Tractus spinothalamicus lateralis

The lateral spinothalamic tract (or lateral spinothalamic fasciculus), is a bundle of afferent nerve fibers ascending through the white matter of the spinal cord, in the spinothalamic tract, carrying sensory information to the brain.

It carries pain, and temperature sensory information (protopathic sensation) to the thalamus.

It is composed primarily of fast-conducting, sparsely myelinated A delta fibers and slow-conducting, unmyelinated C fibers.

These are secondary sensory neurons which have already synapsed with the primary sensory neurons of the peripheral nervous system in the posterior horn of the spinal cord (one of the three grey columns).

Together with the anterior spinothalamic tract, the lateral spinothalamic tract is sometimes termed the secondary sensory fasciculus or spinal lemniscus.

Anatomy

The neurons of the lateral spinothalamic tract originate in the spinal dorsal root ganglia.

They project peripheral processes to the tissues in the form of free nerve endings which are sensitive to molecules indicative of cell damage.

The central processes enter the spinal cord in an area at the back of the posterior horn known as the posterolateral tract.

Here, the processes ascend approximately two levels before synapsing on second-order neurons.

These secondary neurons are situated in the posterior horn, specifically in the Rexed laminae regions I, IV, V and VI.

Region II is primarily composed of Golgi II interneurons, which are primarily for the modulation of pain, and largely project to secondary neurons in regions I and V.