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Cranial Nerves I. II. III. IV. V. VI. Olfactory Optic Oculomotor Trochlear Trigeminal Abducens VII. Facial VIII.Vestibulocochlear IX. Glossopharyngeal X. Vagus XI. Accessory XII. Hypoglossal Fall 2012 Cranial Nerves CN I CN II CN III CN IV CN V CN VI CN VII CN VIII CN IX CN X CN XI CN XII Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Spinal accessory Hypoglossal --------------------Midbrain Midbrain Pons Pons Pons Pons Medulla Medulla Medulla Medulla Spinal Cord / BS Changes A A A A S.L. B B S.L. B B Spinal Cord Brainstem CN Functional Components 4th VENTRICLE SSA GVA SVA S.L. GVE GSA SVE GSE CN Functional Columns 4th VENTRICLE SSA GVA SVA S.L. GVE GSA SVE GSE CN Nuclei Cranial Nerves CN I CN II CN III CN IV CN V CN VI CN VII CN VIII CN IX CN X CN XI CN XII Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Spinal accessory Hypoglossal SSA SSA GSE, GVE GSE SVE, GSA GSE SVE, GVE, GSA, SVA SSA SVE, GVE, GSA, SVA SVE, GVE, GSA, GVA, SVA SVE GSE Cranial Nerves CN I CN II CN III CN IV CN V CN VI CN VII CN VIII CN IX CN X CN XI CN XII Olfactory Optic Oculomotor Trochlear Trigeminal Abducens Facial Vestibulocochlear Glossopharyngeal Vagus Spinal accessory Hypoglossal SSA SSA GSE, GVE GSE SVE, GSA GSE SVE, GVE, GSA, SVA SSA SVE, GVE, GSA, SVA SVE, GVE, GSA, GVA, SVA SVE GSE Corticobulbar Projections No CBs for CN III, IV or VI - through PPRF in pons MOTOR CORTEX V V up VII up VII low VII low VII IX, X IX, X XI XI XII XII CN I • Olfactory Epithelium • Lifespan 2 months • Mitosis of basal cells replace lost receptors • Direct access to stimuli • Unmyelinated axons form CN I – through cribriform plate CN I • Specialized dendrites – olfactory vesicles/knobs CN I • • • As many as 103 afferent fibers may synapse with one mitral or tufted cell Odorant dissolved in aqueous phase of mucus interacts with specific receptor Often many odorants in one “smell” CN I Olfactory Cortices Olfactory bulb Olfactory tract Area subcallosal Medial olfactory stria Intermediate olfactory stria Lateral olfactory stria Anterior commissure Optic tract (cut) Pyriform area Uncus Amygdaloid body Entorhinal area Olfactory System • Anosmia = loss of sense of smell • Result of head injury, chronic nasal infection, or tumor in inferior frontal lobes • Olfactory hallucinations can be the result of temporal lobe seizures • They are often part of the “aura” that precedes a seizure CN II VISUAL IMAGE (BINOCULAR) VISUAL FIELD OF LEFT EYE VISUAL FIELD OF RIGHT EYE Visual field = part of visual world seen by each eye Left Right Monocular Cresent LEFT EYE RIGHT EYE Image is inverted and reversed Binocular VISUAL FIELD of LEFT EYE CN II VISUAL FIELD of RIGHT EYE OPTIC NERVE OPTIC CHIASM OPTIC TRACT Sup. Coll. Pretectum LGN TL PL Calcarine Sulcus Sup LEFT PRIMARY VISUAL CORTEX Inf Interhemispheric Fissure RIGHT CN II LGN VISUAL FIELD PL TL EYE LEFT HEMISPHERE PRIMARY VISUAL CORTEX VISUAL FIELD of LEFT EYE ExtraGeniculate Pathways VISUAL FIELD of RIGHT EYE OPTIC NERVE OPTIC CHIASM OPTIC TRACT Sup. Coll. Pretectum 20% not to LGN LGN TL • Superior colliculus • Suprachiasmatic nucleus • Pretectum LEFT PL Calcarine Sulcus Sup PRIMARY VISUAL CORTEX Inf Interhemispheric Fissure RIGHT Pupillary Light Reflex DIRECT CONSENSUAL Sphincter Pupillae Muscle Sphincter Pupillae Muscle CG CG b.s.c. Pretectum CN III EdingerWestphal Nucleus LEFT Pretectum EdingerWestphal Nucleus RIGHT CN III Visual Lesions Definitions • Lesions always named for visual field deficit, not the physical entity damaged • Think upside down and backwards • Scotoma = small deficit • Anopsia (Anopia) = large deficit Visual Lesionsc Definitions • Homonymous • Deficits the same for both eyes • Heteronymous • Deficits different for both eyes • Hemianopsia • One half of visual field is lost • Quadrantanopsia • One quarter of visual field is lost Visual Lesions Visual Lesions Accommodation Reflex • Functions to keep object in focus as it moves from far to near distance • Pathway poorly understood • Three events occur • • • Medial recti contract Lens thicken Pupils constrict Argyll Robertson Pupil • Involves lesion of pretectum • Pupil is small and irregular • Accommodation reflex present • Pupillary light reflex absent • Mnemonic is ARP - PRA CN III EW III Nucleus GSE LR6(SO4)3 GVE Sphincter pupillae, ciliary muscles No direct CBs Pupillary Light Reflex DIRECT CONSENSUAL Sphincter Pupillae Muscle Sphincter Pupillae Muscle CG CG b.s.c. Pretectum CN III EdingerWestphal Nucleus LEFT Pretectum EdingerWestphal Nucleus RIGHT CN III CN III Lesion Right CN III nerve or nucleus lesion CN IV IV Nucleus GSE LR6(SO4)3 No direct CBs CN IV Lesion Right CN IV nerve or left nucleus lesion CN V GSA Face, scalp, nasal/oral cavities, dura SVE Muscles of mastication No direct CBs Trigeminal Nuclei Mesencephalic nucleus GSA Midbrain Chief Sensory nucleus Spinal Trigeminal nucleus Motor nucleus C1 C2 Dorsal Horn SVE Trigeminal Dermatomal Distribution Non-overlapping dermatomes, unlike spinal nerves CN V SENSORY ASSOCIATION CORTEX PRIMARY SENSORY CORTEX PRIMARY SENSORY CORTEX VPM VPM SENSORY ASSOCIATION CORTEX WIDESPREAD CORTEX INTRALAMINAR THALAMIC NUCLEI VPL VPL DTTT VTTT Touch, 2-Pt. Discrim., Vibration, Consc. Proprio. CHIEF V SUP. COLL. PAG SPINAL V RETICULAR FORMATION NC NG NG Trigeminal Ganglion Pain & Temp. NC Reflex Movement of Head DORSAL HORN OF SPINAL CORD LEFT RIGHT Trigeminal Corticobulbars MOTOR CORTEX (FACE AREA) MOTOR CORTEX (FACE AREA) Corticobulbar projections through the posterior limb of internal capsule, crus cerebri and basilar pons MOTOR V NUC. MOTOR V NUC. Trigeminal Corticobulbars Lesion MOTOR CORTEX (FACE AREA) MOTOR CORTEX (FACE AREA) Corticobulbar projections lost MOTOR V NUC. MOTOR V NUC. Corneal Reflex Lacrimal Reflex Trigeminal System Lesions • Peripheral nerve lesions • All sensations lost in distribution of division involved • Unilateral motor nucleus lesion • Ipsilateral loss of muscles of mastication (LMN) Trigeminal System Lesions • Unilateral spinal V nucleus lesion • Ipsilateral loss of pain and temperature sense • Unilateral chief V nucleus lesion • Ipsilateral loss of discriminative senses (touch, 2-pt, vibration, proprioception) • Unilateral VTTT, VPM, internal capsule or Area 3,1,2 lesion • Contralateral loss of all modalities CN VI GSE LR6(SO4)3 No direct CBs VI Nucleus CN VI Lesion Right CN VI nerve lesion Right CN VI nucleus lesion CN VII GSA Skin around ear, EAM SVA Anterior 2/3 tongue SVE Muscles facial expression GVE Lacrimal, submandibular, sublingual glands, nasal/oral mucosa Facial Motor Nucleus Facial Nerve Corticobulbars Eye Eye MOTOR CORTEX FACE AREA (UMNs) MOTOR CORTEX FACE AREA (UMNs) Mouth Eye VII th Nerve Mouth Eye Mouth Mouth FACIAL MOTOR NUCLEUS (LMNs) FACIAL MOTOR NUCLEUS (LMNs) VII th Nerve Bilateral CBs Upper Contralateral CBs Lower CN VII Lesions b c CN VIII Cochlear Nuclei SSA Hearing CN VIII – Auditory Pathways PRIMARY AUDITORY CORTEX PRIMARY AUDITORY CORTEX auditory radiation LATERAL LEMNISCUS MEDIAL GENICULATE NUCLEUS LATERAL LEMNISCUS MEDIAL GENICULATE NUCLEUS b.i.c. INF. COLL. R.A.S. d.a.s. Spiral Ganglion DCN VCNp VCNa LEFT SUP. OLIVE i.a.s. v.a.s. SUP. OLIVE TRAP. BODY DCN VCN NUC. LAT. LEMN. INF. COLL. c.i.c. R.A.S. CTT CTT RET. FORM. RET. FORM. NUC. LAT. LEMN. RIGHT LATERAL LEMNISCUS LATERAL LEMNISCUS Auditory Lesions • Unilateral lesions of cochlea, cochlear nerve or cochlear nuclei • Profound ipsilateral hearing loss • Unilateral lesions above cochlear nuclei • No significant hearing loss • Bilateral central lesions • Profound hearing loss • SON lesions • Difficulty localizing sounds in space; Not deaf Auditory Lesions - Definitions • Presbycusis • Hearing loss associated with age • Gradual, bilateral • Most common cause of hearing loss • Hypacusis • Reduction in hearing • Anacusis • Absent hearing Conduction Deafness • Problem in external or middle ear • Sound wave energy does not reach oval window • Causes • • • • Excess cerumen Foreign matter in external auditory canal Otosclerosis which fixes the footplate of the stapes Otitis media • May be reversible • Hearing aids may be helpful Sensorineural Deafness • Problem in inner ear • Disease of cochlea, CN VIII, or cochlear nuclei • Causes • • • • • • Toxic drugs Long exposure to loud noises Rubella, cytomegalovirus, syphilis Diabetes Ménière’s disease Acoustic neuroma Weber Test • Will localize hearing loss • 256 Hz tuning fork on vertex of skull • Ask patient to localize sound • Sound in both ears if patient is normal • Louder in ear with conduction deafness • Louder in normal ear in patient with sensorineural deafness Rinne Test • Compares air vs. bone conduction • Tuning fork on mastoid process, then next to ear • Air > bone conduction in normal patient • Bone > air in conduction deafness • Air > bone in sensorineural deafness Weber vs RinneTests Weber Test Rinne Test Normal Sound perceived as coming from Air conduction > bone midline conduction Conduction Deafness Sound perceived as coming from Bone conduction > air affected ear conduction on affected side Sensorineural Deafness Sound perceived as coming from Air conduction > bone normal ear conduction CN VIII SSA Balance, equilibrium Vestibular Nuclei CN VIII – Vestibular Pathways Medial Rectus Muscle III III VI VI Lateral Rectus Muscle mlf VESTIBULOCEREBELLUM PPRF jrb VEST NUC. PPRF VEST NUC. membranous labyrinth SCARPA’S GANGLION MVST (in mlf) MVST (in mlf) LVST VENTRAL HORN OF SPINAL CORD (CERVICAL) Extensor Muscles LEFT VENTRAL HORN OF SPINAL CORD (ALL LEVELS) Neck Muscles RIGHT VOR LEFT DIRECTION of Medial Rectus Muscle III VI VI PPRF + SCARPA’S GANGLION VEST NUC. RIGHT Lateral Rectus Muscle mlf endolymph flows membranous labyrinth III EYES endolymph flows PPRF VEST NUC. SCARPA’S GANGLION HEAD TURNS TO LEFT LIGHT Light Reflex DIRECTION of EYES Medial Rectus Muscle III III VI VI Lateral Rectus Muscle mlf PPRF SUP. COLL. LEFT VEST NUC. PPRF VEST NUC. RIGHT Optokinetic Reflex • Track an object while head is stationary • Railroad Nystagmus • Slow component first • Fast component second FEF Voluntary Left Hemisphere OEF DIRECTION of EYES Medial Rectus Muscle III III VI VI Lateral Rectus Muscle FEF = saccades OEF = smooth pursuit mlf PPRF SUP. COLL. LEFT VEST NUC. PPRF VEST NUC. RIGHT Nystagmus • Consists of slow and fast components • Always named for direction of fast component • Physiologic • • • • Seen after head rotations Activation of vestibular system Slow component opposite direction of head turn - VOR Fast component in direction of head turn - cortex • Pathologic / Clinical • When it occurs spontaneously • Most common finding in vestibular disorders WARM WATER AMPULLA FLOW of ENDOLYMPH COWS SCARPA’S GANGLION + VEST. NUCLEI VEST. NUCLEI PPRF PPRF VI VI III III MEDIAL RECTUS SLOWLY SACCADICALLY LATERAL RECTUS COLD WATER AMPULLA FLOW of ENDOLYMPH COWS SCARPA’S GANGLION VEST. NUCLEI VEST. NUCLEI PPRF PPRF VI VI III III MEDIAL RECTUS SLOWLY SACCADICALLY BY COMPARISON, THE CONTRALATERAL VESTIBULAR NUCLEI ARE MORE ACTIVE, AND THUS THE IPSILATERAL PPRF IS MORE ACTIVE. LATERAL RECTUS Oculocephalic Reflex • • • Test integrity of vestibular system in comatose patient • Rotate head side-to-side; Activate VOR If brainstem is intact • Eyes slowly opposite direction of head movement • Positive / Present (normal) doll’s eye reflex If brainstem is not intact • Eyes in same direction of head movement • Negative / Absent (abnormal) doll’s eye reflex Vertigo • Peripheral • • • • 75 % of all cases Occurs intermittently More distressing than central vertigo Nystagmus always present • Central • 25 % of all cases • Nystagmus may or may not be present • Other deficits often seen due to brainstem involvement FEF Cortical Lesions Left Hemisphere OEF DIRECTION of EYES Medial Rectus Muscle III III VI VI FEF = gaze preference to side of lesion OEF = no smooth pursuit ability to side opposite lesion Lateral Rectus Muscle mlf PPRF SUP. COLL. LEFT VEST NUC. PPRF VEST NUC. RIGHT CN IX Nucleus of Solitary Tract (NTS) GSA Misc ear, pharynx SVA Posterior 1/3 tongue SVE Stylopharyngeus Bilateral CBs GVE Parotid gland Nucleus Ambiguus CN X NTS GVA Thorax / abdomen Dorsal Motor Nucleus of Vagus viscera SVA Epiglottis GSA Ear, TM, dura GVE Paras to thorax / abdomen viscera SVE Pharynx, larynx Bilateral CBs Nucleus Ambiguus CN XI SVE Trapezius and SCM Bilateral CBs CN XII Hypoglossal Nucleus GSE Intrinsic and all extrinsic tongue muscles except palatoglossus Contralateral CBs CN XII Corticobulbars Contralateral CBs CN XII Lesions Contralateral CBs Contra UMN lesion OR Ipsi LMN lesion NORMAL Alternating Hemiplegias UMNs in MOTOR CORTEX CST Midbrain LMNs of III MR, IR, SR, IO, LPS, Parasymp. Pons LMNs of VI Lateral Rectus Medulla LMNs of XII Spinal Cord Muscle LCST LMNs in Ventral Horn ACST Tongue Ms. Alternating Hemiplegias UMNs in MOTOR CORTEX CST Midbrain Alternating Oculomotor Hemiplegia (Superior Alternating Hemiplegia) - Ipsilateral LMN signs for CN III - Contralateral UMN signs for CST LMNs of III LESION MR, IR, SR, IO, LPS, Parasymp. Pons LMNs of VI Lateral Rectus Medulla LMNs of XII Spinal Cord Muscle LCST LMNs in Ventral Horn ACST Tongue Ms. Contra UMN Signs •Paresis (generalized) •Increased DTRs •Increased muscle tone •Spasticity •Babinski sign present •Clonus may be present •Disuse atrophy Alternating Hemiplegias UMNs in MOTOR CORTEX CST Midbrain LMNs of III MR, IR, SR, IO, LPS, Parasymp. Pons Alternating Abducens Hemiplegia (Middle Alternating Hemiplegia) - Ipsilateral LMN signs for CN VI - Contralateral UMN signs for CST LMNs of VI LESION Lateral Rectus Medulla LMNs of XII Spinal Cord Muscle LCST LMNs in Ventral Horn ACST Tongue Ms. Contra UMN Signs •Paresis (generalized) •Increased DTRs •Increased muscle tone •Spasticity •Babinski sign present •Clonus may be present •Disuse atrophy Alternating Hemiplegias UMNs in MOTOR CORTEX CST Midbrain LMNs of III MR, IR, SR, IO, LPS, Parasymp. Pons LMNs of VI Lateral Rectus Medulla Alternating Hypoglossal Hemiplegia (Inferior Alternating Hemiplegia) - Ipsilateral LMN signs for CN XII - Contralateral UMN signs for CST Spinal Cord Muscle LMNs of XII LCST LMNs in Ventral Horn ACST LESION Tongue Ms. Contra UMN Signs •Paresis (generalized) •Increased DTRs •Increased muscle tone •Spasticity •Babinski sign present •Clonus may be present •Disuse atrophy
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