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Investigation of cranial nerves. V pair: trigeminal nerve (n. Trigeminus)
Last reviewed: 23.04.2024
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The motor branches of the trigeminal nerve innervate the muscles that provide the movements of the lower jaw (chewing, temporal, lateral and medial pterygoids, maxillofacial, the anterior abdomen of the two-abdominal); muscle that strains the eardrum; muscle stretching the palatine curtain. Sensitive fibers provide the main part of the scalp of the head (facial skin and frontal parietal part of the scalp), the mucous membrane of the nasal cavity and mouth, including the frontal and maxillary sinuses; part of the ear canal and tympanic membrane; eyeball and conjunctiva; front two-thirds of the tongue, teeth; periosteum of the facial skeleton; a solid cerebral membrane of the anterior and middle cranial fossae, the cerebellum detects. The branches of the V nerve are the ophthalmic, maxillary and mandibular nerves.
Sensitivity on the face is provided by both the trigeminal nerve and the upper cervical spinal nerves.
Pain, tactile and temperature sensitivity are consistently checked in the zones of innervation of all three branches of the V pair on both sides (use a pin, a soft hair brush, a cold surface of a metal object - a neurological hammer, a dynamometer). Synchronously touching the symmetrical points in the forehead (I branch), then the cheeks (II branch), the chin (III branch).
Dissociated violation of the sensitivity of the face, i.e. Violation pain and temperature sensitivity during preservation tactile evidence of lesions of the nucleus of the spinal path trigeminal nerve (nucl. Tractus spinalis n. Trigemini ) while retaining the basic sensitive nucleus of trigeminal nerve located in the dorsolateral part of the tire axle (nucl pontinus n. Trigemini). This disorder most often occurs with syringobulbomyelia, ischemia of the posterolateral divisions of the medulla oblongata.
Neuralgia of the trigeminal nerve is characterized by sudden short and very intense repeated bouts of pain, so short that they are often described as a chamber or an electric shock. The pain extends to the innervation zones of one or more branches of the trigeminal nerve (usually in the region of the II and III branches and only in 5% of cases in the region of the I branch). With neuralgia of loss of sensitivity on the face usually does not happen. If trigeminal pain is combined with impaired surface sensitivity, neuralgia-neuropathy of the trigeminal nerve is diagnosed.
The corneal (corneal) reflex is examined using a patch of cotton wool or a strip of newsprint. Ask the patient to look at the ceiling and, without touching the eyelashes, lightly touch the cotton wool to the edge of the cornea (not to the sclera) from the lower part (not above the pupil!). Evaluate the symmetry of the reaction to the right and left. Normally, if V and VII nerves are not damaged, the patient flinches and flashes. Preservation of the sensitivity of the cornea in the presence of paralysis of facial muscles is confirmed by the reaction (blinking) of the contralateral eye.
To assess the motor portion of the trigeminal nerve, evaluate the symmetry of opening and closing the mouth, noting whether there is a displacement of the mandible to the side (the jaw is shifted toward the weakened pterygoid muscle, the face thus appears skewed).
To assess the strength of the chewing muscles, the patient is asked to strongly clench his teeth and palpate m. Masseter on both sides, and then try to unclench the clenched jaws of the patient. Normally, the doctor can not do it. The strength of the pterygoid muscles is evaluated with the movements of the lower jaw to the sides. The revealed asymmetry can be caused not only by the paresis of the chewing muscles, but also by bite disorders.
To cause the mandibular reflex the patient is asked to relax the muscles of the face and slightly open his mouth. The doctor puts the index finger on the patient's chin and strikes lightly with a neurological mallet from top to bottom along the distal phalanx of that finger, first from one side of the lower jaw, then from the other. The chewing muscle on the side of the blow is shortened and the lower jaw rises (the mouth closes). In healthy people, the reflex is often absent or difficult to call. The increase of the mandibular reflex indicates a bilateral defeat of the pyramidal tract (cortico-nuclear pathways) above the middle sections of the bridge.
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