Cranial Nerves
Pundit Asavaritikrai, PhD, MD.
Department of Anatomy, Faculty of Science
Mahidol University
neuronum@yahoo.com
Overview
• Brain Stem
– Ascend./Descend. P’w
– Vital centres
• Consciousness
• Respiration
• CVS
– Cranial nerves
Cranial Nerves
& Cranial Nerve Reflexes
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CN I
CN II
CN III, IV, & VI
CN V
CN VII,
CN VIII
CN IX & X
CN XI
CN XII
Memorize 2-3 sections/division
Midbrain
Pons
Open Medulla
Closed Medulla
CN I & II
• CN I & II
– brain extension
– not real nerves
– Special sensory afferents
CN I Olfactory Nerve
• Olfaction
• Memory and Behavior
• Pheromones
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Anterior olfactory nucleus
Amydala
Piriform cortex
Enthorhinal cortex
CN II Optic Nerve
• Vision
• Intraocular movement
(+ III)
• Blinking (+ V & VII)
• Circadian rhythm
The III, IV & VI
CN III Oculomotor Nerve
• Intraocular movement
– Autonomic
• Lens shape
• Pupil size
• Extrinsic Eye movement
– Coordinate with CN IV & VI
Control of Pupil Size
• Parasympathetic
• #1 = Edinger-Westphal nuc.
• #2 = ciliary ganglion
– pupillary constrictor
– fibers travel in outer
margin of CN III
Pupillary Light Reflex
• In: CN II
– Pretectal area
– Posterior Com.
• Out: CN III-EW nuc.
Relative Afferent Pupillary Defect (RAPD)
(CN II  CN III)
Adie’s Pupil
• Abnormally dilated pupil
• Can be tonic, sectional,
vermiform iris
• Abnormal postganglionic
parasympathetic fibers
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
Sympathetic Control of Pupil
• Sympathetic
• #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
Ptosis
• Abnormal CN III
– LPS
– NMJ (Myasthenia)
• Sympathetic
– Superior tarsal m.
• Does not involve
CN VII (ปิ ดไม่สนิท)
CN III, IV, & VI
CN III, IV, VI
• Function
• Coordination
• Control of coordination (conjugation)
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
Disorders of the MLF
• Internuclear
Ophthalmoplegia
CN III, IV, & VI:
Coordination of Eye Movements
Coordination of Eye Movements
• Conjugate eye movement
• Dysconjugate eye movement (vergence)
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)
CN III, IV, & VI:
Supranuclear Control of
Eye Movements
Supranuclear Control
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
Dysconjugated Eye Movement
• No MLF
• Near vision
– Accommodation
– Pupil constriction
– Vergence
Conjugate Eye Movements
• Yoking mechanism
• Via MLF
E.g. CN VI  contralat. CN III
• Clinical use:
e.g. Internuclear ophthalmoplegia
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
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 (ตามองฟ้องลีชนั่ )
p394
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
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
Vestibulo-ocular
Reflex
• Contralateral CN VI n.
• From CN VI n
–  ipsi. CN III n
Nystagmus
• Vestibular
• Optokinetic
Vestibular 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
Nystagmus
• VOR occurs
– in slow phase
• Fast phase
– is mediated by
– Superior collic.
p398
Doll’s eye phenomenon
& Caloric test
The CN V
• Facial sensation
• Mastication
• Jaw jerk reflex
CN V: Sensory Distribution
Jaw Jerk Reflex
• In: CN V3 (s)
• Mesencephalic Nc
• Out: CN V3 (m)
• Bilat.
• Motor nuc. Of V
CN VII Facial Nerve
•GSA
•SSA
•SSE*
•GVE
Cranial Nerve Motor Nuclei =
A group of Lower Motor Neurons (LMN)
Taste: Gustation
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
Corneal Blink Reflex
CN VIII Vestibulo-Cochlear Nerve
CN VII, IX, X
Mixed
Efferents:
• SVE:
– 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
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)
CN IX Glossopharyngeal Nerve
CN X Vagal Nerve & XI Spinal
Accessory Nerve
Gag Reflex
CN XI, XII
CN XII Hypoglossal Nerve
References
• Nadeau SE, et al, Medical Neuroscience 1st Ed.,
2004: pp 358-418 (Cycle 8), Saunders.
• Haines DE, et al, Fundamental Neuroscience for
Basic and Clinical Application, 3rd Ed., 2006: pp
209-228 Elsevier.
Fathers of Neuroscience
Camillo Golgi
(1843-1926)
Santiago Ramon y Cajal
(1852-1934)
Father of Neurosurgery
& Father of Neurology
Harvey Williams Cushing
(1869-1939)
Jean-Martin Charcot
(1825-1893)
A CLINICAL LESSON AT "LA SALPETRIERE."
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Pierre Janet, William James, Pierre Marie, Albert Londe, Sigmund Freud,
Charles-Joseph Bouchard, Axel Munthe, and Alfred Binet