Cranial Nerve V, The Trigeminal Nerve
Cranial Nerve V is tested by assessing facial sensation to light touch and pain on the forehead (V1), cheeks (V2) and chin (V3). This is performed with use of a cotton wisp and safety pin. Temperature can be tested by applying hot or cold objects (tuning fork dipped in hot or cold water) if an abnormality in pain or light touch is discovered. Muscular innervation is tested by palpating the temporal and masseter muscles and having patient clench teeth while observing for deviation of jaw or asymmetry in muscle contraction.
The corneal reflex tests for both CN V and CN VII. A patient is asked to look away from examiner while a cotton wisp is used to touch cornea. If the corneal reflex is intact, both eyes will blink. This reflex assumes an intact CN VII (as the sensory limb of the reflex is CN V and the motor limb is CN VII).