Cranial Nerves Flashcards
CN I
Olfactory tract
CN II
Optic tract
CN III
Oculomotor
CN IV
Trochlear
CN V
Trigeminal
CN VI
Abducent
Which cranial nerve comes of the back of the brain stem
CN IV trochlear
CN VII
Facial
CN VIII
Vestibulocochlear
CN IX
Glossopharyngeal
CN X
Vagus
CN XII
Hypoglossal
CN XI
Accessory
How to examine the olfactory nerve
Ask the patient if they have noticed change in sense of smell
- characteristic smelling objects eg peppermint , can be used to further discriminate pathologies, asking patient to close eyes and examining each nostril in turn
How to examine the oculomotor, trochlear and abducens nerves
Pupillary light reflex
Ask the patient to fixate on a distant target
Shine a pen torch into each eye in turn, bringing the beam in quickly from the lateral side
Observe both the direct (ipsilateral) and consensual (contralateral) response
Pupillary accommodation – The accommodation reflex involves both convergence of the eyes (requiring adduction of both eyes) and simultaneous constriction of the eyes
Ask the patient to look at an object held at distance
Bring the object to within 10cm of the patient, asking the patient to follow it with their eyes
Watch the pupils for equal convergence and constriction
Ask the patient to look straight ahead and check for signs of nystagmus or ptosis
Ocular movements
Ask the patient to keep their head still and follow an object
Move the object around in an H formation, assessing both horizontal and vertical gaze
Watch the pupils to assess the eye movements and any signs of nystagmus
Checking the conjugate gaze may also be warranted at this point
Ensure to ask the patient to let you know if they experience any double vision throughout
How to examine the optic nerve
Visual Acuity (VA) – Assess VA with a Snellen chart. Keep glasses on to correct for any refractory errors
Stand the patient 6m away from the chart, covering each eye separately with their hand in turn
Find the line of print which the patient can comfortably read at
Visual Fields
Ask the patient to cover their left eye with their left hand and then cover your right eye with your right hand. The patient must continue to look straight ahead
Move your hand to the patient’s upper temporal visual field quadrant
Gradually move your finger to the centre of their vision from the periphery and ask the patient to inform you as soon as they see your finger moving
Repeat for the lower temporal, upper nasal, and lower nasal fields, then repeat on the other eye
How to examine the trigeminal nerve
Both sensory and motor branches of the trigeminal nerve should be tested:
Sensation requires both light touch and pin prick assessment
Demonstrate to the patient what to expect from the light touch and pin prick sensations
Ask the patient to close their eyes and gently touch the forehead, cheeks, and chin regions (assessing ophthalmic, maxillary, and mandibular branches respectively)
Ensure to ask the patient to let you know if they experience any changes in sensation either side or cannot feel the sensation
Motor function is checked by the muscles of mastication
Ask the patient to clench their teeth tight and palpate for the contraction in the temporalis muscle and masseter muscle
Ask the patient to open their mouth, move their jaw from side to side, then close their mouth
Testing of the corneal reflex should not be performed unless sensory impairment suspected, as it is uncomfortable to the patient
How to examine the facial nerve
assessment of the muscles of facial expression:
Initially assess for symmetry in the face at rest
Ask the patient to perform the following movements
Raise their eyebrows
Close their eyes tightly
Blow out their cheeks
Smile
These movements should also be able to be completed against the examiner’s resistance
How to examine the vestibulocochlear nerve
should cover both cochlear and vestibular function:
Hearing can be assessed by whispering a number into each ear separately, making a distracting noise with your fingers in the contralateral ear, and asking the patient to repeat
If any hearing loss suspected, perform Rinne’s and Weber’s test
Balance has no truly satisfactory test for assessment
Formal vestibular testing can be performed
How to examine the Glossopharyngeal and vagus nerve
Ask the patient to cough (assessing CN X)
Ask the patient to open the mouth wide and say ‘ah’, using a tongue depressor to visual the palate and posterior pharyngeal wall (assessing CN IX and X)
The soft palate should move upwards centrally
Testing of the gag reflex should not be performed unless bulbar impairment is suspected, as it is uncomfortable to the patient.
How to examine the accessory nerve
Sternocleidomastoid can be assessed by asking the patient to turn their head to each side, against the examiners resistance
Trapezius can be assessed by asking the patient to shrug their shoulders, against the examiners resistance
How to examine the Hypoglossal nerve
Ask the patient to open their mouth and inspect the tongue for any wasting or fasciculation
Ask the patient to protrude the tongue and move from side to side
