Anatomy of the Auditory System Flashcards

What is presbycusis and what anatomical changes in the cochlea underlie it?

Answer: Age-related sensorineural hearing loss primarily from progressive loss of outer hair cells in the basal cochlea (high-frequency region), stria vascularis degeneration, and spiral ganglion neuron loss

Presbycusis (age-related hearing loss) results from cumulative cochlear damage: OHC loss predominantly in the basal (high-frequency) region, stria vascularis metabolic degeneration, and spiral ganglion neuron loss—producing the characteristic bilateral, symmetric, high-frequency sensorineural hearing loss.

What is benign paroxysmal positional vertigo (BPPV) and which part of the inner ear anatomy is involved?

Answer: Brief episodes of intense rotational vertigo triggered by specific head positions, caused by calcium carbonate crystals (otoconia) displaced from the utricle into a semicircular canal (usually posterior), causing abnormal cupula deflection

BPPV occurs when otoconia (calcium carbonate crystals) from the utricle's macula detach and migrate into a semicircular canal (80-90% posterior canal), creating abnormal fluid currents that stimulate the cupula with certain head positions, causing brief intense vertigo.

What is Meniere's disease, what is the underlying pathophysiological mechanism, and what are its four cardinal symptoms?

Answer: A disorder of endolymphatic hydrops (excess endolymph pressure in the membranous labyrinth); cardinal symptoms are episodic vertigo, fluctuating low-frequency sensorineural hearing loss, aural fullness, and tinnitus

Meniere's disease involves endolymphatic hydrops—increased endolymph volume distending the membranous labyrinth. Classic tetrad: episodic vertigo (minutes to hours), fluctuating low-frequency sensorineural hearing loss, tinnitus (often low-pitched), and aural fullness.

What is the significance of the dead region concept for hearing aid fitting?

Answer: A cochlear region with no functional inner hair cells or neurons, meaning sounds amplified into that frequency region cannot be transduced even with maximum gain—requiring frequency lowering strategies instead

A cochlear dead region is a frequency region where IHC and neural function is absent—amplifying sound into this region with hearing aids provides no benefit and may cause distortion; identification guides decisions to use frequency lowering or to avoid amplifying those frequencies.

What is the difference between sensorineural and conductive hearing loss in terms of which anatomical structures are affected?

Answer: Sensorineural loss involves pathology in the cochlea, auditory nerve, or central pathways; conductive loss involves pathology in the outer ear (canal, pinna) or middle ear (tympanic membrane, ossicles, Eustachian tube)

Conductive hearing loss arises from obstruction or dysfunction in the sound-conducting pathway (outer or middle ear), while sensorineural hearing loss arises from cochlear hair cell or nerve damage—they are distinguished by air-bone gap on audiometry.

What is an acoustic neuroma (vestibular schwannoma) and what are its primary audiological symptoms?

Answer: A benign tumor arising from Schwann cells of the vestibular branch of CN VIII, typically presenting with unilateral progressive sensorineural hearing loss, unilateral tinnitus, and sometimes imbalance—requiring medical referral

Acoustic neuroma (vestibular schwannoma) is a benign tumor of the vestibular nerve's Schwann cells. It typically presents with unilateral, asymmetric, progressive SNHL and unilateral tinnitus—a key red flag requiring urgent ENT or neurology referral.