ICD-11

The trigeminal nerve is a mixed nerve with three divisions, ophthalmic, maxillary and mandibular divisions, that provides sensory innervation to the face and mucous membrane of the oral and nasal cavities and motor innervations to the muscle of mastication, tensor tympani, tensor veli palatine, mylohyoid and anterior belly of the digastric muscle. The trigeminal nuclear complex extends throughout the brainstem, hence it is susceptible to many pathologic processes including demyelination, ischemia, haemorrhage, infectious and non-infectious inflammation and neoplasm leading to symptoms of trigeminal nerve involvement. Compression of the sensory nerve root outside the brain stem by a vascular loop leads to trigeminal neuralgia. Symptoms and signs depend on the site of the lesion. In general, a trigeminal nerve disorder is associated with hemisensory facial loss, deviation of the jaw to paralysed side on opening of the mouth, and loss of the corneal reflex.