[Macroscopic and microscopic changes of the vestibulocochlear nerve after Gamma Knife treatment]. / Makroskopische und mikroskopische Veränderungen des N. vestibulocochlearis nach Gamma-Knife-Therapie.

We report on a case in which macroscopic and microscopic changes of the vestibulocochlear nerve could be observed after radiosurgery of an intrameatal vestibular schwannoma. This case shows for the first time a morphological correlate for undesirable effects after radiosurgical treatment of a vestibular schwannoma and indicates that despite a certain distance to the actual tumor, degenerative changes in neural structures can be expected.

MRI surveillance following concurrent cochlear implantation in cases of vestibular schwannoma resection.

OBJECTIVE: Cochlear nerve preserving translabyrinthine vestibular schwannoma (VS) resection enables concurrent cochlear implantation. Implantation in patients with VS raises important concerns including the ability to undergo postoperative magnetic resonance imaging (MRI) monitoring of residual tumor growth or tumor recurrence, specifically with a retained magnet. We aim to assess the feasibility of MRI monitoring and the impact on image quality with retained cochlear implant (CI) magnets. METHODS: Retrospective review of post-operative head MRI scans in CI recipients with a retained CI magnet, after cochlear nerve preserving translabyrinthine excision of VS. The ability to visualize the ipsilateral and contralateral internal auditory canal (IAC) and cerebellopontine angle (CPA) were assessed. RESULTS: A total of eight surveillance head MRI were performed in six patients. In one case, in which the receiver was positioned lower, the view of the ipsilateral IAC and CPA was distorted. In all other cases, the views of both the ipsilateral and contralateral IAC and CPA were overall unimpaired. DISCUSSION: Imaging artifact only very rarely impedes adequate visualization of the ipsilateral IAC or CPA in CI recipients. In anticipation of the need for further IAC and CPA imaging, it would be advisable to place the receiver in an exaggerated superior-posterior position to further decrease obscuring artifact. Thus, serial monitoring of VS tumors can be performed safely with preservation of image quality with a retained receiver magnet. CONCLUSIONS: When placing the CI receiver-stimulator farther posterior-superiorly, excellent visualization of the IAC and CPA can be accomplished without significantly impairing the image quality.

Sporadic and NF2-associated vestibular schwannoma surgery and simultaneous cochlear implantation: a comparative systematic review.

PURPOSE: Cochlear implantation (CI) in patients with sensorineural hearing loss caused by a vestibular schwannoma (VS) represents a unique subtype of hearing rehabilitation, as the outcome may be compromised by vestibulocochlear nerve injury as part of the natural VS history or due to iatrogenic trauma induced by surgical tumor removal. This paper aims to review and report contemporary knowledge and practice regarding feasibility and outcomes of simultaneous vestibular schwannoma resection and cochlear implantation to serve as a reference and guide for future surgery and studies. METHODS: The current literature was searched systematically according to the PRISMA guidelines and after criteria-based selection, 29 studies were identified, including a total of 86 patients who had undergone surgical resection of a vestibular schwannoma and subsequent cochlear implantation in a single procedure. RESULTS: The postoperative outcomes were reported with a high degree of heterogeneity, hindering a proper meta-analysis. However, pooling those cases with reported speech discrimination outcomes demonstrated mean scores equivalent to moderate-to-high performance. A few cases had no audibility. A positive cochlear nerve test result was not a secure positive predictor of success. Complications were rare. CONCLUSION: NF2-associated and sporadic VS had good and comparable postoperative outcomes despite significant differences in tumor size, location and surgical approach.

Radiosurgery treatment is associated with improved facial nerve preservation versus repeat resection in recurrent vestibular schwannomas.

BACKGROUND: Vestibular schwannomas (VSs) are benign neoplasms of the Schwann cells of cranial nerve VIII, and treatment of VS typically involves surgical resection. However, tumor recurrence may necessitate reintervention, and secondary treatment modalities include repeat surgical resection or adjuvant radiosurgery. The purpose of this study is to examine the scientific literature in order to determine whether surgical resection or radiosurgery for recurrent VS results in better tumor control, hearing preservation, and preservation of facial nerve function. METHODS: The PubMed, Scopus, Embase, Cochrane, and Web of Science databases were searched for studies reporting on patients undergoing either radiosurgery or repeat surgical resection after primary surgical resection for recurrent VS. Statistical analyses were performed on the compiled data, primarily outcome data involving tumor control, hearing preservation, and preservation of facial nerve function. RESULTS: We analyzed the data of 15 individual studies involving 359 total patients, and our results reveal that tumor control rates are comparable between adjuvant radiosurgery (91%, CI: 88-94%) and secondary resection (92%, CI 75-98%). However, adjuvant radiosurgery was shown to preserve good facial nerve function better (94%, CI 84-98%) compared to secondary surgical resection (56%, CI 41-69%). CONCLUSION: With comparable tumor control rates and better preservation of good facial nerve function, this study suggests that secondary radiosurgery for recurrent VS is associated with both optimal tumor control and preservation of good facial nerve function.

An allograft mouse model for the study of hearing loss secondary to vestibular schwannoma growth.

Vestibular schwannoma is a benign neoplasm arising from the Schwann cell sheath of the auditory-vestibular nerve. It most commonly affects both sides in the genetic condition Neurofibromatosis type 2, causing progressive high frequency sensorineural hearing loss. Here, we describe a microsurgical technique and stereotactic coordinates for schwannoma cell grafting in the vestibular nerve region that recapitulates local tumor growth in the cerebellopontine angle and inner auditory canal with resulting hearing loss. Tumor growth was monitored by bioluminescence and MRI in vivo imaging, and hearing assessed by auditory brainstem responses. These techniques, by potentially enabling orthotopic grafting of a variety of cell lines will allow studies on the pathogenesis of tumor-related hearing loss and preclinical drug evaluation, including hearing endpoints, for NF2-related and sporadic schwannomas.

Microvascular decompression for typewriter tinnitus-case report.

BACKGROUND: Microvascular decompression has been tested as a treatment for tinnitus. METHODS: However, only a fraction of patients appear to benefit from surgery if the combination of findings such as paroxysmal vertigo, ABR changes and tinnitus is used to select patients for microvascular decompression. RESULTS: Instead, a more specific syndrome of staccato or "typewriter" tinnitus, which is highly responsive to carbamazepine, was suggested to be caused by a neurovascular conflict. CONCLUSION: We present the first case of typewriter tinnitus with complete long-term symptom relief following microvascular decompression of the vestibulocochlear nerve. We suggest that this specific syndrome is caused by a neurovascular conflict and treatable by microvascular decompression.

Surgical treatment of jugular foramen meningiomas.

OBJECT: We present our experience with surgery of jugular foramen meningiomas with special consideration of clinical presentation, surgical technique, complications, and outcomes. METHODS: This retrospective study includes three patients with jugular foramen meningiomas treated by the senior author between January 2005 and December 2010. The initial symptom for which they sought medical help was decreased hearing. In all of the patients there had been no other neurological symptoms before surgery. The transcondylar approach with sigmoid sinus ligation at jugular bulb was suitable in each case. RESULTS: No death occurred in this series. All of the patients deteriorated after surgery mainly due to the new lower cranial nerves palsy occurred. The lower cranial nerve dysfunction had improved considerably at the last follow-up examination but no patient fully recovered. Two of three patients with preoperatively impaired yet functional hearing deteriorated after surgery with no subsequent cranial nerve VIII function improvement. In one case postoperative stereotactic radiosurgery was performed due to non-radical tumour resection (Simpson Grade IV) and tumour remnant proved stable in the 4-year follow-up. None of the patients have shown signs of tumour recurrence in the mean follow-up period of 56 months. CONCLUSIONS: Jugular foramen meningiomas represent one of the rarest subgroups of meningiomas and their surgical treatment is associated with significant risk of permanent cranial nerve deficits.

Microvascular decompression of cochleovestibular nerve in patients with tinnitus and vertigo.

AIM: The aim of this study was to investigate the patient selection, indications for operation, surgical methods and effects of microvascular decompression (MVD) for treatment of intractable and incapacitating tinnitus and vertigo. MATERIALS AND METHODS: A total of 35 patients were recruited from January 2009 to June 2010 for the MVD surgery. RESULTS: Arterial compression of cochleovestibular nerve was found in all the 35 patients. The immediate effect of MVD was observed in 22 patients with tinnitus and 10 patients with vertigo. The follow-up data for the effect of MVD showed complete resolution of tinnitus in 14 patients and vertigo in 6 patients. CONCLUSIONS: Vascular compression of cochleovestibular nerve in cerebellopontine angle may be one of the causes of intractable and incapacitating tinnitus and/or vertigo. MVD may be a safe and effective surgical procedure for treatment of severe tinnitus and/or vertigo in patients.

Use of piezosurgery for internal auditory canal drilling in acoustic neuroma surgery.

BACKGROUND: Piezosurgery is based on microvibrations generated by the piezoelectrical effect and has a selective bone-cutting ability with preservation of soft tissue. This study examined the applicability of Piezosurgery compared to rotating drills (RD) for internal auditory canal (IAC) opening in acoustic neuroma (AN) surgery. MATERIALS AND METHODS: Piezosurgery was used in eight patients for IAC drilling in AN surgery. After exposition of the IAC and tumor, the posterior wall of the IAC was drilled using Piezosurgery instead of RD. Piezosurgery was evaluated with respect to practicability, safety, preciseness of bone cutting, preservation of cranial nerves, influences on neurophysiological monitoring, and facial nerve and hearing outcome. RESULTS: Piezosurgery was successfully used for selective bone cutting, while cranial nerves were structurally and functionally preserved, which could be measured by means of neuromonitoring. Piezosurgery guaranteed a safe and precise cut by removing bone layer by layer in a shaping way. Compared to RD, limited influence on neurophysiological monitoring attributable to Piezosurgery was noted, allowing for continuous neuromonitoring. No disadvantage due to microvibrations was noticed concerning hearing function. The angled tip showed better handling in right-sided than in left-sided tumors in the hands of a right-handed surgeon. The short, thick handpiece may be improved for more convenient handling. CONCLUSION: Piezosurgery is a safe tool for selective bone cutting for opening of the IAC with preservation of facial nerve and hearing function in AN surgery. Piezosurgery has the potential to replace RD for this indication because of its safe and precise bone-cutting properties.

Intraoperative continuous monitoring of evoked facial nerve electromyograms in acoustic neuroma surgery.

BACKGROUND: Preservation of facial nerve function is one of the most important goals in acoustic neuroma surgery. We have been using intraoperative continuous monitoring of evoked facial nerve electromyograms (EMGs) since 1997 in acoustic neuroma surgery. We therefore investigated surgically treated patients to clarify the usefulness of this monitoring, and to determine safety criteria for preserving facial nerve function. METHODS: This intraoperative continuous monitoring of evoked facial nerve EMG is a method for checking the EMG evoked by continuous direct electrical stimulation of the facial nerve during tumor excision. The greatest advantage of this method is the ability to identify changes in EMG in real time. We retrospectively investigated 216 patients with surgically treated acoustic neuroma to identify correlations between parameters in this monitoring and postoperative facial nerve function immediately and 1 year after surgery. RESULTS: In these patients, the functional preservation rate of the facial nerve (House and Brackmann grade 1 or 2 at 1 year after surgery) was 98.6% with a 98.2% mean tumor resection rate. Amplitude preservation ratio correlated significantly with facial nerve function both immediately and 1 year after surgery. To avoid severe facial nerve palsy, a warning criterion of amplitude preservation ratio >50% appears useful. CONCLUSIONS: Postoperative course of facial nerve function appears predictable using intraoperative continuous monitoring of evoked facial nerve EMGs. This monitoring is useful to increase the tumor excision rate while avoiding severe postoperative facial nerve palsy in acoustic neuroma surgery.

Culprit vascular patterns and surgical outcomes of hemifacial spasm caused by an AICA segment passing between cranial nerve VII and VIII: A series of 25 cases.

OBJECTIVE: To report the vascular anatomic characteristics and surgical outcomes of hemifacial spasm (HFS) caused by an anterior inferior cerebellar artery (AICA) segment passing between cranial nerve VII (CN VII) and cranial nerve VIII (CN VIII). PATIENTS AND METHODS: This case series study retrospectively reviewed records of 1040 consecutive patients treated with MVD for HFS in our hospital in 10 years. 25 patients had the culprit vessel recorded as an AICA segment passing between CN VII and CN VIII. Vascular anatomic characteristics were reviewed from intraoperative microscopic videos. The clinical outcomes were followed up at 3-month and 1-year time points. RESULTS: The culprit AICA segments feature 3 discrete anatomic patterns. The patterns denoted as pattern A, B, and C were identified in 19(76%), 3(12%), and 3 (12%) of the 25 patients respectively. Postoperative spasm relief were achieved in 19(76%), 22(88%), and 23 (92%) of the patients at immediately after surgery, 3-month, and 1-year follow-up respectively. 3(12%) of them have permanent postoperative cranial nerve deficits, including one patient with hearing loss and 2 patients with vocal cord palsy. CONCLUSIONS: Though an AICA segment passing between CN VII and CN VIII is common, very rarely it was deemed the culprit for HFS in our patients. We used fREZ centered definition and operation. We found the culprit AICA segments feature 3 discrete anatomic patterns. We observed good spasm relief outcome and relatively fewer complications with CN VII and CN VIII. Identifying the 3 anatomic patterns may help with a smooth decision-making when vascular compression by an AICA segment passing between CN VII and CN VIII is suspected.

Applying artificial intelligence to longitudinal imaging analysis of vestibular schwannoma following radiosurgery.

Artificial intelligence (AI) has been applied with considerable success in the fields of radiology, pathology, and neurosurgery. It is expected that AI will soon be used to optimize strategies for the clinical management of patients based on intensive imaging follow-up. Our objective in this study was to establish an algorithm by which to automate the volumetric measurement of vestibular schwannoma (VS) using a series of parametric MR images following radiosurgery. Based on a sample of 861 consecutive patients who underwent Gamma Knife radiosurgery (GKRS) between 1993 and 2008, the proposed end-to-end deep-learning scheme with automated pre-processing pipeline was applied to a series of 1290 MR examinations (T1W+C, and T2W parametric MR images). All of which were performed under consistent imaging acquisition protocols. The relative volume difference (RVD) between AI-based volumetric measurements and clinical measurements performed by expert radiologists were + 1.74%, - 0.31%, - 0.44%, - 0.19%, - 0.01%, and + 0.26% at each follow-up time point, regardless of the state of the tumor (progressed, pseudo-progressed, or regressed). This study outlines an approach to the evaluation of treatment responses via novel volumetric measurement algorithm, and can be used longitudinally following GKRS for VS. The proposed deep learning AI scheme is applicable to longitudinal follow-up assessments following a variety of therapeutic interventions.

Long-term effects of vestibular compensation on balance control and sensory organisation after unilateral deafferentation due to vestibular schwannoma surgery.

The time-course of central adaptive mechanisms after vestibular schwannoma surgical removal allows, 3 months after surgery (middle term), a satisfactory recovery of balance control. However, the long-term evolution of postural control beyond the end of usual medical follow-up remains unknown. This longitudinal prospective study aimed to assess the long-term effects of vestibular compensation on balance control and sensory organisation in patients operated on for vestibular schwannoma. Thirty-six patients with vestibular schwannoma underwent vestibular and sensory organisation tests, shortly before and 3 months, 6 months and 1 year after surgery. Postural control performances improved 3 months after surgery compared with before surgery; they continued to improve at 6 and 12 months after surgery, especially in conditions highly soliciting vestibular information. In the long term, strategies based on sensorimotor and/or behavioural substitution seem to be reinforced and fine-tuned, particularly in complex postural situations, for which only vestibular information is reliable to control balance.

Exercise with visual feedback improves postural stability after vestibular schwannoma surgery.

We analyzed the effect of 2-week individualized visual feedback-based balance training on the postural control of patients undergoing retrosigmoid microsurgical removal of vestibular schwannoma. We performed prospective evaluation of 17 patients allocated into two groups: feedback group (9 patients, mean age 37 years) and standard physiotherapy group (8 patients, mean age 44 years). Patients in both the groups were treated once per day by intensive rehabilitation from 5th to 14th postoperative day. Rehabilitation of patients in the feedback group was performed using the visual feedback and force platform. Results were evaluated on the beginning and at the end of rehabilitation program (e.g. 5th and 14th postoperative day). Outcome measures included posturography during quiet stance under four different conditions by the modified Clinical Test for Sensory Interaction of Balance. Body sway was evaluated from center of foot pressure. Compensation of Center of pressure (CoP) parameters in stance on firm surface was similar in the control and feedback groups. However, in stance on foam surface with eyes closed the patients from the feedback group were better compensated and CoP parameters differed significantly (p < 0.05). This prospective clinical study suggests that specific exercises with visual feedback improve vestibulospinal compensation in patients after vestibular schwannoma surgery and thus can improve their quality of life.

A Study of Outcome of Pediatric Cochlear Implantation in Patients with Cochleovestibular Nerve Deficiency.

OBJECTIVES: A cochleovestibular nerve deficiency (CVND) could compromise stimulation of nerve by electrical pulses delivered from a cochlear implant, thereby hindering activity along auditory pathway. The evaluation of children with congenital hearing loss with a high-resolution magnetic resonance imaging is presently the investigative modality of choice to diagnose CVND. The aim of this study was to determine the outcomes in pediatric cochlear implant recipients with a diagnosis of CVND. The objectives included (1) to study the prevalence of CVND among children with prelingual congenital severe to profound hearing loss; (2) to assess post cochlear implantation (CI) outcomes in children with CVND using categories of auditory performance (CAP), speech intelligibility rating (SIR), and cortical auditory evoked potentials (CAEPs); and (3) to propose a management protocol for these children. MATERIALS AND METHODS: All CI procedures performed during the study period in children 5 years or younger were included in study. All patients who were older than 5 years or had syndromic associations, multiple disabilities, second side or revision CI were excluded from the study. Children with unilateral cochleovestibular nerve aplasia and all other cases of CVND (type IIa and IIb) were advised to undergo CI on side with more radiologically robust nerve and/or cochlea anatomy. Children with bilateral CVND were included in group A, and age-matched cochlear implant candidates with normal cochleovestibular nerve anatomy were included in group B for statistical comparison of outcomes. RESULTS: In group A, post CI CAP and SIR, CAEP amplitude and latency at 12 months showed statistically significant difference (p<0.05) compared with preoperative values. However, mean score of CAEP latency and amplitude and SIR score was worse for group A compared with group B at 12 months, which was statistically significant (p<0.05). CONCLUSION: This study supports the fact that CI is a viable option to be offered in children with CVND (type IIa and IIb) for the development of auditory perception and speech.

Auditory frequency-following response: neural or artifact?

An electrical response which reproduces the waveform and frequency of the sound stimulus can be recorded from the central neural pathway for audition. Controversy has existed for some years over whether this frequency-following response (FFR) is neural or an artifact such as remote pickup of the cochlear microphonic or cross talk in the recording system. Two experiments resolve this issue by demonstrating that the frequency-following response depends upon functionally intact neural pathways. The frequency-following response, as well as auditory evoked potentials, is abolished by section of the eighth nerve; it is reversibly abolished by cooling of the cochlear nucleus.

Middle fossa approach: microsurgical anatomy and surgical technique from the neurosurgical perspective.

BACKGROUND: The purpose of this study was to call attention to the subtemporal approach directed through the petrous apex to the IAM. We studied the microsurgical anatomy of the middle floor to delineate a reliable angle between the GSPN and the IAM to precisely localize and expose the IAM from above. A new technique for the elevation of middle fossa floor in an anterior-to-posterior direction has also been examined in cadaveric dissections and performed in surgery. METHODS: The microsurgical anatomy of the middle fossa floor was studied in 10 adult cadaveric heads (20 sides) after meatal drilling on the middle fossa. Five latex-injected specimens were dissected in a stepwise manner to further define the microsurgical anatomy of the middle fossa approach. The middle fossa approach is illustrated in a patient for the decompression of the facial nerve to demonstrate the surgical technique and limitations of bone removal. RESULTS: Elevation of middle fossa dura in an anterior-to-posterior direction leads to early identification of the GSPN, where the nerve passes under V3. The most reliable and easily appreciated angle to be used in localizing the IAM is between the IAM and the long axis of the GSPN, which is approximately 61 degrees . Beginning drilling the meatus medially at the petrous ridge is safer than beginning laterally, where the facial and vestibulocochlear nerves become more superficial. The cochlea anteromedially, vestibule posterolaterally, and superior semicircular canal posteriorly significantly limit the bone removal at the lateral part of the IAM. CONCLUSIONS: The surgical technique for the middle fossa approach which includes an anterior-to-posterior elevation of middle fossa dura starting from the foramen ovale and uses the angle between the IAM and the long axis of the GSPN to localize the meatus from above may be an alternative to previously proposed surgical methods.

Fusion as an evolutionary principle of the vertebrate labyrinth.

OBJECTIVES: This study was undertaken to demonstrate changes in the innervation of vestibular and auditory sense organs with the evolutionary ascent of the vertebrate labyrinth. METHODS: Dissected labyrinths and their nerve supply prepared by the Sudan black B technique of Rasmussen were examined and photographed with a Canon A100 camera interfaced with a Zeiss operating microscope. RESULTS: In lizards and alligators, the utricular sense organ is represented by 2 small maculae, each with a separate nerve branching off the ampullary nerves to the anterior and lateral canal cristae. These 2 maculae fuse into a bilobed macula with ascent in frogs and pigeons, eventually becoming a single large macula with its nerve supply from the superior vestibular division in guinea pigs, cats, lions, monkeys, and humans. Along with these changes, there is a fusion of the lateral and anterior canal ampullary nerves and of the bifurcating branches of the vertical canal ampullary nerves. The saccular macula is single, but receives a dual innervation from the superior division (anterior ramus) and the inferior division (posterior ramus) of the eighth nerve in alligators, pigeons, guinea pigs, cats, lions, monkeys, and humans. The main innervation is usually from the inferior division; however, saccular innervation is from the inferior division in lizards and from the superior division in frogs. The auditory sense organ is represented by a curved tube with a low-frequency receptor (lagena) at its distal end in lizards, alligators, and pigeons. In mammals, in which there is a coiled cochlea with a variable number of turns, low frequencies are recorded at the apical turn. This configuration may represent fusion of the lagena into the apical end of the auditory sense organ. CONCLUSIONS: Fusion of sense organs and of their nerve supply appears to be an evolutionary principle in the vertebrate labyrinth.

Radiobiology of vestibular schwannomas: mechanisms of radioresistance and potential targets for therapeutic sensitization.

Vestibular schwannomas (VS) are benign tumors arising from the Schwann cells of cranial nerve VIII. Historically the prevailing therapy for patients with VS has been microsurgical resection. More recently, stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy have gained acceptance as effective alternatives. Although the side effect profile and rates of tumor control appear to be favorable for SRS, there is a subset of radioresistant tumors that continue to progress despite properly administered radiation treatment. In this review, the authors summarize what is known about the mechanism of radioresistance in VS at the clinical and molecular level. An improved understanding of the radiobiological behavior of VS may help guide appropriate patient selection for SRS and potentially aid in the design of novel therapies to treat radioresistant tumors.

Atypic geniculate neuralgia: atypic anatomic correlation of cranial nerve roots and AICA.

Geniculate neuralgia is a rare cause of craniofacial pains. The anterior inferior cerebellar artery is the offending vessel which compress nervus intermedius in the patients with typical geniculate neuralgia. We report a patient whose pain was atypical for either geniculate neuralgia and trigeminal neuralgia. At operation the anterior inferior cerebellar artery was coursing with the nerves and was separated. After the decompression the pain resolved immediately.