The Trigeminal Nerve
The trigeminal nerve is the fifth cranial nerve and has three well defined divisions: the ophthalmic branch, maxillary branch and mandibular branch. Their fibers contain various types of nervous tissue (e.g. sensory or motoric) running through selected branches. The branches of the trigeminal nerve innervate a large area including the whole forehead, face, lateral regions of the head and the most upper part of the neck.
The nuclei of the trigeminal nerve are located in the brainstem and the upper part of the spinal cord.
- The mesencephalic nucleus of trigeminal nerve is found in the lateral region of the periaqueductal grey matter in the midbrain. It contains the first neurons responsible for the proprioception of the jaw and intraocular muscles, temporomandibular joints, the teeth and the upper and lower jaw.
- The principal nucleus of trigeminal nerve is located in the dorsolateral pontine tegmentum. Its main task is the tactile sensation.
- The spinal nucleus of trigeminal nerve is a long nucleus sensory nucleus stretching from the pons down into the upper three segments of the spinal cord's dorsal horn. It is primarily concerned with the pain and temperature sensation.
The Ophthalmic Branch
This first branch of the trigeminal nerve is responsible for the innervation the forehead, the nose and the ophthalmic regions of the face. It exits the skull through the superior orbital fissure in the bony orbit. Both the ophthalmic branch and the maxillary branch of the trigeminal nerve supply the nasal cartilage with terminal branches.
The Maxillary Branch
The second branch provides nervous receptors for the face from below the eye to the upper jaw. One important nerve branching off the maxillary nerve is the superior alveolar nerve which supplies the upper teeth within the oral cavity.
The Mandibular Branch
The third branch of the trigeminal nerve covers the sensation of the lowest part of the face, the lower jaw and the floor of the oral cavity. Furthermore it supplies all jaw muscles with motoric branches including the muscles of mastication. One important branch innervating the tongue is the lingual nerve.
Trigeminal neuralgia is one of the pathological presentations involving the trigeminal nerve. It is described as a severe pain in the face with a sudden and erratic onset. The pain is chronic and progressive (gradually getting worse with time). There are three different types of trigeminal neuralgia: typical (or idiopathic), atypical and symptomatic. The typical type is the most common one where no cause can be found. The symptomatic trigeminal neuralgia occurs secondary to other conditions, e.g. multiple sclerosis, tumors, post-infectious or post-traumatic. Therapy options include anticonvulsants and augmentative surgery however in most cases there is no cure.