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Download Neurology Session 1 – Cranial Nerves
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NEUROLOGY SERIES FOR 2ND YEARS Alex Parker DISEASE TOPICS • Cranial nerve lesions • Stroke • TIA • Brain Haemorrhage • Cerebellum (DANISH) • Multiple Sclerosis • Motor Neuron Disease • Space Occupying Lesion • Parkinson’s Disease • Huntington’s Disease • Myelopathy vs Radiculopathy • Peripheral Nerve Disorders (Guillain-Barré) • Myasthenia Gravis SESSION ONE CRANIAL NERVES CRANIAL NERVES Oh Oh Oh To Tri And Finger Virgins Girls Vagina And Hymen • Cranial nerve I – Olfactory • Some • Cranial nerve II – Optic • Say • Cranial nerve III – Oculomotor • Money • Cranial nerve IV – Trochlear • Matters • Cranial nerve V – Trigeminal • But • Cranial nerve VI – Abducens • My • Cranial nerve VII – Facial • Brother • Cranial nerve VIII – Vestibulocochlear • Says • Cranial nerve IX – Glossopharyngeal • Big • Cranial nerve X – Vagus • Boobs • Cranial nerve XI – Accessory • Matter • Cranial nerve XII – Hypoglossal • More CRANIAL NERVES Remember: 2 – 2 – 4 – 4 2 not on the brainstem 2 from the midbrain 4 from the pons 4 from the medulla oblongata CRANIAL NERVES 1 5 8 10 3 9 2 12 11 7 6 4 OLFACTORY NERVE - I • Anatomy: Olfactory tract ends at uncus of the temporal lobe • Function: Sense of smell • Sign/Symptoms of a lesion: Change in smell • Causes of a lesion: Head injury, Parkinson’s disease, recurrent URTI OPTIC NERVE - II • Anatomy: OPTIC NERVE - II • Function: SENSORY • • • Transmits visual information Pupillary Reflex (afferent pathway, with CNIII) Accommodation (afferent pathway, with CNIII) • Clinical Testing: • Virsual Acuity • • • • • • Colour vision Visual Fields Pupillary Reflex • • • Snellen chart at 6m Remember to ask about glasses/contacts Cover one eye Swinging torch test Blind Spot Fundoscopy OPTIC NERVE - II • Signs & Causes of damage: • Visual inattention • • • Decreased Visual Acuity • • • Optic Atrophy (+ pale optic disc) MS, frontal tumour, glaucoma, optic nerve compression Increased Blind Spot • • Loss of awareness of one side of vision Parietal Lobe Lesion Optic neuritis, Raised ICP, Glaucoma Marcus Gunn Pupil (Relative Afferent Pupillary Defect) • • • Observed during the swinging torch test Patient's pupils constrict less (therefore appearing to dilate) when a bright light is swung from the unaffected eye to the affected eye. Damaged optic nerve pathway – Optic neuritis (pain on moving eye, loss of central vision, RAPD, papilloedema) • Papilloedema (swollen optic discs) • Visual field defects – see next slide OPTIC NERVE - II • Signs & Causes of damage: • Afferent pupillary defect – a) no direct constriction when light shone in affected eye nor consensually constriction in non-affected b) direct constriction when light is shone in non-affected eye and consensually constriction by affected eye VISUAL FIELD DEFECTS VISUAL FIELD DEFECTS VISUAL FIELD DEFECTS 1. Central scotoma - caused by inflammation of the optic disk (optic neuritis) or optic nerve (retrobulbar neuritis) 2. Right Monocular vision loss - from a complete lesion of the right optic nerve 3. Bitemporal hemianopia - caused by pressure exerted on the optic chiasm by a pituitary tumour 4. Right nasal hemianopia - caused by a perichiasmal lesion (eg. calcified internal carotid artery) 5. Right homonymous hemianopia - from a lesion of the left optic tract 6. Right homonymous superior quadrantanopia - caused by partial involvement of the optic radiation by a lesion in the left temporal lobe (Meyer’s loop) 7. Right homonymous inferior quadrantanopia - from partial involvement of the optic radiation by a lesion in the left parietal lobe 8. Right homonymous hemianopia - from a complete lesion of the left optic radiation 9. Right homonymous hemianopia w/t macular sparing - caused by a posterior cerebral artery occlusion OCULOMOTOR, TROCHLEAR, ABDUCENS – III, IV, VI • Anatomy: • • • iii) ventral midbrain through bony orbit via superior orbital fissure SR, MR, IR, IO iv) dorsal midbrain courses ventrally around midbrain through superior orbital fissure SO vi) inferior pons long tortuous intracranial route enter via superior orbital fissure LR OCULOMOTOR, TROCHLEAR, ABDUCENS – III, IV, VI • Function: MOTOR • • • • Movements of the eye Pupillary Reflex (efferent - CNIII) Accommodation (CNIII with CNII) Elevating the eyelid (CN III by sympathetically innervating levator palpebrae superioris) • Clinical Testing: • Eye movement • • • • Accommodation • • • • Draw an H with your finger “Tell me if you see double vision” Look for nystagmus and/or opthalmoplegia Hold finger in the distance “Keep looking at my finger” Move finger towards pts nose Pupillary Reflex • Direct and Consensual OCULOMOTOR, TROCHLEAR, ABDUCENS – III, IV, VI SR3 IO3 MR3 LR6 Nose IR3 SO4 3RD NERVE PALSY • Signs & Causes of damage: • Divergent squint & Diplopia (eye down and out + double vision) • • Ptosis (eyelid to droop or close completely) • • • • Paralysis of extraocular muscles (SR, IR, MR) Paralysis of levator Horner’s syndrome Myasthenia gravis Efferent pupil defect (causing a dilated pupil) • • • • Paralysis of sphincter pupillae Tumour Aneurysm Brainstem stroke 3RD NERVE PALSY • Signs & Causes of damage: c) affected pupil can not constrict to light directly but non-affected pupil can constrict consensually d) affect pupil cannot constrict consensually either when light is shone in non-affected pupil but non-affected pupil can 4TH NERVE PALSY • Signs & Causes of damage: • Eye Up & Out + Diplopia when looking down (often complain of trouble walking downstairs) • • • Paralysis of SO4 Tumour Aneurysm 6TH NERVE PALSY • Signs & Causes of damage: • Convergent squint + horizontal diplopia (person is trying to look straight but left eye can not abduct therefore is stuck looking inward) • • • Paralysis of LR6 Tumour Aneurysm OFF TOPIC: HORNER’S SYNDROME • Miosis (constricted pupil) • Ptosis (a weak, droopy eyelid) • Anhidrosis (decreased sweating) • +/- Enophthalmus (inset eyeball) • Caused by ipsilateral damage to the sympathetic trunk • • Pancoast tumour (bronchogenic carcinoma on apex of lung) MS, Brain tumour, Thyroid lump, Trauma, Congenital… OFF TOPIC: INTERNUCLEAR OPHTHALMOPLEGIA • Lesion in the medial longitudinal fasciculus • Causes failure of ADDUCTION of eye on affected side • For example in a right sided INO: • • • On looking to the right - it is normal because abduction is not affected On looking to the left – left eye abducts normal, but right eye fails to adduct and remains looking straight Subsequently there is nystamgmus in left eye as it attempts to compensate OFF TOPIC: CONJUGATE DEVIATION • Complete/partial defect of BOTH eyes to move in a particular direction • Arises from supranuclear lesions of the pathways controlling eye movement (i.e. above III, IV and VI) • Massive destructive lesions of the brainstem/cerebral hemisphere • Eyes can tell us what’s going on!!! • • • A – Partial Seizure B – Destructive Lesion (stroke, tumour, MS) C – Destructive Pontine Lesion TRIGEMINAL NERVE – V • Anatomy: • 3 branches: Ophthalmic Maxillary Mandibular TRIGEMINAL NERVE – V • Function: BOTH • Ophthalmic branch (V1) • • Maxillary branch (V2) • • SENSORY SENSORY Mandibular (V3) • • SENSORY MOTOR for muscles of mastication • Clinical Testing: • Sensory • • • Motor • • • Ask pt to close eyes and say ‘yes’ when they feel you touch their face Move from side to side Jaw opening against resistance (pterygoid muscles) Jaw clench – palpate temples (masseter muscles) Reflexes • • Corneal reflex Jaw jerk TRIGEMINAL NERVE – V • Signs & Causes of damage: • Loss of corneal reflex, paralysed muscles of mastication (deviation of jaw towards side of lesion with unilateral lesions) and loss of facial sensation • • • • • Trigeminal Neuralgia (inflammation/demyelination of trigeminal nerve sudden, explosive severe pain along the trigeminal nerve) • • • CN V palsy Neoplasm Infection + ipsilateral hearing loss – acoustic neuroma Compression of a vessel Similar symptoms + vesicular eruption – Herpes Zoster Infection (shingles) Brisk jaw reflex • Bilateral UMN lesion FACIAL NERVE – VII • Anatomy: Two Zombies Buggered My Cat • • • • • Temporal Zygomatic Buccal Mandibular Cervical FACIAL NERVE – VII • Function: BOTH • • • Convey motor impulses to muscles of facial expression Parasympathetic innervation of lacrimal/nasal and palatine/submandibular/sublingual glands Convey sensory TASTE impulses for anterior 2/3rd of tongue • Clinical Testing: • Sensory • • • Ask if pt has noticed a change in taste Or ask to differentiate salty, sour and bitter flavours Motor • • • • Raise eyebrows (differentiates between UMN and LMN) Screw up eyes – try to pull open (Bell’s sign – upgaze on attempted eye closure) Puff out cheeks Big smile FACIAL NERVE – VII • UMN vs LMN lesion • UMN: Forehead sparing • • • • Stroke MS Tumour LMN: Entire Facial Palsy • • • • Bell’s Palsy (acute idiopathic <72hrs) Parotid Tumour Acoustic neuroma Herpes Zoster VESTIBULOCOCHLEAR – VIII • Anatomy: • Fibres from hearing (cochlea) & equilibrium (vestibule) apparatus internal acoustic meatus merge to form vestibulocochlear VESTIBULOCOCHLEAR – VIII • Function: SENSORY • • Bring sensory info from the hearing and equilibrium receptors in the inner ear to the brain Clinical Testing: • Sensory – Hearing • • • • Occlude external meatus of one ear and whisper a number and letter into patent ear Ask them to say it back Repeat for other ear Special test – Sensorineural defect vs Conductive defect • Weber Test • Tuning fork on forehead • Rinne’s Test • Tuning fork placed on mastoid process • Sensorineural defect • Weber test – sound will be louder in normal ear • Rinne’s test – air conduction is louder than bone conduction • Conductive defect • Weber test – sound will be louder in affected ear • Rinne’s test – bone conduction is louder than air conduction VESTIBULOCOCHLEAR – VIII • Signs & Causes of damage: • Conductive Hearing Loss • • • • • Sensorineural Hearing Loss: • • • • • • Ear disease Otitis externa/media Paget’s disease Perforated ear drum Congenital Acquired Presbycusis (ageing) Noise induced Ototoxicity (drugs) Attacks of dizziness and deafness • Acoustic neuroma (benin tumour – as it grows, it can compress adjacent CN V-VII) GLOSSOPHARYNGEAL – IX • Anatomy: • Emerges from medulla and leave skull via jugular foramen to run to throat GLOSSOPHARYNGEAL – IX • Function: BOTH • Sensory • • Taste receptors on the posterior 1/3rd of tongue & pharynx Relays chemoreceptor information from carotid body located near the fork (bifurcation) of the carotid artery • Relays baroreceptor information from carotid sinus at the base of the internal carotid • Motor • Innervation of the stylopharyngeus, which elevates the pharnyx in swallowing VAGUS – X • Anatomy: • Only cranial nerve to extend beyond head and neck region. Emerges from medulla through skull via jugular foramen descend through neck region into thorax and abdomen. • Function: BOTH • • • • Motor parasympathetic innervation of organs Motor innervation of swallowing Sensory information from viscera Sensory from aortic body (chemoreceptor & baroreceptor) HYPOGLOSSAL – XII • Anatomy: • • Medulla exit from the skull via hypoglossal canal tongue Function: MOTOR • Motor innervation of the tongue GLOSSOPHARYNGEAL, VAGUS, HYPOGLOSSAL (BULBAR) – IX, X, XII • Clinical testing – done together Bulbar Function • Ask about a change in taste. Can assess it as well • Look for uvula deviation • Assess speech & swallow • Gag reflex Tongue • Appearance • Movements with resistance • Tongue deviates to side of weakness BULBAR PALSY (LMN – IX, X, XII) VS PSEUDOBULBAR (UMN) Bulbar Features • • • • • • Causes • • • • • • • Pseudobulbar Nasal speech Absent jaw reflex Uvula deviation Nasal regurgitation of food Reduced/absent gag reflex Wasted, fasciculating tongue • MND Diptheria Polio Myasthenia gravis Guillain-Barré Tumour Brainstem vascular disease • • • • • • • • • • • Slow, monotonous speech, sometimes explosive Brisk jaw reflex Dysphagia Brisk gag reflex Shrunken immobile tongue Emotional lability Assoc UMN limb signs MND Bihemispheric vascular disease MS Tumour Extrapyramidal disease ACCESSORY– XI • Anatomy: • • • • Roots begin on the cervical spine (C1-C5) Travel up through the foramen magnum Join cranial fibres Loop round and back down through the jugular foramen to muscles of the neck and upper back ACCESSORY– XI ACCESSORY– XI • Function: MOTOR • Innervates the sternocleidomastoid & trapezius muscle • Clinical Testing • • Ask patient to turn their head against resistance (sternocleidomastoid) Ask patient to shrug their shoulders against resistance (trapezius) • Signs and causes of damage: • Loss of power to sternocleidomastoid and trapezius • • • • CNXI palsy Tumour Stroke Trauma QUICK FIRE MCQS A malignant tumour is damaging the patient's glossopharyngeal nerve. They will experience a) loss of taste over the anterior two-thirds of the tongue. b) loss of somaesthetic sensation over the anterior two thirds of the tongue. c) loss of taste and somaesthetic sensation over the posterior third of the tongue. d) paralysis of the muscles of the tongue. A malignant tumour is damaging the patient's glossopharyngeal nerve. They will experience a) loss of taste over the anterior two-thirds of the tongue. b) loss of somaesthetic sensation over the anterior two thirds of the tongue. c) loss of taste and somaesthetic sensation over the posterior third of the tongue. d) paralysis of the muscles of the tongue. A patient is stabbed in the neck. You suspect damage to the accessory nerve in the posterior triangle. You would test nerve function by asking the patient to a) extend their neck against resistance. b) extend their neck without impairment. c) lift their shoulders against resistance. d) lift their shoulders without impairment. A patient is stabbed in the neck. You suspect damage to the accessory nerve in the posterior triangle. You would test nerve function by asking the patient to a) extend their neck against resistance. b) extend their neck without impairment. c) lift their shoulders against resistance. d) lift their shoulders without impairment. Loss of somatic sensation over the anterior two-thirds of the tongue indicates damage to the a) lingual branch of the mandibular trigeminal nerve. b) chorda tympani branch of the facial nerve. c) lingual branch of the glossopharyngeal nerve. d) hypoglossal nerve. Loss of somatic sensation over the anterior two-thirds of the tongue indicates damage to the a) lingual branch of the mandibular trigeminal nerve. b) chorda tympani branch of the facial nerve. c) lingual branch of the glossopharyngeal nerve. d) hypoglossal nerve. Examination of a patient indicates that they have a medially directed strabismus (squint). This could be due to damage to the a) oculomotor nerve. b) trochlear nerve. c) ophthalmic trigeminal nerve. d) abducens nerve. Examination of a patient indicates that they have a medially directed strabismus (squint). This could be due to damage to the a) oculomotor nerve. b) trochlear nerve. c) ophthalmic trigeminal nerve. d) abducens nerve. A patient suffers damage to the orbit in a road traffic incident resulting in damage to the third cranial nerve. Which of the following signs will be present? a) Pupillary constriction and a medial strabismus b) Pupillary dilatation and a medial strabismus c) Pupillary constriction and a lateral strabismus d) Pupillary dilatation and a lateral strabismus A patient suffers damage to the orbit in a road traffic incident resulting in damage to the third cranial nerve. Which of the following signs will be present? a) Pupillary constriction and a medial strabismus b) Pupillary dilatation and a medial strabismus c) Pupillary constriction and a lateral strabismus d) Pupillary dilatation and a lateral strabismus Which of the following statements is true of the pupillary light reflex? a) Its efferent limb is carried in the optic nerve b) It is mediated by the inferior colliculi in the midbrain c) It is a consensual reflex d) Its afferent limb is carried in the oculomotor nerve Which of the following statements is true of the pupillary light reflex? a) Its efferent limb is carried in the optic nerve b) It is mediated by the inferior colliculi in the midbrain c) It is a consensual reflex d) Its afferent limb is carried in the oculomotor nerve The seventh cranial nerve supplies a) taste buds on the posterior third of the tongue. b) muscles of the soft palate. c) muscles of the lower lip. d) the parotid salivary gland. The seventh cranial nerve supplies a) taste buds on the posterior third of the tongue. b) muscles of the soft palate. c) muscles of the lower lip. d) the parotid salivary gland. TILL NEXT TIME…