Idiopathic Sudden Hearing Loss: Is There a Role for Complementary Treatment?

Dear Editor:

The human cochlea has a finite number of nonregenerative hair cells that, when lost, leads to permanent sensorineural hearing impairment. Sudden sensorineural hearing loss is defined as a loss of at least 30 dB in three contiguous frequencies over a time course of 72 hours or less. A cause could not be identified in up to 90% of patients, and this condition is referred to as idiopathic sudden sensori-neural hearing loss (ISSNHL). The hearing in some patients with ISSNHL spontaneously recovers, suggesting recovery of cochlear hair cells that have not been irreversibly damaged. It also suggests that certain medical interventions may have the potential to enhance recovery of hair cells that are still viable and prevent permanent damage. The evidence so far has only strongly supported the clinical use of intratympanic steroid perfusion therapy. ¹

In recent years, a growing body of evidence points to the importance of free-radical formation in sensorineural hearing loss due to different known etiologies such as those related to loud noise, aminoglycosides, and aging. ² It is conceivable that this also holds true for ISSNHL where excess reactive oxygen species generation results in oxidative stress and cellular damage. In fact, in the treatment of patients with ISSNHL, the oral addition of the anti-oxidant l-N-acetylcysteine (l-NAC) resulted in better hearing compared to using corticosteroids alone. ³ The role of l-NAC in ISSNHL warrants further evaluation as it has already been safely utilized in a wide range of other clinical conditions, and high concentrations can possibly be delivered topically through the middle ear while minimizing systemic side-effects. ⁴

The American Academy of Otolaryngology–Head and Neck Surgery has recommended an option of using hyperbaric oxygen therapy within 3 months of diagnosis of ISSNHL. ¹ However, the existing studies are small and of poor quality, and although they suggest hearing improvement, the clinical significance remains unknown. ⁵ It may appear contradictory that ISSNHL should respond to the seemingly opposing effects of antioxidants and hyperbaric oxygenation. Pervaiz and Clément (2002) observed that cell death could be a result of either oxidative or reductive stresses, depending on the quantity and type of reactive oxygen species. ⁶ It may well be that cell deaths due to oxidative stress are prevented by antioxidants, whereas those due to reductive stress respond to hyperbaric oxygen therapy.

In recent years, it has been shown that acupuncture offered benefit in some patients with ISSNHL. ⁷ Acupuncture has been demonstrated to affect the pattern of otoacoustic emissions, which is a manifestation of outer hair-cell activities. ⁸ How acupuncture is able to affect cochlear structures remains unknown, but a possibility is via the efferent medial olivocochlear auditory pathways. ⁹

Therefore, in the treatment of ISSNHL, it is not unreasonable to believe that there is a possible complementary role for antioxidants, hyperbaric oxygen, and acupuncture, and this should be substantiated by further studies. The focus of these studies should be on the early stages of the condition, when the chance of hair-cell damage still being reversible is likely to be higher.