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n trigeminus
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200
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886
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Sensory areas of the head, showing the general distribution of the three divisions of the fifth nerve
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Distribution of the maxillary and mandibular nerves, and the submaxillary ganglion
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Ophthalmic Nerve <BR> Maxillary Nerve <BR> Mandibular Nerve
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Trigeminal+Nerve
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A08800800120760
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The is the fifth (V)
Cranial Nerve , and carries sensory information from most of the face, as well as motor supply to the
Muscles Of Mastication (the muscles enabling chewing),
Tensor Tympani (in the middle ear), and other muscles in the floor of the mouth, such as the
Mylohyoid and
Anterior Digastric Muscle .
It is named ''trigeminal'' because it divides into three branches:
The ophthalmic, maxillary, and mandibular branches leave through various ,
Foramen Rotundum and
Foramen Ovale , respectively. The
Mnemonic device ''standing room only'' can help one remember that the V
1 segment branch passes through the
superior orbital fissure, V
2 passes through the foramen
rotundum, and V
3 passes through the foramen
ovale.
The trigeminal nerve is the major cutaneous sensory nerve of the head, and is responsible for sensation over most of the skin on the head.
While all three trigeminal branches carry sensory information, only the mandibular branch carries motor input. The mandibular nerve supplies motor fibres to the
Temporalis ,
Lateral Pterygoid ,
Medial Pterygoid ,
Masseter (the four main
Muscles Involved In Mastication ),
Tensor Veli Palatini ,
Mylohyoid , the anterior belly of the
Digastric Muscle , and the
Tensor Tympani .
The trigeminal nerve caries
Proprioceptive fibers from the tissues it innervates as well as from the muscles supplied by the
Facial Nerve .
As the trigeminal nerve contains both sensory and motor fibers, and also branches into different regions, these should be tested separately and on both sides of the face.
To test the sensation, the skin is touched lightly (for instance with ,
Cheek s and
Chin , as well as around the
Nose and
Mouth .
The
Corneal Reflex is dependent on the trigeminal nerve sensing touching the eye (as well as the
Facial Nerve for the motor response). This can be done with a wisp of cotton wool, and approaching from the side (so the person being investigated doesn't blink at the sight approaching). The corneal reflex elicits a blink with both eyes, and feels very uncomfortable for the patient.
To test whether the motor pathways are functional, the temporalis and masseter muscles may be felt. The temporalis can be felt contracting at the temples (just lateral to the eyes) when a person is chewing (or clenching and unclenching his/her teeth). The masseter can be felt just above the angle of the jaw in the same movement.
The strength of the jaw muscles can be tested by holding a person's jaw closed and telling the person to open it (which tests the pterygoids) and opening the jaw and getting the person to close it (which tests the masseters). The jaw muscles are normally quite strong, and should have little difficulty overcoming pressure from a hand.
If there is unilateral damage to the motor root of the trigeminal nerve, the jaw will tend to deviate towards the paralysed side.
The
Jaw Jerk Reflex will be very brisk if there is any
Upper Motor Neuron damage above the
Pons .
