Lateral spinothalamic tract (anterolateral system)
Second-order tract · contralateral pain temperature
Crossed second-order axons ascend in the contralateral anterolateral funiculus carrying pain and temperature, layered with sacral fibres outermost and cervical fibres innermost. In the medulla it runs laterally (as the spinal lemniscus) before joining the medial lemniscus in the pons and ending in the VPL and intralaminar thalamic nuclei.
Traced from the start
- Nociceptors and thermoreceptors (free nerve endings)
- Dorsolateral tract of Lissauer and dorsal horn synapse (Rexed laminae I, II and V)
- Anterior (ventral) white commissure
- Lateral spinothalamic tract (anterolateral system)
Detail
- Modalities
- Pain and temperature of the contralateral body
- Somatotopy
- Sacral fibres lateral, cervical fibres medial
- Brainstem position
- Lateral medulla (lateral medullary syndrome territory)
- Also projects to
- Reticular formation and intralaminar thalamus (arousal and affective components of pain)
When it goes wrong
Brown-Sequard hemisection
Contralateral loss of pain and temperature beginning one to two segments below the lesion
Lateral medullary (Wallenberg) syndrome from posterior inferior cerebellar or vertebral artery occlusion
Loss of pain and temperature on the contralateral body but the ipsilateral face (spinal trigeminal tract), with ipsilateral Horner's syndrome, ataxia, vertigo, nystagmus, dysphagia and hoarseness; no limb weakness
Extramedullary compression (meningioma, disc, metastasis)
Outer sacral fibres are damaged first, so the sensory level ascends from below and there is no sacral sparing
Intramedullary lesion (syrinx, ependymoma)
Sacral sparing: perineal pain and temperature sensation is preserved while higher dermatomes are lost
Anterior spinal artery infarction (aortic surgery or dissection, hypotension)
Bilateral loss of pain and temperature below the level with paraplegia and sphincter loss; vibration and joint position sense are preserved
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