Cranial Nerves Flashcards
What should you consider during the general observation, before starting the examination?
- Posture, gait and symmetry
- Any abnormal movements
- Whether the patient is wearing glasses or hearing aids
What is the test for the olfactory nerve?
A simple screening question to check if the patient has had any problems with their sense of smell
if there is any doubt, test using strong smelling food such as coffee or citrus fruit
When assessing the optic nerve, what four different aspects need testing?
- Pupillary reflexes to light and accommodation
- Visual acuity
- Visual fields
- Fundoscopy
What is the first stage in assessing pupillary light reflexes?
Test for the direct and consensual pupillary reflexes
direct pupillary light reflex:
- shine a light into the left pupil
- the left pupil should constrict to light
consensual light reflex:
- shine a light into the right pupil
- look for pupil constriction on the left side
Then check the opposite side
What is the second stage in the pupillary light reflex test?
Test for pupillary accommodation
- hold your index finger approximately 1 metre away from the patient and gradually move it towards their nose
- both pupils should constrict as the eyes converge and accommodate to continue focusing on the finger
What equipment is used to assess visual acuity?
Snellen Chart
this is designed to test visual acuity at a specific distance
the patient CAN wear glasses/contact lenses to read the chart, and each eye should be tested separately
How are visual fields usually assessed?
By checking that the patient can detect movement in each of the four quadrants of the visual field
testing is done by confrontation (testing with the patient sat opposite you)
each eye is tested separately, so the patient covers one eye and you cover the eye directly opposite to their covered eye
What is important to remember about positioning when conducting the visual field examination?
Position yourself and the patient at an arm-length apart, with your eyes level
this is important as you are testing the patient’s visual field in comparison with your own
How is the visual field examination actually conducted?
Ask the patient to say ‘yes’ when they see your fingers move
test all 4 quadrants of the visual field by gradually moving your fingers from the periphery of the visual field towards the centre
Why is fundoscopy used?
It allows for direct visualisation of the retina
How is the fundoscopy examination conducted?
- Place your hand on the patient’s forehead and look for the red reflex
- Use your right eye to visualise the back of the patient’s right eye
- Start by locating a vessel, follow it to the optic disc and repeat until you have followed all 4 vessels
- Finish by asking the patient to look directly into the light to visualise the macula
Why are the oculomotor (3), trochlear (4) and abducens (6) nerves tested together?
They work synergistically in normal eye movement
How is the examination of the oculomotor, trochlear and abducens nerves conducted?
- Start by looking or any asymmetry of eye position at rest, and checking for ptosis
- Move your finger along horizontal and vertical planes, then by making a letter H
- Ask the patient if they experience any double vision
- Note any nystagmus, which is likely to occur at extremes of gaze
What would a normal examination of the oculomotor, trochlear and abducens nerves look like?
The eyes will move smoothly and synchronously
where a cranial nerve abnormality exists, they eyes will NOT move synchronously and this will cause the patient to experience double vision
What is the test for the sensory division of the trigeminal nerve?
Light sensation:
- test using cotton wool in each of the 3 divisions - ophthalmic, maxillary, mandibular
- compare each side to the other
Sharp touch sensation:
- the test is repeated using a neurotip
When is the corneal reflex tested?
It is not routinely tested unless a lesion is suspected as it is very uncomfortable for the patient
the afferent pathway for the reflex is the trigeminal nerve
the efferent pathway for the reflex is the facial nerve
How is the corneal reflex tested?
Touch the cornea (not sclera) with cotton wool
in a normal examination, both eyes should blink
What is involved in testing for the motor division of the trigeminal nerve?
It involves testing the muscles of mastication
- Temporalis
- Masseter
- Pterygoids
How is the motor division of the trigeminal nerve tested?
- Ask the patient to clench their teeth while you palpate temporalis and masseter
- Test the pterygoid muscles by asking the patient to open their jaw and keep it open against resistance
- Ask the patient to move their jaw from side to side
What should a normal examination of the motor division of the trigeminal nerve look like?
- You should be able to feel contraction of temporalis and masseter
- You should not be able to overcome the strength of the pterygoids
- Jaw movement should be equal on both sides
How is the facial nerve tested for?
It involves testing the muscles of facial expression
- Frontalis
- Orbicularis oculi
- Orbicularis oris
- Buccinators
What questions should you ask the patient when testing the facial nerve?
First observe for any facial asymmetry
- “please could you raise your eyebrows as high as you can and keep them there - don’t let me push them down”
- “squeeze your eyes tight - hold them there, don’t let me open them”
- “show me your teeth and purse your lips”
- “blow out your cheeks and keep them there”
In a normal examination, facial movement will be symmetrical
What 3 tests are used to assess the vestibulocochlear nerve (8)?
It involves a simple screening test to identify hearing problems
- Clinical hearing test
- Rinne’s test
- Weber’s test
What is involved in the clinical hearing test?
- Ask the patient if they have experienced any hearing difficulty
- Explain that you will whisper a number into each ear in turn and ask them to repeat it
What should you do if hearing difficulty is detected during the clinical hearing test?
Further testing to distinguish between conductive and sensorineural deafness can be done using Rinne’s test and Weber’s test
What is Rinne’s test used for?
It uses a tuning fork to ascertain whether bone conduction is louder than air conduction
it is used to measure conductive hearing impairment
What are the 3 stages in Rinne’s test?
- Ask the patient if they can hear the vibrating tuning fork held at the entrance to the external auditory canal
- this is sound A for Air conduction
- place the tuning fork on the bony prominence of the mastoid process
- this is sound B for Bone conduction
- ask which sound your patient perceives as being the loudest
What is meant by a positive Rinne’s test?
Normal hearing
sound A (air conduction) is louder than sound B (bone conduction)
What is meant by Rinne’s test being negative?
Conductive hearing impairment
bone conduction is louder than air conduction
Why must Weber’s test be performed when Rinne’s test is positive?
Rinne’s test can be positive in patients with complete sensorineural deafness in one ear
air conduction and bone conduction are both reduced equally
What is the purpose of Weber’s test?
It is designed in conjunction with Rinne’s test to further investigate unilateral hearing impairment
How is Weber’s test conducted?
- Place vibrating tuning fork in the centre of the patient’s forehead
- ask whether they hear this equally on both sides, or whether they perceive the sound to be louder in one ear
- in normal hearing, the sound is detected equally on both sides
What could it mean if a hearing impairment is detected in Weber’s test?
If the sound localises to one ear, this can mean that there is either:
- Ipsilateral conductive hearing loss - which can be confirmed by the findings from a negative Rinne’s test
- Contralateral sensorineural hearing loss
Why are the glossopharyngeal (9) and vagus (10) nerves assessed together?
They both supply sensation and the muscles controlling movement of the mouth and throat
How are the glossopharyngeal and vagus nerves assessed?
- Ask patient to give a cough
- Then ask patient to open their mouth whilst you look at the soft palate
- Ask the patient to say “aaaah”
In a normal examination, the palate should rise equally on both sides
When is the Gag reflex assessed?
What does it test for?
It is not routinely tested on a well patient
- Touch the posterior pharynx first to one side, and then the other, with a wooden stick
- This causes the palate to rise and the patient to “gag”
the afferent (sensory) pathway of this reflex is the glossopharyngeal nerve
the efferent (motor) pathway of this reflex is the vagus nerve
What does the accessory nerve (11) supply?
Trapezius and sternocleidomastoid muscles
How is the accessory nerve assessed?
Strength of trapezius:
- ask patient to shrug their shoulders and keep them raised whilst you push down
Strength of sternocleidomastoid muscles:
- ask patient to turn their head first to one side and then the other
- ask them to keep this position against resistance
in normal examination, movement and power of the muscles should be equal on both sides
What does the hypoglossal nerve supply?
The tongue
How is the hypoglossal nerve tested for?
- Ask patient to stick out their tongue, looking for any wasting or fasciculation
- Ask patient to move their tongue to one side, and then the other
- Ask them to move their tongue into one cheek and keep it there against resistance, then check the other side
What would a normal and abnormal examination of the hypoglossal nerve show?
Normal examination:
- movement and power of the tongue should be equal on both sides
Abnormal examination:
- tongue deviates towards the side of the lesion
- the inactive fibres are overpowered by the functioning muscle fibres on the opposite side
How should the cranial nerve examination be concluded?
- Thank the patient
- Consider the findings and how to present them in a logical and fluent order
- Consider the possible clinical significance of these findings
What is important to remember at the start of the cranial nerves examination?
- Greet the patient and introduce yourself
- Explain your role
- Explain what you are going to do, why you need to do it, and gain consent to proceed with the examination
