Effect of drill-induced noise on hearing in non-operated ear

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.

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.

Intraoperative Monitoring of Auditory Function During Lateral Skull Base Surgery

OBJECTIVE

We present a unique case of a patient with a jugular foramen tumor with serviceable hearing. This study discusses the audiometric results and intraoperative electrocochleographic (ECochG) findings recorded during tumor removal to illustrate the potential utility of this technique in skull base surgery.

PATIENTS

A 22-year-old female patient presented with a jugular foramen schwannoma and associated symptoms of right-sided otalgia, mild hearing loss, and blurry vision.

INTERVENTIONS

Intraoperative ECochG responses during an infratemporal fossa approach: click and tone burst (1, 2, 4 kHz) stimuli were used and presented at 90 dB nHL.

MAIN OUTCOME MEASURES

Intraoperative ECochG testing using frequency-specific tone bursts and clicks before and after tumor resection.

RESULTS

The compound action potential magnitudes, cochlear microphonic, and summation potential were recorded pre- and post-tumor removal. For statistical analysis, a paired t test with significance set at p < 0.05 was used. The compound action potential magnitudes increased at all test frequencies (p < 0.01) while the summation potential and cochlear microphonic remained relatively stable (p > 0.05). Audiometric testing demonstrated an improvement of the preoperative mild right-sided hearing loss after tumor resection (pure-tone average for 0.5, 1, 2, and 4 kHz of 30 dB HL preoperation and 7.5 dB HL after tumor resection).

CONCLUSIONS

Intraoperative ECochG may allow for real-time monitoring during complex skull base surgery.

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.