cranial nerves

1. Cranial Nerves
Dr. Sai Sailesh Kumar G
Associate Professor
Department of Physiology
NRIIMS
dr.goothy@gmail.com

2. Cranial nerves
 There are 12 cranial nerves.
 Motor, sensory and mixed nerves.
 3rd to 12th nerves arise from brain stem and
innervates facial, cranial and cervical tissues.
 The 1st and 2nd nerves consist of central nervous
tissues.

3. Cranial nerves
Motor Sensory Mixed
Occulomotor Olfactory Trochlear
Optic Vestibulo-cochlear Trigeminal
Abducent Facial
Accessory Glossopharyngeal
Hypoglossal Vagus

4. Olfactory Nerve
(First Cranial Nerve)

5. Olfactory Nerve
 These are derived from the central processes of the bipolar
olfactory neurons
 Situated in the olfactory zone in the nasal mucous membrane
 Olfactory neurons are grouped into 15-20 bundles on each side
 Human brain can distinguish about 3000 different odours
 Smell is considered to be the first sensation to appear in vertebrate
evolution
 Olfactory pathway do not pass through thalamus

6. Olfactory Nerve
 Carries the sensation of smell
 So the this nerve is tested by various olfactory stimuli
 Anosmia – the absence of sense of smell which is rarely bilateral
 Anosmia may result from a fracture of the anterior cranial fossa

7. Olfactory Nerve
 Make the subject to sit comfortably
 Instruct the subject to smell, identify and name the odor
 Instruct the subject to occlude his/her one nostril by hand
 Instruct the subject to close his eyes
 Make the subject to smell the test material
 Test each nostril separately and compare

8. Olfactory Nerve

9. Optic Nerve
(Second Cranial Nerve)

10. Optic Nerve
 Nerve of vision
 Second sensation to appear in the evolution
 Human eyes respond to visual spectrum 400 nm to 700 nm ( from
blue to red)
 Rods and cones of the retina acts as photoreceptors
 Rods are concerned with dim light
 Cones collect information from bright light
 Both rods and cones are absent at the optic disc which forms
blind spot of retina

11. Optic Nerve
 Carries sensation of vision
 Examination of this nerve reveals intactness of the visual pathway,
field of vision and acuity of vision

12. Optic Nerve- field of vision
 Confrontation test.
 Ask the subject to sit on a stool comfortably in an erect position
 Sit on a stool infront of the subject in such a way that your eyes and
subject eyes remain at the same level and at a distance of about 3 feet.
 Ask the subject to fix his gaze at the tip of your nose
 Ask the subject to close one of his eyes and close your opposite eye
 Move your finger midway between you and the subject to test the field of
vision of your quadrants. Bring your finger from the periphery of four
quadrants to the centre of the visual field and ask the subject to say yes
when he sees the finger.

13. Perimeter

14. Optic Nerve- Visual acuity
 Snellen’s chart. – distant vision
 Ensure that the snellen’s chart is well illuminated
 Make the subject to stand at a distance of 20 feet from the chart
 Perform the test without spectacles and with spectacles if he uses one
 Ask the subject to cover one eye with his cupped hand
 Ask the subject to read down the chart as far as he can
 Note the line and its distance to which the subject is able to read
comfortably
 Repeat the procedure with the other eye

15. Optic Nerve- Visual acuity
 Snellen’s chart – distant vision
 If the subject is unable to read the top letter, move the subject
towards the chart, until the subject can read the top letter
 Visual acuity is recorded according to the ratio
 V=d/D
 d- distance at which the subject reads the chart
 D-Distance at which letters should be read
 Record the observations

16. Optic Nerve- Visual acuity
 Jaegar’s chart – near vision
 Make the subject to sit comfortably in a well-illuminated room
 Perform the test without spectacles and with spectacles if he uses one
 Ask the subject to cover one eye with his cupped hand
 Hold the chart at 35 cm distance or 14 inches from the eye
 Ask the subject to read from above downwards
 Note the smallest type of letters that the subject can read comfortably
 Repeat the procedure with the other eye
 Record the observations

17. Snellen’s chart – distant vision

19. Jaegar’s chart – near vision

20. Occulo motor Nerve,
Trochlear nerve and
Abducent cranial nerves
(Third, fourth and sixth Cranial Nerves)

21. Occulo motor Nerve,
(Third Cranial Nerves)

22. IIIrd cranial nerves
 Somato-motor and visceromotor components
 Somatomotor fibers supply all extraocular muscles except the
superior oblique and lateral rectus
 Visceromotor fibers supply sphincter pupillae and ciliaris muscle

23. IIIrd cranial nerves
 Unilateral complete lesion
 Ptosis of upper eyelid
 Squint
 Loss of accommodation for near vision
 Diplopia

24. Trochlear nerve and
(fourth Cranial Nerves)

25. IVth cranial nerves
 Conveys somato-motor fibers
 Supplies only the superior oblique muscle of eyeball

26. Abducent cranial nerves
(sixth Cranial Nerves)

27. VIth cranial nerves
 Somato-motor fibers to supply the lateral rectus muscle of eye ball
 The nucleus of the nerve is situated beneath the floor of fourth
ventricle
 Anducent nucleus consist of large and small multipolar neurons

28. III,IV and VI th cranial nerves
 Make the subject to sit comfortably
 Ask the subject to look at a distant object
 Observe for presence or absence of drooping of upper eyelids
 Observe for presence/ absence of squint

29. III,IV and VI th cranial nerves
 Diplopia
 Ask the subject to report if double vision occurs while following the
movements of your index finger
 Ask the subject to close his one eye with the hand
 Place your index finger in front of the subjects eye and then move
to extreme right, then to the left, then upwards and then
downwards
 Record the observation
 Repeat the procedure on other side and record the observation
 Repeat the procedure with subject’s both eyes open and record the
observation

30. III,IV and VI th cranial nerves
 Nystagmus
 Instruct the subject to look at the tip of your index finger and to
follow its movements
 Place your index finger in front of the subject’s eye, then move to
the extreme right, then to the left, then upwards and then
downwards.
 Observe presence or absence of nystagmus
 Repeat the procedure on the other side and record the
observation.

31. III,IV and VI th cranial nerves
 Ocular movements
 Instruct the subject to look at the tip of your index finger and follow
its movements with his eye
 Place your index finger in front of the subject’s eye, then move
your finger in medial, superior, lateral, inferior and oblique
directions
 Observe the ocular movements in all the directions
 Repeat the procedure on the other side and record the
observation.

32. III,IV and VI th cranial nerves
 Pupil
 Compare the size of the two pupils
 Observe the shape and contour of the two pupils

33. III,IV and VI th cranial nerves
 Mobility
 Reaction to light
 Light reflex

34. Pupillary reflexes
 Mediated by third cranial nerve
 Light reflex- direct, indirect
 Light reflex- direct
 Make the subject to sit comfortably
 Ask the subject to fix his gaze at a distant object
 Shine a bright light in one eye with the torch
 Observe immediate constriction of pupil in the same eye
 Elicit the light reflex on the other side and compare

35. Pupillary reflexes
 Mediated by third cranial nerve
 Light reflex- direct, indirect
 Light reflex- indirect
 Make the subject to sit comfortably
 Ask the subject to fix his gaze at a distant object
 Hold the cardboard on the forehead and bridge of the nose
 Shine a bright light in one eye with the torch
 Observe immediate constriction of pupil of both eyes
 Elicit the light reflex on the other side and compare

36. III,IV and VI th cranial nerves
 Mobility
 Reaction to accommodation
 Accommodation reflex

37. Pupillary reflexes
 Mediated by third cranial nerve
 Accommodation reflex
 Make the subject to sit comfortably
 Ask the subject to fix his gaze at a distant object
 Bring your index finger midway between and near the eyes of the
subject
 Ask the subject to look at the tip of the index finger
 Observe the constriction of pupil and convergence of eyes.

38. Trigeminal Nerve
(Fifth Cranial Nerve)

39. Sensory Functions
 Make the subject to sit comfortably
 Test for sensory modalities
 Fine touch
 Crude touch (Pressure touch)
 Tactile localization
 Two point discrimination (tactile discrimination)
 Vibration,
 Pain and temperature
 Overall skin and mucus membrane of face and compare both the
sides
 Elicit corneal and conjuctival reflexes

40. Corneal reflex
 Mediated by opthalmic division of trigeminal nerve
 Make the subject to sit comfortably
 Ask the subject to fix his gaze at a distant object or the ceiling
 Bring the cotton wisp from the side of the subject and touch the
lateral edge of the cornea at its conjunctival margin
 Observe that the subject blinks his eyes
 Elicit the corneal reflex on the other side and compare.

41. Corneal reflex

42. Conjunctival reflex
 Mediated by opthalmic division of trigeminal nerve
 Make the subject to sit comfortably
 Ask the subject to fix his gaze at a distant object or the ceiling
 Bring the cotton wisp from the side of the subject and touch the
bulbar part of conjunctiva
 Observe that the subject blinks his eyes
 Elicit the corneal reflex on the other side and compare.

43. Motor Functions
 Masseter
 Make the subject to sit comfortably
 Ask the subject to clench his teeth
 Palpate and compare the prominence of masseter muscles
 Temporalis
 Repeat the procedure for temporalis muscle
 Lateral pterygoid
 Ask the subject to open his mouth
 Observe the position of the jaw
 If there is paralysis of lateral pterygoid muscle, the jaw deviates
towards the paralyzed side.

44. Cranial nerves
 There are 12 cranial nerves.
 Motor, sensory and mixed nerves.
 3rd to 12th nerves arise from brain stem and
innervates facial, cranial and cervical tissues.
 The 1st and 2nd nerves consist of central nervous
tissues.

45. Cranial nerves
Motor Sensory Mixed
Occulomotor Olfactory Trochlear
Optic Vestibulo-cochlear Trigeminal
Abducent Facial
Accessory Glossopharyngeal
Hypoglossal vagus

46. Facial Nerve
(Seventh Cranial Nerve)

47. Facial Nerve
 Sensory functions
 Make the subject to sit comfortably
 Instruct the subject to identify the taste by pointing to the word “ sweet, salt,
bitter and sour” written on the cards
 Ask the subject to protrude his tongue
 Apply the test solution with the help of a glass rod to the surface of the
protruded tongue
 Record the observation
 Ask the subject to rinse his mouth
 Repeat the procedure with each test solution and record the observation

48. Facial Nerve
 Motor functions
 Occipito - frontalis
 Ask the subject to frown
 Observe the wrinkles on the forehead
 Orbicularis occuli
 Ask the subject to shut his eyes tightly
 Try to open the eyes while the subject attempts to keep them close
 Observe that it is impossible to open the eyes against the subject effort

49. Facial Nerve
 Motor functions
 Buccinator
 Ask the subject to inflate his mouth with air and blowout the cheeks
 Tap with finger on each inflated cheek
 Observe that no air escapes from the mouth
 Orbicularis oris
 Ask the subject to show his upper teeth
 Observe that subject is able to do it

50. Facial Nerve
 Motor functions
 Platysma
 Ask the subject to clench his teeth
 Observe the prominence of platysma in the neck

51. Vestibulo cochlear Nerve
(Eighth Cranial Nerve)

52. Vestibulo cochlear Nerve
 Rinne’s test
 Make the subject to sit comfortably
 Instruct the subject to raise the index finger when sound is heard and to put down the
finger when sound is no longer heard
 Vibrate the tuning fork by striking the prongs against the hypothenar eminence
 Immediately place the base of the vibrating tuning fork on the subject mastoid process
of one side
 Once the subject stops hearing, hold the vibrating tuning fork near to the subject’s
external ear
 Ask the subject to indicate if the sound is heard
 Record the observation and repeat the procedure on other side

53. Vestibulo cochlear Nerve
 Rinne’s test
 Positive- Air conduction is better than bone conduction
 Negative- Bone conduction is better than air conduction

54. Vestibulo cochlear Nerve
 Weber’s test
 Instruct the subject to raise both index fingers if sound heard by both the ears
is equal
 Instruct the subject to raise the two fingers on the side if sound is better heard
 Vibrate the tuning fork by striking the prongs against the hypithenar eminence
 Immediately place the base of the vibrating tuning fork on the subjects
forehead
 Record the observation
 Compares hearing by bone conduction of both the ears

55. Glossopharyngeal Nerve &
vagus nerve
(Ninth and Tenth Cranial Nerve)

56. Glossopharyngeal Nerve
 Make the subject to sit comfortably
 Do the procedure as for testing sensory function of seventh cranial
nerve
 Posterior 1/3rd of tongue

57. Vagus Nerve
 Make the subject to sit comfortably
 Elevation of palate required to spell Egg, Rub
 Ask subject to speak these
 If he can be able to do his phonation is normal
 Ask for nasal regurgitation of fluid ( normally absent)
 Pharyngeal reflex/ gag reflex
 Palatal reflex

58. Accessory Nerve
(Eleventh Cranial Nerve)

59. Accessory Nerve
 Trapezious
 Make the subject to sit comfortably
 Stand behind the subject
 Place your hands on subject’s shoulders
 Ask the subject to shrug both shoulders against resistance

61. Accessory Nerve
 Sternomastoid
 Place your hand on subject’s cheek
 Ask the subject to move the chin to side against resistance
 Observe that subject is able to do it
 Repeat the procedure on other side
 Record the observation
 Ask the subject to flex the head against the examiners resistance

62. Hypoglossal Nerve
(Twelth Cranial Nerve)

63. Hypoglossal Nerve
 Responsible for all functions of the tongue
 Supplies opposite side of tongue
 Mixing of food
 speech

64. Hypoglossal Nerve
 Hypoglossal nerve
 Make the subject to sit comfortably
 Ask the subject to protrude his tongue as far as possible
 Observe that tongue protrudes straight ( no deviation)
 Ask the subject to move tongue from side to side and to lick each
cheek with it
 Observe that the subject is able to do it

65. THANK YOU