamic tract is involved in the transmission of vibration and proprioception information, but is not directly involved in pain transmission.
**Clinical Pearl / High-Yield Fact**
A ventrolateral cordotomy is a classic example of a neurosurgical procedure that targets the spinothalamic tract to alleviate pain. It is essential to understand the anatomy and physiology of pain transmission to appreciate the effectiveness of this procedure.
**Correct Answer:** C. The anterior spinothalamic tract is involved in the transmission of vibration and proprioception information, but is not directly involved in pain transmission.