Audiological Characteristics of Vestibular Schwannoma Patients With Normal Pure-Tone Audiometry

OBJECTIVE

To investigate the audiological characteristics of vestibular schwannoma (VS) patients with normal pure-tone audiometry (PTA) results.

STUDY DESIGN

A retrospective study.

SETTING

Forty-two VS patients with normal PTA results from October 2016 to October 2022 were included.

METHODS

Normal PTA was defined when the hearing threshold is ≤25 dB hearing loss (HL) in each test frequency and the PTA is ≤25 dB HL. Results of multiple audiological tests such as the auditory brainstem response (ABR), distortion product otoacoustic emission (DPOAE), multiple auditory steady-state responses threshold (ASSR), and speech discrimination score were retrospectively reviewed. Demographic data of these patients were also been collected.

RESULTS

According to our results, the ABR and average ASSR threshold of the affected side were statistically significantly higher in VS patients with normal PTA. ABR waveforms on the affected side also showed more abnormalities. The DPOAE pass rates of the affected side were lower than the unaffected side while the amplitude and signal-to-noise ratio rate was also lower. In addition, we used magnetic resonance imaging 3-dimensional reconstruction images to measure the volume of tumors in these patients. We also found that higher ABR threshold means lager tumor size in patients with normal PTA.

CONCLUSION

VS patients with normal PTA result cannot be assumed to have no impairment of hearing function. ABR, DPOAE, and ASSR results showed the characteristic changes in the affect ear. ABR threshold has the highest sensitivity for hearing abnormalities and is strong relative with tumor size in patients with normal PTA.

The Influence of Asymmetric Hearing Loss on Peripheral and Central Auditory Processing Abilities in Patients With Vestibular Schwannoma

OBJECTIVES

Asymmetric or unilateral hearing loss (AHL) may cause irreversible changes in the processing of acoustic signals in the auditory system. We aim to provide a comprehensive view of the auditory processing abilities for subjects with acquired AHL, and to examine the influence of AHL on speech perception under difficult conditions, and on auditory temporal and intensity processing.

DESIGN

We examined peripheral and central auditory functions for 25 subjects with AHL resulting from vestibular schwannoma, and compared them to those from 24 normal-hearing controls that were matched with the AHL subjects in mean age and hearing thresholds in the healthy ear. Besides the basic hearing threshold assessment, the tests comprised the detection of tones and gaps in a continuous noise, comprehension of speech in babble noise, binaural interactions, difference limen of intensity, and detection of frequency modulation. For the AHL subjects, the selected tests were performed separately for the healthy and diseased ear.

RESULTS

We observed that binaural speech comprehension, gap detection, and frequency modulation detection abilities were dominated by the healthy ear and were comparable for both groups. The AHL subjects were less sensitive to interaural delays, however, they exhibited a higher sensitivity to sound level, as indicated by lower difference limen of intensity and a higher sensitivity to interaural intensity difference. Correlations between the individual test scores indicated that speech comprehension by the AHL subjects was associated with different auditory processing mechanisms than for the control subjects.

CONCLUSIONS

The data suggest that AHL influences both peripheral and central auditory processing abilities and that speech comprehension under difficult conditions relies on different mechanisms for the AHL subjects than for normal-hearing controls.

Temporal lobe injury with middle fossa approach to intracanalicular vestibular schwannomas: a systematic review

There are several surgical approaches for vestibular schwannoma (VS) resection. However, management has gradually shifted from microsurgical resection, toward surveillance and radiosurgery. One of the arguments against microsurgery via the middle fossa approach (MFA) is the risk of temporal lobe retraction injury or sequelae. Here, we sought to evaluate the incidence of temporal lobe retraction injury or sequela from a MFA via a systematic review of the existing literature. This systematic review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Relevant studies reporting temporal lobe injury or sequela during MFA for VS were identified. Data was aggregated and subsequently analyzed to evaluate the incidence of temporal lobe injury. 22 studies were included for statistical analysis, encompassing 1522 patients that underwent VS resection via MFA. The overall rate of temporal lobe sequelae from this approach was 0.7%. The rate of CSF leak was 5.9%. The rate of wound infection was 0.6%. Meningitis occurred in 1.6% of patients. With the MFA, 92% of patients had good facial outcomes, and 54.9% had hearing preservation. Our series and literature review support that temporal lobe retraction injury or sequelae is an infrequent complication from an MFA for intracanalicular VS resection.

The otologic approach in the management of posterior petrous surface meningiomas

PURPOSE

Report our experience in the management of posterior petrous surface meningiomas (PPSMs), and identify features that affect hearing, facial nerve (FN) function, and control of the disease.

METHODS

Retrospective case series of 131 patients surgically managed for PPSMs. FN status, hearing and tumour radicality were assessed and compared between patients with tumours of different locations (Desgeorges classification) and internal auditory canal involvement (IAC).

RESULTS

At the time of surgery 74.8% of patients had a hearing loss. Hearing was mostly unserviceable in tumors attached to the meatus. Pure tone audiometry did not correlate to IAC extension, while speech discrimination scores were statistically worse when the tumor occupied the IAC (unpaired t test, p = 0.0152). Similarly, extrameatal tumors undergoing removal by otic preserving techniques maintained postoperative hearing, whereas hearing worsened significantly in tumors involving the IAC (paired t test, p = 0.048). The FN was affected preoperatively in 11.4% of cases. Postoperative FN palsy was significantly correlated to the IAC involvement (Fisher's exact test, p = 0.0013), while it was not correlated to tumor size. According to the Desgeorges classification, a postoperative FN palsy complicated the majority of anteriorly extending tumors and, two-fifths of meatus centred tumors. 75% of posterior located tumors had a postoperative FN grade I HB.

CONCLUSIONS

Since the involvement of the IAC by the tumor affects both hearing and FN function, the IAC is of primary importance in PPSMs and should be studied and addressed as much as the tumor location in the CPA.

Arachnoid Cysts of the Internal Auditory Canal: Multiplanar Magnetic Resonance Imaging With Audio-Vestibular Correlates

OBJECTIVES/HYPOTHESIS

To investigate prevalence, radiological characteristics, and functional correlates of arachnoid cysts (AC) of the internal auditory canal (IAC) region, including associations of nerve compression with auditory/vestibular symptoms and asymmetrical audiogram or vestibular testing.

STUDY DESIGN

Retrospective study.

METHODS

T2-weighted magnetic resonance imaging (MRI) studies of IACs were retrospectively analyzed from 1247 patients with asymmetric auditory or vestibular symptoms. Patients with radiological findings of AC of the IAC were identified. Multiplanar analysis was used to analyze cyst position in the IAC and assess nerve displacement or compression. Size, position, and presence of nerve compression were correlated with symptoms.

RESULTS

Twenty-four patients had a cyst in the middle or fundus in the IAC. Diameter (P = .04) and position (P = .002) of AC were associated with symptoms. Sagittal analyses identified displacement versus compression (P = .003) more reliably than axial imaging. Symptom laterality was associated with the site of radiological abnormality. Vestibular nerve compression was associated with vertigo (P = .0001), and cochlear nerve compression was associated with auditory symptoms (P < .0001).

CONCLUSIONS

In a retrospective series of patients undergoing MRI of IACs for asymmetric auditory or vestibular impairment, clinical symptom profile correlated with blinded assessment of IAC lesions.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:2323-2331, 2021.

[Hearing classification in patients with vestibular schwannoma using German-language test procedures]

BACKGROUND

Hearing function in patients with vestibular schwannoma is often classified according to the Gardner and Robertson (1988) or the American Academy of Otolaryngology-Head and Neck Surgery (AAO-HNS, 1995) systems. These classification systems are based on English-language test procedures, there is no German-language equivalent. The aim of the study was to investigate the influence of various target parameters on hearing classification and to derive a recommendation for the use of German-language test methods.

MATERIALS AND METHODS

The rules for speech audiometry based on English-language test procedures were applied to German speech test materials. In 91 patients with vestibular schwannoma, pure tone hearing thresholds, speech recognition thresholds, and speech discrimination at different sound pressure levels were measured. The patients were categorized according to the Gardner and Robertson and AAO-HNS classifications.

RESULTS

In both the Gardner-Robertson and the AAO-HNS classifications, the number of patients in the hearing classes with serviceable hearing function (measured as Pure Tone Average across three (3PTA) or four (4PTA) frequencies) was highest when using the 3PTA_{0,5;1;2 kHz} condition, followed by 4PTA_{0,5;1;2;3 kHz}, 4PTA_{0,5;1;2;4 kHz}, and 4PTA_{0,5;1;2;"3"kHz}. If maximum word recognition score (WRS_max) was used instead of word recognition 40 dB above the sensation level (WRS_40SL), more patients were classified into the hearing classes with serviceable hearing function, irrespective of the mean pure tone hearing threshold.

CONCLUSION

The Gardner-Robertson and AAO-HNS classifications can be used in German-speaking settings. The Freiburg monosyllabic test can be used to determine speech discrimination scores or maximum word recognition.