DISEASES OF THE INNER EAR 1.3 (AB) Flashcards
What is the key feature of Scheibe dysplasia?
Cochleosaccular dysplasia; only the membranous labyrinth is formed.
What is Mondini dysplasia?
Partial bony and membranous labyrinth; arrest at the 6th week leading to a 1.5 coil cochlea.
What is Michel’s aplasia?
Complete absence of all bony and membranous structures in the inner ear.
What is a key feature of Large Vestibular Aqueduct (VA) Syndrome?
Enlarged vestibular aqueduct, often bilateral and asymmetric.
What additional symptom is commonly seen in Large VA Syndrome apart from hearing loss?
Dizziness.
What is the leading cause of sensorineural hearing loss (SNHL) in children?
Infections.
What causes serous (toxic) labyrinthitis?
Degradation of the tissue fluid environment within the ear due to bacterial toxins and perilymph contamination.
What is the key clinical presentation of serous labyrinthitis?
Sudden onset of SNHL with acute vertigo.
What is the cause of suppurative labyrinthitis?
Bacterial invasion leading to profound hearing loss and acute vertigo.
What is the most common etiology of deafness associated with meningitis?
Suppurative labyrinthitis.
How does bacterial infection reach the inner ear in suppurative labyrinthitis?
Via a fistula between the middle ear and the inner ear.
What is Ramsay Hunt syndrome?
Herpes zoster oticus with facial paralysis, herpetic skin eruptions, and possible hearing loss and vertigo.
What viral infection is a common cause of congenital and progressive SNHL in children?
Cytomegalovirus (CMV).
What type of hearing loss is associated with measles?
Bilateral, moderate to profound SNHL.
What is the main mechanism of aminoglycoside ototoxicity?
Entry into hair cells leading to cell death.
Which aminoglycosides are cochleotoxic?
Kanamycin, Tobramycin, Amikacin, Neomycin, Dihydrostreptomycin.
Which aminoglycosides are vestibulotoxic?
Gentamicin, Streptomycin.
What is the risk factor for neomycin toxicity?
Renal disease (CKD), prolonged use, increased serum levels, age, loop diuretics.
What type of hearing loss do loop diuretics cause?
Reversible SNHL.
What are the symptoms of quinine toxicity?
Tinnitus, SNHL, visual disturbances.
What is the toxic dose of salicylates that can cause tinnitus?
6-8 g/day.
What type of hearing loss does salicylate toxicity cause?
Reversible SNHL within 72 hours.
What is Noise-Induced Hearing Loss (NIHL)?
A common occupational disability caused by repeated exposure to loud sounds.
What frequency is most affected in NIHL?
4 kHz.
What is the typical progression pattern of NIHL?
Progresses most rapidly in the first 10-15 years of exposure.
What is acoustic trauma?
Hearing loss caused by a single exposure to a hazardous noise level.
What is the key audiometric finding in acoustic trauma?
Permanent Threshold Shift (PTS) without Temporary Threshold Shift (TTS).
What is the maximum allowable duration for exposure to 90 dB noise according to OSHA?
8 hours.
What is the maximum allowable duration for exposure to 100 dB noise according to OSHA?
2 hours.
What is the most common type of temporal bone fracture?
Longitudinal.
How does longitudinal temporal bone fracture affect hearing?
It uncommonly extends through the labyrinth and typically affects high-frequency hearing.
What is the effect of transverse temporal bone fracture on hearing?
Almost always traverses the labyrinth, leading to complete loss of cochlear and vestibular function.
What is labyrinthine concussion?
Blunt trauma to the ear leading to temporary or permanent SNHL.
What is a perilymphatic fistula?
A pathologic communication between the perilymphatic space of the inner ear and middle ear.
What are the possible causes of a perilymphatic fistula?
Congenital defects (e.g., Mondini dysplasia), barotrauma, direct or indirect trauma to the temporal bone, or complications of stapedectomy surgery.
What condition is associated with perilymphatic fistula and CSF leak?
Mondini dysplasia.
What clinical presentation suggests a perilymphatic fistula?
Sudden SNHL and vertigo after head trauma, barotrauma, lifting, or straining.
What is the main cause of radiation-induced cochlear damage?
Free radicals.
What percentage of patients undergoing radiotherapy involving the cochlea develop SNHL?
0.5
What radiation dose is considered detrimental to the cochlea?
> 45Gy.
What factors increase the risk of radiation-induced SNHL?
Advanced age, preexisting hearing loss, and adjuvant ototoxic chemotherapeutic agents.
What is the latency period for radiation-induced SNHL?
0.5 to 2 years after treatment.
What systemic disorder is associated with 4-10% of SNHL cases?
Multiple sclerosis.
What systemic disorder presents with pulsatile tinnitus and SNHL?
Benign intracranial hypertension.
What is the typical hearing loss pattern in basilar migraine?
46% of cases present with bilateral low-frequency SNHL.
What other symptoms are associated with basilar migraine-related SNHL?
Episodic vertigo, tinnitus, aural fullness, distortion, and recruitment.
What vascular condition can lead to SNHL due to AICA involvement?
Vertebrobasilar arterial occlusion.
What is Cogan syndrome?
A prototypic autoimmune disorder that affects the inner ear.
What is the most common pattern of hearing loss in presbycusis?
Worse for high frequencies.
Which gender is more commonly affected by presbycusis?
Men.
What is the progression pattern of presbycusis?
Gradual, with an accelerating rate of hearing loss over time.
What is Schuknecht’s classification of presbycusis?
Sensory, neural, and strial/metabolic types.
What is the characteristic hearing loss pattern in sensory presbycusis?
Steep high-frequency hearing loss with preserved speech perception due to degeneration of the organ of Corti.
What is the characteristic hearing loss pattern in neural presbycusis?
Down-sloping high-frequency hearing loss with a disproportionate loss of speech perception due to degeneration of spiral ganglion cells.
What is the characteristic hearing loss pattern in strial/metabolic presbycusis?
Flat SNHL with preserved speech perception due to degeneration of the stria vascularis.
What are the key auditory tests for diagnosing hearing loss?
Pure tone audiometry, auditory brainstem response, auditory steady-state response evaluation, otoacoustic emission, and impedance testing (tympanometry).
What is the gold standard imaging modality for diagnosing potential retrocochlear hearing losses?
MRI with gadolinium enhancement.
What imaging technique is used for detailed cochlear evaluation?
High-resolution CT scan with 1 mm cuts.
Why are 1 mm cuts used in high-resolution CT scans of the cochlea?
To avoid missing small structures, as standard CT scan cut sizes are 5 mm.
