|Diagram showing a few of the connections of afferent (sensory) fibers of the posterior root with the efferent fibers from the ventral column and with the various long ascending fasciculi. (Lissauer's fasciculus visible in upper left.)|
|Diagram of the principal fasciculi of the spinal cord. (Lissauer's fasciculus visible in upper right.)|
|Gray's||subject #185 762|
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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.
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.
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