Module 11: Cranial Nerve Exam

how can we test the olfactory nerve?

using lemon extract, coffee beans, or other distinctive scents, we can test the smell of the patient by having them close their eyes, block one nostril, and see if they can identify the scent that is held about 10 cm away. when comparing the sides should see if the scents are the same on either side.

which cranial nerve does the visual acuity test assess?

CN II (the optic nerve)

what is the procedure for the visual acuity test?

use the snellen chart either on the wall 20 feet away, or the pocket snellen that is held arms length away. patient will then cover one eye and read the smallest line possible and repeat with the other eye

what test can we use to assess both CN II and III?

Pupillary response test

what is the procedure of the pupillary responses test?

instruct the pt to look straight ahead and focus on a spot on the wall behind, place the hand on the bridge of the nose to block light into the non tested eye, and shine eye in the eye, looking for pupil constriction in the tested eye first in a direct light reflex, and then the opposite eye for an indirect light reflex

what is the normal response of pupillary light reflex?

both pupils should constrict equally when shine the light in each eye

what nerves are tested when observing ocular alignment?

CN III, CN IV, and Cn VI

what would ocular alignment look like if either CN III, IV, or VI was damaged?

if oculomotor damaged see the eye turned outward at rest, if trochlear damaged see the eye turned up and out at rest, and if abducens damaged see the eye turned medially at rest

what cranial nerves are testing when testing extraocular movements?

CN III, CN IV, and CN VI, should see full eye movement in the “H” patten and the absence of nystagmus

what would be abnormal findings that would indicate CN III damage?

ptosis, weakness with upward and or inward movements, and resting eye position turned outward, also double vision

what abnormal findings would suggest CN IV involvements?

double vision with downward pursuits, weakness with downward and or torsional movements, resting eye position drifting upward, and if torsional movements are involved will compensate by tilting head in the opposite direction of the palsy

what abnormal findings would suggest damage to CN VI?

weakness with lateral eye movements, resting eye position turned outwards, also double vision

which cranial nerve would the visual field test assess?

The visual field test assesses the optic nerve, CN II, which is responsible for vision and peripheral awareness. this test should cover all 4 visual quadrants of the eye

what is accommodation and convergence testing used to assess?

Accomodation and convergence testing are used to assess the function of CN III, oculomotor nerve, to evaluate the eye's ability to focus on near objects (through pupil constriction) and to appropriately converge.

what tests can be used to assess CN V?

fascial sensation with light touch and sharp/dull discrimination for the sensory branches (maxillary, mandibular, and opthalamic), and the muscles of mastication assessment for the motor branch in which the patient opens the mouth against the therapists’ hand resistance or to bite down

what does the jaw jerk reflex test?

The jaw jerk reflex tests the integrity of CN V, the trigeminal nerve, specifically assessing the function of the motor branch by evaluating the reflex response during stimulation of the jaw. normal response would have no reflexive movement of the jaw

which test can be used to assess CN VII?

evaluation of facial expression (pt should smile, puff out cheeks, raise eyebrows, wrinkle the nose, close eye tightly and should see symmetry)

which nerves are testing with the corneal reflex?

The corneal reflex tests CN V (trigeminal nerve) for sensory input and CN VII (facial nerve) for motor response. It involves the blinking of both eyes in response to corneal stimulation of one eye (the white of the eye) when the patient is looking medially

what are the two special tests for hearing?

The two special tests for hearing are the Rinne test and the Weber test. These tests evaluate air and bone conduction of sound and help determine the type of hearing loss.

what is the difference between conductive and sensorineural hearing loss?

Conductive hearing loss occurs when sound is not conducted efficiently through the outer ear canal to the eardrum and the tiny bones of the middle ear, while sensorineural hearing loss results from damage to the inner ear (cochlea) or the auditory nerve pathways to the brain. Conductive loss is often treatable with medical or surgical interventions, whereas sensorineural loss is typically permanent.

what are the causes of conductive vs sensorineural hearing loss?

Conductive hearing loss can be caused by ear infections, fluid in the middle ear, eardrum perforation, or ossicle abnormalities. Sensorineural hearing loss may result from aging, noise exposure, genetic factors, acoustic neuroma, ototoxicity (medication adverse effect) or damage to the inner ear or auditory nerve.

list the symptoms of conductive hearing loss compared to sensorineural hearing loss

for conductive see fullness or pressure in the ears, ear pain, and ear popping. for sensorineural hearing loss see muffled hearing, harder to hear in noisy environments

what nerves does the “Ah Test” assess?

CN IX and X, should see the uvula elevate symmetrically, if deviates will deviate to the NORMAL side

what does the gag reflex assess?

The gag reflex assesses the integrity of CN IX (glossopharyngeal) and CN X (vagus) nerves, facilitating the contraction of the pharyngeal muscles in response to stimulus in the back of the pharynx, abnormal won’t feel the tongue depression (damage to CN IX) and won’t have gag reflex

what nerve does the tongue protrusion test assess?

The tongue protrusion test assesses the integrity of CN XII (hypoglossal nerve), which controls tongue movement. A deviation of the tongue to one side indicates possible weakness or damage to the side of the deviation if a LMN lesion or away form the side of the lesion if a UMN lesion