Trigeminal Nerve Pathway - michaelrees/Trigeminal_Stimulation GitHub Wiki

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Background

The Trigeminal nerve has 3 branches: Opthalmic (V1), maxillary (V2), and mandibular (V3). The trigeminal nerve is responsible for innvervating the skin, mucous membranes, and sinuses in the face. The V1 and V2 branches are located immediately above and below the eye respectively, and consist solely of sensory afferent fibers. The mandibular branch (V3), which runs along the course of the jaw-line, contains the only motor fibers within the nerve.

In addition to the sensory fibers, some nerve tracts of the trigeminal nerve contain post-ganglionic neurones of parasympathetic ganglia travelling with them. Inadvertent activation of these neurones could potentially cause side effects

Receptor types

SVE - Special Visceral Efferents - (only V3). Project to motor nucleus of the trigeminal

GSE - General Somatic Efferents - conduct sensations of touch, pain, temp, as well as muscle proprioception

project to principle trigeminal nucleus, trigeminal spinal nucleus (Spinal Nucleus V) AND TRIGEMINAL GANGLION

GP - General Proprioception -

project to mesencephalic Trigeminal Nucleus

Pathway

As Trigeminal nerve stimulation primarily focuses on stimulation of the V1 and V2 branches of the nerve, the additional motor pathways of the trigeminal nerve (which travel along only the V3 branch), will be ignored in this analysis

Pathway will be explained from sensory terminals on the face --> brain

the peripheral processes of the three trigeminal nerve branches terminate underneath the skin, where they connect to receptors for pain, and temperature.

The three trigemininal nerves converge in the Trigeminal Ganglion (also known as the semilunar or gasserian ganglion), which houses the cell bodies of these neurons. The trigeminal ganglion is located lateral to the cavernous sinus, in a region known as the trigeminal cave. The trigeminal ganglion is somatotopically organized: the opthalamic branch contains its cell bodies in the lower segment of the trigeminal ganglion, the maxillary in the middle, and the mandibular in the upper.

From the Trigeminal Gangion, the cell bodies project their central processes into the brainstem, in a fiber bundle called the Spinal Tract V. The Spinal Tract V terminate at three sensory nuclei: mesencephalic, principal sensory, and Spinal Nucleus V, all of which are adjacent to the trigeminal ganglion, and located in the Pons. All fibers conveying pain and temperature information in the face project to the caudal part of Spinal Nucleus V.

The cell bodies within the Spinal Nucleus then projects axons upwards, which cross the midline parallell to the medial lemniscus. These axons ascend the spinothalamic tract, and ultimately relay in the thalamic nuclei, at which point they project to the cerebral cortex (mostly the somatosensory cortex).

Nucleus Solitarius

Sensory information from the oral cavity is transmitted to the rNST by the facial, glossopharyngeal, vagus, and trigeminal nerves

http://www.ncbi.nlm.nih.gov/books/NBK2541/

See photos below:

Sources

[1] http://teachmeanatomy.info/head/cranial-nerves/trigeminal-nerve/

[2] http://emedicine.medscape.com/article/1873373-overview

[3] http://www.neuroanatomy.wisc.edu/virtualbrain/BrainStem/03CNV.html

[4] http://www.blackwellpublishing.com/patestas/chapters/15.pdf