spinothalamictraktio

The spinothalamic tractio, commonly known as the spinothalamic tract, is a major ascending somatosensory pathway that conveys nociceptive, thermal, and crude touch information from the body to the brain. It is part of the anterolateral system and consists of two clinically important components: the lateral spinothalamic tract, carrying pain and temperature, and the anterior (ventral) spinothalamic tract, carrying crude touch and pressure.

Origin and decussation: First-order neurons enter the spinal cord and synapse on second-order neurons in the dorsal horn, particularly in the nucleus proprius and the substantia gelatinosa. The second-order neurons cross midline at or near the level of entry through the anterior white commissure and then ascend in the contralateral anterolateral column as the spinothalamic tract. The fibers project through the brainstem to the thalamus.

Thalamic relay and cortical targets: Most fibers terminate in the ventral posterior lateral nucleus (VPL) of the thalamus. Third-order neurons then project via the posterior limb of the internal capsule and thalamocortical radiations to the primary somatosensory cortex (postcentral gyrus). Some projections also reach the insula or cingulate cortex, contributing to the affective and emotional aspects of pain.

Clinical relevance: Lesions of the spinothalamic tract typically produce contralateral loss of pain and temperature beginning a few segments below the lesion, while crude touch may be variably affected. Syringomyelia can disrupt crossing fibers at the anterior white commissure, producing a cape-like bilateral loss of pain and temperature across the shoulders. Understanding this pathway helps in localizing sensory deficits and diagnosing spinal cord injuries.