Skip to content
Robotic Spine Universe

Learn · Pathway

The spinothalamic tract

The route for pain and temperature. Its fibres synapse as soon as they enter the cord and cross there, so a lesion of one side of the cord affects pain on the other side of the body.

Updated 2026-10-026 sources

Depth:

Why it matters

Pain and temperature warn of harm. The spinothalamic tract pathway is primarily responsible for pain and temperature sensations from below the neck [1].

What it is

The pathway, like the dorsal column system, begins with neurons in a dorsal root ganglion [1]. Its name comes from its second neuron, which has its cell body in the grey matter of the cord and connects to the thalamus [1].

Pain and temperature are transduced by free nerve endings: nociceptors for pain and thermoreceptors for temperature [2].

How it works

  1. The first neuron's axon enters the dorsal horn and synapses there with the second neuron [1].
  2. The second neuron's axon crosses within the cord, at the same level at which the information entered, and ascends to the thalamus [1].
  3. Thalamic neurons project to the somatosensory cortex of the postcentral gyrus [1].
Cerebral cortexThalamusSpinal cord (tract)Dorsal hornSkinmidlinepatient leftpatient rightspinal cordPain or temperaturereceptor, right sideDorsal hornsecond neuronSpinothalamic tractleft sideThalamusthird neuronPrimary sensory cortex
Spinothalamic tractPain and temperature fibres from the right side synapse in the right dorsal horn; the second neuron crosses within the cord and climbs the left side to the thalamus and sensory cortex.
  • Excitatory synapse (filled arrowhead)
  • Inhibitory synapse (bar)
  • Modulatory (open circle)
  • Signal or data flow, not a synapse (dashed)
  • Midline crossing (decussation)
Figure 1. Spinothalamic tract. Pain and temperature fibres from the right side synapse in the right dorsal horn; the second neuron crosses within the cord and climbs the left side to the thalamus and sensory cortex.[1] Schematic
  • In both this pathway and the dorsal column pathway the second neurons project across the midline, here within the spinal cord.[1]

Simplified: In the PAM50 atlas this region is the spinal lemniscus (spinothalamic and spinoreticular tracts).

Text description of this diagram
  1. Pain and temperature fibres from the right side synapse in the right dorsal horn; the second neuron crosses within the cord and climbs the left side to the thalamus and sensory cortex.
  2. Pain or temperature (right side, Skin) to Dorsal horn (right side, Dorsal horn); signal or data flow (not a synapse); synapse on entry.
  3. Dorsal horn (right side, Dorsal horn) to Spinothalamic tract (left side, Spinal cord (tract)); signal or data flow (not a synapse); crosses the midline at the spinal cord.
  4. Spinothalamic tract (left side, Spinal cord (tract)) to Thalamus (left side, Thalamus); signal or data flow (not a synapse); synapse in the thalamus.
  5. Thalamus (left side, Thalamus) to Primary sensory cortex (left side, Cerebral cortex); signal or data flow (not a synapse).

In the dorsal horn, fibres carrying pain, heat and itch end mainly in laminae I and II [3]. Stressed or damaged tissues release chemicals that activate receptor proteins in nociceptors [2].

In the PAM50 white-matter atlas used for this site's cross-sections, the region is labelled the spinal lemniscus, which combines the spinothalamic and spinoreticular tracts [4].

When it does not behave

Because the spinothalamic pathway crosses as soon as it enters the cord and ascends on the opposite side, a hemisection of the cord spares pain from the same side below the lesion; pain from the other side is lost [5]. A case report describes this pattern after a tumour inside the cord [6].

How we see and measure it

The sensory examination tests pain and temperature across the dermatomes; mistaking painful stimuli for light touch, or the reverse, may point to damage in the ascending pathways, such as a hemisection [5].

Common misconceptions

Misconception: Pain travels to the brain on the same side it comes from.

The second neuron crosses in the cord at the level of entry, so pain ascends on the opposite side [1].

Check yourself

Where is the first synapse of the spinothalamic pathway?

In the dorsal horn of the cord, where the first neuron meets the second [1].

A lesion cuts the right half of the cord. On which side is pain lost below it?

The left side: the right-sided spinothalamic tract carries pain from the left side of the body [5].

Read next

References

  1. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, et al.. 14.2 Central Processing. Anatomy and Physiology 2e. OpenStax. 2022. https://openstax.org/books/anatomy-and-physiology-2e/pages/14-2-central-processing
  2. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, et al.. 14.1 Sensory Perception. Anatomy and Physiology 2e. OpenStax. 2022. https://openstax.org/books/anatomy-and-physiology-2e/pages/14-1-sensory-perception
  3. Rivera-Arconada I, Baccei ML, López-García JA, Bardoni R. An electrophysiologist’s guide to dorsal horn excitability and pain. Frontiers in Cellular Neuroscience. 2025;19. doi:10.3389/fncel.2025.1548252
  4. Lévy S, Benhamou M, Naaman C, Rainville P, Callot V, Cohen-Adad J. White matter atlas of the human spinal cord with estimation of partial volume effect. NeuroImage. 2015;119:262-271. doi:10.1016/j.neuroimage.2015.06.040
  5. Betts JG, Young KA, Wise JA, Johnson E, Poe B, Kruse DH, et al.. 16.4 The Sensory and Motor Exams. Anatomy and Physiology 2e. OpenStax. 2022. https://openstax.org/books/anatomy-and-physiology-2e/pages/16-4-the-sensory-and-motor-exams
  6. Kaballo MA, Brennan DD, El Bassiouni M, Skehan SJ, Gupta RK. Intramedullary spinal cord metastasis from colonic carcinoma presenting as Brown-Séquard syndrome: a case report. Journal of Medical Case Reports. 2011;5(1). doi:10.1186/1752-1947-5-342

For learning only. This page does not diagnose, predict outcomes or recommend treatment. Corrections are welcome: how to suggest one.