Loss of pain and temperature information from the left lower limb below the L4 dermatome, complete loss of discriminative touch and conscious proprioception information from the right lower limb below the L2 dermatome, and loss of voluntary control of the

Question

right lower limb below the L2 dermatome indicates which one of the following?
A. Brown-Séquard syndrome produced by a hemisection of the cord at L4 on the right side
B. Brown-Séquard syndrome produced by a hemisection of the cord at L4 on the left side
C. Brown-Séquard syndrome produced by a complete transection of the cord
D. Brown-Séquard syndrome produced by a hemisection of the cord at L2 on the right side
E. Brown-Séquard syndrome produced by a hemisection of the cord at L2 on the left side

Answer 1

ANS: D
Rationale: A hemisection (i.e., damage to the right or left half of the cord) interrupts pain and temperature sensation from the contralateral body because the axons transmitting nociceptive and temperature information cross to the opposite side of the cord soon after entering the cord. As a result of collateral branching of nociceptive axons in the dorsolateral tract, the complete loss of pain sensation occurs two to three dermatomes below the level of the lesion. Because discriminative touch and conscious proprioception information ascends on the same side of the cord as it entered, these sensations are lost ipsilateral to the lesion. Paralysis also occurs ipsilaterally. The pattern of loss is called Brown-Séquard syndrome.