Hearing loss and otology Flashcards
How to recognize conductive hearing loss on an audiogram
Bone conduction thresholds are in normal range, but air conduction thresholds are decreased (air bone gap)
How to recognize sensory hearing loss on an audiogram
Changes in pure tone hearing thresholds
Conductive hearing loss
Disorders of the external ear canal, tympanic membrane, and middle ear ossicular chain that impair the transmission of sound (sound conduction) to the cochlea.
Sensory hearing loss
Involves the sensory transduction apparatus within the cochlea (usually loss of hair cells)
Neural hearing loss
Loss involves disorders of the 8th nerve and central auditory pathways. The inner hair cell is often considered part of the neural component as it is directly linked to the auditory nerve. Neural hearing loss typically manifests as changes in word recognition scores or the clarity of hearing.
Common types of pathology underlying sensory hearing loss
Hair cell loss (most common)
Endolymphatic hydrops
Loss of endocochlear potential
Cholesteatoma
A cause of conductive hearing loss
Causes of conductive hearing loss
Otitis media (ear infection) TM perforation Cholesteatoma Otosclerosis Congenital aural atresia
Causes of hair cell loss (sensory)
Presbycusis (age-related changes; higher frequencies most affected)
Noise trauma (preventable; chronic and acute)
Ototoxicity (aminoglycosides, chemo; treat with ASA and antioxidants)
Genetic factors
Most common causes of neural hearing loss
8th nerve tumors
Auditory neuropathy
Multiple Sclerosis
Genetics of hearing loss
50% are genetic
70% of the genetic cases are non-syndromic
75% of the non-syndromic cases are AR
50% of these AR cases involve mutations in connexin 26
Endolymphatic hydrops
(Meneire’s disease)
Endolymph compartment of inner ear is expanded
Episodes of vertigo, hearing loss, tinnitus
Unknown cause
Causes of loss of endocochlear potential
Issues with metabolism or blood supply of inner ear
Suspect vascular dysfunction/vasculitis, metabolic causes, or immune system-related disorders
How to recognize neural hearing loss on an audiogram
Often asymmetric (only one ear affected) Low word recognition score in one ear
Vestibular Schwannoma and treatment
(Acoustic Tumor)
6% of all intracranial tumors
Can cause neural hearing loss
Treatment: observation (in older people when small), surgical resection (if larger), stereotactic radiosurgery (focused radiation treatment can control growth of them when smaller)
