A young woman is evaluated by a neurosurgeon because of injuries she received in an explosion. She has numerous lacerations of the front and back torso and bruising of the craniofacial region. Neurological examination shows lack of movement in her right lower extremity with hyperreflexia, and loss of proprioception and fine touch in this extremity, but pain and temperature sensation are intact. Pain and temperature sensation are absent in the left lower limb. Movement and reflexes are normal in the left lower extremity and upper extremities.
A lesion in which of the following locations can explain her neurological examination?
A young woman is evaluated by a neurosurgeon because of injuries she received in an explosion. She has numerous lacerations of the front and back torso and bruising of the craniofacial region. Neurological examination shows lack of movement in her right lower extremity with hyperreflexia, and loss of proprioception and fine touch in this extremity, but pain and temperature sensation are intact. Pain and temperature sensation are absent in the left lower limb. Movement and reflexes are normal in the left lower extremity and upper extremities.
A lesion in which of the following locations can explain her neurological examination?
💡 Explanation
**Core Concept**
The neurological examination findings suggest a lesion affecting the spinal cord, specifically a hemisection or "Brown-Séquard syndrome," which is characterized by ipsilateral weakness, loss of proprioception, and loss of fine touch, and contralateral loss of pain and temperature sensation.
**Why the Correct Answer is Right**
The correct answer, a hemisection of the right side of the spinal cord at the level of the first lumbar segment, can explain the neurological examination findings because the corticospinal tracts, which control voluntary movement, are located in the lateral and anterior columns of the spinal cord. The loss of proprioception and fine touch in the right lower extremity is due to the involvement of the posterior column-medial lemniscus pathway, which transmits these sensations. The loss of pain and temperature sensation in the left lower extremity is due to the involvement of the spinothalamic tract, which crosses at the level of the spinal cord and is located in the anterior commissure. The first lumbar segment is a common level for such lesions due to the presence of the conus medullaris, where the spinal cord terminates.
**Why Each Wrong Option is Incorrect**
**Option A:** A hemisection of the left side of the spinal cord at the level of the first lumbar segment would result in contralateral weakness, loss of proprioception, and loss of fine touch in the left lower extremity, which is not consistent with the examination findings.
**Option B:** A hemisection of the left side of the spinal cord at the level of the fourth sacral segment would result in a cauda equina lesion, affecting the lower sacral roots and resulting in a different pattern of neurological deficits.
**Option D:** A hemisection of the right side of the spinal cord at the level of the fourth sacral segment would result in a similar pattern of deficits as option C, but at a lower level of the spinal cord, which is not consistent with the examination findings.
**Clinical Pearl / High-Yield Fact**
Remember that the spinothalamic tract crosses at the level of the spinal cord, resulting in contralateral transmission of pain and temperature sensation. This is a critical concept in localizing spinal cord lesions.
**✓ Correct Answer: C. Hemisection of the right side of the spinal cord at the level of the first lumbar segment of the cord**
✓ Correct Answer: C. Hemisection of the right side of the spinal cord at the level of the first lumbar segment of the cord
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