Cranial Nerve Testing
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Labelled diagram of cranial nerves
Labelled diagram of cranial nerves. Image by by jlcampbell104 is marked under CC0 1.0

Olfactory I

Quick method – ask the patient if:
  • They notice smells in the morning (e.g. coffee, toast)
  • They notice smells that others do
  • They think their sense of smell is poor

If they say yes to any of these questions, ask if they have a blocked nose or a cold at the moment, to save you doing unnecessary further investigation! If they say ‘yes’ ask if they think this is the source of their reduced sense of smell.
Also ask about taster here, in case you forget later! Sense of taste is likely to be impaired when the sense of smell is impaired!

Proper Method – odours on cotton wool is a bit old fashioned. Usually now clinical testing involves scratchcards with a scratch and sniff panel. These cards are usually from the USA, and have flavours like ‘Blureberry pie’
  • Test one nostril at a time, occluding the other nostril
  • If you find any defects, look in the nostril for any polyps or foreign bodies, or infection etc.

Optic II

Assess visual acuity

Start by asking a few basic questions:

  • Do you wear glasses or contact lenses?
  • Do you have any (other) problems with your vision?

Then, ask the patient to take off their glasses, and have a good look at and around the eyes (e.g. swelling, erythema, ptosis), before beginning your formal examinations:

  • Snellen Test ask them to stand at 6 metres (measure it out if you need to) and read out the lowest set of letters they can see. In a traditional test, there will be 11 rows of letters, the row with 8th row being the smallest a person with 6/6 vision can read. The biggest letters represent 6/60 vision. Often a smaller 3m Snellen test is used on the ward due to lack of space! Patients should wear their normal glasses – if they have any. You are not an optician – just looking for any serious visual defects! Make sure to test one eye at a time! – ask the patient to cover their eye; just asking them to close it isn’t good enough (as it can be difficult for patient,s and they may partially close the eye you are assessing, which obviously has implications for your results!)
  • Near Vision – using the appropriate booklet, ask the patient to read some lines to test near vision
  • Ishiahara plates – for colour vision – these are characteristic patterns – usually coloured blobs make up a pattern with a number in the middle. The dots are different colours, but the same brightness. A person with normal vision is able to pick out that the number is a different colour, and can read the number. There are usually several plates with different coloured numbers to test all types of colour defects.

Visual fields 

Sit at arm’s length away from the patient and perform the following tests:

  • Visual inattention – test the extremities of the visual fields with both eyes open. Test one side at a time, then both sides together.
  • Visual filed defects – test eyes separately. Test the four quadrants of vision for each eye. Cover your opposite eye to compare to your visual fields.
  • Assess the size of blind spot

Pupillary Light Reflex

Assess pupillary light reflex for ipsilateral and contralateral eye. The optic nerve only carries afferent fibres of the pupillary light reflex.
  • Shining a light into either eye should constrict both pupils simultaneously.
  • RAPD – relative afferent pupillary defect aka Marcus-Gunn pupilshining light in the affected eye will result in no constriction of either pupil. Often the result of MS, or massive retinal detatchment.
  • Horner’s syndrome – responses are normal, but on the affected side there is ptosis, and often the pupil is abnormally constricted in relation to the other pupil. It will still respond to light and ark, however.
  • III nerve (efferent) palsy –dilated pupil that does not respond to direct or consensual light. The eye may point down and out (total palsy), or may point in other directions (partial palsy).

Miosis – means ‘constricted pupil’!

  • Eye drops – pilocarpine
  • Unilateral – Horner’s syndrome, Holmes-Adie pupil
  • Bilateral – opiate overdose, brain-stem stroke, bilateral Horners
Mydriasis – means ‘dilated pupil’!
Fixed oval pupil – likely to be glaucoma
Grossly irregular pupil – most likely cause is adhesion that are the result of iritis.
The following external link has an interactive ‘Eye Simulator’ to test reflexes:

Accommodation reflex

  • Ask the patient to look at a point in the distance (ideally more than 6m away)
  • In a normal accommodation reflex, as the eyes focus on a near object from a far one, the pupils will constrict, and the eyes will converge.
  • Hold your finger (or another appropriate object) about 15cm infront of the patient’s face, and ask them to look at this object. Note the response of the pupils and eye alignment.  Diabetes and syphilis can cause a condition whereby the eyes do not constrict in response to light, but do constrict when the accommodation reflex is tested. This is known as Argyll-Robertson pupils.


  • Look at the optic disc and retina. If the patient wears glasses, they should remove them. Ask the patient to look straight ahead, but slightly upwards (this moves the optic disc into the best viewing position). This is easiest if you ask them to look at the join between the wall and the ceiling behind me.
  • Use a medium sized circle of light from the ophthalmoscope. Shine the light into the pupil, and look from a distance to check the red reflex.
  • Then, you will have to get very close to the patient to be able to focus on the retina. If you put your hand on the patient’s forehead, and then rest your head on your hand you will probably get close enough (i.e. you are very close – perhaps only a couple of cm away!)
  • Once you can see the retina comment on…

The optic disc – is it normal colour? Normal size? Normal shape?

  • Papilloedema / optic nerve swelling. It is only truly papilloedema when the cause is raised ICP. In other cases, we just call it ‘optic disc swelling’. The disc will also be a red/pin colour, and its margins will be blurred. Causes:
    • Raised ICP
    • Mass lesion
    • Malignant hypertension
    • Bremember don’t do a lumbar puncture if there is raised ICP – thus if there is papilledema, don’t do lumbar puncture!
    • CT should usually be performed if papilledema is present.
  • Optic nerve swelling may be cause by MS – where the optic disc is directly affected by the inflammatory reaction
  • Optic atrophy – causes an abnormally pale and small disc
  • Optic cup – this is the small circle inside the disc through which the vessels enter. It is normally very small compared to the optic disc. Conditions that increase the size of the cup relative to the disc are called ‘cupping’ . these can include glaucoma and ischaemia of the optic nerve.

The vessels – do they form the normal arc? Are they tortuous? Can you see any haemorrhage?
The retina – any abnormalities (e.g. cotton wool spots, exudates)
Cloudy appearance? – if so, likely to be cataracts.
Ask the patient to look up, down, left and right so you can get a view of all the areas of the retina.
Ask the patient to look directly at the light – so you can see the macula. Don’t do this for too long!
Finally, move away slightly, or refocus the ophthalmoscope to look in the vitreous for floaters, and to look at the iris and sclera.

Diabetic eye changes:

Background retinopathy

  • Hard exudates
  • Dot haemorrhages

Proliferative retinopathy

  • New vessel formation (away from the normal arcades positions of the vessels)
  • Scarring (photo-coagulation scars)
Retinis Pigmentosa

Oculomotor III

Ask the patient to follow your finger. Have your finger about30cm away from the patient’s face, and move it in an H shape to test all the eye movements.
Ask the patient if they experience double vision at any time

Oculomotor nerve palsy – Complete / incomplete, Medical/surgical

Trochlear IV

Suberior obliquethis causes a lot of confusion in medical students. This muscle will point the eye downwards, when the eye is looking medially!
If it was to ever act on the eye alone (when no other muscle are acting on the eye) then yes, it might make the eye look laterally. However, in clinical practice, this never happens!

Ask the patient if they ever experience double vision. Ask them to look directly downwards, then far to the left, and far to the right.

Trochlear Nerve palsy –this can be difficult to detect as it is subtle. It also often presents with other palsies / lesions.

Trigeminal V

Test their sensory function. Touch patient with cotton wool in the 3 regions (ophthalmic, maxillary, mandibular) on both sides of the face.
The ophthalmic (touch on forehead), the maxillary (touch on cheek bones), and the mandibular (touch on chin). If they can’t feel in an of these regions, then they might have a lesion in the corresponding cranial nerve.
Be wary in the mandibular region – that along the region of the mandibular bone, sensory function is actually due to C2, so it is best practice to touch just laterally to the mouth.
Test the integrity of the motor function of the mandibular (V3) branch of the trigeminal nerve:

  • Ask them to clench jaw. You should be able to feel the temporalis and masseter
  • Ask them to open their jaw against the resistance of your hand.
  • Ask them to move jaw from side to side – this is done by the pterygoid muscles.
Test the corneal reflex – touch their cornea with a cotton wool bud. The patient should close their eyes. This test the ophthalmic branch of the trigeminal nerve and the zygomatic branch of the facial nerve.

Abducens VI

Lateral rectus – if its not working, you’ll have trouble looking laterally. Ask the patient if they have experienced double vision. Ask them to look directly far to the left and directly far to the right.

Abducens palsy – patient is unable to abduct the eye

Facial VII

  • Test the integrity of the sensory chorda tympani branch of the facial nerve supplying the anterior 2/3 of the tongue. Ask the patient to stick out their tongue. You should dry their tongue with a paper towel. Pipette sucrose onto the tip and sides of the tongue. Then they have to be able to taste it before they put their tongue back in. Then they can put their tongue back in to tell you if they tasted it or not! IF you have time you should do it with all 4 liquids! Sweet, sour, bitter & salty.
  • Test the integrity of the deep petrosal nerve (a branch of the facial nerve supplying the lacrimal gland) Ask if they have dry mouth or dry eyes.
  • Test the integrity of the main branch of the facial nerve, which has 5 branches and supplies the muscles of the face: from top to bottom: Frown/lift eyebrows (temporal), close eyes tightly (orbits occuli), Smile with lips closed and whilst showing teeth), Purse lips, Blow out cheeks (check the air doesn’t come out when you apply pressure to cheeks!)

Vestibulocochlear VIII

  • Test hearing. Whisper and ask them to repeat. Weber’s test. Rinne’s test.
  • Ask them to walk in a straight line –heel to toe. Close their eyes and stand on one foot – be ready to catch them if they fall!
There are two types of deafness:
  • Conduction Deafness – where sound is impaired from reaching the receptors of the inner ear.
  • Sensory-neural deafness –  where there is a problem in the receptors of the inner ear, the vestibule-cochlear nerve, or in the brain.
We can detect which type of deafness is present by using 2 different tests:

Rinné’s Test

DO NOT HIT THE TUNING FORK ON ANYTHING! Pluck it, or hit in on your hand.
The healthy normal ear is more sensitive to air conducted sound than to bone conducted sound.This test involves places a vibrating tuning fork on the mastoid process behind your ear, then when the sound is no longer heard, bring it round to your ear, and yu should still be able to hear the sound.

Weber’s Test

You should place a vibrating tuning fork in the midline of your skull, and it should make an equal sound in both ears. If it doesn’t then there is a problem. This test is useless on its won though, because it doesn’t tell you what the problem is! Just that there is a problem.
If there is conductive deafness in one ear, the sound will be louder in that ear because background noise is being blocked out and so you ficus more on the sound you can hear, so it is louder. However, an ear may also appear louder, if the other one is relatively quieter due to sensory-neural deafness in the quieter ear.
With the help of Rinne’s test you can identify if there is conduection deafness or not in the louder ear, and thus identify whether the difference in loudness of ears is due to conduction of sensory-neural deafness.
Sensory-Neural Deafness

This can be complete 100% deafness, or any amount between normal hearing and complete deafness. In the vast majority of cases it is caused by degeneration of the hair cells in the organ of corti. This occurs normally in old age and results in loss of high frequencies (above 1 kHz). The higher the frequency, the greater the loss. This type of deafness is known as Presbycusis. Noise trauma can also cause deafness. Typically this has a hearing loss in the range of 4kHz (like the graph on the previous page). Both of these conditions will normally present in both ears. Sensorineural deafness in only one ear is possible due to brain/vestibulocochlear neve damage and should be investigated with an MRI scan.

Conduction Deafness
This can be caused by a perforated tympanic membrane, or by a middle ear infection, such as otitis media. Otitis media is a painful inflammation of the middle ear usually caused by viral infection. It is more common in children due to their shorter eustachian tubes, but it normally resolves itself as the child grows. Grommets may be inserted to aid ventilation of the middle ear (which is the normal function of the eustachain tube. In otitis media the sound conduction deafness is caused by accumulation of fluid in the middle ear, impairing movement of the mechanical apparatus of the middle ear, and thus reducing the strength of conduction to the cochlea. Otitis media is common in colds and flu, but will usually settle within 72 hours. It may last for several years in children.

Glossopharyngeal IX

  • Test taste on postierior 1/3 of tongue. Same procedure as facial, but put the stuff on the posterior 1/3 of the tongue.
  • Ask if they have a dry mouth. The parotid gland is innervated by this nerve. The facial nerve passes through the parotid gland but does not innervate it.
  • Test gag reflex – spatula on the lateral side of the pharynx.

Vagus X

  • Test motor function. Ask them to say ‘ahh’ their soft palate should go up, and the dangly bit (uvula) should go down. Infection of uvula is called uvulitis and it should sit on their tongue.
  • Test swallowing. Ask them to swallow water if available.
  • Test speech – ask them to repeat a sentence. If their voice sounds nasal they may have a defect of the Vagus nerve, because the palate may not be raised, and so the sound may be directed through the nasal cavity.

Accessory XI

Test the integrity of the sternocleidomastoid and trapezius. Ask them to rotate their head against resistance (SCM), and to shrug their shoulders against resistance (trapezius).

Hypo​glossoal XII

Asses tongue movements. It will deviate to the weaker side. Ask if they have ever noticed any trouble talking because their tongue won’t do what they want it to.
Always explain what you’re doing! Say what you would expect to see if it was damaged.


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Dr Tom Leach

Dr Tom Leach MBChB DCH EMCert(ACEM) FRACGP currently works as a GP and an Emergency Department CMO in Australia. He is also a Clinical Associate Lecturer at the Australian National University, and is studying for a Masters of Sports Medicine at the University of Queensland. After graduating from his medical degree at the University of Manchester in 2011, Tom completed his Foundation Training at Bolton Royal Hospital, before moving to Australia in 2013. He started almostadoctor whilst a third year medical student in 2009. Read full bio

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