Table of Contents
Trigeminal Nerve Definition
The trigeminal nerve (CN V) is the biggest cranial nerve, carrying sensory information from the scalp, face, eye orbit, paranasal sinuses, and a portion of the tongue, as well as acting as a motor for the mastication and facial expression muscles.
The trigeminal nerve is a mixed nerve with sensory and motor components that separates into three divisions: the ocular, maxillary, and mandibular branches.
Trigeminal Nerve Function
The function of the trigeminal nerve is likewise divided into these three divisions or branches, each with its unique set of functions. The ocular nerve branch (CN V1), the maxillary nerve branch (CN V2), and the mandibular nerve branch (CN V3) all have different functions.
The trigeminal nerve begins in the midbrain and ends in the medulla oblongata, and it is made up of four nuclei or groupings of CNS nerve cells. Sensory nuclei make up three of these nuclei (the mesencephalic, principal sensory, and spinal nuclei).
The motor nucleus, the fourth, sends out nerves that assist in jaw movement. The various branches of the trigeminal nerve are responsible for everything you feel on and in your face, the front of your scalp, and the mucous membranes of your mouth, nose, and sinuses.
The thick trigeminal nerve ganglion near the end of the main trunk of the trigeminal nerve, directly in front of the outer ear. The three branches or divisions start from the trigeminal ganglion. The branches and the regions they serve – the ophthalmic, maxillary, and mandibular zones.
CN V1 Function
Sensory (afferent) ophthalmic branch function – afferent in this context implies that sensory impulses are transmitted to the trigeminal nerve. Although the ophthalmic branch nerve is the smallest of the three, it performs a significant function.
Sensory input from the cornea, iris, ciliary body, lacrimal gland, and conjunctiva is controlled by the sensory properties of CN V1. This branch also links portions of the nasal cavity’s mucous membranes with the sphenoidal and frontal sinuses.
CN V1 is also linked to the skin of the eyelids, brows, forehead, and nose. Finally, the trigeminal nerve’s ophthalmic branch is responsible for the membranes that surround the brain and separate the cerebellum and cerebrum.
The ophthalmic branch, like the rest of the trigeminal branches, starts in the trigeminal ganglion and splits into three smaller nerves: the lacrimal nerve, frontal nerve, and nasociliary nerve.
It is not required to know the names of these minor branches, but because they serve special purposes, it is worthwhile to mention them. The lacrimal gland, upper eyelid, and conjunctiva are all innervated by the lacrimal nerve.
The supraorbital and supratrochlear branches of the frontal nerve innervate the upper eyelid, conjunctiva, and scalp, respectively, while the latter innervates the upper eyelid, conjunctiva, and forehead. The four divisions of the nasociliary nerve give sensory innervation to the mucous membranes of the sinuses and nose.
Finally, the iris, cornea, and ciliary bodies, which govern the shape of the eye lens, convey sensory information to the brain through the long nasociliary nerve. Although some sources claim that the ophthalmic nerve dilates the pupils and generates tears, these activities are performed by other nerve fibres that run alongside CN V1.
CN V2 Function
The maxillary branch (CN V2) provides feeling in the face’s mid-region (nasal cavity, sinuses, and maxilla). It is divided into four sections, each of which is further divided, resulting in a richly-innervated and highly sensitive face as well as brain membranes.
When the teeth in the upper jaw get infected, for example, the superior alveolar nerves ensure that we feel the unpleasant discomfort of toothache.
CN V3 Function
The mandibular nerve, also known as CN V3, is a mixed nerve that supplies efferent motor fibres and afferent sensory fibres to the lower face, upper neck, oral cavity mucosa, and lower jaw gums and teeth.
This branch also divides into inferior alveolar nerves, which innervate the lower jaw’s teeth and, unlike the superior alveolar nerve, include motor fibres. Mastication, or chewing, requires the use of the strong muscles that surround the mandible and maxilla.
Damage to this part of the trigeminal nerve can provide a weird sensation when eating and affect the way we chew our food altogether. One of the motor branches of the mandibular branch innervates the lateral pterygoid muscle, which is an example of trigeminal nerve function in the jaw.
You may test this nerve by bringing your lower jaw forward to create an underbite, or by just opening your mouth with your bottom jaw down. You may also move your jaw from side to side thanks to this motor nerve.
The sensory buccal nerve branch of the mandibular nerve, which allows humans to sense a sensation on the cheek, is another example of a trigeminal nerve function.
Trigeminal neuralgia is a painful condition that affects the trigeminal nerve. Trigeminal neuralgia is also known as painful tic, tic douloureax, and tic douloureax. The pain comes and goes, most often as a result of internal inflammatory processes, a lack of blood flow, nerve injury, or direct pressure on the nerve.
Trigeminal neuralgia patients are diagnosed and treated by special teams in many neurological departments. Females above the age of 50 are more likely to get trigeminal neuralgia. Symptoms appear quickly, are generally brief, and affect just one side of the face.
Chewing, cleaning one’s teeth, chatting, or simply being lightly touched or exposed to cold temperatures can all cause pain. The CN V2 and CN V3 trigeminal branches are the ones most impacted by trigeminal neuralgia. Other diseases that can cause face discomfort include Herpes zoster, migraine, multiple sclerosis, and Tolosa-Hunt syndrome.
Secondary trigeminal neuralgia is the term for pain caused by the trigeminal nerve. Idiopathic trigeminal neuralgia is a kind of trigeminal neuralgia that has all of the symptoms but no identifiable aetiology.
Trigeminal pain can be caused by a variety of factors, but the easiest to identify is blood vessel pressure directly on the trigeminal nerve. Blood arteries are extremely near to nerves, and if they press into or wrap around a nerve, a neurovascular loop is formed.
Damage to the myelin sheath of nerve fibres and (surgical) trauma are two other reasons directly connected to the nerves; nevertheless, the majority of cases are idiopathic, meaning we don’t know why.
Local anaesthetics or Botox injections, as well as painkillers and anticonvulsants (carbamazepine) that interrupt blood vessel spasms that may cause a temporary decrease in blood flow to the nerve, may be used as conservative treatments.
Trigeminal neuralgia surgery is a complicated decompression technique that is not without danger. Surgeons must identify the location of a neurovascular loop or compression and gently unwrap or release the nerve from the tissues or arteries that cause pressure.
These treatments can take many hours to complete and do not guarantee a positive outcome. Stereotactic radiosurgery (gamma knife or CyberKnife), which is often used to treat brain tumours, has proven helpful in treating some cases of trigeminal neuralgia. Unfortunately, this type of face discomfort is tough to manage and much more difficult to cure.
Trigeminal Nerve Citations
- Trigeminal Neuralgia. N Engl J Med . 2020 Aug 20;383(8):754-762.
- Neuroanatomy, Cranial Nerve 5 (Trigeminal). PMID: 29489263
- The Trigeminal Nerve Injury. Oral Maxillofac Surg Clin North Am . 2020 Nov;32(4):675-687.
- The trigeminal nerve: an illustrated review of its imaging anatomy and pathology. Clin Radiol . 2013 Feb;68(2):203-13.