The trigeminal nerve is the fifth cranial nerve. It emerges directly from the surface of the pons, and supplies sensation to the face and motor supply to the muscles of mastication. Sensation to the face is essential for things like the corneal reflex. In addition, the muscles of chewing are also integral to daily life.
The trigeminal nerve is also known as cranial nerve 5. The word trigeminal comes from the word ‘tri’ meaning three, and the word ‘Gemini’ meaning twins. There are three trigeminal nuclei. The mesencephalic nucleus of the trigeminal nerve contains first order neurons that detect proprioception from the jaw, temperomandibular joints, teeth and intraocular muscles. The principal nucleus of the trigeminal nerve lies in the dorsolateral pontine tegmentum, and detects tactile sensation. The spinal nucleus detects pain and temperature, and stretches from the pons to the first three dorsal horn segments of the cervical spinal cord.
It emerges directly from the pons, and passes to a region known as Meckel’s cave (an arachnoid pouch filled with cerebrospinal fluid and located near the apex of the petrous portion of the temporal bone). Here it divides into three branches.
These are the ophthalmic (V1), maxillary (V2), and the mandibular (V3). They are responsible for providing sensation to the face. The mandibular division also innervates the muscles of mastication i.e. the temporalis, medial and lateral pterygoids, and the masseter. The divisions all exit the skull through different foramina. V1 passes through the superior orbital fissure, V2 passes through the foramen rotunda, and V3 passes through the foramen ovale. Both the ophthalmic and maxillary divisions supply the nasal cartilage via their terminal branches. The superior alveolar nerve is a branch of the maxillary division and supplies the teeth of the maxilla. The lingual nerve (provides sensation to the tongue and) and the inferior alveolar nerve (supplies the teeth of the mandible) are branches of the mandibular division.
Trigeminal neuralgia- This is a sudden and sharp stabbing pain in the distribution of the trigeminal nerve, that lasts for a few seconds to a few minutes. Pain is typically brought on by light touching of the face e.g. shaving, brushing teeth and washing. It has been described as the worse pain imaginable by patients who suffer from it. There are several theories about the cause of the disease, including compression of the nerve by surrounding arteries (mist commonly the superior cerebellar artery), and focal demyelination.
Developmental precursor- Metencephalon (secondary brain vesicle)
Muscles- Masseter, medial pterygoid, lateral pterygoid, temporalis
Dermatome- The face, via the Ophthalmic, maxillary and mandibular divisions.
Tri implies three (the nerve has three divisions)
Recall the nerve supplies sensation to the face, and the V3 division innervates the muscles of mastication
The trigeminal nerve is the fifth cranial nerve. It supplies sensation to the face and motor supply to the muscles of mastication.
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