Brown sequard syndrome is characterized by ___________

Correct Answer: A. Pain and temperature loss on the opposite side

Brown-Séquard syndrome results from hemisection of the spinal cord, causing a characteristic crossed sensory-motor dissociation. The key discriminator is understanding the decussation (crossing) levels of different spinal tracts. Ipsilateral to the lesion: motor loss (corticospinal tract crosses at medulla) and fine touch/proprioception loss (dorsal column crosses at medulla, rostral to cord). Contralateral to the lesion: pain and temperature loss (spinothalamic tract crosses within 1–2 segments of entry in the spinal cord itself). This crossed pattern is pathognomonic. Pain and temperature sensation is mediated by A-delta and C fibers that synapse in the dorsal horn and immediately cross via the anterior white commissure before ascending as the spinothalamic tract. Therefore, a hemisection at any cord level produces ipsilateral motor + fine touch loss but contralateral pain and temperature loss—the hallmark of Brown-Séquard syndrome. This is clinically relevant in India where spinal cord injuries from falls, road traffic accidents, and tuberculosis of the spine are common causes of incomplete cord syndromes.

Why the other options are wrong

B. Only pain lost on the same side — This is wrong because pain and temperature loss in Brown-Séquard is contralateral, not ipsilateral. Additionally, the syndrome is characterized by loss of BOTH pain and temperature together (spinothalamic tract), not pain alone. This option confuses the side of the lesion with the side of sensory loss and isolates pain incorrectly. C. Pain and temperature lost on the same side — This is wrong because it places pain and temperature loss on the ipsilateral side, which is anatomically incorrect. Pain and temperature cross immediately in the spinal cord (within 1–2 segments), so they are lost on the opposite side of the lesion. This is a common trap—students may confuse it with ipsilateral motor loss. D. Fine touch lost on the opposite side — This is wrong because fine touch (discriminative touch, proprioception) is mediated by the dorsal columns, which cross at the medulla, not in the spinal cord. Therefore, fine touch loss is ipsilateral to the lesion, not contralateral. This option reverses the correct pattern and is a classic NBE distractor.

High-Yield Facts

Mnemonics

*IPSI-CONTRA Rule for Brown-Séquard IPSIlateral = Motor + Fine touch (cross at medulla, rostral). CONTRAlateral = Pain + Temperature (cross in cord, caudal). Use: Immediately after reading 'hemisection' or 'Brown-Séquard' to lock in the crossed pattern. Early vs. Late Crossing Spinothalamic = Early (1–2 segments in cord) → contralateral. Dorsal columns = Late* (medulla) → ipsilateral. Use: When comparing which sensations are lost on which side.

NBE Trap

NBE pairs "pain and temperature" with "same side" (option C) to trap students who confuse Brown-Séquard's crossed dissociation with ipsilateral sensory loss, or who forget that spinothalamic crossing happens in the spinal cord itself, not at the medulla.

Clinical Pearl

A patient with TB spine causing cord hemisection at T5 will have right leg weakness and loss of vibration sense (ipsilateral motor + dorsal column), but pain/temperature loss on the left leg and trunk (contralateral spinothalamic). This crossed pattern is the bedside clue that distinguishes Brown-Séquard from complete cord transection (all modalities lost bilaterally below the lesion).

_Reference: Guyton & Hall Textbook of Medical Physiology, Ch. 48 (Spinal Cord Reflexes and Spinal Shock); Robbins & Cotran Pathologic Basis of Disease, Ch. 28 (Central Nervous System)_