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Recent Advances in Hearing and Balance Research

Hair Cells

  • Identification of molecular components of tip links,5 function of TRIOBP,6 and activity of stereocilin7 has advanced understanding of hair cell transduction, the pivotal point at which hair cells convert sound vibrations into an electrical signal.
  • Recent biophysical characterizations of the molecular motor prestin that drives outer hair cell electromotility, including its interactions with cytoskeleton, anions and membrane constituents,8-10 have led to a deeper understanding of how this cell provides for mammalian cochlear amplification,11, 12 the metabolically vulnerable process that boosts our ability to hear so well.
  • Researchers have generated hair-like cells from both mouse embryonic stem cells and mouse induced pluripotent stem cells (iPSCs), providing hope that similar hair cell-like cells can be generated from human stem cells.13
  • Advances in DNA sequencing, genetics, and protein purification have helped identify molecules essential for sound sensation, which may offer the possibility of specific treatments for individual defects.6,14-16

Hearing Loss

  • Dozens of new gene defects in hereditary hearing loss have been identified in recent years to better predict the course of hearing loss and develop therapeutic interventions.
  • New analyses of national epidemiologic data suggest that the prevalence of hearing loss may have stabilized or could even be in decline.17, 18 Accurate estimates of these trends are critical, given their long-term implications for public health and health care systems.
  • Adenoviral vectors have introduced a growth factor, called brain-derived neurotrophic factor (BDNF), within the cochlea of guinea pigs.19 This approach may improve survival of the auditory nerve in a cochlea without hair cells, or regrow auditory nerve fibers to be stimulated by the electrodes of a cochlear implant.
  • A Phase III clinical trial concluded that injecting steroids directly into the middle ear was comparable to oral prednisone in treating sudden sensorineural hearing loss, a key finding for people who cannot take oral steroid therapy because of diabetes, hypertension, or other conditions.20

Otitis Media

  • Research has advanced understanding of the innate immune system, cell signaling, and gene expression patterns in OM.21
  • Genome sequencing of middle ear pathogens has identified genes important for virulence and disease progression, as well as potential vaccine candidates.22-25
  • Several new mouse strains with spontaneous chronic OM have been characterized and the individual mutations identified. These models will further our understanding of the genetic, morphological, and functional abnormalities of this disorder in the middle ear and eustachian tube.26, 27

Balance Disorders

  • Increased understanding of comorbid relationships among balance disorders, migraine, and anxiety will lead to better therapies.28
  • The effectiveness of canal repositioning maneuvers for the treatment of benign paroxysmal positional vertigo (BPPV) has been established, offering clinicians a range of choices in selecting the treatment best suited to a person’s needs.29
  • The development of a vestibular prosthesis from a re-engineered commercial cochlear implant provides a means of stimulating the semicircular canals, which are part of the vestibular system. The prosthesis could act as a treatment for Ménière’s disease and other balance disorders.30

Hearing Aids and Implantable Hearing Devices

  • Advances in the digital technology of hearing aids provide noise reduction, directional hearing, and feedback suppression. Binaural hearing aids further improve sound source localization and spatial separation.31 Combined use of a hearing aid and a cochlear implant (in opposite ears or the same ear) helps communication more than either device alone.32
  • Research in pediatric cochlear implants has identified an age range in which the auditory system is most sensitive to electrical stimulation.33
  • Infrared cochlear nerve stimulation and intra-nerve electrodes are experimental cochlear implant designs that offer more precise stimulation of specific nerve sites.34
  • The auditory brainstem implant (ABI) stimulates the part of the brain that processes sound. It is typically used in cases where the auditory nerve has been surgically removed due to tumor growth, such as in people with neurofibromatosis 2 (NF2). Recently, use of the ABI has been expanded to other adults35 and children,36, 37 some of whom approach performance levels similar to cochlear implant users.
  • The use of binaural cochlear implants has improved directionality and performance in noise.38, 39

Tinnitus

  • Abnormal brain activity of auditory and non-auditory areas is involved in the perception of, and negative reaction to, tinnitus. New therapies will use brain stimulation to treat tinnitus.40, 41
  • The use of vagus nerve stimulation paired with a variety of tones over an extended period has been effective in the treatment of noise-induced tinnitus in an animal model.42

Auditory Processing

  • Advances in brain imaging along with behavioral studies of auditory perception have increased our understanding of real-world auditory processing and of various auditory neuropathies.43-45
  • The integration of auditory activity with other sensory systems (balance, movement and body position, vision) and cognitive function (learning, memory, attention) has advanced understanding of normal and abnormal auditory function in the real world.46
  • Electophysiologic studies of adults with normal hearing have revealed that stimulus-specific cues in auditory training can be detected physiologically,47 indicating that future therapy may be successfully tailored to specific individual needs and abilities.