A nurse is performing a cranial nerve assessment on a school-age child.
Which of the following findings indicates proper functioning of the child’s trigeminal nerve?
A.
The child maintains balance when standing with eyes closed.
B.
The child has symmetrical jaw strength when biting down.
C.
The child exhibits a gag reflex when stimulated with a tongue blade.
D.
The child correctly identifies specific scents.
The correct answer and Explanation is :
The correct answer is:
B. The child has symmetrical jaw strength when biting down.
Explanation:
The trigeminal nerve (cranial nerve V) is primarily responsible for sensation in the face and for motor functions involved in chewing. It has three main branches:
- Ophthalmic (V1) – Sensory input from the forehead, upper eyelids, and nose.
- Maxillary (V2) – Sensory input from the lower eyelids, upper jaw, and upper teeth.
- Mandibular (V3) – Sensory input from the lower jaw, lower teeth, and part of the ear, as well as motor control of the muscles responsible for mastication (chewing).
To assess proper functioning of the trigeminal nerve, the nurse might evaluate both sensory and motor functions. Testing jaw strength is specifically assessing the motor function of the mandibular branch (V3).
Symmetrical Jaw Strength: By asking the child to bite down, the nurse can assess the strength of the masseter and temporalis muscles, which are controlled by the mandibular branch of the trigeminal nerve. If the jaw strength is symmetrical when the child bites down, this suggests that the motor function of the trigeminal nerve is intact, indicating proper nerve function.
Why Other Options Are Incorrect:
A. Balance with Eyes Closed: This tests the vestibulocochlear nerve (cranial nerve VIII), not the trigeminal nerve. The ability to maintain balance with eyes closed is related to the vestibular system.
C. Gag Reflex: The gag reflex is mediated by the glossopharyngeal nerve (cranial nerve IX) and the vagus nerve (cranial nerve X), not the trigeminal nerve.
D. Identifying Scents: This tests the olfactory nerve (cranial nerve I), which is responsible for the sense of smell.
In summary, symmetrical jaw strength when biting down is a direct assessment of the trigeminal nerve’s motor function, making it the correct indicator of proper functioning for this nerve.