F.Benoudiba,JLSarrazin,ALadoux,JBBillaud,DDucreux

NeuroradiologyDepartment

CHUKremlinBicêtre

hearing: Sense organ

Hanoi,nov2015

• 3 distinct parts • The acoustic meatus •  Pinna •  External acoustic meatus •  Acoustic wave propagation •  Protection of the middle ear and resonance

Anatomy and physiology of hearing

•  Eardrum •  Middle ear •  Contents: •  Auditory ossicles Amplify the

vibration of the eardrum • Malleus, uncus and stapes

•  Eustachian tube: connecting the middle ear to the rhinopharynx: equalizing air pressure on both sides of the eardrum • Adaptation of impedance • Transformation vibration wave

to mechanical energy

Middle ear

• Mastoid • Communication with the mastoid air cells and the epitympanic recess

• windows • Round window • Oval window

Middle ear

• Content: • Facial Nerve

Middle ear

•  Vestibule and semi circular canals: Balance •  Cochlea •  Hearing part of the inner ear • 35mm long • Spiral around a bony

structure • 2 spires 1/2 • 2 scala separated by the

spiral lamina • Filled with peri lymph

Stapes

Fenestravestibuli

Apexofcochlea

ScalavestibuliScalaTympani

OrganeofCorti

Inner ear

• Scala Media • Triangular-shaped duct

•  contain the organ of hearing: Organ of Cort • Filled with endolymph

Organe of Corti

Scalavestibuli

Scalatympani

Inner ear

• Organe of Corti

Tectorialmembran

Outerhaircells(10500)3rows(W)

Innerhaircells(3500fibers)1row

Cochlearnerve10/CCI

Basilarmembran

Inner ear Reissner’smembran

Central auditory system : Cochlear Nucleï

Posterior Nucleus

Anterior nucleus

UnilateralafferentsSoundintensity,fréquencyandduration

Cochlear Nucleus: superior olivary complex

Bilatéral Information •  Spatial location •  Binaural interaction •  Motor response to a sound

Lateral lemniscus

Spatial location

Inferior Colliculus

Ø  Crossroad between acsending and descending fibers

Ø  Complex auditory information Ø  located just below the visual processing centers

Auditory Thalamus Medial geniculate nucleus Posterior group of thalamus Reticular nucleus

§  Auditory lateralization

Primary auditory cortex: area 41

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41 42

Hemispheric inter connexion

1. Anterior commissure of the cerebrum connecting the temporal lobe

2. Auditory tract over corpus callosum

MRI auditory system

SOUND: Air pressure vibration

Vibration of the eardrum

MAE

Sound =Mechanical Energy

focus

Ossicles amplification

Endolymph fluid agitation Hydraulic pressure OHC: amplification IHC: frequency

Cochlear nerve = Electrical energy

Electrochemical signals to brain

Physiology of Audition

• Cochlea tonotopy: •  Cochlea is capable of exceptional sound analysis, in

terms of both frequency and intensity. •  Higher frequencies cause movement in the base

of the cochlea, and deeper frequencies work at the apex.

• Cochlear nuclei tonotopy •  Apex fibers: surface of nucleus •  Base fibers: depth of nucleus

Physiology of Audition

Physiology of Audition Auditory messages are conveyed permanently to the brain via two types of pathway: the primary auditory pathway which exclusively carries messages from the cochlea the non-primary pathway (also called the reticular sensory pathway) which carries all types of sensory messages.

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Neurophysiology of audition •  Primary auditory cortex: tonotopic

representation. Topographic map of cochlea

•  Stimulation:auditory hallucinations contralateral ear

•  Secondary auditory cortex: spatial localisation of sound, memory audition

•  Stimulation: auditory illusions

•  Broca’s area: articulation of speech

•  Wernicke’s area: speech perception

Neurophysiology of audition

•  Some examples in music:

•  Left hemisphere : rythm

•  Right hemisphere : Melody et Harmony

•  Primary auditory cortex: height and sound volume

•  Secondary auditory cortex: Harmony, Melody and Rythm

•  Motor cortex: vocals and playing an instrument

•  Hippocampus: memory

•  Cerebellum: rythm pathways (beat the measure, tapping the feet to the beat)

Corpus callosum

TemporalvariationofbrainactivityinducedbyaclassicalmusicstimuliConnectopediawithRTConTrackTechnology

•  Medical history

•  Uni or bilateral deafness

•  Acquired, evolutive

•  Otoscopy

•  Tympanometry

•  Acoustic reflex (if recruitment: endo cochlear lesion)

•  Audiometric tests:

•  Rinne CA>CO Nl ou SP

CO>CA ST

•  Weber: Nl: vibration both ear

ST: sick side

SP: healthy side

Clinical diagnosis

• Audiogram: •  Tonal : graph

•  Vocal : patient’s ability to understand words

AEP: Electric activity cochlea

• 

Clinical diagnosis ST

SP

SMixte

Unconformity tonal and vocal: retro cochlear lesion

brainstem

HEARING LOSS

• A number of pathological, genetic and epigenetic factors can cause hearing loss

• May involve any part of the sensory structure

• 3 types Conductive earing loss EAM

ME

Sensorineural : Inner ear, IAM, central

Mixed : SP + Conductive

Imaging

Deafness

Conductive Sensorineural

CT IV - Cone beam

MRI

IAM Inner ear

Brain

+/- CT

Malformations Trauma otosclerosis

Conductive earing loss: causes

Mechanical obstruction

Infectious

Tumor

Trauma

Earwax, external epidermal Cholesteatoma

Malformation

Coforign body

Exostosis et osteoma

EMO

External otitis

Benign

Malignant

•  EAM

Conductive earing loss: causes

Malformation

Inflammatory

•  Middle ear

Ossicles

windows

Chronic

Suppurative otitis

tympanosclerosis

Cholesteatoma

Conductive earing loss: causes

Otosposclerosis

Traumatic •  Middle ear

Tumor

Meningioma

Adenoma

Paraganglioma

Hémangioma VII

Schwanomma VII

Sensorineural earing loss: causes

Inner ear

Malformation •  Cochlea •  Aquecduct dilatation

Otosclerosis Paget Osteogenesis imperfecta

Labyrinthic schwanomma Labyrinthic hemorrage

Traumatic

Presbyacousia

Toxics Endolymphatic papilloma

Sensorineural earing loss: causes

MAI

Malformation Agenesia, hypoplasia CN

Infectious

Schwanomma

Meningioma

Lymphoma Metastasis

Inflammatory

Sensorineural earing loss: causes

PCA

Schwanomma VIII, VII, IX,X,XI,XII

Cystic lesions EC, AC

Meningioma

Lipoma

Aneurysm

Cartilaginous tumor (chondroma, chondrosarcoma)

Sensorineural earing loss: causes

Central

Traumatic

Inflammation

ischemic

Infectious

Siderosis

Dementia Parkinson

Central deafness • Surdité Verbale: •  Impossibilité de reconnaître les mots entendus. •  Possibilitédeparolespontanée•  Atteinte bilatérale cortex temporal.

• Agnosie auditive: •  Impossibilité de reconnaître les sons et bruits

environnants. •  Infarctus capsules externes ou corps genouillés

• Amusie •  Impossibilité de reconnaître la musique

•  The auditory system has a complex organization

•  It revolves around a dual relationship : •  Anatomical structure with perceptual function

•  Complex structure combining perception and cognition.

•  The deafness causes are many and varied and a good knowledge of anatomy , physiological , clinical and para-clinical and etiological diagnostic will approach adapted diagnosis to a single symptom but with multiple etiologies.