Trigeminal lemniscus

The trigeminal lemniscus, also called the trigeminothalamic tract, is a part of the brain that conveys tactile, pain, and temperature impulses from the skin of the face, the mucous membranes of the nasal and oral cavities, and the eye, as well as proprioceptive information from the facial and masticatory muscles.

The trigeminal lemniscus is composed of second order neuronal axons in the brainstem. It carries sensory information from the trigeminal system to the ventral posteromedial (VPM) nucleus of the thalamus.

This tract was historically considered a cephalic division of the medial lemniscus due to the close proximity of the two ascending tracts.^[1] Like the dorsal column medial lemniscus (DCLM) system, the trigeminal lemniscus carries tactile and proprioceptive sensations. However, the trigeminal lemniscus also carries pain and temperature sensations from the contralateral orofacial region, just as the spinothalamic pathway carries these sensations from the contralateral body. Thus, the trigeminal lemniscus of the head is functionally analogous to both the DCLM and spinothalamic systems of the body.

Divisions

The trigeminal lemniscus contains two main divisions:

• The anterior (ventral) trigeminothalamic tract, consisting of second order neuronal axons from the principal (chief sensory) nucleus and spinal trigeminal nucleus. These fibers cross the midline and ascend to the contralateral thalamus.
• The posterior (dorsal) trigeminothalamic tract, consisting of second order neuronal axons from the principal (chief sensory) nucleus. These fibers do not cross the midline, and ascend to the ipsilateral thalamus.

References

Sources

• Anthoney, T. R. (1993). Neuroanatomy and the neurologic exam: a thesaurus of synonyms, similar-sounding non-synonyms, and terms of variable meaning.^[1] CRC Press.
• Snell, R. S. (2010). Clinical neuroanatomy. Lippincott Williams & Wilkins.