Post on 14-Dec-2015
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Cranial Nerves
Pundit Asavaritikrai, PhD, MD.Department of Anatomy, Faculty of Science
Mahidol Universityneuronum@yahoo.com
Overview
• Brain Stem– Ascend./Descend. P’w– Vital centres
• Consciousness• Respiration• CVS
– Cranial nerves
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
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
• 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 margi
n 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• #1 = T1 lateral neurons• #2 = SCG
– Pup. dilator, tarsus m, sweat gl.
• Defects: Horner’s syndrome
(เล็�ก แห้�ง ตก ไม่ งอก)• Causes:
– pulmonary apex– lateral medulla (+vestibular defects; vertigo) =
Wallenberg syndrome
Sympathetic Control of Pupil
Ptosis
• Abnormal CN III– LPS– NMJ (Myasthenia)
• Sympathetic– Superior tarsal m.
• Does not involve CN VII (ปิ�ดไม่ สนิ�ท)
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, ligh
t, noise, noxious stimuli– Processor = Area 7 (parietal)– Executor = Area 8 & SC
contralat. PPRFparamedian pontine reticular
formation (pontine gaze centers)
PPRF excites CN VI LRe.g. Lt. Frontal eye field excites
contralateral CN VI
• Clinical use– eye movements towards the side of
lesion (ตาม่องฟ้�องล็�ชั่��นิ) 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 VIinhibit 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 ofsaccadic 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 waterSaccades 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)
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Pierre Janet, William James, Pierre Marie, Albert Londe, Sigmund Freud,
Charles-Joseph Bouchard, Axel Munthe, and Alfred Binet