Cranial Nerve V- Trigeminal Nerve

By: Varsha Kumari

INTRODUCTION:

The trigeminal nerve (CN V) is the fifth and the largest cranial nerve, that serves as a significant conduit for sensory input from the head and neck in addition to providing motor innervation to the muscles of mastication (Go et al., 2001).

STRUCTURE AND FUNCTION:

The trigeminal nerve (cranial nerve V) originates from three sensory nuclei—the mesencephalic, principal (or chief) sensory, and spinal nuclei of the trigeminal nerve—as well as one motor nucleus, the motor nucleus of the trigeminal nerve. These nuclei are distributed along the brainstem, extending from the midbrain to the medulla. At the level of the anterolateral surface of the mid-pontine region, the fibers from the sensory nuclei converge to form the sensory root, while the fibers from the motor nucleus form the motor root. Both roots converge and pass anteriorly through the prepontine and the cerebellopontine angle cistern, before entering a CSF-filled space called the Meckel’s cave or trigeminal cave (Huff et al., 2024; The Trigeminal Nerve (CN V) – Course – Divisions – TeachMeAnatomy, n.d.). Inside Meckel’s cave, the sensory root expands into the trigeminal ganglion, from which three major divisions emerge:

Ophthalmic nerve (V1) – It is a purely sensory branch that innervates the scalp, eyes, nose, and forehead. The nerve also provides sympathetic efferent fibers to the pupillary dilators, ciliary body, iris, and lacrimal gland, as well as afferent fibers to the conjunctiva and cornea.

Maxillary nerve (V2) – The maxillary division of the trigeminal nerve innervates the middle third of the face, including the lower eyelid, lateral aspect of the nose, upper teeth and gums.

Mandibular nerve (V3) – The mandibular nerve is the largest branch of the trigeminal nerve and exits the skull through the foramen ovale. Unlike the other divisions, V3 carries both sensory and motor fibers. It conveys sensation from the lower third of the face, including the jaw, lower lip, floor of the mouth, and anterior two-thirds of the tongue. The motor root of V3 passes inferior to the sensory root along the floor of trigeminal cave and innervates the muscles of mastication—masseter, temporalis, medial and lateral pterygoids as well as the anterior belly of the digastric and the mylohyoid muscle (Gillig & Sanders, 2010; Huff et al., 2024).

TRIGEMINAL NEURALGIA: 

It is a chronic neurological disorder that causes acute, severe, electric shock-like facial pain along the sensory distribution of trigeminal nerve, sometimes referred to as a “lightning bolt” sensation. These short, paroxysmal episodes can occur on multiple occasions during the day.
The disorder is usually unilateral and can affect any of the three divisions of the trigeminal nerve (CN V) but frequently affects the maxillary (V2) and mandibular (V3) branches. The most common underlying cause is vascular compression of the trigeminal nerve root, most commonly by the superior cerebellar artery (Huff et al., 2024; Khawaja & Scrivani, 2023a).

DIAGNOSIS: The diagnosis of Trigeminal Neuralgia (TN) is made clinically, based on diagnostic criteria outlined in the International Classification of Headache Disorders, 3rd edition (ICHD-3), through a thorough patient history and physical examination. This is crucial, as there is no specific laboratory test available to definitively confirm the diagnosis. However, Magnetic Resonance Imaging (MRI) is the first-line investigation to identify secondary causes of TN, such tumors or multiple sclerosis (Khawaja & Scrivani, 2023b).

MANAGEMENT:

First-line treatment for Trigeminal Neuralgia (TN) is medical therapy, with carbamazepine being the FDA-approved drug for its management. In patients who do not respond adequately or cannot tolerate carbamazepine, second-line therapies include other antiepileptics such as gabapentin, clonazepam, lamotrigine, phenytoin, and valproic acid. Surgical intervention is considered for refractory cases, and common procedures involve microvascular decompression, percutaneous rhizotomy, and peripheral nerve blocks (Kikkeri & Nagalli, 2024).

REFERENCES:

1. Gillig, P. M., & Sanders, R. D. (2010). The Trigeminal (V) and Facial (VII) Cranial Nerves: Head and Face Sensation and Movement. Psychiatry (Edgmont), 7(1), 13. https://pmc.ncbi.nlm.nih.gov/articles/PMC2848459/
2. Go, J. L., Kim, P. E., & Zee, C. S. (2001). The trigeminal nerve. Seminars in Ultrasound, CT, and MR, 22(6), 502–520. https://doi.org/10.1016/S0887-2171(01)90004-6
3. Huff, T., Weisbrod, L. J., & Daly, D. T. (2024). Neuroanatomy, Cranial Nerve 5 (Trigeminal). StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK482283/
4. Khawaja, S. N., & Scrivani, S. J. (2023a). Trigeminal Neuralgia. Dental Clinics of North America, 67(1), 99–115. https://doi.org/10.1016/J.CDEN.2022.07.008
5. Kikkeri, N. S., & Nagalli, S. (2024). Trigeminal Neuralgia. StatPearls. https://www.ncbi.nlm.nih.gov/books/NBK554486/
6. The Trigeminal Nerve (CN V) – Course – Divisions – TeachMeAnatomy. (n.d.). Retrieved May 5, 2025, from https://teachmeanatomy.info/head/cranial-nerves/trigeminal-nerve/