Lesion of the marked structure leads to:
**Question:** Lesion of the marked structure leads to:
A. Loss of pain sensation
B. Loss of temperature sensation
C. Loss of proprioception
D. Loss of deep tendon reflexes
**Correct Answer:** D. Loss of deep tendon reflexes
**Core Concept:** Deep tendon reflexes (DTRs) are involuntary responses that occur when a specific stimulus is applied to a specific point on the body, such as the patellar or biceps reflexes. These reflexes are part of the somatosensory system and are essential for assessing the integrity of the spinal cord and peripheral nerves.
**Why the Correct Answer is Right:** When there is a lesion in the spinal cord (e.g., due to trauma, infection, or tumor), the transmission of the sensory and motor information is compromised. This can result in loss of deep tendon reflexes. The deep tendon reflexes are tested by stimulating the appropriate nerve and observing the reflex response, which involves the spinal cord and upper motor neurons.
**Why Each Wrong Option is Incorrect:**
A. Loss of pain and temperature sensation: Lesions involving the spinal cord would primarily affect deep tendon reflexes (DTRs), not pain and temperature sensation. Pain and temperature sensation are part of the primary sensory system, which is not directly related to the spinal cord and upper motor neurons involved in DTRs.
B. Loss of temperature sensation: Similar to option A, temperature sensation is part of the primary sensory system, which is not directly related to deep tendon reflexes.
C. Loss of proprioception: Proprioception refers to the sense of body position and motion, and is distinct from deep tendon reflexes. Lesions affecting proprioception would involve the cortex, cerebellum, or peripheral nerves, not the spinal cord and upper motor neurons.
**Clinical Pearl:** Deep tendon reflex assessment is an essential clinical examination skill for assessing the integrity of the spinal cord and peripheral nerves. A decreased or absent DTR indicates a potential spinal cord lesion and should prompt further evaluation and imaging, if necessary.