spinothalamic

The spinothalamic tract, also called the anterolateral system, is a sensory pathway that transmits nociceptive (pain), thermoreceptive (temperature), and crude touch information from the body to the brain. It complements other sensory pathways such as the dorsal columns by conveying sensations that are not precisely localized.

The pathway begins with first‑order neurons in the dorsal root ganglia. These neurons enter the spinal cord and synapse in the dorsal horn, particularly in the substantia gelatinosa and nucleus proprius. The second‑order neurons cross to the contralateral side via the anterior white commissure and then ascend in the spinothalamic tract within the anterolateral funiculus. The tract reaches the thalamus, where fibers predominantly project to the ventral posterolateral nucleus (VPL). Third‑order neurons then convey information to the primary somatosensory cortex (postcentral gyrus), allowing conscious perception of the sensations.

Two main components are recognized: the lateral spinothalamic tract, which primarily carries pain and temperature, and the anterior (or cruder) spinothalamic tract, which transmits crude touch and pressure. Sensory input from the face is carried by separate pathways via the trigeminal system to the thalamus (VPM), rather than by the spinal spinothalamic tract.

Clinical significance includes characteristic patterns of deficit after lesions. Because the tract decussates near entry, damage to the spinothalamic pathways often produces contralateral loss of pain and temperature below the level of a spinal lesion, while dorsal column modalities and motor pathways may be affected on the ipsilateral side in syndromes such as Brown-Séquard.