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MBBS QUESTION #10162
Question 1
A patient with spinal cord hemisection (Brown-Séquard syndrome) shows ipsilateral loss of proprioception and fine touch below the lesion, together with contralateral loss of pain and temperature. This pattern reflects the differing decussation levels of which two pathways?
  • Dorsal columns (decussate in medulla) and spinothalamic tract (decussate near level of entry)✔️
  • Corticospinal tract and dorsal columns (both decussate at the same spinal level)
  • Spinocerebellar tracts only
  • Vestibulospinal and rubrospinal tracts
Correct Answer Explanation
The dorsal columns ascend ipsilaterally and decussate only in the medulla (internal arcuate fibers), whereas the spinothalamic tract decussates almost immediately at the segmental level of entry. This difference explains the classic dissociated sensory pattern in Brown-Séquard syndrome.