Lesion of the left dorsolateral funiculus at the T6 level produces which precise pattern of deficit?

• A Right leg loss of vibration and proprioception below T6; left leg loss of pain and temperature below T8
• B Left leg loss of vibration and proprioception below T6; right leg loss of pain and temperature below T8 ✓
• C Bilateral loss of pain and temperature below T6 with preserved proprioception
• D Left leg loss of all modalities below T6 with preserved contralateral sensation

Explanation

The dorsolateral funiculus (lateral column) on the left contains the left lateral corticospinal tract and ascending left dorsal column fibers. Damage at T6 on the left disrupts the left dorsal column (ipsilateral vibration/proprioception loss below T6) and the left lateral spinothalamic tract (which carries crossed pain/temperature fibers that entered 2 segments below, approximately T8 level, giving contralateral — right — loss below T8). This is the Brown-Séquard pattern: ipsilateral motor and dorsal column loss; contralateral spinothalamic loss 1–2 segments lower.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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