1. Cranial Nerves Pundit Asavaritikrai, PhD, MD.
Department of Anatomy, Faculty of Science
Mahidol University

2. Overview Brain Stem Ascend./Descend. P’w Vital centres Cranial nerves
Consciousness
Respiration
CVS
Cranial nerves

3. Cranial Nerves & Cranial Nerve Reflexes
CN I
CN II
CN III, IV, & VI
CN V
CN VII,
CN VIII
CN IX & X
CN XI
CN XII

5. Memorize 2-3 sections/division

6. Midbrain

8. Pons

9. Open Medulla

10. Closed Medulla

12. CN I & II CN I & II brain extension not real nerves
Special sensory afferents

13. CN I Olfactory Nerve Olfaction Memory and Behavior Pheromones
Anterior olfactory nucleus
Amydala
Piriform cortex
Enthorhinal cortex

14. CN II Optic Nerve Vision Intraocular movement (+ III)
Blinking (+ V & VII)
Circadian rhythm

15. The III, IV & VI

16. CN III Oculomotor Nerve
Intraocular movement
Autonomic
Lens shape
Pupil size
Extrinsic Eye movement
Coordinate with CN IV & VI

17. Control of Pupil Size Parasympathetic pupillary constrictor
#1 = Edinger-Westphal nuc.
#2 = ciliary ganglion
pupillary constrictor
fibers travel in outer margin of CN III

18. Pupillary Light Reflex
In: CN II
Pretectal area
Posterior Com.
Out: CN III-EW nuc.

19. Relative Afferent Pupillary Defect (RAPD) (CN II  CN III)

20. Adie’s Pupil Abnormally dilated pupil
Can be tonic, sectional, vermiform iris
Abnormal postganglionic parasympathetic fibers

21. Argyll-Robertson’s Pupil
Associated with Syphillis
Normal pupil accommodation
Does not constrict to light
Pretectal area damage
Prostitute’s pupil = Accommodate but does not react

22. Sympathetic Control of Pupil
#1 = T1 lateral neurons
#2 = SCG
Pup. dilator, tarsus m, sweat gl.
Defects: Horner’s syndrome
(เล็ก แห้ง ตก ไม่งอก)
Causes:
pulmonary apex
lateral medulla
(+vestibular defects; vertigo) = Wallenberg syndrome

23. Ptosis Abnormal CN III Sympathetic
LPS
NMJ (Myasthenia)
Sympathetic
Superior tarsal m.
Does not involve CN VII (ปิดไม่สนิท)

24. CN III, IV, & VI

25. CN III, IV, VI Function Coordination
Control of coordination (conjugation)

26. MLF (medial longitudinal fasciculus)
Internuclear connection
Nonvestibular pathways
(among CN nuclei)
VI-contralateral III
III-VII, VII-V, V-XII, XII-VII
Vestibular pathways:
Eye
Ear
Neck
Limb extensors
p389

27. Disorders of the MLF
Internuclear Ophthalmoplegia

28. CN III, IV, & VI: Coordination of Eye Movements

29. Coordination of Eye Movements
Conjugate eye movement
Dysconjugate eye movement (vergence)

30. Dysconjugate Eye Movement
Vergence
‘dysconjugate but still coordinate’
involving vergence center in the midbrain, no MLF
Near triad (Accommodation)
Stimulus: Near object
Executor: cerebral cortex
 SC
 pretectal area
Ocular vergence (midbrain RF, both sides)
Lens rounding up (EW, both sides)
Pupil constriction (EW, both sides)

31. CN III, IV, & VI: Supranuclear Control of Eye Movements

32. Supranuclear Control 1. Gaze 3. Vestibulo-ocular reflex 4. Nystagmus
Idea  there must be some control above III, IV, VI (= supranuclear control)
1. Gaze
Saccades (quick)
Smooth persuit (slow)
Foveation
3. Vestibulo-ocular reflex
4. Nystagmus

33. Dysconjugated Eye Movement
No MLF
Near vision
Accommodation
Pupil constriction
Vergence

34. Conjugate Eye Movements
Yoking mechanism
Via MLF
E.g. CN VI  contralat. CN III
Clinical use:
e.g. Internuclear ophthalmoplegia

35. 1. Smooth Persuit
Conjugate movement that maintains foveation of a moving object
Can be Voluntary or Involuntary
Mechanisms
Stimuli = retinal slip
Processor = Area 19 & 39 (Angular gyrus)
Executor = Area 8    ipsilateral CN VI
 contralateral CN III

36. 2. Reactive gaze (Saccadic eye movement)
Rapid jerky involuntary conjugate movement
(Faster than smooth persuit)
Stimuli = changing point of fixation, light, noise, noxious stimuli
Processor = Area 7 (parietal)
Executor = Area 8 & SC
 contralat. PPRF
paramedian pontine reticular formation (pontine gaze centers)
 PPRF excites CN VI  LR
e.g. Lt. Frontal eye field excites contralateral CN VI
Clinical use
eye movements towards the side of lesion (ตามองฟ้องลีชั่น)
p394

37. 3. Vestibulo-Ocular Reflex (VOR)
Conjugate movement that maintains eye position while head moves
~ involuntary/reflexive smooth persuit
Stimuli = warm water, head turning to that side
Processor & Executor = vestibular nuc.
inhibit ipsilateral CN VI
inhibit MLF contralateral CN III

38. 3. Vestibulo-Ocular Reflex (VOR)
Ex. Stimulation of Rt. Vest. Nuc.
 inhibit Rt. CN VI & LR
 eyes deviate to left
Ex. Inhibition of Rt. Vest. Nuc by:
cold water in the Rt.
turning head to the Lt.
lesion of Rt. vestibular input
 Rt LR turns the eye to the Rt
Clinical use:
Doll’s eye reflex

39. Vestibulo-ocular Reflex
Contralateral CN VI n.
From CN VI n
 ipsi. CN III n

40. Nystagmus
Vestibular
Optokinetic

41. Vestibular Nystagmus Physiologic nystagmus: Optokinetic nystagmus
Relationship between
smooth persuit (slow phase), and
saccadic eye movement (fast phase)
‘E.g. Right nystagmus refers to the fast phase of
saccadic eye movement to the right’
Types:
Physiologic nystagmus:
Optokinetic nystagmus
Vestibular nystagmus
Cold caloric testing*
 slow eye (VOR) will move the eyes to the side of cold water
Saccades will move the eyes to opposite side of cold water
(COWS)
Pathologic nystagmus:
Nystagmus at rest
Positional nystagmus
Vertical nystagmus
Pendular nystagmus

42. Nystagmus VOR occurs Fast phase in slow phase is mediated by
Superior collic.

43. p398

44. Doll’s eye phenomenon & Caloric test

45. The CN V
Facial sensation
Mastication
Jaw jerk reflex

46. CN V: Sensory Distribution

47. Jaw Jerk Reflex In: CN V3 (s) Out: CN V3 (m) Mesencephalic Nc Bilat.
Motor nuc. Of V

48. CN VII Facial Nerve
GSA
SSA
SSE*
GVE

49. Cranial Nerve Motor Nuclei = A group of Lower Motor Neurons (LMN)

50. Taste: Gustation

51. UMN lesion of Facial Nerve
Upper Face:
Dual innervation
Lower Face:
Contralateral Innervation
*UMN lesion of CN VII
Contralateral paralysis of (only) the lower face

52. Corneal Blink Reflex

53. CN VIII Vestibulo-Cochlear Nerve

54. CN VII, IX, X SVE: GVE: Mixed Efferents: CN VII motor nuclei: Face
Bilat. & Contralat. Ctc. Innerv.
Defects: facial palsy
Ambiguus nuclei (IX & X): Pharynx & Larynx
Bilateral cortical innervation
Defects: dysphagia
GVE:
Sup. & Inf. Salivatory nucleus
Dorsal motor nucleus of X

55. CN VII, IX, X Afferents: GSA: pharynx/ear SVA: taste
Solitary nucleus & tract (VII, IX, X)
GVA: pressure receptor, thoracic, abdomen
Medullar reticular formation
IX baroreceptors (carotid a.)
X baroreceptors (LV, aortic arch)

56. CN IX Glossopharyngeal Nerve

57. CN X Vagal Nerve & XI Spinal Accessory Nerve

58. Gag Reflex

59. CN XI, XII

60. CN XII Hypoglossal Nerve

61. References
Nadeau SE, et al, Medical Neuroscience 1st Ed., 2004: pp (Cycle 8), Saunders.
Haines DE, et al, Fundamental Neuroscience for Basic and Clinical Application, 3rd Ed., 2006: pp Elsevier.

62. Fathers of Neuroscience
Camillo Golgi
( )
Santiago Ramon y Cajal
( )

63. Father of Neurosurgery & Father of Neurology
Harvey Williams Cushing ( )
Jean-Martin Charcot
( )

64. A CLINICAL LESSON AT "LA SALPETRIERE."
Joseph Babinski, Georges Gilles de la Tourette, Henri Parinaud
Pierre Janet, William James, Pierre Marie, Albert Londe, Sigmund Freud,
Charles-Joseph Bouchard, Axel Munthe, and Alfred Binet