[LEC] Lec 5.2 - Neuroana 3.docx

CRANIAL NERVES

• Damage: ipsilateral
• Spinal nerve damage: contralateral
• CN Name: Oh Oh Oh To Touch And Feel A Girl’s Vagina Ahh Heaven
• CN Function: Some Say Marry Money But My Brother Says Big Brain Matters More

Introduction

CN 1: Olfactory

• Smell / olfaction
• Function: Purely sensory
• Lesion/impairment: Anosmia (loss of smell)

CN 2: Optic

• Vision
• Function: Purely sensory
• Lesion/impairment: anopsia (loss of vision)

CN 3: Oculomotor

• Function: Purely motor
• PERRLA

CN 4: Trochlear

• Function: Purely motor
• Innervates superior oblique (SO4)
  • Down
  • In
• Causes in-torsion: inward rotation of eyes

CN 5: Trigeminal

• Mastication
  • MMT: closure of mouth
  • Biting a burger: closure
  • L: opens mouth
  • Masseter: strongest muscle in the body
• “TriCHEWminal”
• Function: Motor & Sensory
• Lesion/Impairment: trigeminal neuralgia 🡪 Tic Doloureux

3 divisions

• V1: Ophthalmic
• V2: Maxillary
• V3: Mandible

CN 6: Abducens

• Function: Purely motor
• Innervates lateral rectus (LR6): abducts eyes
• Lesion/Impairment: diplopia (double vision; horizontal – most common)

CN 7: Facial

• Lesion/Impairment: Bell’s Palsy / Prosopoplegia (paralysis of the face)

CN 8: Vestibulocochlear

• Auditory (cochlea) & Balance (vestibulo)
• Lesion/impairment: Meniere’s disease
  • Vertigo: umiikot vision
  • Tinnitus: ringing in the ear
  • Sense of fullness dt high pressure

CN 9: Glossopharyngeal

• Taste & swallowing
• 9 & 10
  • Innervates pharynx
  • Gag / swallowing reflex
  • Dysphagia

CN 10: Vagus

• Chin-tuck: facilitate swallowing

CN 11: Spinal Accessory

• Innervates SCM & Trapezius muscles

CN 12: Hypoglossal

• Tongue movements
  • Tongue deviation:
  • contralateral to lesion (CVA)
  • ipsilateral to lesion (PNS/LMNL)
• Innervates most tongue muscles except for palatoglossal

Location of the Cranial Nerves

• Brainstem

  • Except:
  • CN 1: Telencephalon (cerebrum & basal ganglia)
  • CN 2: Diencephalon (SHET - Subthalamus, Hypothalamus*, Epithalamus, Thalamus)
  • Supplied by Posterior Circulation (Vertebrobasilar artery)

  

1. Midbrain

• proprioception
• CN 3 & 4

1. Pons

• Bridge
• CN 5, 6, 7 (motor), 8

1. Medulla

• CN 7 (sensory: nervus intermedius), 8, 9, 10, 11, 12

Brainstem Stroke Syndrome

• Cerebrum: Anterior circulation
• Brainstem: Posterior circulation

1. Weber

• Medial basal of the Midbrain
• CN 3

1. Benedikt

• Tegmentum of the midbrain
• CN 3

1. Locked-in

• Vertical eye movements are spared
• Bilateral Basal of the Pons
• All CNs

1. Millard-Gubler

• Lateral Pons
• CN 6, 7

1. Wallenberg / Pica Syndrome

• PICA: Posterior-inferior cerebellar artery
• Lateral medulla: spinal nucleus only
• CN 5 (sensation of pain & temperature)
• Dysphagia
• (+) Horner’s syndrome
• Crossed hemianesthesia
  • Loss of pain & temperature sense in
  • Face: ipsilateral
  • Body: contralateral

*evan’s part*

CN 2: Optic

• *evan’s part*

Amaurosis Fugax (Monocular Blindness)

• Anterior Circulation
  • Involved Internal Carotid Artery (ophthalmic A.)

Tests

• Snellen’s Chart
  • 20 ft distance
  • central visual acuity
  • N = 20/20 acuity
• Confrontation Test
  • Peripheral Visual Acuity

Additional Tests

• Ishihara: color vision testing
• Tonometry: intra-pressure measurement
  • Glaucoma = ↑ Intraocular pressure
• Retinoscopy: refraction error

Visual Pathway

• Parts

1. Optic Nerve
2. Optic Chiasm
3. Optic Tract
4. Optic Radiation
5. Occipital Cortex: Brodmann 17

Lesion	Manifestation
Optic Nerve	Monocular Blindness (IPSI)
Optic Chiasm	Bitemporal Hemianopsia - loss of peripheral vision
Optic Tract/ Optic Radiation/ Occipital Cortex	Homonymous Hemianopsia: contralat fr visual field
Optic Radiation: Upper fibers (parietal lobe)	Quadrantanopiacontralat
Optic Radiation: Lower fibers(temporal lobe)

Pupillary Light Reflex

• Direct: constrict

• Consensual: constrict even if there's no light

• Afferent: CN2 (Direct)

• Efferent: CN3 (Consensual)

• Normal Reaction

  • (+) Direct Light Reflex
  • (+) Consensual Light Reflex

• pretectal area

  • superior colliculi
  • visual reflex

  

CN 3: Oculomotor

• Edinger-Westphal Nucleus
• PERRLA -> pupils equally round, reacted to light accommodation
• Ptosis may happen in
  • Myasthenia Gravis
  • CN3 palsy
  • Horner’s Syndrome
  • Edema d/t Inferior flexion
• Damage causes: Mydriasis (Dilated Pupil) → Sympathetic
• CN3: constrict damage pupil

CN 3, 4, 6

• Formula: EOM3LR6SO4

Clinical Correlation

CN 5: Trigeminal

• largest
• Gasserian/Semilunar Ganglion
• Tic Douloureux (Trigeminal Neuralgia)
• Mixed

Motor

• Muscles of Mastication

• Additional muscles

1. Digastric (Ant)
2. Mylohyoid (belong to suprahyoid
3. Tensor Tympani - Dampens sound
4. Tensor Veli palatini

Sensory

• Facial Sensation
• 3 divisions
  • V1 - Ophthalmic (most popular): sensory supply of eyeball
  • V2 - Maxillary
  • V3 - Mandibular

CN 7 - Facial Nerve

• Bell’s Palsy
  • aka: Prosopoplegia refrigeration palsy
• Geniculate Ganglion
  • genu = tuhod
  • part of 1973, 1975, 1971 (vagal system)
• Mixed

MOTOR

• Ms of the facial expression
• Other ms:
  • Digastric (posterior belly)
  • Stylohyoid
  • Stapedius
  • smallest ms in the body (found in the ear)
  • affected in “Hyperacusis” (↑’d sensitivity to sound; paralysis of stapedius ms)

Muscles of the Face

EXIT POINTS:

SENSORY

• C7: taste anterior ⅔ of tongue
  • Chorda Timpani - fibers that provide taste sensation
  • Ageusia - loss of taste sensation
• C9: general sensation & taste posterior ⅔ of tongue
• C5: general sensation (pain) anterior ⅔ of tongue

AUTONOMIC

• Salivary Glands
  • Sublingual
  • Submandibular
  • Superior Salivary Mucus
• Lacrimal Glands
  • Great Petrosal Branch
  • Crocodile tears (during mouth movements)

Q1: Lesion CN 7 at the Stylomastoid Foramen will result to which of the following:Ans: Facial PalsyQ2: Bell’s Palsy vs. StrokeIpsilateral Facial Paralysis - Bell’s PalsyContralateral Lower Quadrant Facial Palsy - StrokeCorticobulbar Tract Involvement

CN 8: VESTIBULOCOCHLEAR NERVE

• Meiner’s Disease
• 2 Parts:
  • Vestibular
  • Balance -> Vestibular apparatus
  • Dysequilibrium
  • Vertigo -> BPPV (Benign Paroxysmal Positional Vertigo)
  • Cochlear
  • Hearing -> Organ of Corti (true organ of hearing )
  • Deafness

3 Types of Deafness

• Conduction - sound waves is impaired (outer & inner ear problem)
• Sensorineural - sensory fibers of CN 8 is involved (inner ear problem)
• Cortical - affected Brodmann’s Area 41
  • primary area for hearing
  • Heschl’s gyrus

Tuning Fork Test

• test for auditory acuity
• Weber’s Test
  • tuning fork on vertex
  • test for lateralization
• Rinne Test
  • tuning fork on mastoid process
  • compared tone conduction vs. air conduction

CN 9: GLOSSOPHARYNGEAL NERVE

• Mixed

MOTOR

• Stylophrayngeus muscle

SENSORY

• Taste & general sensation on posterior ⅓ of the tongue

AUTONOMIC

• Parotid Gland - interior salivatory glands
• Monitors carotid body & sinus

CN 10: VAGUS NERVE

• Longest cranial nerve
• 9 & 10 laging magkasama

MOTOR

• Muscles of pharynx
• Muscles of larynx
  • voice box
  • vocal cords
  • phonation (phonaten)
  • Dysphonia - different in sound production
  • Aphonia - absence of sound production (pt with hoarse voice)

SENSORY

• Skin of pinna of external ear
• Sensation to pharynx, larynx, and epiglottis

AUTONOMIC

• Innervates visceral organs of the thorax & abdomen
  • Thorax: heart (↓’d HR) & lungs (bronchodilation)
  • Abdomen: stomach, liver, pancreas, small & large intestine
• 75% of parasympathetic nervous system
• GAG REFLEX
  • swallowing reflex
  • AFF: CAN 9
  • EFF: CN 10
  • absence results to dysphagia
  • Put tongue depressor at the back of the tongue

CN 11: SPINAL ACCESSORY

• Only CN through foramen magnum
• Affected in lateral winging of the scapula (sliding door paralysis)
• Affected in radical neck dissection (CN 11 is cut)
• 2 parts:

1. Cranial Part

• part of vagal system
• innervates pharynx & larynx

1. Spinal Part

• Innervates
  • SCM (C2, C3)
  • C3 = Side Flexion (ipsilateral side) & Rotation (contralateral)
  • Trapezius (C3, C4)
  • C4 = shoulder shrug

CN 12: HYPOGLOSSAL

• Innervates tongue ms (motor component)
• Dysarthria - difficulty in articulation (may affect CN 5, 7, 10)

Tongue Muscles

• Palatoglossus - tongue elevation
  • supplied by the pharyngeal plexus (CN 9 & 10)
• Genioglossus - protrudes tongue forward
• Hyoglossus - tongue depression
• Styloglossus - curls tongue upward & backward

**Only genioglossus, hyoglossus, and styloglossus are innervated by CN 12