LETTER TO THE EDITOR.

Abstract

To the Editor: With great interest we have read the article “patterns of extended high-frequency hearing loss following stapes surgery” by Babbage et al. A significant deterioration of extended high-frequency hearing thresholds following stapes surgery was reported. The authors suggest in their article that pre- and postoperative measurement of extended high-frequency thresholds might guide the surgeon in preventing iatrogenic cochlear damage. Such measurements would be more sensitive in comparing factors such as surgical technique, prosthesis type, and laser type than for instance measuring bone conduction thresholds at 4 kHz. We would like to present a few additions and thoughts to their article. Similar shifts in high-frequency thresholds were found in studies performed by Mair and Laukli (1) and Tange and Dreschler (2). Both of these studies included both stapedotomies and stapedectomies. Stapedotomies have been advocated for better hearing improvements and a lower rate of sensorineural hearing loss (3,4). The opposite has also been reported as well as equivalent rates of sensorineural hearing loss (5–7). It would be interesting to know if there were any differences between the stapedotomy group and the stapedectomy group, albeit the stapedectomy group encompassed only four patients. In the present study, both primary and revision procedures were included. Revision surgery is associated with a higher risk of sensorineural hearing loss of 1 to 8% compared with 1% following primary surgery (8–10). Although the authors do state the potential for extended high-frequency measurements to show decreased cochlear resistance in patients undergoing revision procedures, they do not provide the results for this particular group. In the absence of reliable high-frequency bone conduction threshold measurements, it is not possible to distinguish between conductive and sensorineural hearing loss. High-frequency loss may be a result of surgical trauma, perilymph leakage, and loud sounds generated by drilling close to the sensory cells in the cochlea. Several studies have suggested that obliterative otosclerosis, requiring more extensive drilling and prolonged suctioning, is associated with higher rates of postoperative sensorineural hearing loss (5%) compared with regular otosclerosis (<1%) (10–12). High-frequency conductive hearing loss could be the result of changes in the physical properties of the middle ear structures. Mass loading of the stapes footplate/oval window may produce a conductive hearing loss at higher frequencies (13). The evidence on the effect of piston diameter on high-frequency hearing thresholds is inconclusive with some studies favoring a smaller-diameter piston and some studies favoring a larger-diameter piston (14). With regard to clinical significance of their findings, the authors refer to several studies suggesting spectral information above 8 kHz does contribute to speech perceptions. We would like to add that patients with a greater loss of high-frequency hearing are more at risk of developing tinnitus or tinnitus growing worse following stapes surgery compared with patients with adequate high-frequency thresholds (15). Furthermore, changes in tinnitus scores and patient satisfaction are correlated. Patients experiencing improvement of tinnitus have a median satisfaction score of nine out of 10 postoperatively and patients with worsening of tinnitus have a median satisfaction score of five out of 10 (15). What does this hold for the future and how will we be able to prevent high-frequency hearing loss? It has been hypothesized that antioxidants, such as N-Acetylcysteine, decrease noice-induced hearing loss. One randomized controlled trial in stapedotomy patients did not show an effect of N-Acetylcysteine on postoperative hearing thresholds or tinnitus (16). As stated by the authors in their conclusion, it would be interesting to research the differences between surgical techniques using extended high-frequency thresholds and thereby guiding the otologist towards minimally invasive stapes surgery.