The effect of drill-generated noise in the contralateral healthy ear following mastoid surgery: The emphasis on hearing threshold recovery time

Hearing Loss in the Unoperated Ear After High-Speed Drilling in Otologic and Skull Base Surgery

OBJECTIVE

To evaluate if permanent hearing loss occurred in the unoperated ear of patients undergoing otologic and skull base surgery with high-speed otologic drilling.

STUDY DESIGN

We retrospectively studied 250 patients (mean age 57.8 yr; 120 males, and 130 females) undergoing otologic or skull base surgery with high-speed drilling between 2013 and 2019.

SETTING

The University of Pittsburgh Medical Center.

PATIENTS

We evaluated preoperative and postoperative audiograms for patients undergoing surgery for cochlear implantation (95 patients, 38.0%), cholesteatoma or chronic ear disease (88 patients, 35.2%), repair of lateral skull base encephalocele (26 patients, 10.4%), resection of vestibular schwannoma or meningioma of the cerebellopontine angle (23 patients, 9.2%), lateral temporal bone resection (8 patients, 3.2%), microvascular decompression (7 patients, 2.8%), or other operations involving a high-speed otologic drill (3 patients, 1.2%).

MAIN OUTCOME MEASURES

Hearing threshold shift, measured as the difference between postoperative threshold and preoperative threshold for each frequency. The association of age, gender, tested frequency, and surgery type with hearing threshold shift was investigated with analysis of covariance.

RESULTS

A total of 102 patients (40.8%) had a 10-dB or greater worsening of their hearing in at least one frequency on their postoperative audiogram in the contralateral, unoperated ear. One hundred six subjects (42.4%) had no change in hearing of 10 dB or greater at any frequency. Among patients with longitudinal postoperative audiograms, accelerated age-related hearing loss was observed in low frequencies.

CONCLUSIONS

A significant number of patients demonstrated poorer hearing thresholds in the contralateral, unoperated ear after otologic and skull base surgery.

Risk of hearing loss in the opposite ear after tympanomastoidectomy

PURPOSE

The definitive treatment for chronic suppurative otitis media is surgery. Surgical technique and procedure varies according to individual case findings and pathology and may require mastoidectomies in which the canal wall is preserved or lowered to eradicate disease from mastoid air cells. Surgical treatment of chronic middle ear disease carries a risk of damage to the inner ear. The aim of this study was to investigate whether the noise produced by the tour system following chronic ear surgery causes sensorineural hearing loss, a condition for which not many studies have been published in the literature.

METHODS

The study consisted of a total of 49 patients with type I, type II and type III canal wall preservation and 62 patients with tympanoplasty with canal wall preservation and lowering. Bone and air thresholds were compared before and after middle ear surgery. Changes in bone and air thresholds were compared according to the type of tympanoplasty.

RESULTS

In the ICW-I, ICW-II and ICW-III tympanoplasties, and in the ICW and CWD tympanoplasties, the preoperative and postoperative values of the opposite ear hearing measurements were performed, and did not differ according to the type of surgery. There is no correlation drilling duration and hearing for the opposite ear.

CONCLUSION

The prevention of postoperative sensorineural hearing loss depends on multiple factors, and assessing the magnitude of hearing loss in relation to these factors is important in determining the success of the surgery.

The Relationship between Bone Conduction Hearing Threshold Shifts after Surgery for Chronic Otitis Media with Cholesteatoma According to STAM, EAONO/JOS, and SAMEO-ATO Classifications

Background: This study focuses on the hearing threshold for bone conduction (BC) after middle-ear surgery. Methods: A total of 92 patients (120 ears) were treated for newly diagnosed chronic otitis media with cholesteatoma (2013−2018). BC was examined at frequencies of 0.5, 1, 2, and 4 kHz prior to and 1 year after surgery. STAM classification for cholesteatoma location, EAONO/JOS for stage, and surgery according to SAMEO-ATO classification were applied. The bone conduction threshold was compared for individual frequencies in patients with occurrence/absence of cholesteatoma in different locations. Results: For the occurrence of cholesteatoma in the attic (A), a statistically significant difference was found at 4 kHz (p < 0.001), in the supratubal recess (S1) at 4 kHz (p = 0.003), and for the mastoid (M) at 0.5 kHz (p = 0.024), at 1 kHz (p = 0.032), and at 2 kHz (p = 0.039). Conclusions: Cholesteatoma location can influence the post-operative hearing threshold for bone conduction.

Intraoperative auditory brainstem response monitoring during semicircular canal plugging surgery in treatment of Meniere's disease

BACKGROUND

Three semicircular canal plugging (TSCP) is an optimized treatment for intractable Meniere's disease (MD). However, 20-30% of patients experience hearing loss after TSCP, for reasons that remain unclear.

OBJECTIVE

To evaluate hearing loss resulting from TSCP.

SUBJECTS AND METHODS

This study included 12 patients, which were diagnosed with definite MD and consented to TSCP surgery. Intraoperative auditory brainstem response (ABR) was monitored in each surgical procedure.

RESULTS

After opening the mastoid cavity, the ABR threshold increased to 77.08 ± 9.88 dB nHL. The ABR threshold almost recovered to preoperative levels, to 68.33 ± 7.78 dB nHL, after completing TSC outlining. Exposure of three semicircular canal 'blue lines' had little effect on ABR threshold. The most prominent change on hearing loss was observed after mastoid outlining, when 41.67% of patients showed hearing loss ≥10 dB nHL. None of the patients showed a threshold shift ≥10 dB nHL following the last step.

CONCLUSIONS

TSCP operation itself caused little hearing damage.

SIGNIFICANCE

Ruled out hearing loss as a result of the surgery itself. The reason why 20-30% of patients showed hearing loss in 2-year follow-up visit was not clear, although it may be due to serous fibrous labyrinthitis.

Early Detection of Endolymphatic Hydrops using the Auditory Nerve Overlapped Waveform (ANOW)

Endolymphatic hydrops is associated with low-frequency sensorineural hearing loss, with a large body of research dedicated to examining its putative causal role in low-frequency hearing loss. Investigations have been thwarted by the fact that hearing loss is measured in intact ears, but gold standard assessments of endolymphatic hydrops are made postmortem only; and that no objective low-frequency hearing measure has existed. Yet the association of endolymphatic hydrops with low-frequency hearing loss is so strong that it has been established as one of the important defining features for Ménière's disease, rendering it critical to detect endolymphatic hydrops early, regardless of whether it serves a causal role or is the result of other disease mechanisms. We surgically induced endolymphatic hydrops in guinea pigs and employed our recently developed objective neural measure of low-frequency hearing, the Auditory Nerve Overlapped Waveform (ANOW). Hearing loss and endolymphatic hydrops were assessed at various time points after surgery. The ANOW detected low-frequency hearing loss as early as the first day after surgery, well before endolymphatic hydrops was found histologically. The ANOW detected low-frequency hearing loss with perfect sensitivity and specificity in all ears after endolymphatic hydrops developed, where there was a strong linear relationship between degree of endolymphatic hydrops and severity of low-frequency hearing loss. Further, histological data demonstrated that endolymphatic hydrops is seen first in the high-frequency cochlear base, though the ANOW demonstrated that dysfunction begins in the low-frequency apical cochlear half. The results lay the groundwork for future investigations of the causal role of endolymphatic hydrops in low-frequency hearing loss.

The Effect of Endoscopic Endonasal Transsphenoidal Skull Base Surgery on Cochlear Function

Endoscopic transsphenoidal skull base surgery (ETSS) has become a standard approach in the treatment of sellar and clival lesions, such as pituitary adenoma and chordoma. Due to the close proximity of the clivus and the sella turcica to the inner ear, it is thought that bone drilling in the surgery may have effects on hearing. The aim of this study was to assess the effect of bone drilling in ETSS procedure on cochlear function. This study was performed on 18 patients who underwent ETSS procedure between December 2016 and May 2017. The study was designed as a prospective study. All of the data were prospectively collected. These included demographic data, date of surgery, type of surgery, preoperative pure-tone audiometry, and preoperative and postoperative distortion product otoacoustic emission (DPOAE) measurements. Of the DPOAE measurements of the patients who were operated for pituitary adenoma, there was a statistically significant difference between the signal-to-noise ratio (SNR) measurements at 0.5, 1, 2 and 4 kHz ( p  < 0.05). Additionally, there were no significant differences in preoperative and postoperative SNR measurements of six patients who were selected for clivus chordoma. When the preoperative and postoperative tonal audiometric tests of the patients were compared, no statistically significant difference was found ( p  > 0.05). In conclusion, it is found that bone drilling in ETSS procedure has a negative effect on cochlear function in the early period. This is the first study to evaluate the degree of noise-induced cochlear damage in patients who were gone under ETSS procedure.

The Role of Powered Surgical Instruments in Ear Surgery: An Acoustical Blessing or a Curse?

Ear surgery in many ways lagged behind other surgical fields because of the delicate anatomical structures within the ear which leave surgeons with little room for error. Thus, while surgical instruments have long been available, their use in the ear would most often do more damage than good. This state of affairs remained the status quo well into the first half of the 20th century. However, the introduction of powered surgical instruments, specifically the electric drill used in conventional microscopic ear surgery (MES) and the ultrasonic aspirator, the Sonopet® Omni, in transcanal endoscopic ear surgery (TEES) marked major turning points. Yet, these breakthroughs have also raised concerns about whether the use of these powered surgical instruments within the confines of the ear generated so much noise and vibrations that patients could suffer sensorineural hearing loss as a result of the surgery itself. This paper reviews the intersection between the noise and vibrations generated during surgery; the history of surgical instruments, particularly powered surgical instruments, used in ear surgeries and the two main types of surgical procedures to determine whether these powered surgical instruments may pose a threat to postoperative hearing.

Post-operative Sensorineural Hearing Loss After Middle Ear Surgery

Chronic suppurative otitis media is managed by tympanomastoid surgery often requires mastoid drilling. Sometimes patients develop sensorineural hearing loss after middle ear surgery. Objective of the study was to compare pre and post operative bone conduction thresholds after middle ear surgeries. The study was conducted on 90 patients who had undergone middle ear surgeries, 30 patients of tympanoplasty (group I), modified intact canal wall mastoidectomy and tympanoplasty type-I (group II) and modified radical mastoidectomy (group III) each ware included. Demographic and clinical data were reviewed. Duration of surgery, ossicular and middle ear status and drilling time noted. Pre operative and post operative (after 3-4 months) bone conduction thresholds were compared statistically. A value of p < 0.05 was considered statistical significant. The average pre-operative hearing loss of study group was 43.78 ± 14.22 dB. Though postoperatively mean air conduction threshold improved to 36.07 ± 13.05 dB, six patients presented with deterioration of hearing. Mastoidectomy has been performed in all six. Post-operative worsening of bone conduction was seen in three patients (13.75-21.5 dB), one patient of group II and two patients of group III developed postoperative worsening of bone conduction thresholds. Significant hearing losses may occur after tympanomastoid surgery in few patients. While we are evaluating the results besides reporting average results such individual patient should be identified.

Drill-induced Cochlear Injury During Otologic Surgery: Intracochlear Pressure Evidence of Acoustic Trauma

HYPOTHESIS

Drilling on the incus produces intracochlear pressure changes comparable to pressures created by high-intensity acoustic stimuli.

BACKGROUND

New-onset sensorineural hearing loss (SNHL) following mastoid surgery can occur secondary to inadvertent drilling on the ossicular chain. To investigate this, we test the hypothesis that high sound pressure levels are generated when a high-speed drill contacts the incus.

METHODS

Human cadaveric heads underwent mastoidectomy, and fiber-optic sensors were placed in scala tympani and vestibuli to measure intracochlear pressures (PIC). Stapes velocities (Vstap) were measured using single-axis laser Doppler vibrometry. PIC and Vstap were measured while drilling on the incus. Four-millimeter diamond and cutting burrs were used at drill speeds of 20k, 50k, and 80k Hz.

RESULTS

No differences in peak equivalent ear canal noise exposures (134-165 dB SPL) were seen between drill speeds or burr types. Root-mean-square PIC amplitude calculated in third-octave bandwidths around 0.5, 1, 2, 4, and 8 kHz revealed equivalent ear canal (EAC) pressures up to 110 to 112 dB SPL. A statistically significant trend toward increasing noise exposure with decreasing drill speed was seen. No significant differences were noted between burr types. Calculations of equivalent EAC pressure from Vstap were significantly higher at 101 to 116 dB SPL.

CONCLUSION

Our results suggest that incidental drilling on the ossicular chain can generate PIC comparable to high-intensity acoustic stimulation. Drill speed, but not burr type, significantly affected the magnitude of PIC. Inadvertent drilling on the ossicular chain produces intense cochlear stimulation that could cause SNHL.

The Effect of Mandibulectomy and Mandibulotomy on Cochlear Function

Mandibulectomy and mandibulotomy procedures are performed with the oscillating saw and the acoustic energy generated during the osteotomies is transferred to the cochlea via temporomandibular joint and air conduction. The aim of this study was to assess the effect of mandibulectomy and mandibulotomy on cochlear function. This study was carried out on 15 patients who underwent at an otolaryngology department of a tertiary medical center between January 2013 and August 2015. The study was designed as a prospective study. All of the data were prospectively collected. These included demographic data, date of the surgery, type of surgery, preoperative pure-tone audiometry, preoperative and postoperative distortion product otoacoustic emission (DPOAE) measurements. Of the DPOAE measurements, there was a statistically significant difference between the signal-to-noise ratio measurement on the right ear measurement at 4 kHz (P <0.05). Additionally, there was a statistically significant correlation between the signal-to-noise ratio measurements and the side of the osteotomy (P <0.05). In conclusion, it is found that mandibulectomy and mandibulotomy procedure has a negative effect on cochlear function in the early period. The DPOAEs were diminished on the osteotomy site in day one postoperatively. Results with a longer follow-up time can yield more information on the prognosis of the cochlear damage.