Exam 3 final

Auditory portion of the VIII nerve

The spiral ganglion forms the auditory portion of the 8th cranial nerve.

Main pathway from the ear to the brain

Spiral ganglion → VIII cranial nerve → Cochlear nucleus → Superior olivary complex → Lateral lemniscus → Inferior colliculus → Medial geniculate body → Primary & secondary auditory cortex.

Contralateral pathway

The strongest pathways cross to the opposite side of the brain.

Decussation

Crossing to the opposite side of the brain.

Right Ear Advantage (REA)

The right ear sends its strongest signals to the left hemisphere, where speech is processed.

Sensorineural vs Retrocochlear on audiogram

Exactly the same.

Identifying differences on an audiogram

No, you cannot tell the difference between Sensorineural and Retrocochlear.

'Sensori' refers to

The cochlea / inner ear (hair cells).

'Neural' refers to

The VIII nerve or beyond (neural firing & timing).

Red flags for retrocochlear pathology

Asymmetric hearing, unilateral tinnitus, vertigo, poor word recognition (especially one ear).

Decussate

To cross from one side of the brain to the other.

Ablation

Removal or destruction of tissue.

Commissurotomy

A surgical cut of a commissure (connection between hemispheres).

Ipsilateral

Same side.

Contralateral

Opposite side.

Retrocochlear nystagmus

Abnormal, rhythmic eye movement associated with lesions beyond the cochlea.

VII Cranial Nerve

Facial nerve, controls facial muscles; damage can cause Bell’s Palsy.

Facial nerve damage causes

Middle ear damage or skull fractures.

Auditory Neuropathy Spectrum Disorder (ANSD)

Inner ear detects sound normally, but the VIII nerve fires out of sync.

Causes of ANSD

Defective inner hair cells; desynchronized neural firing along VIII nerve.

Hearing thresholds in ANSD

Can be normal, mildly impaired, or severely impaired; highly variable.

Speech perception in ANSD

Always poor; speech & language delays are common.

Peripheral system in CAPD

Normal; the problem is beyond the VIII nerve.

Characteristics of CAPD

Normal peripheral hearing; trouble with processing auditory information.

Neurological factors causing CAPD

Tumors, lesions, ablations, seizure disorders.

Maturational factors causing CAPD

Developmental lag in CANS; abnormal hemispheric representation/transfer.

Neuromorphological factors causing CAPD

Polymicrogyria (underdeveloped gyri); heterotopia/ectopic brain areas.

Three categories of treatment for CAPD

Environmental modifications (FM system, seating), remediation/therapy, compensatory strategies (note-taking supports, chunking).

Semicircular Canals (SCCs)

Detect angular head movement.

Bony labyrinth

Filled with perilymph.

Membranous labyrinth

Filled with endolymph.

Hair cells (cilia) function

Convert movement into neural signals.

Utricle

Detects horizontal linear acceleration and horizontal head tilts.

Saccule

Detects vertical linear acceleration (up/down movements).

Ampullary cupula

Bulging base of semicircular canals.

Crista / Otoconia

'Ear rocks' that cause BPPV when displaced.

Vestibular nerve

Part of the VIII CN.

Vertigo vs Dizziness vs Unsteadiness

Vertigo: spinning sensation; Dizziness: vague lightheadedness; Unsteadiness: imbalance while walking/standing.

Vestibulotoxins examples

Meclizine, Diazepam, Promethazine, Chlorthalidone, Furosemide, Hydrochlorothiazide, Gentamicin, Dexamethasone.

BPPV stands for

Benign Paroxysmal Positional Vertigo.

Acoustic Neuroma / Vestibular Schwannoma

Compresses hearing & balance portions of VIII nerve; causes unilateral symptoms.

AIED

Autoimmune Inner Ear Disease; immune system attacks inner ear causing fluctuating or sudden hearing loss.

PPPD

Persistent, chronic dizziness without true vertigo.

Meniere’s Disease

Progressive disorder due to too much endolymph; fluctuating SNHL, episodic vertigo, aural fullness, and tinnitus.

Mal de Débarquement

Rocking sensation after cruise or long flight.

Age-related vestibular problems

Due to degeneration of vestibular hair cells, pathways, or CNS.

Syndromes associated with hearing loss

Apert Syndrome, CHARGE Syndrome, Towns-Brocks Syndrome, Treacher Collins Syndrome, Connexin 26 mutation.

Full pathway from ear to brain

VIII CN → Cochlear nucleus → Superior olivary complex → Lateral lemniscus → Inferior colliculus → Medial geniculate body → Primary auditory cortex → Secondary auditory cortex.

Why bilateral pathways are important

They provide redundancy for hearing if one side is damaged.

Right Ear Advantage (REA) explanation

Why the right ear sends signals to the left hemisphere faster.

Hearing Loss Diagnostics

You cannot tell SNHL vs retrocochlear based only on thresholds; you need speech scores + symptoms.

Decussation meaning in hearing

The crossing of auditory pathways from one side to the other.

Why damage above the cochlea causes processing issues

Because it affects how auditory information is interpreted in the brain.

Vestibular System structure

Includes SCCs, utricle, saccule, ampullary cupula, and otoconia.

Vestibular Disorders examples

BPPV, Meniere's disease, AIED, Acoustic Neuroma.

Key Terms in Audiology

Decussation, Ipsilateral, Contralateral, Commissurotomy, Ablation, Retrocochlear.

Symptoms of Vestibular Disorders

Balance issues, vertigo, dizziness, ear fullness, tinnitus.

Speech perception in ANSD

Frequently poor despite normal physical hearing thresholds.

Adaptive strategies for CAPD

Use of note-taking supports, chunking information for easier processing.

Function of otoconia in BPPV

Displacement causes dizziness when they move into semicircular canals.

Types of vestibular movement detected

Rotational movement (SCCs), horizontal (utricle), vertical (saccule).

Why the right ear contributes to speech processing

Because it sends signals to the left hemisphere more directly.

Significance of vestibular system in balance

Essential for detecting and responding to head movements.

Distinction between peripheral vs central hearing issues

Peripheral refers to the cochlea; central refers to processing in the brain.

Importance of nystagmus

Rhythmic eye movements that can indicate vestibular disorders.

Impact of aging on vestibular function

Decreased sensitivity and response time in the vestibular system.

Features of Vestibular Schwannoma

Unilateral hearing loss, balance issues, poor speech recognition.

Causes of fluctuating hearing loss

Can be related to autoimmune conditions like AIED or disorders like Meniere's.

Common treatments for vestibular disorders

Medications, therapy, and lifestyle adjustments.

Asymmetry on audiograms red flag

Indicates possible retrocochlear involvement.

Vestibulotoxins impact on hearing

Can cause dizziness and hearing loss as side effects.

Symptoms of Meniere’s Disease

Episodic vertigo, fluctuating hearing loss, tinnitus, and aural fullness.

Importance of hair cells in the cochlea

Essential for converting sound waves into neural signals.

Function of the medial geniculate body

Relay station for auditory information before it reaches the cortex.

Cochlear nucleus role in hearing

Initial processing point for auditory signals in the pathway.

Superior Olivary Complex function

Crucial for localization of sound in space and processing binaural hearing (information from both ears)

Inferior Colliculus function

Integrates auditory information and regulates reflexive responses to sound.

Auditory Brainstem Response (ABR)

A neurophysiological test that measures the brain's electrical activity in response to sound, primarily used to assess hearing and identify auditory pathway integrity.

Vestibular-Ocular Reflex (VOR)

A reflex that stabilizes vision by coordinating eye movements with head movements, allowing clear vision during motion.

Conductive Hearing Loss (CHL)

A type of hearing loss caused by problems in the outer or middle ear that prevent sound from being conducted to the inner ear. It can often be treated medically or surgically.

Sensorineural Hearing Loss (SNHL)

A type of hearing loss resulting from damage to the inner ear or auditory nerve, which affects sound transmission to the brain. It often requires rehabilitation through hearing aids or cochlear implants.

Mixed Hearing Loss (MHL)

A combination of conductive and sensorineural hearing loss, where both outer/middle ear issues and inner ear/auditory nerve damage contribute to hearing impairment. Treatment may involve both medical/surgical and rehabilitative approaches.

Outer Hair Cell (OHC) function

Outer hair cells amplify sound vibrations in the cochlea, enhancing sensitivity and frequency selectivity for better hearing.

Inner Hair Cell (IHC) function

Inner hair cells are responsible for converting sound vibrations into electrical signals that are transmitted to the brain, playing a crucial role in the auditory perception.