examination of cranial nerves

1. CLINICAL EXAMINATION OF
CRANIAL NERVES BY DR ANUJ SHARMA PG2

2. There are twelve cranial nerves in total.
The olfactory nerve (CN I) and optic nerve (CN II) originate from
the cerebrum. Cranial nerves III – XII arise from the brainstem .
They can arise from a specific part of the brainstem (midbrain,
pons or medulla), or from a junction between two parts:
• Midbrain – the trochlear nerve (IV) comes from the posterior side
of the midbrain. It has the longest intracranial length of all the
cranial nerves.
• Midbrain-pontine junction – oculomotor (III).
• Pons – trigeminal (V).
• Pontine-medulla junction – abducens, facial, vestibulocochlear
(VI-VIII).
• Medulla oblongata
• Posterior to the olive: glossopharyngeal, vagus, accessory
(IX-XI).
• Anterior to the olive: hypoglossal (XII).

3. CRANIAL NERVE 1: OLFACTORY
Function:
Special sensory (special visceral afferent) that is, the special sense of smell.
Olfaction is the sensation of odours that results from the detection of odorous substances aerosolized
in the environment
Examination:
1.Ask the subject if he/she has a subjective olfactory problem.
2.Check air movement through each nostril separately.
3.Check for rash, deformity of nose.
4.One nostril is occluded while the subject sniffs an unknown substance. Ask the patient to name the
substance.
-coffee ,cinnamon , chocolate are useful everyday odours for the bedside testing.
5.Test the other nostril, repeat step 4.

5. Anosmia:
➤In anosmia the sense of smell is absent.
➤ Causes of anosmia:
Closed head injury
Sub frontal meningioma
Previous bacterial meningitis
HIV infection
Sinusitis
Other local nasal disorders
Drugs (e.g. Copper chelating agents, antibiotics)
Parosmia:
A rare abnormality of olfaction in which pleasant odours often seem offensive.
Hallucinations of smell:
➤ May occur as an aura of a temporal lobe seizure.

6. CRANIAL NERVE II : OPTIC NERVE
FUNCTIONS
To carry visual impulses from the retina to the optic chiasma and on
in the optic tract to the LGB; to act as the afferent pathway for the
pupillary light reflex by means of fibres travelling to the superior
colliculus of the midbrain
EXAMINATION
Each eye should be tested separately in assessment of:
1. visual acuity
2. visual fields
3. fundoscopy

7. VISUAL ACUITY
Test each eye separately - Snellen's charts or informally using any
available text. (Do this before fundoscopy-the patient may be
dazzled)
➤ Test Environment
1. Explain the test procedure.
2. Check whether the patient has glasses.
➤ Test procedure
1.Use handheld text or 6 meter wall chart.
2.Ask patient to cover one eye (not close it)and read letters line by
line from the top. Note the last line read with one or no errors.

8. Test interpretation
This is essentially a test of macular vision.
The number of lines indicate the distance that a normally-sighted person
would be able to see it. Visual acuity is expressed as the distance the letters
are read/the distance at which they should be read. The numbers under each
line of the chart indicates the distance at which they should be
read. 6/12 means that at 6 m the patient can just read the line that should
just be visible at 12 m.
Normal acuity is 6/6 or <6/6. Less than that indicates visual impairment.
More severe visual impairment is expressed as:
'counts fingers'
"perceives movement'
-"perceives light

9. VISUAL FIELDS
Test environment
Check the patient can see out of both eyes.
➤ Test procedure
Test the eyes separately asking the patient to cover each eye in turn.
There are two equally acceptable methods.
Both require careful explanation of what the patients is expected to do.
1.By CONFRONTATION- the standard method.
2.By WIGGLING- the quick method.

10. CONFRONTATION TEST
1.Get your head at the patient's eye-level.
2.Cover your own eye opposite to the patient's covered eye.
3.Ask the patient to fix their gaze between your eyes.
4.Ask them to say 'yes' when the pin- head seen out of the corner of
their eyes become red.
5.Holding a 'neurological pin with a red head midway between your
heads slowly bring it in from your extreme upper and lower nasal and
temporal fields.
6.Check when you can see the pin head turn red.
7.Check when they say they can see the pin-head turn red.
8. This allows you to map their visual fields for colour onto yours and
detect any abnormality. (Make sure they can actually fix on the pin-
head-don't hold it too close!)

11. WIGGLING METHOD
1. Keep both your eyes open. (The patient covers one eye.)
2.Ask the patient to fix their gaze between your eyes.
3.Ask them to say 'yes' when they can just see your fingers wiggling
out of the corner of their eyes.
4.Wiggle your fingers behind the patient's head and bring them
slowly round into their extreme upper and lower nasal and temporal
fields until they perceive movement. Do the same for each quadrant
of each eye

12. ➤ Test interpretation
The majority of field defects are quite gross.
The patient won't see anything until the object crosses into the normal field
almost directly in front of the eye.
There are three major defects:
1.Homonymous hemianopia
-The patient is unable to see objects in either the right or the left visual fields.
-The lesion is in the opposite optic tract or optic radiation.
2.Bitemporal hemianopia
-The patient is unable to see objects in either temporal fields.
-The lesion is in the opposite optic nerve.
3. Scotomas
-The patient has a roughly circular area of blindness in either visual fields.
-The lesion is in the same retina.
-If this is suspected the examination methods above need to be modified as
follows:

13. VISUAL FIELD (CENTRAL)
1.Get your head at the patient's eye-level.
2.Cover your own eye opposite to the patient's covered eye.
3.Ask the patient to fix their gaze between your eyes.
4.Tell them you will move the pinhead or other object across their field of
vision.
Ask them to say 'yes' if the pin-head disappears'.
5.Holding a 'neurological pin midway between your heads slowly bring it
across their field of vision.
6.If you are using a red pin it is helpful to ask if the colour changes to
something less bright.

14. FUNDOSCOPY
➤ Test environment
Check whether the patient has glasses. They should remove them and not
whether the lenses are convex (+ve) or concave (-ve). You will need to make
allowances for this when you set up the ophthalmoscope.
Darken the room and allow the patients eyes to accommodate. If they are
still constricted you may need to use tropicamide 0.5% eye drops to dilate
the pupil.
Explain the test procedure.
➤ Test procedure
1.Darken the room if possible.
2.Sit or stand at eye-level with the patient.
3.Adjust the ophthalmoscope lens to between 0 and -4 if neither of you
need glasses.

15. Remove your own glasses.
5.Put the ophthalmoscope to your right eye to examine the patient's
right eye and vice versa.
6.Start looking about 1m from the patient. You should see a bright
pink deflection from the patients eye. This is the red reflex. It means
that there is no opacity preventing light reaching the fundus.
7.Now get the patient to fix on a distant object and look for the optic
disc. This is a pale pink object in the fundus and is seen about
15degree out from the sagittal plane as if you wear aiming for the
back of the patient's other eye. The optic disc is seen as the place
where all the vessels converge. If all you can see is a blur try turning
the focussing wheel.
8. Follow the superior and inferior temporal and nasal arteries and
veins out from the disc and examine the four quadrants of the
fundus.
9.Find the macula. This is a featureless spot two disc widths from the
optic disc on the temporal side.

16. CAUSES OF VISION LOSS

17. CRANIAL NERVE III,IV,VI:
OCULOMOTOR , TROCHLEAR AND
ABDUCENT
FUNCTIONS
CN III- OCULOMOTOR:
-Eyelid and eyeball movement.
CN IV- TROCHLEAR:
-Innervates superior oblique.
-Turns eye downward and laterally.
CN VI- ABDUCENS:
-Innervates lateral rectus
-Turns eye laterally

18. EXAMINATION.
CN II & III EXAMINATION:
- pupil
-accommodation reflex
➤CN III, IV & VI EXAMINATION:
-eye movements
-nystagmus

19. PUPIL
➤ Test environment
Remove the patient's glasses.
Make sure the ambient illumination is not too bright.
Test procedure
Explain the test procedure.
Look at the pupils are they round and equal size.
-small: old age, opiates, Horner's syndrome, pilocarpine, iritis.
-large: young, alcohol, atropine, third nerve palsy.
1. Ask the patient to look straight ahead.
2. Quickly swing a torch beam from the side to illuminate the retina.
3. Look for constriction of that pupil - this is the direct response.
4. Repeat the action and look for constriction in the pupil of the opposite eye - this is the consensual
response.

20. ➤ Test interpretation
1. No response to light, response to accommodation = optic nerve
defect
2. Neither pupil responds to light in the blind eye, both respond to
light in the normal eye = afferent defect
3. Pupil doesn't respond to light in either eye = efferent defect (third
nerve defect)

22. ACCOMODATION REFLEX
➤ Test procedure
• Ask the patient to look at an object in the distance and then at
finger 20 cm from their nose. Both pupils should constrict.
➤ Test interpretation
Pupil reacts to accommodation but not to light = Argyll Robertson
pupil Holmes-Adie pupil, midbrain lesion, ocular blindness.

23. EYE MOVEMENTS
➤ Test procedure
1. Ask the patient to follow your finger or a point object with their eyes and
tell you if they see double.
2. Move the object across the plane of vision and then up and down near
when they are looking to one side. The shape of your movements is the
letter H.
3. Watch for non-parallelism of their visual axes.
4. Watch for nystagmus.
5. Ask them again if they saw double at any time.
6. Ask them to look upwards to test conjugate gaze.

25. ➤ Test interpretation
Principles
1. The eye that is not moving fully sees the peripheral image in diplopia.
2. The diplopia gets worse as the affected eye moves in the direction of pull
of the affected muscle.
3. Diplopia may be caused by a muscle or a nerve lesion.
Paralytic squint
III palsy ptosis, eye deviated from down and out, large fixed pupil.
IV palsy - diplopia when the affected eye looks down whilst looking slightly
inward (towards the nose).
VI palsy-cannot abduct eye, diplopia when looking to side of the lesion.
If a patient sees double in all directions consider third nerve palsy thyroid
eye disease or myasthenia gravis.

26. CRANIAL NERVE V: TRIGEMINAL
NERVE
FUNCTIONS
The important functions are:
1 To carry all forms of sensation from the face, the anterior part of
the scalp, the eye and the anterior two-thirds of the tongue.
2 To give motor power to the muscles of mastication.
3 To carry sensation from the teeth, gums, mucous membranes of
the cheeks, nasal passages, sinuses and much of the palate and
nasopharynx

27. Examination.
Test environment
Explain the procedure for sensory testing.
Test procedure
Touch each of the three divisions with cotton wool testing each side alternatively.
Corneal reflex: touch the edge of the cornea, not the conjunctiva. This reflex is not usually
tested in the conscious patient
Interpretation
The cotton wool should be felt all over the face. Both eyes should blink when the cornea is
touched. Failure indicates damage to the afferent or efferent pathway.
Motor.
Ask the patient to open mouth against resistance.
Mouth should open in the midline
Ask the patient to clench their teeth. Feel for contraction of the masseter and temporalis
muscles.
Interpretation
If the jaw protrudes to one side on opening, this indicates weakness of pterygoids on the
same side..

28. CRANIAL NERVE VII: FACIAL
Functions
For the purpose of neurological examination, the important functions
are the motor innervation of the muscles of expression and facial
movement, including platysma, and of the stapedius. The
intermediate nerve carries secretory fibres to the lacrimal glands
through the greater superficial petrosal nerve and to the salivary
glands through the chorda tympani, which also carries the sensation
of taste from the anterior two-thirds of the tongue.

29. EXAMINATION
MOTOR FUNCTION
Inspection: Facial symmetry at resting position/Atrophy and fasciculations/
Spontaneous blinking/synkinesia/nasolabial fold with forehead
wrinkles/width of palpebral fissure/Observe movements during
spontaneous/voluntary facial expression
Testing the temporal branch: patient is asked to frown and wrinkle his or her
forehead
Testing the Zygomatic branch: patient is asked to close their eyes tightly
Testing the buccal branch: Puff up cheeks (buccinator)/ Smile and show
teeth (orbicularis oris)/ Tap with finger over each cheek to detect ease of air
expulsion on the affected side

30. Examination of Sensory Functions
Hypesthesia of posterior wall of EAM: proximal CN VII lesions
Taste on anterior two-thirds of the tongue: sweet/salty/bitter/sour
Examination of Secretory Functions
Schirmer's test
History and observation: tearing/salivation Lacrimal and nasolacrimal
reflex
Examinations of the reflexes
Little practical value
Corneal Reflex: Afferent- CN V1,efferent- CN VII
Stapedius reflex: by Impedance audiometry, Absence or a reflex less
than half the amplitude is due to a lesion proximal to stapedius nerve
Chvostek's sign

33. CRANIAL NERVE VIII: AUDITORY
NERVE
FUNCTIONS
1 The cochlear nerve. This carries impulses of sound from the hair
cells of the organ of Corti, through the spiral ganglion in the cochlea,
to the cochlear nuclei in the pons. Most fibres cross, run in the lateral
lemniscus to the medial geniculate body and are relayed to the
superior temporal gyrus. But there is some uncrossed upwards
transmission, so that deafness from a unilateral cerebral cortical
lesion is virtually precluded.
2 The vestibular nerve. Impulses arise in the labyrinth by
displacement of endolymph affecting the hair cells in the ampullae of
the semicircular canals, and the otoliths in the saccule and utricle.
Fibres run to the vestibular ganglia and on in the main trunk of the
nerve to the vestibular nuclei in the medulla. These nuclei have
connections with the cerebellum, the oculomotor nuclei via the
medial longitudinal bundle, the nuclei of the upper cervical nerves,

34. EXAMINATION
Test environment
Explain the test procedure.
Ensure a reasonably quiet environment.
Test procedure
Acoustic branch - check their hearing from the external auditory
meatus, either by whispering or by rubbing fingers lightly together.
Interpretation
If you suspect reduced hearing acuity decide if the problem is one of
the sound conduction through the ear (conductive deafness) or
conversion of sound into nerve impulses (sensori-neural deafness).

35. RINNE'S TEST
➤ Test procedure
Place vibrating tuning fork on the mastoid and ask the patient to say
when it has stopped. When the patient says the sound has stopped,
hold the fork at the meatus, rotating it slightly.
Interpretation
If the sound is still heard air conduction>bone conduction this is
found in sensori-neural deafness.
If not heard bone conduction>air conduction - the finding in
conductive deafness.

36. WEBER'S Test
Test procedure
Hold vibrating tuning fork in the middle of the patient's forehead. Ask
in which ear the sound is loudest.
interpretation
It should be heard equally loudly in both ears
It should be located more on one side then conductive deafness
exists on that side or the opposing ear has sensori-neural deafness.
Tests of vestibular function
1. rotational test
2. caloric tests

37. CONDUCTION DEAFNESS
• All diseases of the external
meatus, middle ear, and Eustachian
tubes
• Middle ear infection in suspected
intracranial infection
• Certain middle ear tumours (e.g.
tumours of the glomus jugulare
PERCEPTION DEAFNESS
At cochlear level - Meniere's
disease, advanced otosclerosis, deaf
ness due to drugs, internal auditory
artery occlusions, prolonged
exposure to loud noise
• In the nerve trunk - Old age, post-
inflammatory lesions, toxic lesions,
meningitis, cerebellopontine angle
tumours, trauma
• In the brainstem - Severe pontine
vascular lesions, severe
demyelinating lesions, occasionally
tumour
CAUSE OF VESTIBULAR
DISTURBANCES
1. At labyrinthine level
(a) Meniere's disease
(b) Motion sickness
(c) Drug toxicity
(d) Probably migraine
2. In the vestibular nerve. As for
perception deafness, but add also
'vestibular neuronitis’
3. In the brainstem
(a) Vascular deficiency, especially
vertebrobasilar artery disease
(b) Cerebellar and IVth ventricular
tumours
(c) Acute demyelinating disease,
migraine
4. In the temporal lobe. As an
epileptic manifestation, especially in
children, or as an ischaemic lesion in

38. CRANIAL NERVE IX&X:
GLOSSOPHARYNGEAL &VAGUS
FUNCTION
the following functions are of most importance in neurological
examination
1 To carry common sensation from the pharynx, tonsils, soft palate
and posterior one-third of the tongue.
2 To carry the sense of taste from the posterior one-third of the
tongue (probably almost purely by the IXth nerve).
3 To give motor supply to the palatal and pharyngeal muscles.
4 To give motor supply to the vocal cords (purely the vagus).

39. EXAMINATIONS
Preliminary observation
Notice the pitch and quality of the patient's voice, and of his cough,
and whether there is any difficulty in swallowing his saliva. Ask if
there has been any nasal regurgitation of fluids.
A high-pitched, hoarse voice may mean vocal cord paralysis
A nasal tone that increases if the head is bent forwards means palatal
paralysis, when lying back this can become almost normal.
If the patient chokes on his saliva while talking, there may be both
palatal and pharyngeal weakness
Motor functions
Ask the patient to open his mouth wide. The patient is then asked to
say 'Ah' while breathing out, followed by 'Ugh' while breathing in. In
each case, the palate should move symmetrically upwards and
backwards, the uvula remaining in the midline, and the two sides of
the pharynx should contract symmetrically.

40. Sensory functions
A throat swab, with the cotton wool safely attached, is passed to one side of
the back of the throat, while the tongue is gently and slowly depressed.
Touching any part of the palate, tonsil or the back of the tongue will
normally result in contraction of the pharynx, elevation of the palate and
retraction of the tongue. This is called the gag reflex, and varies in
sensitivity from individual to individual
Taste
Testing taste on the posterior part of the tongue is so difficult by normal
means
INTERPRETATIONS
On phonation
The palate moves up and over to one side when there is paralysis of the
opposite side, owing to the pulling movement of the unopposed normal
muscle.
In pharyngeal paralysis, the muscles will also appear to move towards the
normal side, so resembling a flat sheet being drawn across that it is called
the 'curtain movement’(caused by lmn lesion)
If there is no movement of the palate and pharynx, there should also be
dysphagia, nasal regurgitation and nasal speech, and this usually indicates
either a bilateral medullary nuclear lesion or a umn lesion

41. ON TESTING SENSATION
Unilateral absence of the gag reflex may be due to loss of sensation,
or motor power or both. Phonation will have shown if one side is
paralyzed. If due to loss of sensation alone, stimulation of the normal
side will produce a normal symmetrical reflex. This rare event would
be due to a glossopharyngeal lesion. If the defect, however, is due to
combined motor and sensory paralysis, stimulation of the normal side
will cause the palate to be pulled towards that side. This more
common finding indicates a combined lesion of glossopharyngeal and
vagus nerves

42. CRANIAL NERVE XI: ACCESSORY
NERVE
Functions
To supply motor power to the upper part of the trapezii and to the
sternomastoid, and so to influence the posture and movements of the
head and shoulder girdles
EXAMINATION
1 STERNOMASTOIDS
Place one hand against the right side of the patient's face and ask
him to turn (not bend) his head against it. The left sternomastoid will
stand out clearly . Repeat this in the opposite direction and compare
the two sides for bulk and strength. Then rest a hand on his forehead
and ask him to bend his head forwards. Both sternomastoid will stand
out together and are easily compared . Now ask the patient to sit up.
Normally, the head leaves the pillow first and the movement is easy

43. 2 TRAPEZIUS
Go behind the patient and compare the line and curve of the trapezii
and the position of the scapulae, making certain that he is sitting
symmetrically upright. Then ask him to raise his shoulders towards
his ears. (Asking patients to 'shrug their shoulders' often produces a
most unnatural convulsive movement.) Now try to depress the
shoulders forcibly. Even the most feeble patient is normally able to
resist the manoeuvre

44. INTERPRETATIONS
1. In bilateral sternomastoid weakness, when the patient sits up, the
head seems to be left behind on the pillow and then is raised with
difficulty
2. In unilateral sternomastoid weakness, the patient will fail to turn
his head against resistance to the opposite side
3. Trapezius -weakness results in the shoulder dropping on one side
and the scapula being displaced downwards and laterally, giving a
steeper gradient to the contour of the neck. Shrugging of that
shoulder may be weaker, though not absent, because part of the
trapezius is supplied by cervical nerves
LESIONS OF XI CRANIAL NERVE
NUCLEAR XI NERVE: MND, SPINAL MUSCULAR ATROPHY POLIOMYELITIS
NERVE: POLYNEUROPATHY OR MONO NEUROPATHY
MUSCLE: POLYMYOSITIS, DERMATOMYOSITIS MYASTHENIA GRAVIS ,
OCULOPHARYNGEAL MUSCULAR DYSTROPHY

45. CRANIAL NERVE XII: HYPOGLOSSAL
Functions
To control all movements of the tongue, and certain movements of the hyoid bone and larynx during and
after deglutition
Examination.
➤ Test procedure
Ask the patient to put out the tongue.
➤Interpretation
If deviated then that is the weak side.
Look for fasciculation or wasting with tongue in the mouth.
These indicate an infranuclear lesion

47. COMMON LESIONS OF
HYPOGLOSSAL NERVE
LOWER MOTOR NEURON LESIONS
UNILATERAL
1. SYRINGOMYELIA
2. POLIOMYELITIS
3. TRAUMA
4. ANGIOMAS
5. EARLY MOTOR NEURON DISEASE
BILATERAL
1. PROGRESSIVE BULBAR PALSY
2. SYRINGOMYELIA
UPPER MOTOR NEURON LESIONS
UNILATERAL
1. Profound hemiplegia (due to
vascular accidents or deep-seated
neoplasms)
BILATERAL
. Bilateral vascular accidents
producing a pseudobulbar palsy,
amyotrophiC

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