Akin to the cables transmitting electrical signals, the brain has a set of cranial nerves that serve as messengers of its signals. These nerves help the brain communicate with different parts of the body. “[Among these,] the trigeminal nerve or cranial nerve V is the largest of the twelve pairs originating from the brain,” says Dr Kannan V, consultant neurologist, Medicover Hospitals, Hyderabad.
Having its roots in the brain, its branches weave across the head, extending to different parts of the face. These branches serve as versatile conductors by transmitting signals of pain, touch, and temperature.
Beyond its sensory roles, the trigeminal nerve also plays a part in biting, chewing, and swallowing. Notably, it divides into three distinct branches, each holding specific responsibilities. The characteristics of each of the branches are as follows.
Upper or the Ophthalmic nerve
The trigeminal nerve’s initial branch carries sensory signals from the scalp, forehead, and upper eyelid and tip of the nose. Physical shock, trauma, exposure to toxins and high doses of radiation can damage this nerve. “Damage to this branch can result in the loss of sensation in the associated areas,” says Dr Kannan V. It also compromises the reflex of the eye’s cornea which can affect the corneal functioning.
Middle or Maxillary nerve
This branch transmits sensory information from the lower eyelid and cheek, upper lip, upper teeth and gums, nose, palate, roof of the mouth, and certain sinuses. “[Different factors, including] compromise of the sensory root, infections, iatrogenic injury, or trauma, can damage this nerve, resulting in the loss of sensation in the corresponding regions,” says Dr Kannan.
Lower or Mandibular nerve
This largest branch combines both sensory and motor functions (nerves that control movement). It picks the sensory information from the lower lip, lower teeth, gums, chin, jaw, parts of the external ear, and meninges. Although responsible for touch, position, pain, and temperature sensations from the mouth, this nerve does not convey taste sensations. Trauma, surgical procedures or tumours can affect this branch causing discomfort while biting, chewing, eating and speaking.