INTRODUCTION: ANATOMY UNDERLYING CLINICAL TESTS OF CRANIAL NERVES

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1 INTRODUCTION: ANATOMY UNDERLYING CLINICAL TESTS OF CRANIAL NERVES

2 CRANIAL NERVE I - OLFACTORY I - OLFACTORY NERVE - SMELL TEST: SMELL ODORS (note: not ammonia; pain in nasal cavity CN5 DAMAGE: LOSS OF SENSE OF SMELL (ANOSMIA) also: can be damaged by fractures (blows) to nose

3 CRANIAL NERVE II - OPTIC NERVE Detect light - Test visual acuity, fields II - OPTIC NERVE fibers cross at optic chiasm Retina DAMAGE OPTIC NERVE: loss of vision in one eye DAMAGE VISUAL PATHWAY: more complex visual field deficits

4 OPTIC NERVE - PUPILLARY LIGHT REFLEX PUPILLARY LIGHT REFLEX - LIGHT SHONE IN EYE causes PUPILLARY CONSTRICTION; protective reflex that limits light entering eye (protects photoreceptors) PUPIL 1) SHINE LIGHT IN EYE 2) PUPIL OF EYE GETS SMALLER (CONSTRICTS) 1) STIMULUS (AFFERENT ARM) - light in eye; sensory neurons (photoreceptors in retina) detect light; sensory signals in OPTIC NERVE (CRANIAL NERVE II, detects light) 2) RESPONSE (EFFERENT ARM) - OCULOMOTOR NERVE (CRANIAL NERVE III, innervates pupillary constrictor (smooth muscle, Parasympathetic) Note: Reflex is consensual: Shining light in one eye also causes constriction in the opposite eye

5 CRANIAL NERVES III, IV, VI: EYE MOVEMENTS NOSE CN VI CN IV 1- Resting position of eye depends upon tonic activities in muscles. 2- Damage to any one muscle does not entirely eliminate abduction, adduction, elevation or depression; only get weakness.

6 V. TRIGEMINAL NERVE - TO SKIN OF HEAD - 3 DIVISIONS V1 OPHTHALMIC DIVISION V2 MAXILLARY DIVISON V3 MANDIBULAR DIVISION Boundary- Lateral edge of eye Boundary Lateral edge of mouth V2 V1 V3 Clinically - Test touch (sharp, dull) and temperature

7 SENSORY SUPPLY - BRANCHES OF TRIGEMINAL NERVE TO FACE V2 MAXILLARY - to skin of cheek below orbit - Zygomaticotemporal Zygomaticofacial Infraorbital AT ZT L SO IT ST V1 OPHTHALMIC - to skin above orbit - Lacrimal Supraorbital Supratrochlear Infratrochlear External Nasal Nerve ZF IO EN V3- MANDIBULAR - to skin of jaw and face below angle of mouth - Auriculotemporal Buccal Mental B M NOTE: These are branches of V to face, not ALL branches of V CLINICAL TEST OF V: SUPRAORBITAL N.

8 V - TRIGEMINAL - MOTOR - TEST CLENCH JAW MUSCLES OF MASTICATION TENSOR PALATI - tenses palate in swallowing MASSETER TEMPORALIS LAT. AND MED. PTERYGOID TENSOR TYMPANI - dampen sound ACTIONS - MOST CLOSE MOUTH - MASSETER, TEMPORALIS, MED. PTERYGOID OPEN MOUTH - LAT. PTERYGOID MYLOHYOID - raise floor of mouth in swallowing ANT. BELLY OF DIGASTRIC - opens mouth

9 MOTOR INNERVATION TO MUSCLES OF FACIAL EXPRESSION - FACIAL NERVE (CRANIAL NERVE VII) - leaves skull via stylomastoid foramen - divides in parotid gland into 5 terminal branches 1. TEMPORAL BELL'S PALSY 2. ZYGOMATIC PAROTID SALIVARY GLAND 3. BUCCAL 4. MANDIBULAR 5. CERVICAL ALSO: STAPEDIUS - muscle that dampens sound

10 CLINICAL TEST FOR FACIAL NERVE FUNCTION WRINKLE FOREHEAD BY RAISING EYEBROWS: FRONTALIS SMILE: RISORIUS PURSE LIPS: ORBICULARIS ORIS SHOW TEETH: LEVATOR LABII SUPERIORIS, ZYGOMATICUS MAJOR, ETC.

11 CORNEAL REFLEX - V TO VII AFFERENT ARM OF REFLEX SENSORY STIMULUS TOUCH CORNEA EFFERENT ARM OF REFLEX MOTOR RESPONSE CLOSE EYELID

12 CHEMICAL SENSES - TASTE - in three cranial nerves X - VAGUS - ant. to epiglottis TONGUE IX - GLOSSO- PHARYNGEAL post. 1/3 of tongue VII - FACIAL - ant. 2/3 of tongue

13 SPECIAL SENSES VIII - VESTIBULO- COCHLEAR VIII to 1) cochlea - hearing 2) semicircular canals - balance in petrous part of temporal bone TEST: HEARING; RUB FINGERS; ALSO BONE CONDUCTION WITH TUNING FORK

14 OUTER EAR Tympanic Membrane = Ear Drum EAR MIDDLE EAR INNER EAR in Temporal bone - Sounds (pressure waves in air) produce vibration of Tympanic membrane - Vibrations are transmitted via small bones in middle ear - Vibrations are detectged as sound in cochlear in Inner Ear

15 INNER EAR DETECTS TRANSMITTED VIBRATIONS Weber test tuning fork on calvarium causes bone to vibrate; conducted to directly to cochlea by bone; perceived as sound by patient Can use to test functioning of inner ear (Sensorineural hearing loss) independent of outer, middle ear (Conductive hearing loss) CONDUCTIVE HEARING LOSS - damage to middle ear (tympanic membrane, auditory ossicles (bones) SENSORINEURAL HEARING LOSS - damage to inner ear.

16 BRANCHIOMOTOR - IX GLOSSOPHARYNGEAL AND X VAGUS CN X - most muscles of soft palate CN X - muscles of larynx CN IX - stylopharyngeus CN X - muscles of pharynx soft palate TEST BY HAVING PATIENT SAY AAHH!

17 GAG REFLEX - IX to X AFFERENT ARM OF REFLEX SENSORY STIMULUS TOUCH ORO- PHARYNX EFFERENT ARM OF REFLEX MOTOR RESPONSE PATIENT GAGS - CONTRACT PHARYNGEAL MUSCLES

18 XI - ACCESSORY NERVE Branchiomotor to two muscles TRAPEZIUS Shrug shoulders STERNOCLEIDO- MASTOID Turn head CLINICAL: TORTICOLLIS Contracture of Sternocleidomastoid; Face turned to opposite side

19 HYPOGLOSSAL NERVE (XII) - ALL MUSCLES OF TONGUE - SOMATIC MOTOR GENIO- GLOSSUS INTACT DAMAGE HYPOGLOSSAL NERVE ON ONE SIDE GENIO- GLOSSUS PARALYZED PROTRUDED TONGUE DEVIATES TOWARD SIDE OF LESION - due to unopposed action of the Genioglossus muscle which protrudes tongue.