Experimental erbium laser surgery in the guinea pig cochlea: its use in the study of afferent cochlear neurotransmitters

Lasers in stapes surgery: a review

Background:

Lasers in stapes surgery are used to divide the anterior and posterior crus of the stapes, divide the stapedius tendon and perforate the footplate. The ideal laser should not penetrate deeply into the perilymph (thereby increasing its temperature). It should be conducted through optical fibres, allowing easy manipulation, and should have good water absorption, equating to high bone ablation efficiency.

Objectives:

This review discusses the various different lasers used in stapes surgery with regard to their properties and suitability for this type of surgery. In particular, the laser parameters used are discussed to facilitate their clinical use.

Long-term results of the Er-Yag laser used in stapes surgery

Stapes surgery is performed using both conventional techniques and a variety of laser systems. The Er-Yag laser is a type of pulsation laser deemed by many to be the safest for ear surgery. The aim of this study was to assess the long-term effects of using the Er-Yag laser in stapes surgery and its impact on inner ear function. The study was conducted on 95 ears (48 right and 47 left) that had undergone Er-Yag laser-assisted stapedotomy. The follow-up time was at least 3 years. Pure tone audiometry was performed on all patients. The frequency ranged from 125 to 8,000 Hz. Air conduction and bone conduction were both assessed. Moreover, all patients had their stapedius reflex assessed and were given a Rinne test. The results were evaluated according to the Committee on Hearing and Equilibrium guidelines and then statistically analyzed using the Wilcoxon sequence pair test with a p value of <0.05. A decrease in the hearing threshold of 0.5, 1, and 3 kHz, for both bone and air conduction was observed for all patients (p < 0.0001). The Wilcoxon sequence pair test revealed a statistically significant correlation between the pre- and postoperative treatment mean air-bone gap values (p < 0.0001). No facial nerve paralysis was observed. No Er-Yag laser side effects were observed on inner ear function. The patients also had lower hearing thresholds. These observations demonstrate the usefulness of Er-Yag lasers in stapes surgery.

Localized cell and drug delivery for auditory prostheses

Localized cell and drug delivery to the cochlea and central auditory pathway can improve the safety and performance of implanted auditory prostheses (APs). While generally successful, these devices have a number of limitations and adverse effects including limited tonal and dynamic ranges, channel interactions, unwanted stimulation of non-auditory nerves, immune rejection, and infections including meningitis. Many of these limitations are associated with the tissue reactions to implanted auditory prosthetic devices and the gradual degeneration of the auditory system following deafness. Strategies to reduce the insertion trauma, degeneration of target neurons, fibrous and bony tissue encapsulation, and immune activation can improve the viability of tissue required for AP function as well as improve the resolution of stimulation for reduced channel interaction and improved place-pitch and level discrimination. Many pharmaceutical compounds have been identified that promote the viability of auditory tissue and prevent inflammation and infection. Cell delivery and gene therapy have provided promising results for treating hearing loss and reversing degeneration. Currently, many clinical and experimental methods can produce extremely localized and sustained drug delivery to address AP limitations. These methods provide better control over drug concentrations while eliminating the adverse effects of systemic delivery. Many of these drug delivery techniques can be integrated into modern auditory prosthetic devices to optimize the tissue response to the implanted device and reduce the risk of infection or rejection. Together, these methods and pharmaceutical agents can be used to optimize the tissue-device interface for improved AP safety and effectiveness.

Clinical results after stapedotomy: a comparison between the erbium: yttrium-aluminum-garnet laser and the conventional technique

OBJECTIVE

The objective of this study was to assess whether the use of the erbium: yttrium-aluminum-garnet (Er:YAG) laser has negative effects on inner ear function and to compare the short- and long-term hearing outcome of patients undergoing conventional stapedotomy versus laser stapedotomy.

STUDY DESIGN

Retrospective review of prospectively collected audiometric data of patients with otosclerosis operated on by one experienced surgeon.

SETTING

Academic tertiary referral center.

PATIENTS

A total of 266 stapes surgeries were evaluated for intraoperative findings, of which 209 patients were evaluated for preoperative and postoperative hearing thresholds after a 6- to 452-week (mean, 22 wk) audiological follow-up.

INTERVENTION

One hundred fifteen (43%) of the operations were performed conventionally, using manual perforators for stapedotomy (Group A); in 115 (43%) surgeries, the perforators were used in combination with the Er:YAG laser (Group B), and in 36 (14%) operations, the Er:YAG was used exclusively for footplate perforation (Group C).

MAIN OUTCOME MEASURES

Pure-tone audiometry was performed before surgery, 2 days postoperatively (bone conduction only) and at 5, 26, and 57 weeks postoperatively.

RESULTS

A postoperative temporary threshold shift of the bone conduction could be found in all groups. In Group C, where the laser was used exclusively for footplate perforation, this threshold shift was not only the most significant, but also-in contrast to the other groups-not totally reversible. In all techniques, a satisfactory air-bone gap closure could be achieved. The best long-term results (96% of the patients had <or=20 dB air-bone gap after 57 wk) could be found in Group B.

CONCLUSION

If certain rules to minimize inner ear trauma are followed, the Er:YAG laser is a safe tool in middle ear surgery. Combining both the laser and the conventional technique, instead of the separate use of either technique, leads to superior postoperative hearing results.