Computer generated transcript

Warning!
The following transcript was generated automatically from the content and has not been checked or corrected manually.

MEDICINE MASTERCLASS PRE-CLINICAL SERIES HEARING & VISION SAIRANA ABRAHAMCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESCRANIAL NERVESHEARINGEAR ANATOMY OUTER EAR EAR ANATOMY Pinna OUTER EAR EAR ANATOMY Pinna Auditory Meatus OUTER EAR Pinna EAR ANATOMY External Auditory Meatus OUTER EARMIDDLE EAR ANATOMY Pinna External Auditory Meatus Membrane OUTER EAR MIDDLEEAR ANATOMY EAR ANATOMY Pinna External Auditory Meatus Membrane OUTER EAR MIDDLE EAR ANATOMY Pinna MalleusStapes Incus Auditory Meatus Tympanic Membrane OUTER EAR MIDDLE EAR ANATOMY Pinna Stapes Air-filled tube, connecting Malleus the ear and nasopharynx; Incus it opens to allow equalisation of internal to external pressure, preventing damage to the middle ear. External Auditory Meatus Eustachian tube Tympanic Membrane OUTER EAR MIDDLE EAR ANATOMY Pinna MalleusStapes Oval window Incus Round window External Auditory Meatus Tympanic Eustachian tube Membrane OUTER EAR MIDDLE INNER EAR ANATOMY Pinna Malleus Stapes Incus Auditory Meatus Tympanic Eustachian tube Membrane OUTER EAR MIDDLE INNER EAR ANATOMY Pinna Malleus Stapes Semi-circular canals Incus Cochlea External Auditory Meatus Tympanic Eustachian tube Membrane OUTER EAR MIDDLE INNER SOUND TRANSDUCTION Sound waves are carried via vibration of particles, into the external ear and auditory canal. SOUND TRANSDUCTION Reaches the eardrum, Sound waves are ossicles interact to carried via vibration enable impedance of particles, into thematching (as inner external ear and ear is water-filled). auditory canal. SOUND TRANSDUCTION Reaches the eardrum, Sound waves are ossicles interact to carried via vibration IMPEDANCE MATCHING: enable impedance of particles, into the matching (as inner As it is easier to vibrate gas external ear and particles, than water particles ear is water-filled). auditory canal. (which provide greater resistance), more force is needed. This is managed through the difference in surface area, a large tympanic membrane to small SA of the oval window - increasing the force 1000x. SOUND TRANSDUCTION Reaches the eardrum, The stapes transmits Sound waves are ossicles interact to the vibrations carried via vibration enable impedance through the fluid of of particles, into the matching at the oval the bony labyrinth. external ear and window (as inner ear The round window is water-filled). moves outwards. auditory canal. SOUND TRANSDUCTION Reaches the eardrum, The stapes transmits Sound waves are ossicles interact to the vibrations carried via vibration enable impedance through the fluid of of particles, into the matching at the oval the bony labyrinth. external ear and window (as inner ear The round window is water-filled). moves outwards. auditory canal. The inner ear acts to convert vibration into electrical signals, which are sent to the brain - via the auditory nerve.INNER EAR The cochlea is made up of 3 coiled tubes: Scala Vestibuli (perilymph) Scala Media (endolymph) Scala Tympani (perilymph) Endolymph: high K+, low Na+ and Ca2+ (the opposite of perilymph).INNER EAR Scala Vestibuli (perilymph) Scala Media (endolymph) Scala Tympani (perilymph) Endolymph: high K+, low Na+ and Ca2+ (the opposite of perilymph). The difference between the two fluid ion contents mean there is an 'Endocochlear Potential'. SCALA MEDIA Contains the 'Organ of Corti', with electrochemically sensitive hair cells. They sit on the surface of the Basilar membrane, and are connected superiorly to the Tectorial membrane by stereocilia. The normal endocohlear potential is approximately +80mV. BASILAR MEMBRANE The 'basilar fibres' (on the membrane) change in diameter depending on their location: close to the oval window are short stiff fibres, which pick up high frequencies further away are long fibres, which vibrate best with low frequencies (as this pitch travels the furthest along the tube) BASILAR MEMBRANE The 'basilar fibres' (on the membrane) change in diameter depending on their location: close to the oval window are short stiff fibres, which pick up high frequencies further away are long fibres, which vibrate best with low frequencies The movement of these fibres, as well as the stereocilia connected to the tectorial membrane, in response to vibrations, cause changes in the endocochlear potential. ORGAN OF CORTI The stereocilia bend in a certain direction This causes opening of K+ channels, then depolarisation of the hair cells Voltage-gated Ca2+ channels open, allowing a Ca2+ influx This lead to the release of glutamate (an excitatory neurotransmitter) which allows for an electrical impulse to be to sent via the neuron SBA 1 Sam comes to see his GP complaining of decreased hearing, which has been getting progressively worse over the past two months. Rinne's test is performed, which is positive in both ears. Then a Weber's test finds lateralisation to the right ear. What sort of hearing loss is Sam experiencing? A) Right-sided conductive hearing loss B) Left-sided conductive hearing loss C) Right-sided sensorineural hearing loss D) Left-sided sensorineural hearing loss E) Conductive hearing loss in both ears ANSWER Sam comes to see his GP complaining of decreased hearing, which has been getting progressively worse over the past two months. Rinne's test is performed, which is positive in both ears. Then a Weber's test finds lateralisation to the right ear. What sort of hearing loss is Sam experiencing? A) Right-sided conductive hearing loss B) Left-sided conductive hearing loss C) Right-sided sensorineural hearing loss -(lateralises to opposite side) D) Left-sided sensorineural hearing loss E) Conductive hearing loss in both earsINTERPRETING AUDIOGRAMS Hearing loss can either be due to a sensorineural issue, or a conductive issue (involving structures of the outer and middle ear). WHAT TYPE OF HEARING LOSS DO YOU SEE IN OLD AGE?INTERPRETING AUDIOGRAMS Presbycusis Normally gradual, bilateral, high frequency hearing loss (due to age-related damage to the cochlea).INTERPRETING AUDIOGRAMS Nerve-related hearing loss: Presbycusis - high frequency loss Noise-damage related - low frequency loss Ototoxic drugs (e.g. gentamicin)- all frequencies affectedINTERPRETING AUDIOGRAMS WHAT TYPE OF HEARING LOSS IS SEEN HERE?INTERPRETING AUDIOGRAMS Air conduction deafness: e.g. post recurrent infection, hereditory fibrosis ('otosclerosis')VISION SBA 2 A patient comes into your opthamology clinic complaining of intermittant double vision. On examination you notice these findings in the patient. Given what is seen in these pictures, what nerve palsy is present? A) Facial palsy B) Occulomotor palsy C) Trochlear palsy D) Abducens palsy E) Bell's palsy ANSWER A patient comes into your opthamology clinic complaining of intermittant double vision. On examination you notice these findings in the patient. Given what is seen in these pictures, what nerve palsy is present? A) Facial palsy B) Occulomotor palsy C) Trochlear palsy (CNIV) D) Abducens palsy E) Bell's palsyORBITAL BONES EYE MUSCLES WHAT DOES LR6SO4(AO3) MEAN? EYE MUSCLES WHAT DOES LR6SO4(AO3) MEAN? CNIII also supplies the 'levator palpebrae superiosis' which elevates the eyelid. Damage results in ptosis. EYE MUSCLES LR6SO4(3) EYE MUSCLES Superior rectus: Inferior rectus: EYE MUSCLES Superior rectus: Elevation (intorsion, adduction) adduction)ectus: Depression (extorsion, EYE MUSCLES Superior oblique: Inferior oblique: EYE MUSCLES Superior oblique: Intorsion (depression, abduction) abduction)blique: Extorsion (elevation,EYE MUSCLES VISUAL PATHWAYS Right visual field: The right visual field is mapped by the left-side of both eyes (Rt nasal + Lt temporal). Optic tract Left visual field: The left visual field is mapped by the right-side of Optic radiation both eyes (Lt nasal + Rt temporal). VISUAL PATHWAYS Right visual field: The right visual field is mapped by the left-side ofember - when both eyes (Lt nasal + Rassessing the eyes temporal). everything should Optic tract Left visual field: be inverted and The left visual field is flipped! :) mapped by the right-side Optic radiation both eyes (Rt nasal + Lt temporal). VISUAL PATHWAY LESIONS Where is the lesion? Left Right Optic tract Optic radiation VISUAL PATHWAY LESIONS Where is the lesion? Right optic nerve Optic tract (Rt-sided blindness) MONOCULAR VISION LOSS Optic radiation VISUAL PATHWAY LESIONS Where is the lesion? Left Right Optic tract Optic radiation VISUAL PATHWAY LESIONS Where is the lesion? Optic chiasm Optic tract (e.g. pituitary ademona): BITEMPORAL HEMANOPIA Optic radiation VISUAL PATHWAY LESIONS Where is the lesion? Left Right Optic tract Optic radiation VISUAL PATHWAY LESIONS Where is the lesion? Right optic tract, Optic radiatiOptic tract Occipital lobe LEFT HOMONYMOUS HEMIANOPIA Optic radiation VISUAL PATHWAY LESIONS Where is the lesion? Left Right Optic tract Optic radiation VISUAL PATHWAY LESIONS Where is the lesion? Right inferior optic radiations Optic tract LEFT SUPERIOR HOMONYMOUS QUADRANTANOPIA Parietal (inferior) Optic radiation PiTs Temporal (superior) VISUAL PATHWAY LESIONS Where is the lesion? Right superior optic radiations Optic tract LEFT INFERIOR HOMONYMOUS QUADRANTANOPIA Parietal (inferior) Optic radiation PiTs Temporal (superior) VISUAL PATHWAY LESIONS LEFT HOMONYMOUS HEMANOPIA WITH MACULA SPARING Optic tract Right occipital lobe defect - as there is dual blood supply of MCA & PCA. Optic radiation SBA 3 A patient comes in complaining that recently dust keeps getting in her eye and causing irritation. You decide to perform a cranial nerve examination on her as part of her assessment; when testing her corneal reflex in the right eye, you notice that the left eye blinks but the right eye remains open. Where in the reflex pathway is the issue likely to be, in this patient? A) CNIII - right B) CNV (v1) - right C) CNV (v1) - left D) CNVII - left E) Orbicularis oculi - right ANSWER A patient comes in complaining that recently dust keeps getting in her eye and causing irritation. You decide to perform a cranial nerve examination on her as part of her assessment; when testing her corneal reflex in the right eye, you notice that the left eye blinks but the right eye remains open. Where in the reflex pathway is the issue likely to be, in this patient? A) CNIII - right B) CNV (v1) - right C) CNV (v1) - left D) CNVII - left E) Orbicularis oculi - right (CNVII)THANK YOU FOR JOINING TODAY'S TALK. ANY QUESTIONS? Please fill in the feedback form! :)