[NEURO]LEC_203_CRANIAL NERVES.pdf

(003) CRANIAL NERVES DR. VIADO | 12/09/2020 OUTLINE Olfactory Oh Sensory Some I. INTRODUCTION TO CRANIAL NERV...

(003) CRANIAL NERVES DR. VIADO | 12/09/2020 OUTLINE Olfactory Oh Sensory Some I. INTRODUCTION TO CRANIAL NERVES II Optic Oh Sensory Say II. PURELY SENSORY CRANIAL NERVES A. CN I III Oculomotor Oh Motor Money B. CN II IV Trochlear To Motor Matter C. CN VIII V Trigeminal Touch Both But III. PURELY MOTOR CRANIAL NERVES A. CN III VI Abducens And Motor My B. CN IV VII Facial Feels Both Brother C. CN VI D. CN XI VIII Vestibulocochlear Virgins Sensory Says E. CN XII IX Glossopharyngeal Girls Both Big IV. MIXED CRANIAL NERVES A. CN V X Vagus Vagina Both Boobs B. CN VII XI Accessory Ahh Motor Matter C. CN IX D. CN X XII Hypoglossal Heaven Motor More CRANIAL NERVES FORAMINA OF THE CRANIAL VAULT 12 pairs, Roman numerals I to XII CN Exit Foramina in summary All pass through foramina in base of skull (Foramina) Anterior fossa: Mainly control anatomic structures of the head except: o I - perforations in cribriform plate o Vagus (X) – extends into the thoracic (controls the Middle fossa: heart) and abdominal cavities (controls abdominal o II – optic foramen organs) o III, IV, VI and ophthalmic division of V – o Accessory (XI) – Controls Sternocleidomastoid and superior orbital fissure Trapezius (the one that turns the head from right to left o Maxillary division of V – foramen rotundum or shrugging of the shoulders) o Mandibular division of V – foramen ovale All arise from the brainstem (Nuclei) EXCEPT CN I AND II Posterior fossa: CN Nuclei (Nerve cell body/ Soma origin) o VII and VIII – internal auditory meatus Cranial nerves are collection of axons. o IX, X and XI – jugular foramen Most cranial nerves emerge from the brainstem o XII – hypoglossal foramen except I and II CN III – XI: Brainstem CN I: Basal forebrain CN II: Diencephalon (Thalamus) Page 1 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Page 2 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 SOMATIC VS. VISCERAL FUNCTIONS SOMATOMOTOR FUNCTIONS: Part of the Pyramidal System Sensory Division Involved in control of motor functions in Somatic sensory: the body (Voluntary) Skeletal muscles Originate from the motor cortex General – touch, pain, pressure, Pyramidal pathways vibration, temperature, o Corticospinal tract (Spinal cord-spinal nerves) proprioception in skin, body wall and ▪ Movement of muscles below the limbs head with control from opposite Special – hearing, equilibrium, vision, smell side of the brain ▪ Direct innervation of motor Visceral sensory: neurons of spinal cord thru Anterior (ventral horn cell) Smooth muscles and glands o Corticobulbar/corticonu General – stretch, pain, temp., clear tracts chemical changes and irritation in (Brainstem/Cranial viscera; nausea and hunger nerve) Special – taste ▪ Movement of muscle with control from opposite side of Motor Division brain Somatic motor: ▪ Some movement of muscle in General: motor innervation of all skeletal muscles here is with control from both cortical sides (bilateral) of the Visceral motor: brain. General: motor innervation of smooth and cardiac E.g: facial expression, turning muscle, glands; equivalent to Autonomic Nervous head side to side System (ANS) (parasympathetic and sympathetic ▪ Direct innervation of motor division) neurons of cranial nerve nuclei thru brainstem 1. Somato – Motor - voluntary, originates from the pre-central gyrus Pyramidal o 2 neuron (generally) Pathway – UMN (CNS) to LMN (PNS) o Efferent pathway (away from the brain) o Decussates to the other side at the medullary pyramids o Some cranial nerves have bilateral somatic motor control coming from the cortex E.g: CN VII/ CN XI Example of Bilateral Motor Cortex Control: Accessory Nerve The motor cortex sends control to both Sternocleidomastoid and Contralateral Trapezius o motor cortex damage will present with weakness to contralateral trapezius and bilateral sternocleidomastoid (that means if there is damage on the right cortex, OVERVIEW OF CRANIAL NERVE FUNCTIONS there will be difficulty turning the neck Overview: on both sides) Somato – motor Damage to the Accessory nerve itself – present with Ipsilateral weakness/ paralysis Somato - sensory on both muscles. Viscero – motor Viscero – sensory Special sensory (smell, sight, taste, hearing, balance Page 3 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 UMN vs. LMN Note: Sympathetic innervation to the head – Lateral horn of the spinal cord segments C8 – T5 - Via Superior Cervical ganglion along the internal carotid artery - No sympathetic supply coming from the cranial nerves 4. Viscero – Sensory Primary Sensory Ganglions: o Glossopharyngeal nerve ganglion(IX) receives info about blood pressure o Vagus nerve ganglion (X) 2. Somato – Sensory receives info about heart rate 3 neuron Pathway Secondary Nuclei Afferent pathway o Solitary tract nucleus (Tractus Solitarius) Via Sensory Ganglias: ▪ assimilates the viscero- o Semilunar ganglion (V)/ Trigeminal ganglion sensory information o Geniculate ganglion (VII) from CN IX and X o Vestibular and Cochlear ganglia (VIII) 5. Special Sensory o Glossopharyngeal Nerve ganglia (IX) Smell: Olfactory nerve (I) o Vagus Nerve ganglion (X) Sight/Vision: Optic nerve (II) Somato-sensory innervation: Taste: Facial nerve anterior 2/3 of the tongue (VII), glossopharyngeal nerve posterior 1/3 o Primary neuron: Cranial Nerve Ganglia of the tongue (IX) and vagus nerve back of o Secondary neuron: Brainstem the tongue (X) o Tertiary neuron: Thalamus Hearing: Vestibulocochlear nerve (VIII) Balance: Vestibulocochlear nerve (VIII) 3. Viscero – Motor Motor to the Viscera (Smooth muscles and Glands) CN FUNCTION SUMMARY Nerve Function o Sympathetic – C8 to T5 to the head Note: no sympathetic innervation from the Cranial Olfactory (I) Special sensory: smell Nerves Optic (II) Special sensory: vision o Parasympathetic – Brainstem (CN: III,VII,IX,X) Oculomotor (III) Somato-motor 3 neuron system Viscero-motor o Primary neuron – hypothalamus to the Trochlear (IV) Somato-motor viscero-motor nuclei in the brainstem o Secondary neuron (Preganglionic) – brainstem Trigeminal (V) Somato-motor nuclei to a parasympathetic ganglion Somato-sensory o Tertiary neuron (Post-Ganglionic) Abducens (VI) Somato-motor – Parasympathetic ganglion to effector organ Facial (VII) Somato-motor Somato-sensory 4 Parasympathetic Nuclei in the Brainstem Viscero-motor Located inside brainstem Special sensory: taste Edinger westphal nucleus: Occulomotor nerve (III) Vestibulo-cochlear (VIII) Special sensory: hearing- Superior Salivatory nucleus: Facial nerve (VII) balance Inferior Salivatory nucleus: Glossopharyngeal nerve Glossopharyngeal (IX) Somato-motor (IX) Somato-sensory Viscero-motor Dorsal Vagal nucleus: Vagus nerve (X) Viscero-sensory 4 Parasympathetic Ganglias Special sensory: taste Located outside the CNS Vagus (X) Somato-motor Somato-sensory Ciliary Ganglion: Occulomotor nerve (III) Viscero-motor Pterygo-palatine Ganglion: Facial nerve (VII) Viscero-sensory Submandibular Ganglion: Facial nerve (VII) Special sensory: taste Otic Ganglion: Glossopharyngeal nerve (IX) Accessory (XI) Somato-motor Hypoglossus (XII) Somato-motor Page 4 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 According to Function Note: Olfactory mucosa also gets branches from the Trigeminal nerve Purely Sensory Nerves - reason why some odors have irritable character o Olfactory (I) - smell - explains why even when anosmic, patients can still o Optic (II) - vision detect certain irritating substances (E.g: Ammonia) o Vestibulocochlear (VIII) – **Olfactory nerve is responsible for the smell while Trigeminal hearing and balance Nerve is responsible for general sensation (pain, temperature, Purely Motor Nerves touch, vibration)** o Occulomotor (III) o Trochlear (IV) o Abduscens (VI) o Spinal Accessory/Accessory (XI) o Hypoglossal (XII) PURELY SENSORY NERVES CN I: OLFACTORY NERVE Shortest cranial nerve Origin: Basal forebrain Sense (afferent) of smell (Odors) Oldest / most primitive sensory modality o The “first” CN o Derived from the embryonic nasal placode Can provoke the fastest response > 5 million receptors with the ability to regenerate The olfactory receptors and bulb are in close proximity to the cribriform plate of the ethmoid bone Damage may lead to anosmia (Ipsilateral) Olfactory Ascending (Afferent) pathway Olfactory Ascending (Afferent) Pathway: Olfactory receptor neurons > olfactory bulb > frontal cortex, hypothalamus amygdala, hippocampus Olfactory o Frontal Cortex – conscious perception receptor of smell neurons o Hypothalamus amygdala – motivation (Cribriform and emotional aspect of smell plate) o Hippocampus – odor memory Olfactory bulb > olfactory tract > Right and Left descending pathway to Pontine Olfactory bulb Reticular formation in the Brainstem (Salivation – reflex action) Smell and odorants R & L Olfactory Tract o Qualitative odor sensation: ▪ E.g: smell of flower/perfume Hypothalamus ▪ CN I Frontal cortex amygdala Hippocampus o Somato-sensory overtones of (conscious (motivation and (odor odorants: perception of emotional memory) smell aspect of smell) E.g: warmth, coolness, sharpness and irritation CN V (Opthalmic and Maxillary division) Page 5 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 o Primary Olfactory Cortex - sends nerve fibers to many other centers within the brain to establish connections for emotional and autonomic responses to olfactory sensations Note *In contrast to all other sensory pathways, the olfactory afferent pathway has only two neurons and reaches the cerebral cortex without synapsing in one of the thalamic o Arise from the olfactory receptor nerve cells in the olfactory mucous membrane located in the upper part of the nasal cavity above the level of the superior concha o Olfactory Receptor Nerve Cells - scattered among supporting cells - Consists of a small bipolar nerve cell with a coarse peripheral process that passes to the surface of the membrane and a fine central process. o Olfactory Hairs - project into the mucus covering the surface of the mucous membrane - React to odors in the air and stimulate the olfactory cells. o Olfactory Nerve Fibers - Form by the fine central process which pass through the openings of the cribriform plate of the ethmoid bone to CN II: OPTIC NERVE enter the olfactory bulb - Unmyelinated and are covered with Schwann Vision- Sight cells Pretectal region In conjunction with Oculomotor nerve (CN III) o Olfactory Bulb - ovoid structure which receives axons from the o Light reflex contralateral olfactory bulb through the olfactory tract and possesses o Accommodation reflex several types of nerve cells: - Mitral Cell – largest - Synaptic Glomeruli - rounded areas formed when the incoming Primary Neurons olfactory nerve fibers synapse with the dendrites of the mitral cells Receptors in the Retina o Cones- interpret color of light waves o Tufted cells and granular cells - Smaller nerve cells which also o Rods- interpret the intensity of light synapse with mitral cells. Transforms light into electrical potentials o Olfactory Tract - Narrow band of white matter runs from the posterior Secondary Neurons end of the olfactory bulb beneath the inferior surface of the frontal lobe Bipolar cells of the brain - consists of the central axons of the mitral and tufted cells Link to optic nerve of the bulb and some centrifugal fibers from the opposite olfactory bulb Interconnect rods and cones to produce receptive fields. Note: *As the olfactory tract reaches the anterior perforated Tertiary Neurons substance, it divides into medial and lateral olfactory stria. End in the Lateral geniculate nucleus (LGN) of the thalamus. o Lateral Stria - carries the axons to the olfactory area of the cerebral Some do not run into LGN but run medial to pretectal region cortex: (primary olfactory cortex) periamygdaloid and prepiriform areas o Connects with the Edinger-westphal nucleus of Oculomotor nerve (CN III) o MEDIAL OLFACTORY STRIA carries the fibers that cross the o Visual reflexes (e.g. Light Reflex/Accommodation median plane in the anterior commissure to pass to the olfactory bulb Reflex of the opposite side. Optic Radiation Note: *Entorhinal area (area 28) of the Para-hippocampal gyrus, which Fibers from the Lateral geniculate body to the Primary visual receives numerous connections from the primary olfactory cortex, is cortex called the secondary olfactory cortex o Superior parietal fibers o Inferior temporal fibers *Primary and Secondary Olfactory cortex are responsible for the Quadratic vision appreciation of olfactory sensations Page 6 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Primary Visual Cortex In the chiasma, the fibers from the nasal (medial) half of each Area 17 retina, including the nasal half of the Macula, cross the midline Calcarine sulcus of the occipital lobe. and enter the Optic Tract (OT) of the opposite side. While the Create: fibers from the temporal (lateral) half of each retina, including o Image the temporal half of the macula, pass posteriorly in the optic o Colors tract of the same side o Fusion of images from both eyes. 3. Optic Tract (OT) Location: Course of the Optic Nerve - Emerges from the Optic Chiasma and passes Retina (R&L) → Optic Nerve (R&L) → Optic Chiasm→ Optic Tract posterolaterally around the cerebellar peduncle. (R&L) → Lateral Geniculate Body (R&L) → Optic Radiation R&L Function: - Most of the fibers terminate by synapsing with (Superior- Parietal And Inferior – Temporal) → Visual Cortex: Area 17 nerve cell in the LGB. Few fibers pass the Pre-Tectal Nucleus (R&L) and the Superior Colliculus of the midbrain and are concerned with light reflexes. Some do not run into LGB but run medial to pretectal region o connects with the Edinger westphal nucleus of CN III o Visual Reflexes (e.g: light reflex/accommodation reflex) o PERRLA Pupil Equally Reactive to Light or Accommodation 4. Primary Visual Cortex Optic Radiation o From lateral Geniculate body to the Primary Visual cortex Description: - Its fibers are the axons of the nerve cells of the LGB. Function: - The tract passes posteriorly through the retrolenticular part of the internal capsule and terminates in the Visual Cortex (Area 17). - Visual Cortex (Area 17) – occupies the upper and lower lips of the calcarine sulcus on the medial surface of the cerebral hemisphere. - Visual Association cortex (Area 18 & 19) – Responsible for the recognition of objects and the perception of color. Visual Pathway and Binocular Vision Neurons − Four neurons conducting the visual impulses to Area 17 1. Rods and Cones (RnC) – Specialized receptor in the Retina 2. Bipolar Neurons – Connect the RnC to the ganglion cells. 3. Ganglion Cells – its axons passes to the LGB. 4. LGB nucleus – Axons passes to the Cerebral Cortex. − Binocular Vision Left and right fields of vision projected on portion of 1. Optic Nerve both retinae. Description: Image in the right field is projected on the nasal half - Made up of fibers from the cell axon in the ganglionic layer of the right retina and the left temporal half of the of the retina. It measures 3 – 4 mm at the center of its nasal left retina. side and converges at the Optic Disc and exit from the eye. In the OC, axons from the two retinal halves are - Comparable to a tract within the CNS: combined, forming the left optic tract. Myenlinated Fibers and the sheaths are formed by LGB neurons complete the right field of vision on Oligodendrocytes sheaths the visual cortex of the left hemisphere and visual It leaves the Orbital cavity through the optic canal field (visual cortex of the right hemisphere). and unites with the optic nerve of the opposite side The lower the retinal quadrants (upper field vision) forming optic chiasma. project on the lower wall of the Calcarine sulcus, while the upper retinal quadrants (lower field of 2. Optic Chiasm vision) projects on the upper wall of the sulcus. Description: Macula Lutea is represented on the posterior part of - Its anterolateral angles are continuous with the optic Area 17, and the periphery of the retina is nerves, and the posterolateral angles are continuous with the represented anteriorly optic tracts. Location: - Situated at the junction of the anterior wall and floor of the third ventricle. Decussation of fibers: Page 7 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 VISUAL FIELDS Quadrantanopsia/Quadrantanopia o Optic radiation damage (Parietal/Temporal) o Loss of a quarter of the field of vision o E.g. Right Superior Homonymous Quadrantanopia Other Examples: Note: Nasal Retinas- Temporal field of vision Temporal Retinas- Nasal field of vision Optic Chiasm Nasal Retinas (Temporal field of vision) o Fibers cross the Optic chiasm Temporal Retinas (Nasal field of vision) o Fibers do not cross at the optic chiasm. Remains ipsilateral. Optic Tract / Optic Radiation / Visual Cortex Will carry visual information from: o Ipsilateral Temporal Retinas- (Ipsilateral Nasal field of vision) o Contralateral Nasal Retina- (Contralateral Temporal field of vision) Visual Field Concept Right Visual Field- From temporal retina of the left eye plus the nasal retina of the right eye. Left Visual Field- From the nasal retina of the left eye plus the temporal retina of the right eye. Both nasal retina cross over to the other side at the chiasm while the temporal retinas remain ipsilateral. Anopia/Anopsia Sightlessness The state of being blind/lack of sight Unilateral Anopia- Complete Blindness in one eye. Hemianopsia/Hemianopia Loss of vision in half of visual field/one side of vertical midline. Homonymous Hemianopsia/ Hemianopia (Optic tract/Visual tract) o E.g. Left Homonymous Hemianopia Page 8 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Page 9 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 CN VIII: VESTIBULOCOCHLEAR NERVE CN VIII: Cochlear nerve Purely sensory nerve Spiral Ganglia- nuclei consist mostly of bipolar neuron Transmits sound and equilibrium (balance) information from Sensory organ- Organ of Corti (Primary neuron) the inner ear to the brain o Inner hair cells o Primary neuron Nuclei in the pontomedullary junction consist mostly of o Housed in the spiral ganglion bipolar neurons. Detects sound waves that vibrate the eardrums 2 divisions: o Vestibular nerve (Equilibrium/Balance) Secondary neuron o Cochlear nerve (Hearing) o Superior olivary nucleus o Information from both ears is compared to localize the sound source Third neuron o Medial Geniculate body (Thalamus) Temporal Gyrus o Low frequency- anterolateral cortex o High frequency- posteromedial cortex Anatomy: Emerges from pontomedullary junction at the cerebellopontine angle. Exits via the Internal acoustic meatus (with CN VII) Vestibular apparatus and semicircular canals o Afferent messages associated with sense of equilibrium/ balance. Analysis of Sound Cochlea o Afferent impulses associate with hearing. Associative Auditory Cortex o Comparison with former experiences of sound is done. Integration o Speech- Left Hemisphere (Temporal lobe)- Wernickes and brockas areas o Music- Right Temporal Lobe Page 10 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 CN VIII: Vestibular Nerve Oculomotor (III) Vestibular Ganglia o Moves eyeball in all directions o Nuclei: Cell bodies of bipolar neurons o Adduction is most important action Five Sensory organs: o Elevates eyelid (Levator o 3 cristae (Semicircular canals)- afferent receptor Palpebrae Superioris) in response to rotational acceleration. o Otolith Organs: o Constricts pupils (Ciliary muscle) ▪ Maculae of saccule- vertical acceleration o Accommodates the eye ▪ Maculae of the utricle- linear/horizontal Trochlear (IV) – motor to sup. oblique muscle acceleration Abducens (VI) – motor to lateral rectus muscle Vestibular part Accessory (XI) – motor to sternocleidomastoid and trapezius Symptoms of Damage Hypoglossal (XII) – motor to muscles of the tongue CN III: OCULOMOTOR NERVE Runs in the lateral wall of the cavernous sinus Exits thru Superior orbital fissure and enters Orbit The oculomotor nerve has two motor nuclei: (1) the main motor nucleus and (2) the accessory parasympathetic nucleus 1. Somatic motor neurons Innervates extraocular muscles * Except the superior oblique and the lateraL rectus Via oculomotor nucleus Situated in the anterior part of the gray matter that surrounds the cerebral aqueduct of the midbrain Lies at the level of the superior colliculus Receives corticonuclear fibers from both cerebral hemispheres Receives tectobulbar fibers from the superior colliculus and receives information from the visual cortex Receives fibers from the medial longitudinal fasciculus 2. Preganglionic parasympathetic neurons Receives corticonuclear fibers for the accomodation reflex and fibers from the pretectal nucleus for the direct and consensual light reflexes Via Edinger westphal nucleus Situated posterior to the main oculomotor nucleus Superior CN III fibers – innervates the extraocular muscles Parasympathetic fibers Ciliary Ganglion o Short ciliary nerve ▪ Ciliary muscle – makes lens rounder Hearing loss (Sensorineural) to focus on near objects Vertigo o Constrictor pupillae (Pupillary sphincter) False sense of motion Loss of equilibrium (in dark places) ▪ Decreases the diameter of the Nystagmus pupil (miosis) *ptosis – paralysis of levator palpebrae superioris/ Motion sickness damage on CN III Gaze-evoked tinnitus PURELY MOTOR NERVES Viscero-motor Function Page 11 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Ciliary muscle Lens accommodation/ varies the lens shape Pupillary sphincter/Constrictor pupillae Pupillary constriction (Miosis) Contributes to regulation of eyeball pressure Somato-motor Function Muscles innervated by the oculomotor nerve Superior rectus m. – moves the eye superiorly and laterally, internally rotates the eye in adduction Inferior rectus m. - superiorly and laterally, externally rotates in abduction. Medial rectus m. – moves the eye medially Inferior oblique m. – moves the eye superiorly in adduction and externally rotates it in abduction Levator palpebrae superioris – lifts the Accommodation reflex upper eyelid The “near response” of the eye. Reflex action of the eye in response to focusing on near object, then looking at distant objects Coordinated changes in Convergence, Lens shape Pupillary size Controlled by the parasympathetic nervous system (Via Edinger West nucleus) 3 responses of accommodation : o Pupil constriction (pupillary sphincter) o Lens Shape (Ciliary Muscle) o Convergence (medial rectus) ▪ opposite pupil but no light What will happen if there is a damage on the right was shone. optic nerve and shine a light on the right eye? CN II AND III REFLEX EXAM ANS: NO DIRECT AND CONSENSUAL The pupillary light reaction (Direct and consensual) What will happen if I cut the left oculomotor nerve and o Afferent: Optic nerve (CN II) shine a light on the right eye? o Efferent: Parasympathetic component of the CN III on both ANS: THERE WILL BE DIRECT LIGHT REFLEX sides (bilaterally) BECAUSE IT WILL GO TO THE IPSILATERAL SIDE Direct and Consensual Light Reflexes BUT THE CONTRALATERAL SIDE WILL NO LONGER SEND THE INFORMATION o When a light is shone to one eye, but both pupils constrict. What will happen if I cut the left optic nerve and shine a light o Direct Light Reflex (DLR) on the right eye? ▪ Constriction of the pupil on ANS: LIGHT REFLEX WILL STILL BE INTACT. which the light is shone. o Consensual Light Reflex (CLR) What if there is a damage on the brainstem? ▪ Constriction of the opposite ANS: DILATED PUPIL (sign that a patient is BRAIN pupil but no light was shone. DEAD) Accomodation Reaction What if I cut the oculomotor nerve on the same side? o Afferent: Optic nerve CN II ANS: NO DIRECT LIGHT REFLEX BUT o Efferent: Parasympathetic THERE WILL BE CONSENSUAL REFLEX component of the CN III on both sides (Bilaterally) Page 12 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Extraocular muscle movements CN IV: TROCHLEAR NERVE CN III: Oculomotor Innervates the Superior Oblique muscle o Superior (Up), Inferior (Down) Moves eye inferiorly when adducted and Medial (In- adduction) rectus Internally rotates when abducted o Inferior oblique – Up and In (upward Aids more in abduction adduction) Follows the same course as the CN III o Ciliary muscle (Accomodation) NUCLEUS o found in the anterior part of the gray matter o Levator Palpebrae Superioris (eyelid that surrounds the cerebral aqueduct of the elevation) midbrain CN IV: Trochlear o Lies inferior to the oculomotor nucleus at o Superior oblique the level of inferior colliculus o After leaving the nucleus, the nerve fibers o Down and out (downward abduction) pass posteriorly around the central gray matter to reach the posterior surface of the CN VI: Abducens midbrain o Lateral rectus o Receives corticonuclear fibers from both cerebral hemispheres 6 CARDINAL POSITIONS OF GAZE o Receives the tectobulbar fibers, which connect it to the visual cortex through the superior colliculus o Also receives fibers from the medical longitudinal fasciculus by which it is connected to the nuclei of the third, sixth, and eighth cranial nerve Most slender of all cranial nerves The only cranial nerve to leave the posterior surface of the brainstem, emerges from the midbrain and immediately decussates with the nerve of the opposite side Passes forward through the middle cranial fossa in the lateral wall of the cavernous sinus and enters the orbit through the orbital fissure CN VI: ABDUSCENS NERVE - Draw the eye toward the side of the head - It is a motor nerve, supplies the lateral rectus muscle (turning the eye laterally) - Enter the orbit through superior orbital fissure - Innervates the Lateral Rectus muscle - Abducts the eye - Abduscens nucleus is located in the pons. The small motor nucleus is situated beneath the floor of the upper part of the fourth ventricle, close to the midline and beneath the colliculus facialis. - The nucleus receives afferent corticonuclear fibers from both cerebral hemispheres. It receives the tectobulbar tract from the superior colliculus, by which the visual cortex is connected to the nucleus. It also receives fibers from the medial longitudinal fasciculus,by which it is connected to the nuclei of the third, fourth, and eighth cranial nerves - Course of the Abducent Nerve The fibers of the abducent nerve pass anteriorly through the pons and emerge in the groove between the lower border of the pons and the medulla oblongata. (going up). It passes forward through the cavernous sinus, lying below and lateral to the internal carotid artery. Page 13 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Conjugate Eye Movements 4 TYPES OF EYE MOVEMENT SITE OF CONTROL Motor coordination of the eyes that allows for bilateral fixation on a single object. Saccadic(Command) Frontal lobe Movement of both eyes to maintain binocular gaze Pursuit Occipital lobe “Yoked” eye movement Vestibular- Cerebellar Vestibular nuclei positional(vestibulo- ocular reflex) Convergence Midbrain CN XI: ACCESSORY NERVE o Arises from medulla o Leaves the skull through the jugular foramen o Contributions from spinal radices C1-C6 entering the skull in the foramen magnum o It has a nucleus known as nucleus ambiguous o The nucleus receives corticonuclear fibers from Clinical presentation: Mass Effect on Cavernous Sinus both cerebral hemispheres. o The efferent fibers of the nucleus emerge from the anterior surface of the medullaoblongata between the olive and the inferior cerebellar peduncle. o The nerve runs laterally in the posterior cranial fossa and joins the spinal root. The two roots unite and leave the skull through the jugular foramen. o The nerve fibers emerge from the spinal cord midway between the anterior and posterior nerve roots of the cervical spinal nerves. The fibers form a nerve trunk that ascends into the skull through the foramen magnum. o The only cranial nerve to both enter and exit the skull o Purely motor: Sternocleidomastoid and Cavernous sinus Trapezius muscles o CN (III, IV, V1, V2, VI): Ptosis, diplopia, “Frozen eye”, Opthalmoplegia, facial pain o Occlusion of C5 (venous outflow blockage): Proptosis (exophthalmus), chemosis o Carotid artery encasement: Stroke **Q: What is the first nerve that will be affected if there is sudden development of aneurysm? A: ABDUCENS** Types of Conjugate Eye movements; Site of Control Saccadic (command): rapid movement from one fixation to another; Frontal lobe. Pursuit: the slow eye movement used to maintain fixation to a moving object; Occipital lobe Vestibulo-positional (Vestibulo-ocular reflex): eye movement that compensates for movement of the head to maintain fixation (Doll’s eye - SIGN THAT YOU’RE STILL ALIVE); Cerebellar Vestibular nuclei Convergence: the movement that maintain fixation as an object is brought close the face; Midbrain o Nucleus is innervated from cortex to the contralateral side (Decussation at the medullary pyramids) o Bilateral sternocleidomastoid muscle control from cortex. Page 14 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 o Somatomotor to the: o Sternocleidomastoid o Trapezius muscle o Sternocleidomastoid o Tilt, flexion and rotate the head o Contraction turns the head to opposite side o Trapezius o Shrug the shoulder o Ipsilateral contraction o Note: Ipsilateral cerebral cortex (UMN) supplies the CN XI Damage contralateral trapezius and sternocleidomastoid plus Damage to right motor cortex ipsilateral sternocleidomastoid muscle thus a single o An acute damage to the UMN (Corticobulbar tract) will cause UMN lesion can give rise to signs of both sides. But predominantly contralateral hemiplegia/paresis of the dominant cortex will still be the contralateral cortex sternocleidomastoid and trapezius. o The right cerebral cortex will still be dominant control o Note: Contraction of sternocleidomastoid will turn/rotate the for the Left sternocleidomastoid and trapezius muscle head to the opposite side, tilt head to the ipsilateral side. and vice versa, thus the dominant weakness will still o Weak Left Sternocleidomastoid and Trapezius be on the contralateral side. ▪ Head Tilted towards right/side of UMN lesion (Strong side, which is the right sternocleidomastoid will CN XI: Sternocleidomastoid dominate- supplied by the intact Left motor cortex). ▪ Weak shrug on the left side (Contralateral cortical innervation of Trapezius) Damage to the right accessory nerve (Peripheral Nerve)/ LMN ▪ Weak/paralysis turning/rotating head to left side (contraction of sternocleidomastoid turns head to the opposite side). ▪ Head tilted towards left (opposite intact Accessory nerve will dominate, cannot tilt head towards right side of LMN lesion). ▪ Weak/paralysis of shoulder shrug right (Trapezius: Ipsilateral) Tilt, flexion and rotate the head Q1. Head tilted towards left, plus weak shoulder shrug right, eye o Flexion- contract both Sternocleidomastoid deviated towards left. Where is the lesion? o Tilt- Tilting the head will contract the ipsilateral A. Left UMN/Central Left Cortical/Left Corticobulbar damage sternocleidomastoid ▪ e.g. Right head tilt will contract right Q2. Atrophy of right trapezius and sternocleidomastoid and unable sternocleidomastoid to shrug right shoulder, unable to rotate head towards the left side, o Rotate/Turn side to side-Contraction turns the head to head tilted slightly towards left. opposite side turning A. Right LMN/Accessory nerve damage ▪ E.g. Rotating/Turning towards left will contract the right sternocleidomastoid. CN XI: Trapezius Shrug the shoulder Ipsilateral contraction Page 15 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 CN XII: HYPOGLOSSAL NERVE Brainstem > Hypoglossal nucleus > hypoglossal canal > Intrinsic and Extrinsic tongue muscles Hypoglossal Nerve:CN XII Brain stem Hypoglossus nucleus Hypogloss al canal Intrinsic Muscles of the Tongue Intrinsic tongue muscles: Superior longitudinal m. Inferior longitudinal m. Extrinsic tongue muscle Genioglossus m. Hyoglossus m. Palattoglossus m. Styloglossus m. Note: Palatoglossus is not innervated by CN XII but rather by CN X. Purely motor: intrinsic/extrinsic muscles of the Extrinsic muscle of the tongue tongue The extrinsic muscles originate from bone and Supplies all the intrinsic muscles of the tongue as well as the styloglossus, hyoglossus and the extend to the tongue, Their main function are genioglossus altering the tongue’s position allowing for portrusion, The nerve is involved in controlling tongue, retraction, and side to side movement whistling, movements required for speech and Innervated by the Hypoglossal Nerve (XII) swallowing, including sticking out the tongue and o Genioglossus: arises from the mandible moving it from side to side and portrudes the tongue, it is also known Nucleus gets its information from the contralateral as the “safety muscle” of the tongue since motor cortex it is the only muscle having the forward Hypoglossal nucleus is situated close to the midline action. immediately beneath the floor of the lower part of the fourth ventricle o Hyoglossus: arises from the hyoid bone and depresses the tongue The Tongue o Styloglossus: arises from the styloid Primary organ of taste process of the temporal bone and Manipulate food for mastication elevates and retracts the tongue Phonetic articulation Natural “toothbrush” Innervated by the Vagus Nerve (X) 2 groups of muscle (Intrinsic and Extrinsic) o Palatoglossus: arises from the palatine aponeurosis, and depresss the soft palatae,moves the palatoglossal fold towards the midline, and elevates the back of the tongue. Page 16 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Tongue: Innervation Motor Innervation: o CN XII – intrinsic and extrinsic muscles ▪ Extrinsic: Genioglossus, Hyoglossus, Styloglossus o CN X ▪ Palatoglossus Anterior 2/3 o Taste; Chorda tympani branch of CN VII o General sensation (e.g.: Pain, Temp, Touch, Vibration): Lingual branch of Mandibular nerve (Trigeminal V3) Posterior 1/3 o Taste and General sensation: Glossopharyngeal nerve CN IX Back of tongue (Pharyngeal arch 4)/ Palatal area o Taste and General sensation: Vagus nerve CN X MIXED SENSORY AND MOTOR NERVES Trigeminal nerve (V) Facial nerve (VII) Glossopharyngeal nerve (IX) Vagus nerve (X) CN V: TRIGEMINAL NERVE 1. Mesencephalic Nucleus - Composed of a column of Unipolar Largest cranial nerve Nerve Cells in the lateral part of the a. Sensory Nerve – to greater parts of the head gray matter and around the cerebral b. Motor Nerve – to several muscles including aqueduct and extends inferiorly to the muscles of mastication pons as far as the main sensory c. divided into three branches: nucleus ophthalmic nerve (V1)-sensory - Proprioception of your division maxillary nerve (V2) - temporomandibular joint TMJ, and sensory division muscles of mastication, periodontal mandibular nerve (V3)-mixed motor and sensory ligament. (nuclei of these branches originated from the During mastication, you should know brain stem) what body part is in control: chief Page 17 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 sensory nucleus will sense - Crescent-shaped pressure and touch of your face - Lies within a pouch of the dura mater – and your spinal nucleus will sense the temperature and pain Trigeminal or Meckel Cave sensation of your face >> 3 - Opthalmic, maxillary, and mandibular nerves divisions supply the sensation to arise from the anterior border of the ganglion your face. o N. Opthalmicus Opthalmic Nerve (V1) Note: o Maxillary nerve (V2) Trigeminal neuralgia - a chronic pain condition that o Mandibular nerve (V3) affects the trigeminal nerve, which carries sensation from your face to your brain. If you have trigeminal neuralgia, even mild stimulation of your face — such as from brushing your teeth or putting on makeup — may trigger a jolt of excruciating pain. 2. Chief Sensory nucleus: - Main sensory nucleus - Posterior part of the pons, lateral to the motor nucleus, and continuous below with spinal nucleus - Senses of Pressure and Touch in the face 3. Spinal nucleus: - Continuous superiorly with the main sensory nucleus in the pons - Extends inferiorly through the whole length of the medulla oblongata and into the upper part of the spinal cord as far as the second cervical segment - Temperature and Pain sensation in the face - Sensory fibers of the Spinal Nucleus: C. Trigeminal Nerve & Motor Nucleus: Muscles of Mastication and Tensor Tympani Membrane - Ophthalmic Division - Terminate in the inferior part of the spinal nucleus. Motor nucleus - Maxillary Division - - Has no ganglia Terminate in the middle of - Receives: the spinal nucleus. ✓ Corticonuclear Fibers from both - Mandibular Division - End hemispheres in the superior of the spinal ✓ Fibers from the Reticular Formation, nucleus the Red Nucleus, Tectum, and Medial Longitudinal Fasciculus ✓ Fibers from the Mesencephalic Nucleus forming a Monosynaptic Reflex Arc - Cells give rise to axons forming the motor root. - Supplies the muscles of mastication, (if you’re chewing on something, remember your CN V ) Tenses your tympanic membrane(eardrum) Tensor Tympani, Tensor Veli Palatine, and Mylohyoid and the anterior belly of the digastric muscle B. Trigeminal ganglion Sensory fibers in the trigeminal nerve have their cell bodies in the trigeminal ganglion. Page 18 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 II. CN V2: Maxillary Nerve (Sensory) Contains only Sensory Nerve Fibers Exits through the Foramen Rotundum 1. Greater and Lesser Palatine nerve - Nasopharynx - Posterior part of nasal cavity - Hard and soft palate 2. Superior alveolar nerve - Upper teeth 3. Infra-orbital nerve - Upper Lip, Upper Jaw, Nostrils 4. Zygomatic nerve Zygomatico-Temporal nerve - Lateral side of Forehead I. CN V1: Ophthalmic Nerve (Sensory) Zygomatico-Facial nerve Contains only sensory fibers - Skin of cheekbone Exits through the Superior Orbital Fissure and enters the Orbital Cavity. 1. Lacrimal Nerve - A sensory to Tear Duct, Sclera of Eye, Cornea, Lateral part of Upper Eyelid 2. Frontal Nerve - Supra-Orbital nerve: sensation of Forehead - Supra-Trochlear nerve : Bridge of nose, Medial side of Forehead - Branch to frontal and Ethmoid Sinus 3. Nasocillary Nerve - Sensation of Nasal Cavity, Sphenoid Sinus, Superficial part of nose, Meningeal branch (Tentorium Cerebelli) III. CN V3: Mandibular Nerve (Sensorimotor) Mandibular nerve Contains both sensory and motor fibers Exits through the Foramen Ovale Motor fibers mainly distributed to muscles of mastication 1. Meningeal nerve (Dura in Cranial Fossa) Supratentorial part will be supplied by Meningeal branch of your V3 - The brain has no pain receptors, but there is a pain receptor in your dura supplied by your mandibular nerve. Page 19 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 2. Anterior Division (supply the muscles of mastication) Medial Pterygoid nerve - Tensor Tympani (tenses eardrum) - Tensor Veli Palatine (tenses palate) Masseter nerve - Masseter muscle Deep temporal nerve - Temporal muscle Lateral Pterygoid nerve - Lateral Pterygoid muscle Buccal nerve - Mucosa Oral Cavity 3. Posterior division Auricuolo-Temporal nerve - Side of the head, - Sensory external acoustic meatus Note: - Proprioception TMG Taste is secondary to your facial nerves. Inferior Alveolar nerve Mandibular has a sensory root (only one that has a ganglion) and a motor root (directly - Teeth of the lower jaw attached to the mandibular nerve) - Gums - Skin of the Lower Jaw IV. Somatomotor Functions Mental nerve Muscles of mastication: - Skin Lower Lip - Temporalis muscle Lingual nerve - Masseter, Medial, and Lateral Pterygoid - Parasympathetic and Touch fibers muscles from Chorda Tympani Suprahyoidal muscles: - General sensory to the anterior 2/3 of - Mylohyoid the tongue - Anterior belly of the Digastric muscle Note: There are two nerves supplying suprahyoid muscle: mandibular nerve and facial nerve. Contraction of the suprahyoid muscles will pull up the hyoid bone, allowing you to swallow Suprahyoidal muscles: - Mylohyoid and anterior belly of the Digastric muscle Tensor tympani: - Tensor to the eardrum - Found in the inner ear protection against loud noises. Tensor villi Palatini: - Tensor to the palate V. Mandibular Nerve: Motor to Muscles of Mastication Masseter (superficial and deep head) Temporalis Medial Pterygoid Lateral Pterygoid 1. All supplied by the CN V3 2. All originate in the skull and attached to mandible 3. Paired Page 20 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 CN VII: FACIAL NERVE VI. Somatosensory to the Face Sensory Division I. Brainstem 1. Motoric nucleus (somato-motor) Opthalmic (V1) Forehead Location Maxillary (V2) Cheek / Upper Jaw - Deep in reticular formation of lower Mandibular (V3) Lower Jaw Area part of the pons Voluntary Control Note: - The part of the nucleus that supplies How to test the somatomotor? the muscles of the lower part of the Just tell the patient to open and close his mouth and move face receives only Corticonuclear his mouth from side to side. How to examine somatosensory? Fibers from the opposite cerebral Anything that’s painful to the face comes from your hemisphere. mandibular nerve. Involuntary Control - separate and controls mimetic or VII. CN V: Somatosensory emotional changes in facial Sclera/Cornea of the eye expression. This other pathway forms Anterior 2/3 of the tongue part of the reticular formation Mucosa of nasal cavity, sinuses and oral cavity Teeth 2. Superior salivary nucleus (Parasympathetic) Part of external side of eardrum - Supplies the Submandibular and The meninges in the anterior and middle Sublingual Glands cranial fossa Location: All meninges superior to tentorium cerebelli - Parasympathetic nuclei lie posterolateral Proprioceptive action of to the main Motor nucleus o Temporomandibular joint Superior salivatory o Muscles of mastication - Receives afferent fibers from the o Periodontal ligaments Hypothalamus through the Descending autonomic pathways. Information concerning taste also is received from the nucleus of the solitary tract from the mouth cavity. Lacrimal nucleus - Receives afferent fibers from the hypothalamus for emotional responses and from the sensory nuclei of the trigeminal nerve for reflex lacrimation secondary to irritation of the cornea or conjunctiva. Page 21 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 3. Tractus solitarius nucleus (taste) Sensory nucleus Intermedius nucleus - Upper part sensory nucleus that lies close to the motor nucleus. Geniculate Ganglion - Sensations of taste travel through the peripheral axons of nerve cells situated Step 1. It enters the Cerebellopontine angle and the internal auditory meatus, together with the Vestibulocochlear nerve Note: Fracture to the skull that damages the internal auditory meatus will cause paralysis to the face. with hearing may occur. Step 2. It will then innervate to Stapedius muscle (responsible for reducing loud sound -smallest muscle of the body) Note: Question: What is the blood supply of your stapedius muscle? A: Facial nerve. Q: What is its bone? A: Stapes (smallest bone) Step 3. It enters the facial canal, then goes to the parasympathetic branch of the submandibular and sublingual gland (Supplied by your facial nerve) Step 4. It enters under the parotid gland and now supply the muscles of facial expressions. Page 22 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Canalis facialis Geniculate ganglion Greater petrosal nerve > Sphenopalatine ganglion Lacrimal gland Mucosa nose, sinuses, upper mouth, Eustachian tube, middle ear Chorda tympanic nerve > Submandibular ganglion Parasympathetic for submandibular and sublingual glands Taste fibers 2/3 of tongue Stylomastoid foramen Stylohyoidues muscle + Posterior belly of digastric muscle Posterior auricular nerve o Rudimentary posterior ear muscles o Posterior belly Occipitofrontal muscle. o Small part of skin posterior from ear, part of the ear, part of the external side of ear drum and external acoustic meatus Parotid gland II. Somatomotor Supplied by the glossopharyngeal nerve Muscles of facial expression Temporo-facial division Aka: Emojis o Temporal r. – temporal m. + upper Stapedius Muscle part of orbicular m. 2 Suprahyoid muscles: o Zygomatic r. – lower part of orbicular m., muscles of nose o Stylohyoid o Buccalis r. - buccinator m. and o Posterior belly of the digastric muscle orbicularis oris m. Stapedius Muscle Cervico facial division o Nerve to stapedius (Facial Nerve) o Buccalis r. o Dampens vibration of the Stapes (Control the o Mandibular r. – Mental m. + lower part amplitude of sound waves from external of orbicularis oris m. environment to inner ear) o Cervical r. – platysma m. o Paralysis (damage to CN VII): Increase oscillation of the stapes Branches of the Facial Nerve - “Hyperacusis” Temporalis branches - Normal sounds perceived as very loud Zygomatic branches Note: Buccal branches Smallest bone in the body: Stapes Mandibular branch Smallest muscle in the body: Stapedius muscle Cervical branch Posterior auricular branch III. Somatosensory Outer part of the tympanic sheet Part of outer ear (external auditory meatus) Part of posterior ear (pinna) IV. Visceromotor (Parasympathetic) Parasympathetic visceromotor innervation of o Tear (Lacrimal) gland o Submandibular, Sublingual salivary glands (saliva) o Mucosa of the nose cavity, sinuses, part of buccal cavity, Eustachian tube and the middle ear Page 23 of 31 CMED 1B  (003) CRANIAL NERVES DR. VIADO | 12/09/2020 Lacrimal Gland (Tear) 3. Lacrimal nucleus Sensory (Afferent): Opthalmic nerve (CN V1) - Supplies the Lacrimal gland. 4. Sensory nucleus Visceromotor (Efferent): Greater petrosal nerve - Receives taste fibers from the anterior two- (CN VII) thirds of the tongue, the floor of the mouth, and the palate. V. Special Sense Remember: Note: CN VII Functions Solitary Tract Nucleus (Tractus solitarius) “Face, Ear, Taste, Tear, Saliva” - common nuclei for Taste Face: Muscles of Facial expressio