The lateral spinothalamic tract carries pain and temperature sensation. At which level do the second-order neurons decussate before ascending to the thalamus?

• A At the level of the medulla oblongata
• B At the level of the midbrain
• C Within one or two segments of the level of entry in the spinal cord ✓
• D In the posterior limb of the internal capsule

Explanation

Primary afferent fibers (first-order neurons) carrying pain and temperature enter the dorsal horn and synapse in the substantia gelatinosa (Rexed laminae I and II) at their segmental level. The second-order neurons then cross through the anterior white commissure within one to two spinal cord segments above the level of entry and ascend in the contralateral lateral spinothalamic tract to the ventral posterolateral (VPL) nucleus of the thalamus. This is clinically important in syringomyelia, which destroys fibers at the decussation and produces a 'cape-like' bilateral loss of pain and temperature.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.