Results of ABR in patients with acustic neurinoma

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1 Results of ABR in patients with acustic neurinoma Wyniki słuchowych potencjałów wywołanych pnia mózgu u pacjentów z nerwiakiem nerwu słuchowego Terentieva Kateryna 1, Niemczyk Kazimierz 2, Naumenko Oleksander 1 1 Department of Otorhinolaryngology, Kyiv Medical University, Ukraine 2 Department and Chair of Otolaryngology, Medical University of Warsaw, Poland Article history: Received: Accepted: Published: ABSTRACT: KEYWORDS: Acoustic neuromas comprise about 6% of all intracranial tumors, about 30% of brainstem tumors, and about 85% of tumors in the region of the cerebellopontine angle. Another 10% are meningiomas. Between 2,000 and 3,000 cases of acoustic neuromas are newly diagnosed each year. Advances in radiotherapy as well as research on the growth of these tumors result in a multiplicity of treatments. Preservation of hearing has become increasingly important regardless of the treatment option. Auditory brainstem response (ABR) is the single most significant study in terms of diagnosis and monitoring of acoustic neuromas. The Aim: The aim of this study was to analyze the clinical results of ABRs in patients with acoustic neuromas in different clinical stages, which could indirectly influence the selection of methods used for tumor growth assessment. Material & method: This article was based on the analysis of the clinical data of 97 patients with acoustic neuroma confirmed by MRI. We distinguished 3 kinds of tumors (I-III) depending on their stage in the Koos-Perneczky s scale. The study was retrospective. Results: Forty-nine patients (50.5%) had an abnormal ABR result. We did not find any significant differences in latencies between tumors of different stages when normal ABR recordings were taken into account. However, latencies were prolonged in comparison to normal values. Prevalence of abnormal ABR recordings increased together with clinical stage. Conclusions: a substantial number of patients with acoustic neuromas (ca. 50%), a normal ABR morphology was not detected presence of waves I, III, and V. Prevalence of an abnormal ABR morphology in intrameatal tumors (stage I) is different than in cerebellopontine tumors (stage II, and III). Prevalence of an abnormal ABR morphology does not change between stage II and stage III tumors. When normal ABRs are taken into account, then wave V latencies do not differ significantly between tumors of different size. Sensorineural hearing loss, Acoustic neuroma, Auditory brainstem response (ABR) STRESZCZENIE: Nerwiaki nerwu słuchowego stanowią około 6 proc. wszystkich guzów wewnątrzczaszkowych, około 30 proc. guzów pnia mózgu oraz około 85 proc. guzów okolicy kąta mostowo-móżdżkowego. Kolejne 10 proc. stanowią oponiaki. Corocznie w USA diagnozowanych jest od 2 do 3 tys. nowych przypadków nerwiaka nerwu słuchowego. Progres w radioterapii oraz badania nad wzrostem tych guzów powodują, że procedury postępowania stają się różnorodne. Coraz większe znaczenie przywiązuje się do zachowania słuchu niezależnie od wyboru postępowania terapeutycznego. Najistotniejszym badaniem słuchu w diagnostyce nerwiaków oraz w trakcie wyboru i monitorowania postępowania są potencjały wywołane pnia mózgu (ABR ang. auditory brainstem response). Cel Celem niniejszego badania była analiza wyników badania słuchowych potencjałów wywołanych pnia mózgu u pacjentów z nerwiakami nerwu słuchowego w różnych stadiach zaawansowania, co pośrednio może się przyczynić do wyboru parametrów służących ocenie ewolucji guzów. 40 DOI: /

2 Materiał i metoda: Niniejszy artykuł przedstawia wyniki analiz przeprowadzonych w grupie 97 pacjentów z nerwiakiem nerwu słuchowego potwierdzonym w badaniu rezonansu magnetycznego (MRI ang. magnetic resonanse imaging). Wyróżniono trzy podgrupy guzów (I = III) w zależności od ich zaawansowania w skali Koosa-Perneczky ego. Badanie miało charakter retrospektywny. Wyniki: U 49 (50,5 proc.) pacjentów nie stwierdzono prawidłowego zapisu w badaniu ABR. W przypadkach gdy morfologia zapisu ABR była prawidłowa, stwierdzono, że latencje fal nie różniły się w podgrupach o różnym stadium zaawansowania. Jednak latencje fal były wydłużone w stosunku do wartości prawidłowych. Wraz ze wzrostem zaawansowania klinicznego zwiększał się odsetek zaburzonej morfologii fal w badaniu ABR. Wnioski: U dużej części pacjentów z guzami nerwu VIII (ok. 50 proc.) nie udaje się uzyskać prawidłowej morfologii zapisu ABR - obecność fal I, III i V. Odsetek wyników nieprawidłowej morfologii zapisu ABR różni się między guzami wewnątrzprzewodowymi (stadium I) i wrastającymi do kąta mostowo-móżdżkowego (stadium II i III). Gdy guz wrasta do kąta - w stadium II i III - sytuacja się stabilizuje i odsetek zaburzonej morfologii nie zmienia się istotnie. W przypadkach gdy zapisy ABR mają prawidłową morfologię, latencje fali V nie różnią się istotnie między guzami o różnej wielkości. SŁOWA KLUCZOWE: niedosłuch sensoryczny, nerwiak nerwu słuchowego, słuchowe potencjały wywołane pnia mózgu (ABR) INTRODUCTION Acoustic neuroma, also known as vestibular schwannoma, or acoustic neuroma, is a nonmalignant tumor of the 8th cranial nerve (1). Acoustic neuromas comprise about 6% of all intracranial tumors, about 30% of brainstem tumors, and about 85% of tumors in the region of the cerebellopontine angle. Only about one in 1,000 patients with hearing asymmetry has acoustic neuroma (2). Acoustic neuromas are sometimes identified in asymptomatic patients on radiological exams for other reasons and may be identified in up to 0.02% incidentally (3). Their symptoms may develop at any age but usually occur between the age of 30 and 60 years. Progressive, high-frequency unilateral or asymmetric sensorineural hearing loss is the most common symptom of acoustic neuromas. It is reported to occur in more than 95% of patients (4). The first presumptive case of acoustic neuroma dates back to the second half of the 18th century. As Cushing related in 1777, Sandifort documented a small body adherent to the right auditory nerve, which was found at autopsy in a patient with deafness. Several reports on tumors possibly related to the auditory nerve followed, but it was not until 1830 that Charles Bell gave an accurate description, of what appears to be a definitive case of acoustic neuroma (5). During the last decades of the 19th century, advances in the histological and pathological characterization of tumors led to a more solid correlation of patient s clinical symptoms with the actual diagnosis obtained at autopsy. Sternberg (1900) is credited with the first accurate pathological description of an acoustic neuroma. The advances in diagnostic technology and surgical techniques are depicted in the prognosis and surgical outcome of patients with acoustic neuromas. Anatomical preservation of the facial nerve can now be achieved, depending on the size of the tumor, in more than 98% of patients, the majority of whom also attain preservation of the facial nerve function. The diagnosis of acoustic neuroma is often delayed because the disease is uncommon and the symptoms are consistent with other more frequently occurring conditions. Such a delay usually means that the tumor was allowed to grow and ultimately compress and damage vital structures. The most useful and accurate audiological test for acoustic neuromas remains the auditory brainstem response (ABR). The prerequisite for this test is hearing function sufficient to generate an adequate ABR (6). The test uses computer averaging over time to filter the background noise to generate an electroencephalogram created by the response of the auditory pathway to an auditory stimulus. The waveform represents specific anatomical points along the auditory neural pathway: the cochlear nerve and nuclei (waves I and II), superior olivary nucleus (wave III), lateral lemniscus (wave IV), and inferior colliculi (wave V). For clinical use, the most reliable waves generated are the synchronous discharges of wave I from the cochlear nerve and of wave V from the inferior colliculus (7). Recent reports have suggested that smaller acoustic neuromas are less likely to be detected by ABR. False-negative rates as high as 22% have been reported for tumors with an extrameatal size of less than 15 mm, whereas sensitivity as low as 67% has been reported for intracanalicular tumors (8). MATERIALS AND METODS The aim of this study was to compare the clinical results, audiology studies pure tone audiometry, ABRs, and the stage of acoustic neuroma. This article was based on the analysis of the clinical data of 97 patients with acoustic neuroma confirmed by MRI. Patients with acoustic neuromas were excluded from the study if ABR or MRI data were not available. They were treated and observed at the Clinic of Otolaryngology of the Me- POLSKI PRZEGLĄD OTORYNOLARYNGOLOGICZNY, TOM 4, NR 2 (2015), s

3 A century ago, many patients with acoustic neuromas first sought medical attention when increased intracranial pressure secondary to massive tumor size resulted in symptoms. Improvement in diagnostic techniques and increased clinidical University of Warsaw from 2010 to We divided patients into 3 groups depending on the stage of the tumor. We used the classification of Koos and Perneczky. Among them: 1 st group (44 patients) - stage I; 2 nd group (35 patients) stage II; 3 rd group (18 patients) stage III. Morphology of recordings, latencies of wave V and interval I-V and III-V, were evaluated. Audio Evoked Potential Tester (EPTest, Pracownia Elekroniki Medycznej, Warsaw) was used to measure the latencies of different ABR components. Recordings were performed with rectangular electric clicks via an insert earphone (int. 90 db; frequency rate 11.0/27.0/s; sweep, dur uj; t ms) with a digital low filter at 2000 Hz and a digital high filter at 200 Hz. The ABR was recorded with a one-channel system. The ABR responses of groups of patients were retrospectively considered and compared. Microsoft Office Excel 2013 was used for data management and statistical analysis. Continuous variables are presented as mean ± standard deviation. Comparisons between groups were analyzed with the Student s t-test for continuous variables and the Fisher s exact test for categorical variables. Statistical analysis was considered significant at P <0.05. RESULTS All patients reported symptoms as dizziness, ear noise and hearing loss. Pic.1. The percentage of results of ABR in patients of the first group Pic.3. The percentage of results of ABR in patients of the third group The first group comprised of 44 patients with unilateral or prevalently unilateral sensorineural hearing loss. The mean pure tone threshold in that group was 36.9 (±19.7) db. As a result of ABR, it was noted that in 18 cases (40.91%) waves were not detected. Wave V was recorded in 24 cases (54.55%). Only in 12 (27.27%) cases ABRs were positive and demonstrated sensitivity for extracochlear pathology. Of those, the average latency of wave V was 5.81 (±0.65) ms, interval III-V was 1.86 (±0.38) ms, interval I-V 4.65 (±0.66) ms. Fig. 1 demonstrates summary results of ABR in patients of the first group. The second group consisted of 35 patients. The mean pure tone threshold was 41.6 (±18.3) db. In 21 patients (60.00 %) waves were not detected. In 14 cases (40%), wave V was visualized. In 25.7 % (9 cases) all waves were detected in ABRs - mean latency of wave V was 5.83 (±0.53) ms, interval I-V (±0.6) ms, interval III-V 2.16 (±0.62) ms. Fig. 2 shows summary results of ABR in patients of the second group. The third group was the smallest one and consisted of 18 patients. The mean pure tone threshold was 51.1 (±15.5) db. In 7 cases (38.89%),wave V was noted. In % of cases (10 patients) waves were not detected, in 5 cases (27.78%) ABRs were positive and demonstrated a retrocochlear pathology. Latency of wave V was 5.56 (±0.71) ms, interval III-V 2.29 (±0.72) ms, and interval I-V 4.08 (±0.68) ms. Summary results of ABR in patients are shown in Fig. 1, 2, 3. Within the whole study group, 49 patients (50.5%) had abnormal ABR recordings. Normal ABR recordings (all waves distinguishable) were found only in 25.7%. DISSCUSSION Pic.2. The percentage of results of ABR in patients of the second group 42

4 4,065 1,847 2,165 4, Stage 2,296 4,08 Pic.4 Comparing the intervals I-V and III-V in patients of different groups III-V I-V Linear (II-V) cian awareness made them a rare occurrence today. There remains a sufficiently debated and unresolved question of growth rate of acoustic neuroma, its clinical manifestations due to location and, as a consequence, the choice of treatment. Increasing diagnostic capabilities of ABR and MRI in the pathology of the cerebellopontine angle should be noted. However, because if its availability MRI has become a standard diagnostic tool. Extensive use of ABR and MRI allows for a detection of even smaller tumors. Acoustic neuroma frequently leads to lengthening of interval I-V and III-V. Diagnostic value of ABR for the detection of extracochlear pathology decreases with a decreasing size of an acoustic neuroma. ABR provides information on auditory function and hearing sensitivity. However, it is not a true test of hearing and not a substitute for a formal hearing evaluation and therefore pure tone and verbal audiometry are still used for preoperative evaluation. The comparison of ABR results in three groups of patients (Tab.1) is not easy to interpret. The results showed that in the second group all data are increased relative to the first stage. But in the third group of patients (that corresponds to the third stage of the disease) we noted a slightly decreased interval I-V relative to the second stage. That is why the comparison of latencies of ABRs between different groups could not be easily interpreted. It may be connected with a small amount of data in the third group as well as with tumor decompression in the cerebellopontine angle. The increase in interval I-V associated with the increase in the stage of the disease, considered one of the most reliable diagnostic criterion, indicated a high probability of diagnosing an acoustic neuroma. However, this measure does not differ between groups distinguished with respect to clinical stage. 3 Tab.1 STAGE LATENCY WAVE V INTERVAL III-V INTERVAL I-V (±0.65) ms 1.84 (±0.38) ms 4.06 (±0.66) ms (±0.53) ms 2.16 (±0.62) ms 4.33 (±0.6) ms (±0.71) ms 2.29 (±0.72) ms 4.08 (±0.68) ms Comparison of the intervals I-V and III-V in patients of different groups showed a slight difference in intervals I-V, while intervals III-V in tumors of different clinical stages tend to increase together with the clinical stage. No registration of the ABR curve prevailed in patients of the second group. In group 3, changes of morphology in ABR recordings were of a similar prevalence but tended to decrease. The main limitations of this study are that it was retrospective and included a relatively small number of patients. However, the results can be interpreted in view of the fact that tumor growth in the relatively large space the cerebellopontine angle is possible with no further deteriorations in hearing. Chien Shih et al. (9) performed a retrospective study, based on chart reviews of 30 patients with acoustic neuroma. They reported that 76.7 percent of all patients had an abnormal contralateral wave, and that prevalence increased to 94.4 percent in patients with a tumor size larger than 2 cm. The most frequent changes observed in the results were in contralateral wave I (56.7%) and contralateral wave V (56.7%).When the tumor size was larger than 2 cm, there was a significantly higher prevalence of abnormal wave V and interpeak III-V latencies. Johnson and Selters (10) found that in patients with acoustic neuroma larger than 3 cm, 52.4 percent had an abnormal interpeak III-V latency contralateral to the tumor. In the analyzed material, the majority of tumors were not larger than 1 cm in the cerebellopontine angle and therefore pathologies resulting from compression of the opposite side of the brainstem were not studied It was found, however, that acoustic neuroma, even in the early stages of the disease, may lead to quite prevalent (ca. 40%) changes in ABR morphology as well as changes in intervals I V, and III V. The latency, amplitude and morphology of waves I through V in ABR are important parameters reflecting the functioning status of the peripheral auditory pathway. However, ABR morphology is better correlated with clinical stage. CONCLUSIONS In a large proportion of patients with acoustic neuromas (ca. 50%) a normal morphology of ABR recordings is not POLSKI PRZEGLĄD OTORYNOLARYNGOLOGICZNY, TOM 4, NR 2 (2015), s

5 found. Prevalence of an abnormal ABR morphology in intrameatal tumors (stage I) is different than in cerebellopontine tumors (stage II, and III). Prevalence of an abnormal ABR morphology does not change between stage II, and stage III tumors. When normal ABRs are taken into account, then latencies do not differ significantly between tumors of different size. Our results may point to different mechanisms of growth/development of acoustic neuromas that lead to abnormal ABR morphologies or lengthening of latencies in intrameatal tumors and tumors growing in the cerebellopontine angle. In the case of small, intrameatal tumors, changes in ABR recordings may result from tumor evolution. These findings may be confirmed in prospective studies. References 1. Jamróz B., Niemczyk K.: Acoustic neuromas diagnostic and treatment methods. Otorynolaryngol., 2013; 12(1): Yuri A., Clark J.H., Limb C.J., Niparko J.K., Francis H.W.: Predictors of vestibular schwannoma growth and clinical implications. Otol. Neurotol., 2010; Nageris B.I., Popovtzer A.: Acoustic neuroma in patients with completely resolved sudden hearing loss. Ann. Otol. Rhinol. Laryngol., 2003; 112(5): Borisenko O., Suszko J., Sriebniak I., Miszczanczuk N.: Osobiennosti kliniczeskoj kartiny akusticzeskoj niewrinomy. W: Matieriały jeżegodnoj tradicionnoj osienniej konfieriencii Ukrainskogo naucznogo medicinskogo obszczestwa otolaringołogii LOR-onkołogija i chirurgija gołowy i szei, Reichel O., Wimmer C., Mees K., Suckfull M.: A patient with acoustic neuroma.the reason for the functional disorder of his inner ear?, Laryngorhinootologie, 2001; 80(12): Vokurka E.A., Herwadkar A., Thacker N.A., Ramsden R.T., Jackson A.: Using Bayesian tissue classification to improve the accuracy of vestibular schwannoma volume and growth measurement. Ajnr., 2002; 23: Minina A.: Osobiennosti kliniczeskogo tieczenija akusticzeskoj newrinomy w zawisimosti ot rospołożenija opucholi wo wnutrienniem słuchowom prochodie. Żurnał Wusznych, Nosowych i Gorłowych Chworob, 2013; 3: Wilson D.F., Hodgson R.S., Gustafson M.F., Hogue S., Mills L.: The sensitivity of auditory brainstem response testing in small acoustic neuromas. Laryngoscope, 1992; 102: Shih C., Tseng F.Y. et al.: Ipsilateral and contralateral acoustic brainstem response abnormalities in patients with vestibular schwannoma. Otolaryngol. Head Neck Surg., 2009; 141: Johnson E.W., Selters W.A.: Audiological evaluation for neurotological diagnosis. W: Handbook of Neurotological Diagnosis. red.: House J.W., O Connor A.F. Marcel Dekker Inc., New York 1987, Johnson EW, Selters WA. Audiological evaluation for neurotological diagnosis. In: House, JW, O Connor AF, editors. Handbook of Neurotological Diagnosis. New York: Marcel Dekker Inc.; p Word count: 1652 Tables: 1 Figures: 4 References: 10 Access the article online: DOI: / Full-text PDF: Corresponding author: Kateryna Terentieva, Department of Otorhinolaryngology, Kyiv Medical University, Ukraine, katij88@mail.ru Copyright 2015 Polish Society of Otorhinolaryngologists Head and Neck Surgeons. Published by Index Copernicus sp. z o.o. All rights reserved Competing interests: The authors declare that they have no competing interests. Cite this article as: Terentieva K., Niemczyk K., Naumenko O.: Results of ABR in patients with acoustic neurinoma. Pol Otorhino Rev 2015; 4(2):