Intracanalicular Vestibular Schwannoma Research Articles

Natural History of Hearing Deterioration in Intracanalicular Vestibular Schwannoma

Intracanalicular vestibular schwannomas have a range of treatment options that can preserve hearing: microsurgery, stereotactic radiotherapy, and conservative observation. To evaluate the natural course of hearing deterioration during a period of conservative observation. A retrospective case review was performed on 47 patients with a unilateral intracanalicular vestibular schwannoma. Evaluation of growth was monitored by repeat MRI scanning. Repeated pure-tone and speech audiometry results were evaluated for subgroups of patients showing growth or no growth and by subsite location of tumor in the internal auditory canal. Patients had a mean follow-up of 3.6 years. Over the entire population, the pure-tone average thresholds at 0.5, 1, 2, and 3 kHz and the word recognition scores both significantly deteriorated from 38 to 51 dB HL, and from 66% to 55%, respectively. Overall, 74% of subjects with good hearing, according to the 50/50 rule, maintained hearing above this rule. There were no significant differences in hearing loss by subsite in the internal auditory canal (porus, fundus, central) or by growth status (stable, growing, shrinking). Only 6 patients showed a large hearing change. This happened early during follow-up, with relatively stable hearing after this. Hearing will deteriorate in some intracanalicular vestibular schwannomas, regardless of tumor growth. Hearing deterioration, if on a large scale, most likely occurs early in follow-up. The present results using conservative management in these tumors appear similar to those reported for stereotactic radiotherapy or microsurgery.

Wait-and-see strategy compared with proactive Gamma Knife surgery in patients with intracanalicular vestibular schwannomas

Object The roles of the wait-and-see strategy and proactive Gamma Knife surgery (GKS) in the treatment paradigm for small intracanalicular vestibular schwannomas (VSs) is still a matter of debate, especially when patients present with functional hearing. The authors compare these 2 methods. Methods Forty-seven patients (22 men and 25 women) harboring an intracanalicular VS were followed prospectively. The mean age of the patients at the time of inclusion was 54.4 years (range 20–71 years). The mean follow-up period was 43.8 ± 40 months (range 9–222 months). Failure was defined as significant tumor growth and/or hearing deterioration that required microsurgical or radiosurgical treatment. This population was compared with a control group of 34 patients harboring a unilateral intracanalicular VS who were consecutively treated by GKS and had functional hearing at the time of radiosurgery. Results Of the 47 patients in the wait-and-see group, treatment failure (tumor growth requiring treatment) was observed in 35 patients (74%), although conservative treatment is still ongoing for 12 patients. Treatment failure in the control (GKS) group occurred in only 1 (3%) of 34 patients. In the wait-and-see group, there was no change in tumor size in 10 patients (21%), tumor growth in 36 patients (77%), and a mild decrease in tumor size in 1 patient (2%). Forty patients in the wait-and-see group were available for a hearing level study, which demonstrated no change in Gardner-Robertson hearing class for 24 patients (60%). Fifteen patients (38%) experienced more than 10 db of hearing loss and 2 of them became deaf. At 3, 4, and 5 years, the useful hearing preservation rates were 75%, 52%, and 41% in the wait-and-see group and 77%, 70%, and 64% in the control group, respectively. Thus, the chances of maintaining functional hearing and avoiding further intervention were much higher in cases treated by GKS (79% and 60% at 2 and 5 years, respectively) than in cases managed by the wait-and-see strategy (43% and 14% at 2 and 5 years, respectively). Conclusions These data indicate that the wait-and-see policy exposes the patient to elevated risks of tumor growth and degradation of hearing. Both events may occur independently in the mid-term period. This information must be presented to the patient. A careful sequential follow-up may be adopted when the wait-and-see strategy is chosen, but proactive GKS is recommended when hearing is still useful at the time of diagnosis. This recommendation may be a main paradigm shift in the practice of treating intracanalicular VSs.

Vestibular Schwannoma in Patients with Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSNHL) has several etiologies. It may be a presenting symptom of vestibular schwannoma (VS). This study aimed to establish the incidence of VS in patients with SSNHL, and we report several unusual cases among these patients. We reviewed retrospectively the charts and magnetic resonance imaging (MRI) findings of all adult patients who presented with SSNHL between 2002 and 2008. We utilized three-dimensional fast imaging with steady-state acquisition temporal MRI as a screening method. Of the 295 patients with SSNHL, VS was found in 12 (4%). All patients had intrameatal or small to medium-sized tumors. There were three cases with SSNHL in one ear and an incidental finding of intracanalicular VS in the contralateral ear. There were four cases of VS that showed good recovery from SSNHL with corticosteroid treatment. There were two cases that mimicked labyrinthitis with hearing loss and vertigo. A greater number of cases than expected of VS were detected in patients with SSNHL, as a result of increasing widespread use of MRI. Various unusual findings in these patients were identified. MRI would seem to be mandatory in all cases of SSNHL.

Treatment of Idiopathic Hemifacial Spasm with Radiosurgery or Hypofractionated Stereotactic Radiotherapy: Preliminary Results

Microvascular decompression in the posterior cranial fossa is the first treatment option for hemifacial spasm. For patients not suitable for surgery because of advanced age, poor general conditions or patients who refuse surgery, radiotherapeutic treatment could be an alternative. Only one case of resolution of hemifacial spasm in a patient undergoing radiosurgery for an intracanalicular vestibular schwannoma has been described in the literature. In this article we present three patients affected by idiopathic hemifacial spasm, refractory to medical therapy and botulinum toxin injections, who were treated by radiosurgery in one case and hypofractionated stereotactic radiotherapy in the other two. Radiosurgery, with a single dose of 8 Gy, was used in the first patient affected by idiopathic hemifacial spasm and autoimmune polyneuropathy with severe hypoacusia; hypofractionated stereotactic radiotherapy, with 15 Gy in 5 fractions of 3 Gy each, was preferred in the other 2 cases. In all patients, the target consisted of the vestibulocochlear-facial bundle immediately before its entry into the internal acoustic foramen. A marked improvement of symptoms was observed in 2 patients, and almost complete disappearance in the other case, with no complications, particularly, auditory. The mean follow-up time of 24 months reported here could be judged too short, and our series too small, but the good results observed so far lead us to underline that, as in trigeminal neuralgia, radiosurgery or hypofractionated stereotactic radiotherapy could represent a therapeutic alternative to microvascular decompression for idiopathic hemifacial spasm for patients not suitable for surgery.

Cadaveric Study to Find a Novel Method of Identifying the Internal Acoustic Canal in the Middle Fossa Approach: The Rule of 2s

Introduction: The middle fossa approach is useful for surgically removing intracanalicular vestibular schwannomas. Multiple landmarks and anatomic relationships have been previously described to identify the internal acoustic canal (IAC) via the middle fossa approach. We attempted to identify a reproducible, practical method to quickly identify the IAC.

Hearing preservation and facial nerve function after microsurgery for intracanalicular vestibular schwannomas: comparison of middle fossa and restrosigmoid approaches

Therapeutic options for vestibular schwannomas (VS) include microsurgery, stereotactic radiosurgery and conservative management. Early treatment of intracanalicular vestibular schwannomas (IVS) may be advisable because their spontaneous course will show hearing loss in most cases. Advanced microsurgical techniques and continuous intraoperative monitoring of cranial nerves may allow hearing preservation (HP) without facial nerve damage. However, there are still controversies about the definition of hearing preservation, and the best surgical approach that should be used. In this study, we reviewed the main data from the recent literature on IVS surgery and compared hearing, facial function and complication rates after the retrosigmoid (RS) and middle fossa (MF) approaches, respectively. The results showed that the average HP rate after IVS surgery ranged from 58% (RS) to 62% (MF). HP varied widely depending on the audiometric criteria that were used for definition of serviceable hearing. There was a trend to show that the MF approach offered a better quality of postoperative hearing (not statistically significant), whereas the RS approach offered a better facial nerve preservation and fewer complications (not statistically significant). We believe that the timing of treatment in the course of the disease and selection between radiosurgical versus microsurgical procedure are key issues in the management of IVS. Preservation of hearing and good facial nerve function in surgery for VS is a reasonable goal for many patients with intracanalicular tumors and serviceable hearing. Once open surgery has been decided, selection of the approach mainly depends on individual anatomical considerations and experience of the surgeon.

HEARING PRESERVATION AFTER INTRACANALICULAR VESTIBULAR SCHWANNOMA RADIOSURGERY

Tumor control, facial function preservation, and hearing preservation are important criteria for successful management of intracanalicular vestibular schwannomas, whether observation, microsurgery, or radiosurgery is chosen. We collected data prospectively to assess hearing preservation after intracanalicular vestibular schwannoma radiosurgery. Between 1987 and 2003, 96 patients (65 men and 31 women) underwent gamma knife stereotactic radiosurgery (SRS) for intracanalicular tumors. The median patient age was 54 years (range, 22-80 years). Hearing was graded using the Gardner-Robertson (GR) and the American Academy of Otolaryngology-Head and Neck Surgery classifications. Dose planning was performed on intraoperative stereotactic images using multiple 4-mm isocenters. The median tumor volume was 0.112 mm3 (range, 0.05-0.447 mm3), and the median margin dose was 13 Gy (range, 10-18 Gy). The mean and median audiologic follow-up periods were 42 months and 28 months (range, 12-144 months), respectively. Serviceable hearing was preserved in 31 of 40 (77.5%) patients with initial American Academy of Otolaryngology-Head and Neck Surgery Class A hearing. Serviceable hearing was preserved in 40 of 79 (64.5%) patients with GR Grade I or II pre-SRS hearing. Ninety-two patients had GR Grade I, II, or III hearing before SRS, and GR Grade I, II, or III hearing was maintained in 78 patients (85%). Hearing grades improved in 7 patients. Facial and trigeminal nerve function was preserved in all patients. The tumor control rate (freedom from additional intervention) was 99.0% (95 of 96) at a median follow-up of 28 months (range, 12-144 months). One patient underwent tumor resection 18 months after radiosurgery. SRS is a minimally invasive first-line management option for patients with intracanalicular tumors and provides high rates of hearing preservation with minimal morbidity.

Dilatation du méat acoustique interne et schwannome vestibulaire intracanalaire : quels mécanismes ?

Objectives To present a unique case of unilateral widening of the internal auditory canal (IAC) with no significant contact with an ipsilateral intracanalicular vestibular schwannoma (VS), raising the issue of the cause(s) of this IAC widening. Methods The medical record and radiologic data were reviewed of a patient presenting an enlarged unilateral IAC, which led to the diagnosis of an intracanalicular VS that could not account for the dilation. Results The patient had a unilateral dilation of the IAC that did not match the ipsilateral VS he had. As a result, this case motivated discussion of whether such dilation of the IAC was congenitally asymmetrical or the result of the mechanisms involved in the widening of the IAC. Conclusions Although asymmetry of IAC is a current notion, this case demonstrates a contrario that increased pressure exerted on the walls of the IAC cannot be the only mechanism in such widening.

Audiologic Management of a Patient with a Sudden Hearing Loss and Vestibular Schwannoma in the Contralateral Ear

The case of a 59-year-old male with a sudden-onset sensorineural hearing loss in one ear and an incidental finding of an intracanalicular vestibular schwannoma in the contralateral, normally hearing ear is reported. The patient was successfully fitted with a hearing aid in the ear with the sudden hearing loss, which notably had very poor word recognition. The questionable value of word-recognition scores in determining hearing aid candidacy is discussed. The importance of considering nonaudiologic factors in determining hearing aid candidacy is also highlighted.

Translabyrinthine surgery for disabling vertigo in vestibular schwannoma patients

To determine the impact of translabyrinthine surgery on the quality of life in vestibular schwannoma patients with rotatory vertigo. Prospective study in 18 vestibular schwannoma patients. The study was conducted in a multispecialty tertiary care clinic. All 18 patients had a unilateral intracanalicular vestibular schwannoma, without serviceable hearing in the affected ear and severely handicapped by attacks of rotatory vertigo and constant dizziness. Despite an initial conservative treatment, extensive vestibular rehabilitation exercises, translabyrinthine surgery was performed because of the disabling character of the vertigo, which considerably continued to affect the patients' quality of life. Preoperative and postoperative quality of life using the Short Form 36 Health Survey (Short Form-36) scores and Dizziness Handicap Inventory (DHI) scores. A total of 17 patients (94%) completed the questionnaire preoperatively and 3 and 12 months postoperatively. All Short Form-36 scales of the studied patients scored significantly lower when compared with the healthy Dutch control sample (P < 0.05). There was a significant improvement of DHI total scores and Short Form-36 scales on physical and social functioning, role-physical functioning, role-emotional functioning, mental health and general health at 12 months after surgery when compared with preoperative scores (P < 0.05). Vestibular schwannoma patients with disabling vertigo, experience significant reduced quality of life when compared with a healthy Dutch population. Translabyrinthine tumour removal significantly improved the patients' quality of life. Surgical treatment should be considered in patients with small- or medium-sized tumours and persisting disabling vertigo resulting in a poor quality of life.

Can You Hear Me Now? Long-Term Hearing Preservation in Intracanalicular Vestibular Schwannoma

Introduction: The primary goal of treating intracanalicular vestibular schwannomas (IVS) is often hearing preservation. There are three viable approaches to this goal: watchful waiting, stereotactic radiosurgery, and microsurgical resection. We have favored microsurgical excision via the middle fossa route when hearing preservation is the patient's primary goal, but we have also utilized stereotactic radiosurgery and watchful waiting in appropriate circumstances. We review our experience in achieving the goal of hearing preservation in patients with intracanalicular vestibular schwannoma in whom a minimum of 8 years' follow-up is available. Methods: Consecutive patients evaluated with intracanalicular vestibular schwannoma at our institution were identified from clinic and hospital records and a prospectively managed data base. Pre- and serial postoperative audiometry, clinical evaluation of facial nerve function, and post-treatment complications were extracted from medical records. Serial postoperative contrast enhanced MRI were reviewed for evidence of tumor recurrence. Results: Data collection is ongoing and will be updated for the meeting. Between 1987 and 1997 we performed 36 middle fossa operations for vestibular schwannoma. Hearing preservation was attempted in 35 who had Gardner-Robertson class I or II hearing preoperatively, one of whom is lost to follow-up. Of the 34 patients, serviceable hearing was preserved in 20 (59%). In those with preserved hearing the median word recognition score is 96% and median pure tone average 33 dB. At 36 months of follow-up these values are statistically unchanged, suggesting that hearing, once preserved, is well maintained. Conclusion: When hearing is preserved after microsurgical excision of IVS it appears to be well maintained. Hearing progressively declines in untreated and radiosurgically treated patients followed up to 3 years after treatment or diagnosis. Longer follow-up of surgically treated patients, which will be presented at the meeting, will clarify the relative value of these approaches.

Hearing in Patients with Intracanalicular Vestibular Schwannomas

This paper reports data on the spontaneous course of hearing in 156 patients with purely intracanalicular vestibular schwannomas. The mean pure tone average (PTA) was 51 dB HL and the mean speech discrimination score (SDS) 60% at diagnosis. The risk of a significant subsequent hearing loss (≧10 dB PTA or ≧10% SDS) was 54% during 4.6 years of observation. Patients with normal speech discrimination at diagnosis had a significantly smaller risk of loosing hearing. The hearing loss at diagnosis and during observation was not related to age, gender, diagnostic tumor size, tumor- induced expansion of the internal auditory canal or tumor sublocalization (fundus, central or porus). However, the loss of PTA was smaller in shrinking tumors and the PTA deterioration rate correlated with the volumetric tumor growth rate. After 4.6 years observation, the PTA had increased by 14 dB to 65 dB HL, and the SDS reduced by 17% to 43%. The proportion of patients eligible for hearing preservation treatment as determined by word recognition score class I (70–100% SDS) was reduced to 28% (a 44% reduction), and by AAO-HNS class A to 9% (a 53% reduction).

Sublocalization and Volumetric Growth Pattern of Intracanalicular Vestibular Schwannomas

None of several previous reports on the growth pattern of vestibular schwannomas (VS) have dealt with the sublocalization and volumetric growth pattern of intracanalicular tumors. This paper reports such data from 196 patients. All VS patients have been registered prospectively at one center in Denmark since 1975. Data on intracanalicular tumors were drawn from the database, yielding 196 patients with a diagnostic and at least one control magnetic resonance imaging scan. All images were retrieved and the tumor sublocalization, size, and growth rate determined. The majority (50%) of the tumors was located centrally in the internal auditory canal (IAC), whereas 31% were porus-near and 19% fundus-near. Of the 196 tumors, 88 (45%) displayed growth, 20 (10%) shrinkage, and 88 (45%) remained unchanged. Thirty-eight (19%) tumors grew to extrameatal extension. Growth occurred only within 5 years after diagnosis. In the 88 growing tumors, the mean absolute growth rate was 111mm/year and the relative rate 114%/volume/year. The occurrence of IAC expansion at diagnosis was higher for tumors displaying subsequent shrinkage. Growth occurrence and rate, IAC expansion, and progression to extrameatal extension were not related to tumor sublocalization. Most intracanalicular VS are located centrally in a nonexpanded IAC at diagnosis. Growth occurs within 5 years after diagnosis in up to 45% of the tumors, although only 19% extend into the cerebellopontine angle. IAC expansion, growth occurrence, and rate are not related to tumor sublocalization. These findings justify primary observation of all purely intracanalicular tumors, unless realistic hearing preservation is intended.

Acute neurological complications following gamma knife surgery for vestibular schwannoma

The authors describe an acute facial and acoustic neuropathy following gamma knife surgery (GKS) for vestibular schwannoma (VS). This 39-year-old woman presenting with tinnitus underwent GKS for a small right-sided intracanalicular VS, receiving a maximal dose of 26 Gy and a tumor margin dose of 13 Gy to the 50% isodose line. Thirty-six hours following treatment she presented with nausea, vomiting, vertigo, diminished hearing, and a House-Brackmann Grade III facial palsy. She was started on intravenous glucocorticosteroid agents, and over the course of 2 weeks her facial function returned to House-Brackmann Grade I. Unfortunately, her hearing loss persisted. A magnetic resonance (MR) image obtained at the time of initial deterioration demonstrated a significant decrease in tumor enhancement but no change in tumor size or peritumoral edema. Subsequently, the patient experienced severe hemifacial spasms, which persisted for a period of 3 weeks and then progressed to a House-Brackmann Grade V facial palsy. During the next 3 months, the patient was treated with steroids and in time her facial function and hearing returned to baseline levels. Results of MR imaging revealed transient enlargement (3 mm) of the tumor, which subsequently returned to its baseline size. This change corresponded to the tumor volume increase from 270 to 336 mm3. The patient remains radiologically and neurologically stable at 10 months posttreatment. This is the first detailed report of acute facial and vestibulocochlear neurotoxicity following GKS for VS that improved with time. In addition, MR imaging findings were indicative of early neurotoxic changes. A review of possible risk factors and explanations of causative mechanisms is provided.

Is the middle fossa approach the treatment of choice for intracanalicular vestibular schwannoma?

To compare the 2 surgical techniques most commonly used during vestibular schwannoma (VS) surgery, i.e., the middle fossa (MF) and the retrosigmoid-transmeatal (RS-TM) routes, when hearing preservation is attempted. A longitudinal study of a series of consecutive patients operated on with the 2 techniques by the same surgeon was conducted. Selection criteria included tumor confined to the internal auditory canal (IAC) with a length ranging from 4 to 12 mm and hearing class A or B. Patients were alternately assigned to 1 of the 2 groups regardless of auditory class and distance of the tumor from the IAC fundus. Thirty-five subjects were operated on with the RS-TM technique and 35 via the MF route. No significant differences in auditory and facial nerve function results between the 2 techniques were observed. The RS-TM approach, however, showed better facial nerve results at discharge. VS size, IAC enlargement, and, particularly, the distance from the IAC fundus were found to influence the postoperative results more than the type of approach itself. The MF approach has been described as being the better technique for VS surgery in terms of auditory results. However, this claim lacks statistical substantiation because no prospective studies are to be found in the literature. The present longitudinal investigation shows that the MF approach does not afford any particular advantages over the RS-TM route in terms of auditory results in intracanalicular VS, with the exception of tumors reaching the IAC fundus.

Conservative management versus surgery for small vestibular schwannomas

ConclusionA high rate of deterioration in hearing function and the loss of patient compliance during conservative management should be taken into account when considering hearing preservation strategies for patients with vestibular schwannoma (VS).ObjectiveTo compare conservative management with surgery for solitary small VS.Material and methodsAmong 693 patients followed up for VS between 1991 and 2002, 114 (16%) intracanalicular VSs (stage 1) and 302 (44%) VSs measuring <15 mm in the cerebellopontine angle (stage 2) were included in this study. Initially, surgery was performed in 305 (73%) cases (50 stage 1, 255 stage 2) and 111 (27%) were managed conservatively (64 stage 1, 54 stage 2) by means of annual MRI scans and audiometry. Conservative management was chosen in patients aged >60 years and in those who refused surgery. In this subgroup, the mean follow-up period was 33 months (range 6–111 months).ResultsIn the conservative management group, 47% of VSs showed significant growth, 47% were stable and 6% showed regression. Seventeen patients (15%) were operated on secondarily for tumour growth and 1 (1%) was irradiated for tumour growth and because surgery was contraindicated. Deterioration of hearing function by ≥1 class was observed in 56% of cases, 34% of patients were initially in hearing class D and only 10% showed stable hearing function. Of the conservative management group, 17% were lost during follow-up. After surgery, grade 1 or 2 facial function was obtained in 86% of cases. Following hearing preservation attempts (n=137), 54% of patients were in hearing classes A–C.

Meningioma of the internal auditory canal

A comprehensive literature search identified only 14 well-documented cases of intracanalicular meningioma. A case is presented of meningioma confined to the internal auditory canal which was excised using a sub-occipital retrosigmoid approach. Preoperative MRI and CT scans were suggestive of intracanalicular vestibular schwannoma. Only the intraoperative findings, which were confirmed by the histological data, revealed that the tumor was a meningioma. We review the literature and discuss the diagnostic and therapeutic issues relating to these tumors.

Effect of subpixel magnetic resonance imaging shifts on radiosurgical dosimetry for vestibular schwannoma

Object. The purpose of this study was to evaluate subpixel magnetic resonance (MR) imaging shifts of intracanalicular vestibular schwannomas (VSs) with respect to the internal auditory canal (IAC) as documented on computerized tomography (CT) scanning and to investigate the source of imaging-related localization errors in radiosurgery as well as the effect of such shifts on the dosimetry for small targets. Methods. A shift of the stereotactic coordinates of intracanalicular VSs between those determined on MR imaging and those on CT scanning represents an error in localization. A shift vector places the tumor within the IAC and measures the CT scan/MR image discrepancy. The shift vectors were measured in a series of 15 largely intracanalicular VSs (all &lt; 1.5 cm3 in volume). Using dose volume histogram measurements, the overlap between shifted and unshifted tumors and radiosurgical treatment plans were measured. Using plastic and bone phantoms and thermoluminescent dosimetry measurements, the correspondence between CT and MR imaging targets and treatments delivered using the Leksell gamma knife were measured. Combining these measurements, the correspondence between intended and actual treatments was measured. Conclusions. The delivery of radiation to CT-imaged targets was accurate to the limits of measurement (∼ 0.1 mm). The MR imaging shifts seen in the y axis averaged 0.9 mm and in the z axis 0.8 mm. The corresponding percentage of tumor coverage with respect to apparent target shift decreased from 98 to 77%. This represents a significant potential error when targets are defined solely by MR imaging.

Intracanalicular Meningioma

Intracanalicular meningiomas are extremely rare and difficult to differentiate from intracanalicular vestibular schwannomas. We report an unusual case of a posterior fossa meningioma in the proximal internal auditory canal that was originally diagnosed as a vestibular schwannoma due to its appearance on magnetic resonance imaging. However, closer inspection of the preoperative neuroimages revealed features inconsistent with vestibular schwannoma that suggested the possibility of other less common lesions.

Intracanalicular Meningioma

Intracanalicular meningiomas are extremely rare and difficult to differentiate from intracanalicular vestibular schwannomas. We report an unusual case of a posterior fossa meningioma in the proximal internal auditory canal that was originally diagnosed as a vestibular schwannoma due to its appearance on magnetic resonance imaging. However, closer inspection of the preoperative neuroimages revealed features inconsistent with vestibular schwannoma that suggested the possibility of other less common lesions.