The sensory portion of the trigeminal supplies touch–pain–temperature to the face. The nerve has three divisions: the ophthalmic, maxillary, and mandibular nerves (Figure 61.1). The innervation includes the cornea and conjunctiva of the eye; mucosa of the sinuses, nasal and oral cavities; and dura of the middle, anterior, and part of the posterior cranial fossae. The mandibular division carries the motor portion. The motor portion conveys proprioceptive impulses from the temporomandibular joint.
Areas supplied by the three sensory divisions of the trigeminal nerve.
A lesion of the sensory fibers produces hypesthesia or anesthesia of the area supplied. The corneal reflex is absent when the area of supply is the eye. Proprioception for the temporomandibular joint is absent when there is a lesion of the mandibular division.
The motor division of the nerve supplies the muscles of mastication: masseter, temporal, pterygoid, mylohyoid, and digastric. These muscles produce elevation, depression, protrusion, retraction, and the side-to-side movements of the mandible. The motor division also supplies the tensor tympani and tensor palati muscles.
The mandible upon opening deviates toward the paralyzed side when there is unilateral paralysis of the masticatory muscles. This direction of the mandible is due to the action of normal pterygoids on the opposite side. The mandible droops, and no jaw movement is possible with bilateral paralysis. The involved muscles atrophy in nuclear or infranuclear lesions.
The jaw jerk is one of the deep tendon or stretch reflexes. When it is normal, tapping the mandible produces a brisk contraction. When abnormal, with upper motor neuron lesions, there is a hyperactive or repeating reflex (clonus). With nuclear or infranuclear lesions, the reflex is absent.
Copyright © 1990, Butterworth Publishers, a division of Reed Publishing.