cranial nerves

What is the function of cranial nerve I (Olfactory), and how is it assessed?

Function: Sensory – smell.

Assessment: Have the patient close their eyes, occlude one nostril, and identify a familiar scent. Test each nostril separately.

What is the function of cranial nerve II (Optic), and how is it assessed?

Function: Sensory – vision.

Assessment: Test visual acuity using a Snellen chart and assess visual fields by confrontation.

What is the function of cranial nerve III (Oculomotor), and how is it assessed?

Function: Motor – controls most eye movements, eyelid elevation, and pupil constriction.

Assessment: Assess pupil reaction to light, eyelid position, and extraocular movements.

What is the function of cranial nerve IV (Trochlear), and how is it assessed?

Function: Motor – moves the eye downward and inward through the superior oblique muscle.

Assessment: Have the patient follow your finger through the six cardinal fields of gaze.

What is the function of cranial nerve V (Trigeminal), and how is it assessed?

Function: Both sensory and motor – facial sensation and chewing.

Assessment: Lightly touch the forehead, cheeks, and jaw on both sides. Ask the patient to clench their teeth while palpating the jaw muscles.

What is the function of cranial nerve VI (Abducens), and how is it assessed?

Function: Motor – moves the eye laterally (outward).

Assessment: Ask the patient to follow your finger to the side while observing lateral eye movement.

What is the function of cranial nerve VII (Facial), and how is it assessed?

Function: Both sensory and motor – facial expressions and taste from the anterior two-thirds of the tongue.

Assessment: Ask the patient to smile, frown, raise their eyebrows, puff out their cheeks, and close their eyes tightly. Observe facial symmetry.

What is the function of cranial nerve VIII (Vestibulocochlear), and how is it assessed?

Function: Sensory – hearing and balance.

Assessment: Assess hearing using the whisper test. Weber and Rinne tests may also be performed. Assess balance as indicated.

What is the function of cranial nerve IX (Glossopharyngeal), and how is it assessed?

Function: Both sensory and motor – swallowing, taste from the posterior one-third of the tongue, and sensory limb of the gag reflex.

Assessment: Assess swallowing and, when indicated, the gag reflex. Commonly assessed with cranial nerve X.

What is the function of cranial nerve X (Vagus), and how is it assessed?

Function: Both sensory and motor – swallowing, voice, and parasympathetic control of the heart and digestive tract.

Assessment: Ask the patient to say 'ah' and observe symmetrical palate elevation and a midline uvula. Assess voice quality and swallowing.

What is the function of cranial nerve XI (Accessory), and how is it assessed?

Function: Motor – controls the sternocleidomastoid and trapezius muscles.

Assessment: Ask the patient to shrug their shoulders and turn their head against resistance.

What is the function of cranial nerve XII (Hypoglossal), and how is it assessed?

Function: Motor – controls tongue movement.

Assessment: Ask the patient to stick out their tongue and move it from side to side. Observe for deviation, weakness, or abnormal movements.

Which cranial nerves are involved in swallowing and the gag reflex?

CN IX (Glossopharyngeal) and CN X (Vagus).

CN IX provides the sensory limb of the gag reflex, while CN X provides the motor limb.

Which cranial nerves control eye movement?

CN III (Oculomotor)

CN IV (Trochlear)

CN VI (Abducens)

Which cranial nerves are assessed when a patient smiles and clenches their teeth?

Smiling: CN VII (Facial).

Clenching teeth: CN V (Trigeminal).

Which cranial nerves are purely sensory?

CN I (Olfactory)

CN II (Optic)

CN VIII (Vestibulocochlear).

Which cranial nerves have both sensory and motor functions?

CN V (Trigeminal)

CN VII (Facial)

CN IX (Glossopharyngeal)

CN X (Vagus)