Unilateral Acoustic Neuroma Research Articles

Changes of video head impulse test before and after translabyrinthectomy in patients with acoustic neuroma.

Acoustic neuroma (AN) is a benign tumor that usually affects a patient's hearing and balance function. For the screening and diagnosis of AN, the traditional approach mainly relies on audiological examination and magnetic resonance imaging (MRI), often ignoring the importance of vestibular function assessment in the affected area. As an emerging method of vestibular function detection, video head impulse test (vHIT) has been widely used in clinic, but research on its use in AN diagnosis is relatively limited. This study aims to explore the value of vHIT in the diagnosis of AN, vestibular dysfunction assessment, and postoperative compensation establishment in unilateral AN patients undergoing unilateral AN resection through labyrinthine approach. This retrospective study was conducted on 27 AN patients who underwent unilateral AN resection via labyrinthine approach from October 2020 to March 2022 in the Department of Otolaryngology-Head and Neck Surgery, the Second Xiangya Hospital, Central South University. vHIT was performed 1 week before surgery to assess vestibular function, pure tone audiometry (PTA) was used to assess hearing level, and ear MRI was used to assess tumor size. Follow-up vHIT was conducted at 1 week, 1 month, 6 months, and 1 year post-surgery. The correlation of vHIT with hearing and tumor size was analyzed. Preoperative vHIT showed that the posterior semicircular canal on the affected side was the most common semicircular canal with reduced vestibulo-ocular reflex (VOR) gain. There was a correlation between the VOR gain of vHIT on the affected side and the hearing level (r=-0.47, P<0.05) or tumor size (r=-0.54, P<0.01). The results of vHIT on the affected side showed that the hearing level and mean VOR gain of the anterior semicircular canal increased slightly with time, and the amplitude and saccade percentage of the dominant saccades of the 3 semicircular canals increased, while the latency time decreased, with the most obvious changes occurring 1 week post-surgery. vHIT can effectively monitor the changes of vestibular function in AN patients before and after surgery and has application value in assisting the diagnosis of vestibular dysfunction in AN patients.

Evaluation of subjective visual vertical and horizontal in patients with acoustic neuroma based on virtual reality

ObjectiveTo investigate potential differences in absolute deviation values of subjective visual vertical and horizontal between unilateral acoustic neuroma patients and healthy young adults under varying degrees of static head tilt, as well as the impact of proprioception on these values, with the aim of determining the effect of acoustic neuroma on gravity sensory pathway function in patients.MethodsWe recruited 22 patients diagnosed with unilateral acoustic neuroma and 25 healthy young adults and employed virtual reality technology to assess the absolute deviation values of subjective visual vertical (SVV) and subjective visual horizontal (SVH) under eight different static tilted head positions (Head centered (0° tilt), PdP, Head tilt 15°, 30°, 45° to the left and right), then compare and analyze intergroup differences.ResultsIn the Head-centered position, both SVV and SVH absolute deviated values were significantly higher in the AN group compared to healthy young adults. The AN group exhibited significantly higher absolute deviation values of SVV compared to the healthy group when tilting their head 30° left and right. Additionally, when tilting their heads to the right at 15° and 45° the AN group showed significant increases in SVH absolute deviated values compared to healthy adults. The SVV and SVH absolute deviation values of LAN and SAN groups did not reach statistical significance. The results of the SVV test for PDP position did not show any significant differences among all groups. However, the SVH test revealed that the absolute deviation values of the LAN group was significantly higher than that of healthy individuals.ConclusionOur study shows that the gravity sensing function of patients with unilateral acoustic neuroma is affected to different degrees, however, the degree of gravity sensing function damage of patients has little relationship with tumor size. When acoustic neuroma is larger than 2 cm, the effect of proprioception on patients’ SVH outcome is noteworthy. So, we should pay attention to the postoperative follow-up of patients with acoustic neuroma and the evaluation of vestibular rehabilitation effect. Meanwhile, for patients opting for conservative treatment, it is imperative to monitor the dynamic changes in vestibular function and seize timely opportunities for intervention.

Long-Term Outcome of Unilateral Acoustic Neuromas With or Without Hearing Loss: Over 10 Years and Beyond After Gamma Knife Radiosurgery.

Since the long-term outcomes of 162 patients who underwent gamma knife radiosurgery (GKS) as an initial or adjuvant treatment for acoustic neuromas (ANs) with unilateral hearing loss were first reported in 1998, there has been no report of a comprehensive analysis of what has changed in GKS practice. We performed a retrospective study of the long-term outcomes of 106 patients with unilateral sporadic ANs who underwent GKS as an initial treatment. The mean patient age was 50 years, and the mean initial tumor volume was 3.68 cm3 (range, 0.10-23.30 cm3). The median marginal tumor dose was 12.5 Gy (range, 8.0-15.0 Gy) and the median follow-up duration was 153 months (range, 120-216 months). The tumor volume increased in 11 patients (10.4%), remained stationary in 27 (25.5%), and decreased in 68 patients (64.2%). The actuarial 3, 5, 10, and 15-year tumor control rates were 95.3 ± 2.1%, 94.3 ± 2.2%, 87.7 ± 3.2%, and 86.6 ± 3.3%, respectively. The 10-year actuarial tumor control rate was significantly lower in the patients with tumor volumes of ≥ 8 cm3 (P = 0.010). The rate of maintaining the same Gardner-Robertson scale grade was 28.6%, and that of serviceable hearing was 46.4%. The rates of newly developed facial and trigeminal neuropathy were 2.8% and 4.7%, respectively. The patients who received marginal doses of less than 12 Gy revealed higher tumor control failure rates (P = 0.129) and newly occurred facial or trigeminal neuropathy rates (P = 0.040 and 0.313, respectively). GKS as an initial treatment for ANs could be helpful in terms of tumor control, the preservation of serviceable hearing, and the prevention of cranial neuropathy. It is recommended to perform GKS as soon as possible not only for tumor control in unilateral ANs with hearing loss but also for hearing preservation in those without hearing loss.

Clinical characteristics of acoustic neuroma patients with normal hearing

Objective:To analyze the clinical characteristics of unilateral acoustic neuroma（AN） with normal hearing, so as to provide evidence for early identification AN. Methods:Clinical datas from 73 patients of unilateral AN with normal hearing of Otorhinolaryngology Head and Neck Surgery of Beijing Tiantan Hospital affiliated of Capital Medical University from August 2019 to April 2022 admitted to department were retrospectively analyzed. All patients underwent pure tone audiometry（PTA）, speech discrimination score（SDS）, auditory brainstem response（ABR）, distortion product otoacoustic emission（DPOAE） and head enhanced MRI. Results:The incidence of normal hearing among patients with AN was 10.7%. Male∶female=1∶2.2; the mean age of the patients was（37.3±9.4） years; the mean tumor size was（24.2±11.2） mm. Tinnitus was the most common reason for visit; the patients who had headache and dizziness had larger tumors. Surgery was the main treatment, and the patients who underwent surgery had larger tumors than those of follow-up. Heterogeneous tumors were the most common type of MRI, homogeneous tumors were smaller than heterogeneous and cystic tumors. The sensitivity of ABR in the diagnosis of AN with normal hearing was 95.9%, and that of ≥20 mm tumors was 100%; prolonged Ⅴ-waves were the most common, patients with Ⅴ-wave deletion had larger tumors than those with normal or prolonged Ⅴ-waves. Patients who had the longer the Ⅴ-wave and the longer difference between Ⅰ-Ⅴ wave had larger tumors. DPOAE was not elicited at full frequency in 11 patients. There was no statistically significant difference in age among patients with different symptoms, treatments, types of MRI, ABR and DPOAE. Conclusion:AN of normal hearing was most common in 30-39 years old women. Patients had different symptoms, phenotypes of MRI and ABR. Patients with normal hearing who had tinnitus, dizziness, headache, facial paraesthesia, and recovery after sudden haring loss can be further examination of ABR and DPOAE for early identification AN. The sensitivity of ABR in diagnosis of hearing normal AN was 95.9%, and the abnormal type of Ⅴ-wave is related to tumor size.

Distinctive MicroRNA Profiles in Serum of Patients with Neurofibromatosis Type 2: A Bioinformatic Exploratory Study

The objective of this study was to explore serum microRNA (miRNA) profile characteristic of patients with neurofibromatosis type 2 (NF2), including both sporadic and familial cases, by comprehensive analysis of miRNA expression using next-generation sequencing. Nine patients with NF2 were included in this study. In addition, 7 patients with unilateral acoustic neuroma without a family history of NF2 were invited to participate as the control cohort in the study. Total RNA including the small RNAs was extracted from serum. We comprehensively analyzed the expression of miRNAs using next-generation sequencing, and differentially expressed miRNAs (DEMs) were analyzed. Biological implications of DEMs were analyzed by Gene Ontology/Kyoto Encyclopedia of Genes and Genomes analysis. Distinctive miRNA profiles (16 miRNAs were significantly downregulated, and 4 miRNAs were significantly upregulated) were observed in the comparison between all patients with NF2 and controls. In the NF2 subgroup analysis, 23 miRNAs (including hsa-miR-let7b, hsa-miR-let7c, and hsa-miR-200a) and 7 miRNAs (including hsa-miR-193b) were identified as specifically downregulated miRNAs in sporadic NF2 and familial NF2, respectively. Moreover, hsa-miR-193a and hsa-miR-504 were identified as specifically upregulated miRNAs in sporadic NF2 and familial NF2, respectively. Gene Ontology/Kyoto Encyclopedia of Genes and Genomes analysis showed that identified DEMs were mainly enriched in gene silencing by miRNA, miRNAs in cancer, and regulation of angiogenesis. We were able to identify distinctive miRNA profiles in the serum of patients with NF2, including both sporadic and familial cases, by comprehensive miRNA expression analysis using miRNA sequencing.

Predictive value of facial nerve F wave in facial paralysis after acoustic neuroma surgery

Objective To investigate the predictive value of preoperative facial nerve F wave in postoperative facial paralysis following acoustic neuroma surgery. Methods A retrospective analysis was conducted on 37 patients with unilateral cerebellopontine angle acoustic neuroma without facial paralysis admitted to Department of Neurosurgery, Beijing Tiantan Hospital, Capital Medical University from January 2016 to January 2017. The latency parameters of facial nerve F wave in healthy and affected sides were measured before operation. Facial nerve function was evaluated based on the House-Brackmann (H-B) grading system at 12 months post surgery. Patients with Grade Ⅲ-Ⅵ were categorized into postoperative facial paralysis group (8 cases) and those with Grade Ⅰ was classified as postoperative non-facial paralysis group (29 cases). The preoperative F wave latency, F-M wave latency, F wave side-to-side difference, and F-M wave side-to-side difference were compared between the 2 groups. The operating characteristic curve (ROC) was plotted and the area under the curve (AUC) was calculated to evaluate the predictive value of F wave of facial nerve before operation in postoperative facial paralysis. Results The latency of F wave and F-M wave on the affected side was longer than that on the affected side (both P<0.05). The latencies of F wave and F-M wave on the affected side in the facial paralysis group were longer than that in the non-facial paralysis group (both P<0.05), and the latencies of F wave and F-M wave side-to-side difference in the facial paralysis group were larger than those in the non-facial paralysis group (both P<0.05). The preoperative F-wave latency, F-M wave latency, F-wave latency side-to-side difference and F-M wave latency side-to-side difference could be used to predict the H-B grade of facial nerve after operation (AUC: 0.813, 0.920, 0.793 and 0.996, respectively, all P<0.05). Conclusion The latency and latency side-to-side difference of F wave and F-M wave of preoperative facial nerve in patients with acoustic neuroma seem to be able to predict the risk of postoperative facial paralysis. Key words: Neuroma, acoustic; Facial nerve; Facial paralysis; Latency of F-wave

Five-year outcomes following hypofractionated stereotactic radiotherapy delivered in five fractions for acoustic neuromas: the mean cochlear dose may impact hearing preservation.

The aim of this study was to assess the clinical outcomes of acoustic neuromas (ANs) treated with hypofractionated stereotactic radiotherapy (hypo-FSRT) prescribed at a uniform dose. Forty-seven patients with a unilateral AN were treated consecutively with hypo-FSRT between February 2007 and March 2012. Nineteen patients maintained a serviceable hearing status at the beginning of hypo-FSRT. The prescribed dose was 25Gy delivered in five fractions per week to the isocenter, and the planning target volume was covered by the 80% isodose line. The median follow-up and audiometric follow-up periods were 61 and 52months, respectively. The estimated tumor control rate at 5years was 90% (95% CI 76-96). The existence of the cystic component before hypo-FSRT had a significantly worse impact on tumor control (p = 0.02). The estimated hearing preservation rates at 1, 3 and 5years were 68% (95% CI 42-84), 41% (95% CI 20-62) and 36% (95% CI 15-57), respectively. A borderline significant difference was identified in the mean biological effective dose with an α/β value of 3Gy (BED3) to the ipsilateral cochlea between the preserved hearing and hearing loss groups (19Gy vs. 28Gy) (p = 0.08). Hypo-FSRT delivered in five fractions for unilateral ANs may achieve excellent tumor control with no severe facial or trigeminal complications. The mean BED3 in the cochlea may impact the hearing preservation rate. Therefore, the cochlear dose should be as low as possible.

Evaluation of Auditory Pathways Using DTI in Patients Treated with Gamma Knife Radiosurgery for Acoustic Neuroma: APreliminary Report.

We aimed to evaluate the change in bilateral auditory pathways using diffusion tensor imaging (DTI) after gamma knife radiosurgery (GKR) and to determine the relationship between the radiosurgical treatment variables and DTI findings. In this study 13 patients with unilateral acoustic neuroma and 11controls underwent routine magnetic resonance imaging (MRI) and DTI. The apparent diffusion coefficient (ADC) and fractional anisotropy (FA) were measured from the bilateral auditory pathways in all individuals before and after GKR. Before GKR, subjects' ADC values obtained from the contralateral side were higher at the lateral lemniscus, medial geniculate body and Heschl's gyrus compared to those of the controls. No statistical differences were found in ADC and FA obtained at bilateral auditory pathways before and after GKR. The ADCs measured at the lateral lemniscus were positively correlated with the maximum radiation dose delivered to the brainstem (BS) and the brainstem volume receiving a radiation dose of 10 Gy (BS V10). Anegative correlation was found between the FA measured from the inferior colliculus and the maximum radiation dose to the cochlea. The ADCs at the inferior colliculus were positively correlated with the mean radiation dose to the cochlea. There were no significant differences in the degree of involvement before and after GKR, revealing that GKR did not significantly affect the auditory pathways at 4months. The major factors that may lead to microstructural injury to auditory pathways at the brainstem level are associated with maximum brainstem radiation dose, BS V10, and cochlear dose. These findings may suggest that more attention should be paid to anatomical structures including the cochlea and brainstem during treatment planning of GKR.

Postoperative Headache after Undergoing Acoustic Neuroma Surgery via the Retrosigmoid Approach.

To estimate the duration of postoperative headache after surgery for acoustic neuroma and the effects of age, sex, tumor size, extent of tumor resection, type of skin incision, surgical duration, hearing preservation, and postoperative facial nerve palsy. This retrospective review analyzed clinical data from 97 patients who had undergone surgery for unilateral acoustic neuroma via the retrosigmoid approach >1 year previously. We investigated whether patients had headache at hospital discharge and during attendance at outpatient clinics. We classified postoperative headache as grade 0 (no headache), 1 (tolerable headache without medication), or 2 (headache requiring medication). The period of headache was defined as the interval in days between surgery and achievement of grade 0. The period of medication for headache was defined as the interval in days between surgery and achievement of grade 0 or 1. Kaplan-Meier analysis revealed median durations of medication and headache of 81 and 641 days, respectively. Headache was cured significantly earlier in patients who underwent surgery using a C-type skin incision (P < 0.001). Headache persisted significantly longer among patients who underwent a shorter surgical procedure (P < 0.02). Multivariate analysis confirmed the type of skin incision as a factor independently associated with duration of postoperative headache. Postoperative headache was cured in the majority of patients within about 2 years after surgery. The C-type skin incision is likely beneficial for reducing the duration of postoperative headache, although headache persisted in a small number of patients.

Rapid Increase in Neural Conduction Time in the Adult Human Auditory Brainstem Following Sudden Unilateral Deafness.

Individuals with sudden unilateral deafness offer a unique opportunity to study plasticity of the binaural auditory system in adult humans. Stimulation of the intact ear results in increased activity in the auditory cortex. However, there are no reports of changes at sub-cortical levels in humans. Therefore, the aim of the present study was to investigate changes in sub-cortical activity immediately before and after the onset of surgically induced unilateral deafness in adult humans. Click-evoked auditory brainstem responses (ABRs) to stimulation of the healthy ear were recorded from ten adults during the course of translabyrinthine surgery for the removal of a unilateral acoustic neuroma. This surgical technique always results in abrupt deafferentation of the affected ear. The results revealed a rapid (within minutes) reduction in latency of wave V (mean pre = 6.55ms; mean post = 6.15ms; p < 0.001). A latency reduction was also observed for wave III (mean pre = 4.40ms; mean post = 4.13ms; p < 0.001). These reductions in response latency are consistent with functional changes including disinhibition or/and more rapid intra-cellular signalling affecting binaurally sensitive neurons in the central auditory system. The results are highly relevant for improved understanding of putative physiological mechanisms underlying perceptual disorders such as tinnitus and hyperacusis.

Changes in Gait Detected by Three-Dimensional Motion Analysis in Patients with Acoustic Neuroma

Many patients with acoustic neuroma experience hearing loss, tinnitus, and equilibrium disturbance. Gait studies performed using tactile sensors placed under the feet have indicated that an acoustic neuroma causes unstable gait, even though this cannot be detected by visual observation. Three-dimensional motion analysis is a useful tool to assess gait. The purpose of this study was to use a three-dimensional motion analysis system to quantify the spatiotemporal and kinematic parameters of gait in patients with acoustic neuroma. Seventeen patients with unilateral acoustic neuroma and seven age-, height-, and foot-sizematched healthy subjects participated. Subjects were asked to walk 4 meters in eyes-open and eyes-closed conditions. Gait speed, stride length, stride duration, head movements in the vertical direction and yaw, pitch, and roll dimensions, gait deviation, forefoot motion, and ankle plantar flexion angle at heel strike were quantified. Patients with acoustic neuroma had slower gait with wider step width and shorter stride length along with greater head movement in pitch and roll than controls. In addition, patients with acoustic neuroma had lower ankle plantar flexion angle at heel strike than controls, especially in the eyes-closed condition. These characteristics of gait increase our understanding of the pathophysiological changes caused by acoustic neuroma.

Auditory Pathway Features Determined by DTI in Subjects with Unilateral Acoustic Neuroma.

In the studies concerning the pathology of the auditory pathway in the vestibulocochlear system, few use advanced neuroimaging applications of magnetic resonance imaging (MRI) such as diffusion tensor imaging (DTI). Those who did use reported DTI changes only at the lateral lemniscus and inferior colliculus level. The aim of our study was to determine diffusion changes in the bilateral auditory pathways of subjects with unilateral acoustic neuroma (AN) and compare them with healthy controls. A total of 15 subjects with unilateral AN along with 11 controls underwent routine MRI and DTI. Apparent diffusion coefficient (ADC) and fractional anisotropy (FA) values obtained from the lateral lemniscus, inferior colliculus, corpus geniculatum mediale, and Heschl's gyrus of the auditory pathway were then compared. The subjects' ADC values measured from the contralateral side were significantly higher at the lateral lemniscus, inferior colliculus, and corpus geniculatum mediale compared with those of the controls. Also, decreased FA values were noted at the inferior colliculus for both the contralateral and ipsilateral sides. The highest ADC values were detected in the inferior colliculus of the auditory pathway. In the auditory pathway of subjects with AN, the contralateral side is more affected than the ipsilateral side, the most affected region being the inferior colliculus. DTI is an advanced neuroimaging technique that can be used to determine the presence of microstructural damage to the auditory pathway in subjects with AN, whereas conventional MRI is not sensitive enough to detect damage.

Unilateral Vestibular Schwannomas in Childhood without Evidence of Neurofibromatosis: Experience of 10 Patients at a Single Institute.

We investigated the clinical presentation and management issues of unilateral vestibular schwannomas in childhood without evidence of neurofibromatosis. Ten pediatric patients with unilateral vestibular schwannoma and no evidence of neurofibromatosis were treated by the senior author at Tiantan Hospital from January 1994 to December 2014. The clinical manifestations, neuroimaging findings, treatment methods, and therapeutic results were retrospectively reviewed. The study included 6 male and 4 female patients. The mean age of the patients was 13.9 years (range, 11-15 years). Common clinical features included increased intracranial pressure, hearing loss, and ataxia. The median diameter of the tumors was 5.15 cm. Gross total resection was achieved in 9 of 10 patients via a suboccipital retrosigmoid approach, and the perioperative mortality rate was 10%. The follow-up period ranged from 1 to 12 years. One patient with facial nerve injury recovered to House? Brackmann grade I postoperatively, 5 to grade II-III, and 2 to grade IV-V. Only 1 patient had preserved hearing. The clinical features of pediatric vestibular schwannomas are different from those of adult vestibular schwannomas, and cranial nerve preservation in children is more difficult. When a child presents with hearing loss as well as cognitive disability, a vestibular schwannoma should be highly suspected. Hypervascular vestibular schwannomas in childhood should be managed by multistaged surgeries.

Improved preservation of function during acoustic neuroma surgery.

Restoration of cranial nerve functions during acoustic neuroma (AN) surgery is crucial for good outcome. The effects of minimizing the injury period and maximizing the recuperation period were investigated in 89 patients who consecutively underwent retrosigmoid unilateral AN surgery. Cochlear nerve and facial nerve functions were evaluated during AN surgery by use of continuous auditory evoked dorsal cochlear nucleus action potential monitoring and facial nerve root exit zone-elicited compound muscle action potential monitoring, respectively. Factors affecting preservation of function at the same (preoperative) grade were analyzed. A total of 23 patients underwent standard treatment and investigation of the monitoring threshold for preservation of function; another 66 patients underwent extended recuperation treatment and assessment of its effect on recovery of nerve function. Both types of final action potential monitoring response and extended recuperation treatment were associated with preservation of function at the same grade. Preservation of function was significantly better for patients who received extended recuperation treatment.

Radiosurgery as Treatment for Acoustic Neuroma. Ten Years’ Experience

Introduction and objectiveThe acoustic neuroma is a benign tumour that usually affects the vestibular portion of the vestibulocochlear nerve. It represents 8% of all intracranial tumours and 80% of those arising at the cerebellopontine angle. There are 3 treatment options: microsurgery (the technique of choice), radiosurgery and observation. The objective of the study was to evaluate the results and side effects obtained using radiosurgery as treatment for acoustic neuroma. Material and methodsWe performed a review of all patients treated with radiosurgery (Gamma Knife and linear accelerator) at doses of 1200–1300cGy for unilateral acoustic neuroma in our hospital from January 1999 until January 2010. In all patients we evaluated the overall state, tumour growth control rate (tumour smaller or remaining the same size), the involvement of V and VII cranial nerves and central nervous system disorders. We also assessed follow-up time and changes in hearing thresholds after radiosurgery. ResultsFrom a total of 35 patients studied, with a mean age of 58.29 years and lacking statistically significant differences in gender, the tumour growth control rate was over 90%. The main reason for visit (65.71%) was unilateral and progressive hearing loss. After treatment, 34.28% of patients had hearing loss. The involvement of the cranial nerves (V–VII) was transitory in 100% of cases. Gamma Knife radiosurgery was administered in 82.85% of patients. ConclusionAlthough microsurgery is the treatment of choice for acoustic neuroma, we consider radiosurgery as a valid alternative in selected patients (elderly, comorbidity, small tumour size and sensorineural hearing loss, among others).

Magnetic Resonance Spectroscopy Features of Heschl's Gyri in Patients with Unilateral Acoustic Neuroma: Preliminary Study

To evaluate neurochemical alterations in Heschl's gyri and determine the most affected side in case of unilateral acoustic neuroma using magnetic resonance spectroscopy (MRS). Fifteen patients with unilateral acoustic neuroma were studied. Following routine cranial MRI sequences, MRS of Heschl's gyri on tumor and nontumor sides was obtained. MRS metabolite values of both Heschl's gyri were statistically compared. The values of N-acetylaspartate (NAA) and Cr on nontumor side Heschl's gyrus (HG) were significantly lower than that on tumor side. We found nontumor side HG more affected with lower NAA and Cr values, suggesting neuronal damage and decreased energy metabolism compared to the tumoral side.

Radiocirugía como tratamiento del neurinoma del acústico. Diez años de experiencia

Introduction and objectiveThe acoustic neuroma is a benign tumour that usually affects the vestibular portion of the vestibulocochlear nerve. It represents 8% of all intracranial tumours and 80% of those arising at the cerebellopontine angle. There are 3 treatment options: microsurgery (the technique of choice), radiosurgery and observation. The objective of the study was to evaluate the results and side effects obtained using radiosurgery as treatment for acoustic neuroma. Material and methodsWe performed a review of all patients treated with radiosurgery (Gamma Knife and linear accelerator) at doses of 1200-1300 cGy for unilateral acoustic neuroma in our hospital from January 1999 until January 2010. In all patients we evaluated the overall state, tumour growth control rate (tumour smaller or remaining the same size), the involvement of v and vii cranial nerves and central nervous system disorders. We also assessed follow-up time and changes in hearing thresholds after radiosurgery. ResultsFrom a total of 35 patients studied, with a mean age of 58.29 years and lacking statistically significant differences in gender, the tumour growth control rate was over 90%. The main reason for visit (65.71%) was unilateral and progressive hearing loss. After treatment, 34.28% of patients had hearing loss. The involvement of the cranial nerves (v-vii) was transitory in 100% of cases. Gamma Knife radiosurgery was administered in 82.85% of patients. ConclusionAlthough microsurgery is the treatment of choice for acoustic neuroma, we consider radiosurgery as a valid alternative in selected patients (elderly, comorbidity, small tumour size and sensorineural hearing loss, among others).

Hypofractionated stereotactic radiotherapy of acoustic neuroma

The goal of this work was to evaluate toxicity and local control following hypofractionated stereotactic radiation treatment with special focus on changes in tumor volume and hearing capacity. In all, 29 patients with unilateral acoustic neuroma were treated between 2001 and 2007 within a prospective radiation protocol (7 × 4 Gy ICRU dose). Median tumor volume was 0.9 ml. Follow-up started at 6 months and was repeated annually with MRI volumetry and audiometry. Hearing preservation was defined as preservation of Class A/B hearing according to the guidelines of the American Academy of Otolaryngology (1995). No patient had any intervention after a median imaging follow-up of 89.5 months, one patient showed radiological progression. Transient increase of tumor volume developed in 17/29 patients, whereas 22/29 patients (75.9%) presented with a volume reduction at last follow-up. A total of 21 patients were eligible for hearing evaluation. Mean pure tone average (PTA) deteriorated from 39.3 to 65.9 dB and mean speech discrimination score (SDS) dropped from 74.3 to 38.1%. The 5-year actuarial Class A/B hearing preservation rate was 50.0 ± 14.4%. Radiation increases only minimally, if at all, the hearing deterioration which emerges by observation alone. Presbyacusis is not responsible for this deterioration. Transient tumor enlargement is common. Today radiation of small- and medium-sized acoustic neuroma can be performed with different highly conformal techniques as fractionated treatment or single low-dose radiosurgery with equal results regarding tumor control, hearing preservation, and side effects. Hypofractionation is more comfortable for the patient than conventional regimens and represents a serious alternative to frameless radiosurgery.

Interaural Difference of Wave V Predicting Postoperative Hearing in Gardner-Robertson Class II Acoustic Neuroma Patients

Patients with acoustic neuroma classified in Gardner and Robertson (GR) Class II should be considered to have useful hearing, and patients classified in Class III should be considered to have not-useful hearing. Therefore, it is important for acoustic neuroma surgery to distinguish between postoperative GR Class II and Class III patients by brainstem auditory evoked potentials (BAEPs). We evaluate which BAEP parameter is the best for predicting postoperative GR Class II or III in 36 preoperative GR Class II patients with unilateral acoustic neuroma. Delay in wave V latency, reduction ratio in wave V amplitude, and interaural difference of wave V (IT5) are evaluated by a receiver-operating characteristic (ROC) curve in this study. IT5 is the best distinguishing parameter between postoperative Class II and Class III. IT5 below 1.12 millisecond (msec) should be a good marker to preserve postoperative useful hearing. Thus, comparing the latency of wave V on both sides is important, and surgeons would be able to make more informed decisions during surgery by checking IT5 on BAEPs.

聴神経腫瘍例における歩行運動の3次元動作解析

Many patients with acoustic neuromas complain of hearing loss, tinnitus or equilibrium disturbance. In our previous gait studies using tactile sensors placed under both feet, we demonstrated that the presence of an acoustic neuroma could cause unstable gait. Three dimensional motion analysis is a useful tool to assess abnormal gait performance. The purpose of this study was to examine the gait performance with spatiotemporal and kinematic parameters using three dimensional motion analysis in patients with acoustic neuromas. Seventeen patients (7 males, 10 females; mean age: 64.1±11.1 years old) with a unilateral acoustic neuroma were enrolled in this study. Twenty-one healthy subjects (12 males, 9 females; mean age: 37.6±19.1 years old) served as controls. Subjects were asked to walk freely with eyes open or closed for a distance of nearly 4 m. Spatiotemporal and kinematic components, including gait speed, stride length, stride duration, % stance phase, step width, head movements (vertical, yaw, pitch, and roll), gait deviation, forefoot motion, and angle between foot and floor (foot flexion angle) during walking, were calculated using three dimensional coordinates. At the subject's heel strike during walking, the mean foot flexion angle in the patient group was significantly smaller than the mean value in the healthy subjects. The decrease of the angle in the acoustic neuroma patients may be associated with a gait abnormality caused by vestibular disorders. Based on three dimensional motion analysis, we propose a useful parameter to evaluate the vestibular disorders in patients with an acoustic neuroma.