Cranial nerve examination

1. Cranial nerve
examination

2. Cranial nerves
I.Olfactory
II.Optic
III.Occulomotor
IV.Trochlear
V.Trigeminal
VI.Abducent
VII.Facial
VIII.Auditory
IX.Glossopharyngeal
X.Vagus
XI.Spinal accessory
XII.Hypoglosseal

3. Summary of funCtion of Cranial
nerveS

4. FUNCTIONAL TYPES
Pure sensory
Olfactory
Optic

Auditory
Pure motor
Trochlear
Abducent
Accessory
Hypoglosseal
Mixed nerves
Trigeminal
Facial
Glossopharyngeal
Vagus
Occulomotor

5. Cranial Nerve I: Olfactory

6. Function
Carries the sensation of smell from nasal
mucosa to olfactory bulb

7. Purpose of the test
To determine any impairment of smell is
unilateral or bilateral
Whether impairment is due to any local nasal
disease or neural lesion

8. Method of testing
Small bottles containing
essences of very familiar
odour are required
•Coffee
•Lemon
•Chocolate
•Asafetida etc

9. PROCEDURE
Compress 1 nostril & sniff the taste odour twice
Ask whether he can smell or identify odour
Repeat test on other nostril & ask if smell
is similar in both nostril
Allow odour to disperse & repeat test with other
2 test odour, ask he can distinguish smell

10. Interpretation of result
Who can recognize & name odours quickly (females)
Who can recognize but difficult in naming (males)
Who can smell & know difference but neither recognize
nor naming
•The above 3 should be accepted as normal
Who feel each odour is similar but is distorted &
unpleasant (parosmia)
Those who cant smell anything or is much reduced
compared to the other (anosmia)
Those whose responses are vague & variable

11. Common causes of anosmia
Acute/chronic inflammatory nasal disease
Heavy smoking
Head injury
Intra cranial tumour compressing the
olfactory bulb
Atrophy of olfactory bulb
Chronic meningeal inflammation
Parkinson’s disease

12. Cranial Nerve II: Optic

13. Function
Carries the visual impulses from the retina to
the optic chiasma & in the optic tract to the
lateral geniculate body
The impulse acts as an afferent pathway for
the pupillary light reflex

14. Purpose of the test
To measure aquity of vision & determine if
any disease is due to local occular disease or
neural impairment
To chart the visual field

15. Method of testing
Visual acuity
•The standard snellen’s
chart can be used for vision
& the Jaegar type card can
be used for near vision
[the commonest causes of
visual error lies in the eye only]

16. Visual field
Purpose:
•To chart periphery of visual field
•To detect position, size & shape of the blind spot

17. Confrontation test
Instruct Pt to indicate appearance of
the object
Pt covers left eye & examiner right
Pt & examiner sit face to face
PT moves the test object from outside the
visual field towards midline

18. Common causes
Total unilateral loss of vision: optic nerve
lesion
Homonymous hemianopia: lesion between
optic tract to occipital cortex
Bitemporal hemianopia: lesion of optic
chiasma

19. Occulomotor, Trochlear, Abducent

20. Function
Controls the external occular muscles &
elevators of the lids
Also regulates the pupillary muscles

21. Purpose of the test
Inspect pupils to rule out a local disease,
peripheral lesion or a nuclear involvement
Examine eye movement & determine if
defects is muscular origin or neural
involvement
To detect nystagmus

22. Method of testing
Observation
•Presence & absence of ptosis & squint
•Whether unilateral or bilateral
•Constant or variable
•Size, shape, equality & regularity of the pupils

23. Reaction to light
Reduce illumination of room & vision
should focus on a far object
A bright beam of light is shone from the side
of one eye
Repeat on the other side
[the pupil should constrict briskly]
Shield one eye & perform test on the other
& see for consensual reaction

24. Reaction to convergence &
accommodation for near vision
Fix vision on a distant object & instruct to
look in a near object
Place finger tip in front of the bridge of the
nose (22 cm)
Then return to the far object
Observe pupillary reaction in both

25. Examination of occular movement
Observe lagging of one
or both eye
•Observe nystagmus

26. Analysis of diplopia
Shield one eye with a transparent red shield
Object is moved from left to right, up & down
Ask if -
•He sees 1 or 2 object
•Object lies one above the other or side by side

27. Rules governing analysis of diplopia
Separation of image is greatest in the
direction in which the weak muscle has its
purest action
False image is displaced farthest in the
direction in which the weak muscle should
move the eye

28. Analyzing nystagmus
Watch the patients eye while talking
Ask to look at a definite point & move the
point from left to right & up to down
Hold each end position for 5 sec & assess
nystagmus (direction, rate amplitude)

29. Common causes of paralysis
Pontine lesions
Neoplasms
Vascular accidents
Demyelinating disease
Meningeal inflammation
Tumour of base of skull
Increased intra cranial pressure
Head injury
[Total paralysis of III, IV & VI nerve indicates a lesion in
cavernous sinus (carotid aneurism)]

30. Cranial Nerve V: Trigeminal

31. Function
Carries all forms of sensation from the face,
anterior scalp,eye & the anterior 3
rd
of the
tongue
Also supplies the muscles of mastication

32. Purpose of the test
To determine any sensory impairment
To determine unilateral or bilateral motor
weakness & determine UMN from LMN

33. Method of examination
Superficial sensory asst from mainly 6 areas
(mainly light touch & pain)
•Forehead & upper part of the side of nose
(ophthalmic)
•Malar & upper lip region (maxillary)
•Chin & anterior part of tongue (mandibular)

34. Interpretation
Total loss of sensation: lesion of ganglion or
sensory root
Total sensory loss over 1 division: partial
lesion of ganglion or root
Touch only lost: pontine lesion affecting
sensory nucleus
Pain & temp lost: dissociate anesthesia
(seringobulbia)

35. Corneal reflex
Using a cotton piece the
cornea is teased
Normal response is a
bilateral blink
(facial nerve forms the
efferent loop of the reflex arc)

36. Interpretation
No closure: ophthalmic division of the facial
nerve
No response in either lid when abn. is tested
& bilateral blink when normal is tested: V
nerve lesion
No response of the affected side whichever
side is tested: VII nerve lesion

37. Motor assessment
Muscles of mastication
Have Pt bite against resistance
Have Pt protrude mandible
against resistance
Have Pt go into lateral
excursive movts against
resistance
Jaw jerk

38. Common causes
Tumours of base of skull
Chronic meningeal lesion
Trigeminal sensory neuropathy
Acoustic neuroma
Syringomyelia
Multiple sclerosis

39. Cranial Nerve VII: Facial

40. Function
Supplies the muscles of facial expression
including platysma & stapedius muscle
Secretomotor fibers to the lacrimal gland &
the salivary gland
Carries sensation of taste from anterior 2/3
of tongue & general sensation from external
acoustic meatus

41. Purpose of the test
To detect any unilateral or bilateral
weakness of facial muscles (UMN or LMN)
Detect impairment of taste

42. Method of testing
Observation
•Symmetry and asymmetry of
face
•Nasolabial fold & wrinkle on
forehead
Ask the Pt to close the
eyes, raise the eyebrows,
blow out the cheek,
whistle etc

43. Examination of taste
The four primary taste (sweet, salt, sour,
bitter) can be carried out by using sugar,
salt, vinegar & quinine
The side of the tongue is moistened by the
test substance
Ask the Pt to indicate taste by pointing

44. Secretomotor function
The flow of tears of two side can be
compared by giving ammonia to inhale
which will result in tearing of eye
The flow of saliva can be tasted by keeping a
spicy substance in the tongue & the tip is
raised to observe the sub maxillary salivary
flow

45. Reflexes
Corneal reflex
Nasopalpebral reflex: tap on the
nasopalpebral ridge will produce
closure of both eyes. In bells palsy
there is failure to close on the
affected side

46. Common causes of facial paralysis
Neoplasm affecting thalamus: unilateral
emotional paralysis
Parkinsonism : bilateral emotional paralysis
CVA neoplasm, MND: bilateral UMN palsy
Bell’s palsy
GBS

47. Cranial Nerve VIII: Vestibulocochlear

48. Function
Carries the impulses of sound from the hair
cell of organ of corti to cochlear nucleus in
pons
Control balance through vestibular nerve

49. Purpose of the test
To determine any deafness is bilateral or
unilateral
Whether deafness is due disease of middle
ear or cochlear nerve
To determine the disturbance of vestibular
functions

50. Test of hearing
Observe if the patient turns
one ear towards you
Evaluate hearing using a
ticking watch, rub fingers
together, whisper.

51. Rinne’s test
Strike a tuning fork gently, hold it near one
external meatus & ask the Pt if he can hear it
Place it on the mastoid, ask if he can still
hear it & instruct him to say “NOW” when
sound ceases, & keep it on the external
meatus again (normally the note is still
audible)

52. Interpretation
In middle ear deafness – the note is not heard
In nerve deafness – air & bone conduction
are reduced but air remains better

53. Weber’s test
The fork is place on the vertex
Ask the Pt if he can hear the sound all over
the head, in both ears or in one ear
In nerve deafness the sound appear to be
heard on the normal ear
On chronic middle ear disease it is conducted
to the abnormal ear

54. Common causes of deafness
Disease of external & middle ear &
Eustachian tube
Prolonged exposure to loud noise
Old age
Meningitis
Demyelinating disease
Deafness due to drugs

55. Test of vestibular function
Observe equilibrium as patient
walks or stands
Observe abnormal eye movts
Ask for -
•Dizziness
•Falling
•Nausea and vomiting

56. Cranial Nerve IX: Glossopharyngeal

57. Function
General Sensory: posterior 1/3
of tongue, tonsil, skin of
external ear, tympanic
membrane & pharynx
Visceral Motor:
parasympathetic stimulation of
parotid gland, & controls blood
vessels in carotid body
Visceral Sensory:
subconscious sensation
from carotid body & sinus
Special Sensory: carries
taste from posterior 1/3
of tongue
Branchial Motor:
Supplies styolopharyngeus
muscle

58. Cranial Nerve X: Vagus

59. Function
General Sensory: posterior meninges,
concha, skin at back of ear, external
tympanic membrane, pharynx &
larynx
Visceral Motor: parasympathetic
stimulation to smooth muscle &
glands of pharynx, larynx; thoracic
& abdominal viscera & cardiac
muscle
Visceral Sensory: from larynx,
trachea, esophagus, & thoracic &
abdominal viscera, stretch
receptors & chemoreceptors
Motor: superior, middle, inferior
constrictors; levator palati,
salpingopharyngeus,
palatopharyngeus, palatoglossus

60. Purpose of the test
To test the elevation of palate & contraction
of pharynx
To examine the movts of vocal cords
[note: the IX & X nerve are tested together]

61. Method of testing
Notice the pitch & quality of voice, cough &
difficulty in swallowing saliva
Ask the Pt to open his mouth wide after a few
movts ask to say “AH” while breathing out &
“UGH” while in
The palate should move symmetrically upwards
& backwards, the uvula in mid line & two sides
of pharynx contract symmetrically

62. Common causes of lesion
Poliomyelitis
Syringobulbia
Posterior fossa tumor
Advanced parkinsonism
Myasthenia gravis
Enlarged cervical glands
Surgical operation of the neck

63. Cranial Nerve XI: Accessory

64. Function
Supplies
sternocleidomastoid
& trapezius muscles

65. Purpose of the test
To detect wasting & weakness, unilateral or
bilateral of the muscles

66. Method of testing

67. Common causes of paralysis
MND
Poliomyelitis
Polyneuropathy
Trauma in the neck or base of skull
Tumour at jugular foramen
Syringomyelia

68. Cranial Nerve XII: Hypoglossal

69. Function
Control movts of the tongue, hyoid bone &
larynx during & after deglutition
Supplies 3 of 4 extrinsic
muscles of tongue &
all intrinsic muscles of
tongue

70. Purpose of the test
To inspect the surface of the tongue
To detect wasting, weakness & involuntary
movts
To examine voluntary muscle control

71. Method of testing
Ask the Pt to protrude the
tongue & observe for
•Reduction in size of affected side
•Excessive ridging & wrinkling
•Restricted protrusion
•Deviation towards one side

72. Common lesions
Syringomyelia
Poliomyelitis
MND
Profound hemiplegia
ALS

73. 13
th
Cranial nerve
Known as cranial nerve zero or Terminal
Nerve
It projects from nasal cavity, enters
brain just a little bit ahead of other
cranial nerves as a microscopic plexus of
unmyelinated peripheral nerve fascicles

74. FunCtion
The nerve is vestigial or related to
sensing of pheromones
Regulates sexual behavior in mammals