Posterolateral tract

Overview
The posterolateral tract (fasciculus of Lissauer, tract of Lissauer, dorsolateral fasciculus) is a small strand situated in relation to the tip of the posterior column close to the entrance of the posterior nerve roots.

Composition and path
It contains centrally projecting axons carrying discriminative pain information (location, intensity and quality), which enter the spinal column ascend or descend one or two spinal segments in this tract before penetrating the grey mater of the dorsal horn where they synapse on second-order neurons. The axons of these second-order neurons cross the midline and ascend in the anterolateral quadrant of the contralateral half of the spinal cord, where they join the spinothalamic tract. The second-order neurons ultimately synapse on neurons in the ventral posterior lateral nucleus (VPL) of the thalamus.

It consists of fine fibers which do not receive their myelin sheaths until toward the close of fetal life.

In addition it contains great numbers of fine non-mylinated fibers derived mostly from the dorsal roots but partly endogenous in origin.

These fibers are intimately related to the substantia gelatinosa which is probably the terminal nucleus.

The non-mylinated fibers ascend or descend for short distances not exceeding one or two segments, but most of them enter the substantia gelatinosa at or near the level of their origin.

Clinical significance
During a complete occlusion of the ventral artery of the spinal cord, it is the only tract spared along with the dorsal columns.

Eponym
The tract of Lissauer was named after German neurologist Heinrich Lissauer (1861-1891).