There are twelve cranial nerves (aka nerves in the head). Each has nerve has a specific role and its function can easily be tested. Below is a summary of each Cranial Nerve (#) - what it does - how to test function.
#1 – smell – test sense of smell (using an essential oil or rubbing alcohol).
#2 – visual acuity and fields – test visual acuity (Snellen eye chart) and look into eye using opthalmoscope.
#3 – pupillar (pupil) reactions – inspect size, shape, and functioning of pupils.
#4 (along with 3 and 6) – extraoccular (eye) muscle movements – test eye muscle movements
#7 – facial movements – note symmetry of the face, ask patient to raise eyebrows, frown, close eyes tightly, show upper and lower teeth, puff out cheeks, and smile (testing face muscles).
#8 – hearing – whisper near patient to test their hearing.
#9 (and 10) – swallowing and gagging – say "ah" to see soft palate rise, move the tongue, and test gag reflex.
#11 – shoulder and neck movements – shrug shoulders and turn head to each side against resistance.
#12 – tongue – inspect the tongue and ask patient to say "light, tight, dynamite" to test tongue movements.