Clinical Profile and Results Obtained in Patients Treated by Auditory Brainstem Implants

INTRODUCTION

Cochlear implants have been able to treat some types of hearing loss, but those related to cochlear nerve impairment made it necessary to find new ways to manage these deficits; leading to auditory brainstem implants (ABI).

AIM

Our objective is to present the clinical profile of patients treated through an ABI and the results obtained from 1997 to 2017.

MATERIAL AND METHODS

On the one hand, patients with statoacoustic nerve tumours (VIIIcranial nerve) were selected, and on the other hand, patients withoutVIII tumours with congenital malformations of the inner ear. Before and after the placement of the ABI, hearing was assessed through tonal audiometry, from which the PTA (Pure Tone Average) and the CAP (Categories of Auditory Performance) scale were obtained.

RESULTS

A total of 20 patients undergoing ABI surgery were included. Eight were of tumour cause (40%) and 12 non-tumour (60%). In 15 subjects (75%) a suboccipital approach was performed and in 5 (25%) translabyrinthine. The mean of active electrodes before the implantation of Cochlear® (Nucleus ABI24) was 13/21 (61.90%) versus 8.5/12 (70.83%) of the Med-el® (ABI Med-el). An improvement in the mean PTA of 118.49dB was found against 46.55dB at 2years. On the CAP scale, values of1 were obtained in the preimplantation and of 2.57 (1-5) in the 2-year revision.

CONCLUSION

The ABI is a safe option, and with good hearing results when the indication is made correctly.

Clinical role of electrocochleography in children with auditory neuropathy spectrum disorder

OBJECTIVES

To assess electrocochleography (ECochG) to tones as an instrument to account for CI speech perception outcomes in children with auditory neuropathy spectrum disorder (ANSD).

MATERIALS & METHODS

Children (<18 years) receiving CIs for ANSD (n = 30) and non-ANSD (n = 74) etiologies of hearing loss were evaluated with ECochG using tone bursts (0.25-4 kHz). The total response (TR) is the sum of spectral peaks of responses across frequencies. The compound action potential (CAP) and the auditory nerve neurophonic (ANN) in ECochG waveforms were used to estimate nerve activity and calculate nerve score. Performance on open-set monosyllabic word tests was the outcome measure. Standard statistical methods were applied.

RESULTS

On average, TR was larger in ANSD than in non-ANSD subjects. Most ANSD (73.3%) and non-ANSD (87.8%) subjects achieved open-set speech perception; TR accounted for 33% and 20% of variability in the outcomes, respectively. In the ANSD group, the PTA accounted for 69.3% of the variability, but there was no relationship with outcomes in the non-ANSD group. In both populations, nerve score was sensitive in identifying subjects at risk for not acquiring open-set speech perception, while the CAP and the ANN were more specific.

CONCLUSION

In both subject groups, the TRs correlated with outcomes but these measures were notably larger in the ANSD group. There was also strong correlation between PTA and speech perception outcome in ANSD group. In both subject populations, weaker evidence of neural activity was related to failure to achieve open-set speech perception.

[Tinnitus in patients with hemifacial spasm: a treatable combination?]

BACKGROUND

About 5-15% of people in the Western world will suffer from an extended period of tinnitus during their lifetime. This is often a non-treatable, disabling disorder. Tinnitus can be classified as pulsatile or non-pulsatile. Pulsatile tinnitus can be caused by a treatable neurovascular compression.

CASE DESCRIPTION

Here we describe two patients, a 68-year old woman and 40-year old man suffering from pulsatile tinnitus and hemifacial spams due to neurovascular compression of the facial and acoustic nerve in the anterior cranial fossa. After microvascular decompression using the Jannetta procedure, in which a sponge was placed between the blood vessel and the nerve, the tinnitus and hemifacial spasm disappeared.

CONCLUSION

Recognition of hemifacial spasm in patients with tinnitus is important because the symptoms are treatable when it is due to neurovascular compression. Because hemifacial spasm can manifest in subtle forms - for instance unilateral blinking - this important symptom can easily be overlooked.

Auditory brainstem implantation after unsuccessful cochlear implantation of children with clinical diagnosis of cochlear nerve deficiency

OBJECTIVES

We compared the perceptual auditory abilities of 21 children with suspected cochlear nerve deficiency (CND) and a surgically verified absent cochlear nerve (CN) who first underwent cochlear implantation (CI) and subsequently underwent auditory brainstem implantation (ABI).

METHODS

In this retrospective cohort study, from 2000 to 2011, 21 children initially underwent CI at an outside institution and failed to progress in their perceptual auditory abilities. Before CI, all of the children had severe to profound sensorineural hearing loss and a diagnosis of CND. Magnetic resonance imaging (MRI) documented an absent CN in 13 children and a small CN in 8 children. We performed explantation of the cochlear implant and simultaneous ABI on the same side. We performed MRI if no previous MRI results were available. All surgical videos were reviewed to determine the presence or absence of the CN. Measures of the patients' perceptual auditory abilities obtained after CI and after ABI were converted to the Category of Auditory Performance (CAP) scale.

RESULTS

At surgery, all patients demonstrated an absent CN. After CI, all patients had a CAP score of 2 or less (mean, 0.52 +/- 0.68). After ABI, all patients had a CAP score of 2 or more (mean, 4.33 +/- 1.68); the improvement was statistically significant (p < 0.001). The complication rates were similar for CI and ABI.

CONCLUSIONS

In this cohort of patients who had poor performance after CI, ABI achieved significantly improved performance as measured by the CAP and was shown to successfully rehabilitate hearing. Cases of a small CN may in reality represent an absent CN. Although this cohort was selected from patients with failed CI, the results have implications for the selection of device for patients with CND, in that ABI is a potential alternative to CI in select cases. In patients who fail to progress with intensive rehabilitation with CI or who have no progression in evoked auditory brainstem response, ABI must be considered early.

Auditory neuropathy spectrum disorder: predictive value of radiologic studies and electrophysiologic tests on cochlear implant outcomes and its radiologic classification

CONCLUSION

The width of the bony cochlear nerve canal (BCNC) and the size of the cochlear nerve are reliable predictors of long-term speech perception abilities for children with auditory neuropathy spectrum disorder (ANSD) after cochlear implantation (CI). In addition, electrical stapedial reflex (ESR) and electrical compound action potential (ECAP) also have considerable value in predicting postoperative speech perception abilities in these children.

OBJECTIVES

To assess whether speech perception abilities after CI in children with ANSD can be predicted from the results of radiologic studies and electrophysiologic tests.

METHODS

Fifteen children with ANSD underwent CI. The width of the BCNC and the size of the cochlear nerve were measured using preoperative CT and MRI. The results of early postoperative ESR, ECAP, and implant evoked electrical auditory brainstem response were reviewed. The latest speech perception test scores were also reviewed.

RESULTS

Radiologic findings of normal BCNC and normal cochlear nerve correlated with excellent speech perception abilities after CI. A narrow or obliterated BCNC and a deficient cochlear nerve correlated with poor speech perception abilities. Children with good speech perception abilities showed robust responses on ESR and ECAP, but there were no responses from any of the children with poor speech perception abilities.

A 47-year old male with a cerebellopontine angle tumor

A 47-year old man presented with a five-year history of fluctuating hearing impairment in the left ear. There was no tinnitus or vertigo. Imaging studies demonstrated a contrast-enhancing cerebellopontine angle mass in the left internal auditory canal. Surgically the lesion was attached to the cochlear nerve. Pathological evaluation revealed what is best described as an angiolipomatous hamartoma of the cochlear nerve. Similar lesions have only rarely been described.

Microsurgery for vestibular schwannoma after gamma knife radiosurgery

BACKGROUND

We evaluated the clinical characteristics of microsurgery for vestibular schwannoma (VS) after failed gamma knife radiosurgery (GKS).

METHOD

Twelve patients, 5 men and 7 women aged 19 to 70 years (mean 54.5 years), who underwent microsurgery after failed GKS for VS were studied retrospectively.

FINDINGS

The median interval between GKS and microsurgery was 28.8 months (range, 6.6-120 months) and 4 patients had undergone previous microsurgery. The mean volume of tumour at GKS was 6.9 cm(3) (range, 0.5-19.7 cm(3)) and the mean prescription dose to the tumour margin was 12.3 Gy. Microsurgery involved the lateral suboccipital approach in all patients. Tumour expansion involved solid enlargement in 7 patients, cystic enlargement in 3, and central necrosis in 2. Bleeding was slight in all patients except in one, probably because of the previous irradiation. Adhesion to the brain stem was severe in 7 patients. Identification of the facial nerve was easy in 5 operations and difficult in 7. Dissection of the tumour from the facial nerve was difficult in most interventions because of severe adhesions or colour change. Severe adhesions between the trigeminal nerve and the tumour was observed in 2 patients. The tumour was subtotally removed except around the internal auditory canal in most patients. Only one residual tumour increased in size and needed second GKS. The function of the facial nerve deteriorated in 3 patients, was unchanged in 7, and improved in 2. All patients had lost hearing on the affected side at the time of microsurgery.

CONCLUSIONS

Microsurgery for VS after failed GKS presents some technical difficulties. Dissection of the tumour from the facial nerve or brain stem is likely to be difficult. We recommend subtotal resection without dissection of the facial nerve and tumour, because growth of the residual tumour was rare in our series.

Vestibular schwannoma volume as a predictor of hearing outcome after surgery

OBJECTIVES

To validate the prognostic capacity of several preoperative and intraoperative parameters of hearing preservation after vestibular schwannoma surgery.

STUDY DESIGN

A retrospective study of a consecutive series of 29 patients treated with the enlarged middle cranial fossa approach. Quantitative parameters were tumor volume, linear tumor size, pure-tone and speech audiometry, pure-tone average, speech discrimination score, speech reception threshold, auditory brainstem response (ABR; intra-aural interpeak latency I-V, interaural wave V latency difference), and the vestibular caloric test (speed and frequency). Qualitative parameters were fundus involvement by the tumor (in magnetic resonance imaging and surgical record), nerve of tumor origin (in magnetic resonance imaging and surgical record), ABR parameters (well-shaped ABRs: waves I, III, and V present; presence of wave V).

METHODS

All patients were divided into 2 groups on the basis of postoperative hearing: preserved hearing (55%) or nonpreserved hearing (45%). The Kolmogorov-Smirnov test was used to evaluate normality of distribution for continuous data. The t test was applied for normally distributed continuous data and the Mann-Whitney test for nonnormally distributed continuous data. The chi2 test was used for comparisons of categoric data.

RESULTS

Tumor volume was found to be the only statistically significant prognostic parameter for hearing preservation (p = 0.007). The cutoff point for the "critical" tumor volume for hearing preservation was calculated to 0.20 cm. None of the other parameters reached statistical significance.

CONCLUSION

Tumor size is a predictive factor for hearing preservation after vestibular schwannoma surgery, and patients with smaller tumors, based on volume measurement, have significantly better chances for retaining hearing. This has an impact on decision making and timing of surgery.

Assessment of the anatomical relationship between the arcuate eminence and superior semicircular canal by computed tomography

The anatomical relationship between the arcuate eminence (AE) and the superior semicircular canal (SSC) was examined by computed tomography (CT) in 52 petrous bones of 26 patients. After acquiring volume data by multidetector CT, 1-mm thick oblique bone window images perpendicular to the SSC were obtained from the axial images. The distances between the AE and the SSC, and the SSC and the superior surface of the petrous bone were measured. The AE corresponded exactly with the SSC in only 2/52 petrous bones, and corresponded well in 7/52. The AE was lateral to the SSC in 25/52 cases, medial to the SSC in 6/52 cases, intersected in 3/52 cases, and was indiscernible in 9/52 cases. The distance between the SSC and the petrous surface was 0 mm in 45/52 petrous bones, 1 mm in 5/52, 2 mm in 1/52, and 3 mm in 1/52. The SSC typically does not correspond exactly with the AE, and is generally located just under the surface of the petrous bone. Planning of the middle cranial fossa approach requires location of the SSC by CT.

Microvascular decompression of cochlear nerve for tinnitus incapacity: pre-surgical data, surgical analyses and long-term follow-up of 15 patients

The level of success of neurovascular decompression in ponto-cerebellar angle for hemifacial spasm and trigeminal neuralgia has already established the reality of the pathology to explain such symptoms. However, cochlear nerve compression syndrome by vascular loop is still a controversial topic. We have performed a retrospective cases review with long-term follow-up (5-7 years) concerning the results of microvascular decompression surgery of the cochlear nerve via an endoscopy assisted retrosigmoid approach on 15 patients suffering from unilateral incapacitating tinnitus with abnormal auditory brainstem response and an offending vessel on magnetic resonance imaging. During the surgery, a vascular compression was found on every patient. In a long-term follow-up, 53.3% (8 cases) of our tinnitus cases improved and 20% (3 cases) of them were completely cured. The ABR returned to normal in all patients who had good clinical results (diminished or disappeared tinnitus). When a vertebral artery loop (5 cases) was concerned we obtained 80% of good clinical results. No one showed amelioration or sudden aggravation of their hearing. Three cases required surgical correction of cerebrospinal fluid leak and one case developed spontaneously regressive swallowing problems. Such microvascular decompression surgery of the cochlear nerve appears to be successful in treating incapaciting tinnitus in particular when a vertebral artery loop is observed. Therefore, in such a case, one might recommend neurovascular decompression surgery, keeping in mind that the complications of this surgery should be minimized by a careful closure of the retrosigmoid approach. In order to ensure a better selection of patient more accurate cochlear nerve monitoring and functional MRI should be a promising assessment.

Does Packing the Eustachian Tube Impact Cerebrospin al Fluid Rhinorrhea Rates in Translabyrinthine Vestibular Schwannoma Resections?

OBJECTIVE

To calculate cerebrospinal fluid (CSF) leak rates for translabyrinthine (TL), middle cranial fossa (MCF), and retrosigmoid/suboccipital (SO) craniotomies performed for removal of vestibular schwannoma (VS) and analyze whether packing the eustachian tube (ET) in TL VS resections impacts CSF rhinorrhea rates.

STUDY DESIGN

Retrospective.

SETTING

Tertiary care center.

METHODS

Chart review.

RESULTS

Three hundred fifty-nine VS resections were reviewed in 356 patients ranging from 10 to 86 years of age. Two hundred thirty-one TL, 70 MCF, 53 SO, and 5 combined TL/SO procedures were analyzed. Total CSF leak rates (incisional, otorrhea, and rhinorrhea) were 14.2% for TL, 11.4% for MCF, and 13.2% for SO approaches. Differences in overall CSF leak rates were not statistically significant. For those who underwent TL craniotomies, 2 groups of patients were identified based on whether their ETs were packed during surgery. In 1 group, the incus was removed, the aditus enlarged, the ET packed, and the middle ear filled with muscle. In the second group, the aditus, epitympanum and middle ear were packed without removing the incus, and the ET was not packed. Of 148 patients who had their ET packed, 12 developed CSF rhinorrhea (8.1%). The CSF rhinorrhea rate for patients who did not have ET packing was 5.9% (3 of 51 patients). This difference was not statistically significant (p = 0.80). When Proplast was used to pack the ET (121 patients), the CSF rhinorrhea rate was 5.8%. Unfortunately, this material extruded in 4 of 121 patients (3.3%) and presented clinically as delayed purulent otorrhea.

CONCLUSION

Cerebrospinal fluid leak rates were similar in patients undergoing TL, SO, and MCF approaches, and CSF rhinorrhea was not decreased by ET packing. Patients whose ETs are packed with Proplast are at risk for extrusion and otorrhea years after their initial VS resection.

Diagnosis and Management of Intracochlear Schwannomas

OBJECTIVE

To describe and analyze a series of intracochlear schwannomas.

METHODS

From 1987 to 2005, 19 patients with schwannomas involving the cochlea were included in this series. Clinical, audiovestibular, and imaging data concerning initial and follow-up visits were collected.

RESULTS

The mean age was 54 years (range, 25-71 yr). The series comprised 10 women and 9 men, 18 solitary tumors and 1 neurofibromatosis Type 2 patient. The mean diagnosis delay was 11 years (range, 1-31 yr). At diagnosis, a total or profound hearing loss (Class D of American Academy of Otolaryngology-Head and Neck Surgery classification) was noted in 17 patients (89%), and a severe loss (Class C) was reported in 2 patients (11%). Facial paresis was reported in 2 patients (11%; Grades 2 and 4 of House and Brackmann classification). Magnetic resonance imaging showed an involvement of the posterior labyrinth in 8 patients (37%), an extension of the schwannoma to the internal auditory meatus in 8 patients (37%), and a cerebellopontine angle extension in 7 patients (32%). In 11 patients (58%), the schwannoma was removed through a transotic route. In the 8 remaining patients, a watch-and-rescan policy was decided. The postoperative course was uneventful. Postoperative follow-up period was 27 months (range, 6-88 mo). Postoperative facial function was assessed as Grade 1 in 7 patients, as Grade 2 in 4, and as Grade 4 in 1 patient.

CONCLUSION

The diagnosis of intracochlear schwannomas can be difficult on magnetic resonance imaging. The diagnosis should be considered in all unilateral hearing losses.

Cochlear implantation in children with auditory neuropathy: outcomes and rationale

CONCLUSION

Children with auditory neuropathy (AN) obtain considerable benefit from cochlear implantation. Their performance outcomes are as good as those of implanted children with sensorineural hearing loss (SNHL). The neural status of children with AN would be comparable to that of children with SNHL and be suitable for cochlear implantation.

OBJECTIVE

The purpose of this study was to evaluate the outcomes of cochlear implantation in children with AN and to assess the status of auditory nerve in these patients.

SUBJECTS AND METHODS

Nine children with AN who underwent cochlear implantation were included. Their performance outcomes which were measured by Categories of Auditory Performance (CAP), Monosyllabic Word (MW) test for phonemes, and Common Phrases test were compared with those of matched implanted children with SNHL. To assess the status of auditory nerve in children with AN, the slopes of amplitude growth functions of electrically evoked compound action potentials (ECAPs) in implanted children with AN were compared to those of implanted children with SNHL.

RESULTS

There were no statistically significant differences between two groups in performance outcomes (CAP, p=0.1200; MW test, p=0.5768; Common Phrases test, p=0.3337). No significant difference was found in the slopes of ECAP amplitude growth functions (p=0.970) between two groups, which shows that spiral ganglion cell populations may be comparable in these two groups.

INTRANEURAL PERINEURIOMA OF THE VIIITH CRANIAL NERVE

OBJECTIVE

The authors describe the clinical and pathological features of the second reported case of an intraneural perineurioma involving a major intracranial nerve and the first case of this entity involving the VIIIth cranial nerve.

CLINICAL PRESENTATION

A 59-year-old woman presented with a long history of dizziness, tinnitus, hearing loss, and unstable gait. A magnetic resonance imaging scan revealed a small intrameatal lesion, which showed no clear progression from 2000 to 2006.

INTERVENTION

As a result of worsening symptoms and a suspected vestibular schwannoma, an attempt of tumor resection through a retrosigmoid approach was performed. This revealed diffusely infiltrated and fusiform enlarged vestibular and cochlear nerves, with no identifiable border between the main tumor mass and normal nerve. An en bloc nerve-tumor mass excision was performed. The pathological findings confirmed the diagnosis of an intraneuronal perineurioma.

CONCLUSION

The experience with this unique case and the experience of others with the management of extracranial intraneural perineuriomas lead the authors to conclude that the most reasonable surgical management of this tumor at this location is a nerve-tumor cross-section resection.

Acoustic neuroma (vestibular schwannoma): surgical results on 240 patients operated on dorsal decubitus position

OBJECTIVE: To evaluate the result of the surgical treatment of vestibular schwannoma (VS) operated in dorsal decubitus (mastoid position). METHOD: 240 patients with a VS underwent a retrosigmoid craniotomy for tumor resection in dorsal decubitus (mastoid position). The function of 7th and 8th cranial nerves was monitored during surgery and the opened internal auditory canal (IAC) was reconstructed using a vascularized dura flap, muscle and fibrin glue. RESULTS: Complete tumor removal was achieved in 99% of the cases, with a mortality of 1.6%. The facial nerve function was preserved in 85% of cases and hearing in 40% of the patients (with preoperative hearing) with tumors of up 1.5 cm in diameter. The incidence of cerebrospinal fluid leak was 5.8% and meningitis 2.9%. Venous air embolism was registered in 3% of cases; it was not associated to mortality. CONCLUSION: Surgical removal of VS in dorsal position has several advantages; the morbidity and mortality are very low.

The Influence of Prophylactic Vasoactive Treatment on Cochlear and Facial Nerve Functions after Vestibular Schwannoma Surgery

OBJECTIVE

Facial nerve paresis and hearing loss are common complications after vestibular schwannoma surgery. Experiments with facial nerves of the rat and retrospectively analyzed clinical studies showed a beneficial effect of vasoactive treatment on the preservation of facial and cochlear nerve functions. This prospective and open-label randomized pilot study is the first study of a prophylactic vasoactive treatment in vestibular schwannoma surgery.

METHODS

Thirty patients were randomized before surgery. One group (n = 14) received a vasoactive prophylaxis consisting of nimodipine and hydroxyethylstarch which was started the day before surgery and was continued until the seventh postoperative day. The other group (n = 16) did not receive preoperative medication. Intraoperative monitoring, including acoustic evoked potentials and continuous facial electromyelograms, was applied to all patients. However, when electrophysiological signs of a deterioration of facial or cochlear nerve function were detected in the group of patients without medication, vasoactive treatment was started immediately. Cochlear and facial nerve function were documented preoperatively, during the first 7 days postoperatively, and again after long-term observation.

RESULTS

Despite the limited number of patients, our results were significant using the Fisher's exact test (small no. of patients) for a better outcome after vestibular schwannoma surgery for both hearing (P = 0.041) and facial nerve (P = 0.045) preservation in the group of patients who received a prophylactic vasoactive treatment.

CONCLUSION

Prophylactic vasoactive treatment consisting of nimodipine and hydroxyethylstarch shows significantly better results concerning preservation of the facial and cochlear nerve function in vestibular schwannoma surgery. The prophylactic use is also superior to intraoperative vasoactive treatment.

Typewriter tinnitus: a carbamazepine-responsive syndrome related to auditory nerve vascular compression

Six subjects with similar unilateral tinnitus that was fully suppressed by carbamazepine have been identified. Their ages at the time of the sudden onset of their tinnitus ranged from 39 to 87 years (mean 67). The 3 men had right ear tinnitus. Two of the 3 women had left ear tinnitus. All 6 described a staccato quality of their intermittent tinnitus ('like a typewriter in the background, pop corn, Morse code'). Five of the 6 subjects had no other hearing or vestibular complaints; their audiograms were symmetric and consistent with their ages. Vascular compression of the auditory nerve ipsilateral to the tinnitus was detected in 4 of the 5 subjects imaged. The similarities between typewriter tinnitus and other cranial nerve syndromes associated with vascular compression (trigeminal neuralgia, hemifacial spasm, and glossopharyngeal neuralgia) suggest that surgical decompression of the auditory nerve can relieve medication-refractive cases of typewriter tinnitus.

Aggressive vestibular schwannomas showing postoperative rapid growth - their association with decreased p27 expression

Vestibular schwannomas (VSs) are relatively slow growing tumors. However, some rapidly regrow or recur after surgical resection. The objective of this study was to identify those molecular characteristics predicting rapid recurrence after surgical resection. Immunohistochemically determined expressions of several cell cycle regulators and apoptosis-associated proteins in 12 cases of aggressive VS (AVS) and in 15 control cases of usual VS (UVS) cases were compared. The expressions of p53 and Bax (pro-apoptotic protein), Bcl-2 (anti-apoptotic protein), Fas, and Fas-L (apoptotic death receptor and ligand), caspase 3 (apoptotic effector caspase proteins), and p27 and p21 (cyclin-dependent kinase inhibitors) were analyzed using tissue array blocks. Loss of p27 expression was observed in 8 of 12 AVS cases (67%) and in 3 UVS cases (20%); p21 was expressed in all cases. Loss of Bax was observed in 3 AVS and 3 UVS cases. The anti-apoptotic protein, Bcl-2, was expressed in 9 AVS (75%) and 11 UVS (73%), and p53, Fas-L, and caspase 3 were negative and Fas was positive in all AVS and UVS cases. Of these, only the loss of p27 was statistically significant (P = 0.02). The loss of p27 in AVS may explain the unusually high proliferative potential of AVS versus UVS, and p27 may be a predictor of VS aggressiveness. The expressions of other apoptosis associated proteins were not significantly different in the two groups. This may be the first report to identify a molecular entity associated with aggressive VS. However, further studies are required.

Cerebrospinal Fluid Leak Rate after the Use of BioGlue in Translabyrinthine Vestibular Schwannoma Surgery: A Prospective Study

OBJECTIVE

To determine the effectiveness of BioGlue surgical adhesive in dural and middle ear closure after translabyrinthine vestibular schwannoma surgery.

STUDY DESIGN

A prospective study.

SETTING

Tertiary neurotological referral center.

PATIENTS

There were 24 patients in the BioGlue series. BioGlue was used in the same manner in all cases. All patients received similar postoperative care.

INTERVENTIONS

We studied the use of BioGlue and its possible effect on further reducing our department's cerebrospinal fluid leak rate for translabyrinthine vestibular schwannoma surgery.

MAIN OUTCOME MEASURES

Postoperative events were documented that enabled us to determine the overall cerebrospinal fluid leak rate (including incidence of various leak routes and morbidity).

RESULTS

The overall cerebrospinal fluid leak rate was 62.5% (15 of 24). Rhinorrhoea was the commonest route (80%), followed by postaural wound leak (33.3%) and external auditory canal otorrhoea (33.3%). Forty percent of cases had more than one cerebrospinal fluid leak route; 73.3% of leak cases required lumbar drain insertion, 40% needed pressure bandaging, and 66.7% had to undergo formal surgical repair. Forty percent had recurrent leaks after the initial episode had completely ceased. The mean extra stay in hospital as a result of the cerebrospinal fluid leak was 13.3 days.

CONCLUSION

Our preliminary prospective study of the use of BioGlue for dural and middle ear closure in translabyrinthine vestibular schwannoma surgery demonstrated poor results. The high cerebrospinal fluid leak rate associated with the unusual presentations and ensuing management difficulties in controlling these leaks lead us to recommend that BioGlue not be used in translabyrinthine vestibular schwannoma surgery. The manufacturers have noted our results and have considered adding our recommendation to the product data sheet.

Glioneural hamartoma of the VIIIth nerve

Hamartomas of the cerebellopontine angle or internal auditory canal are very rare and only four cases have been reported. We report an unusual case of a glioneural hamartoma of the VIIIth nerve with clinical, radiological and audiometric similarity with vestibular schwannoma.

Auditory brainstem implant (ABI): new frontiers in adults and children

Previous studies have considered only patients with neurofibromatosis type 2 (NF2) older than 12 years as candidates for an auditory brainstem implant (ABI). Our study expands the potential criteria to include both children and adult subjects with other cochlear or cochlear nerve malfunctions who either would not benefit at all from a cochlear implant (eg, cochlear nerve aplasia or avulsion) or whose benefit was or would be severely compromised (eg, cochlear ossification, cochlear fracture).

STUDY DESIGN

In our department, over the period from April 1997 to September 2002, 29 patients, 20 adults and 9 children, were fitted with ABIs. Their ages ranged from 14 months to 70 years. Thirteen subjects had tumors, 10 NF2 and 3 solitary vestibular schwannoma, and 16 patients had a variety of nontumor (NT) cochlear or cochlear nerve diseases. A retrosigmoid-transmeatal approach was used in T and a retrosigmoid approach in NT patients. The electrode array was inserted into the lateral recess of the fourth ventricle and correct electrode positioning was monitored with the aid of electrically evoked auditory brainstem responses (EABRs).

RESULTS

Correct implantation was achieved in all patients. No complications were observed due to implantation surgery or related to ABI activation or long-term use. Auditory sensations were induced in all patients with various numbers of electrodes (from 5 to 15). Different pitch sensations were identifiable with different electrode stimulation. Closed-set word recognition, open-set sentence recognition, and speech tracking scores achieved by the patients are reported in detail. The auditory performance of the patients showed significantly better outcomes than controls (Multicentric European clinical investigations on ABI with NF2).

CONCLUSION

We have shown that the indications for the ABI can be extended to include NT patients with severe cochlear and/or cochlear nerve abnormalities. The degree of auditory benefit varies as a function of the underlying pathological conditions, with NT subjects exhibiting significantly better outcomes than the T patients.

Prediction of the origin of intracanalicular neoplasms with high-resolution MR imaging

Correct diagnosis of intracanalicular neoplasms is important to avoid unnecessary operations or an unsuitable surgical approach. We investigated the capability of high-resolution three-dimensional MR imaging in predicting the origin of intracanalicular neoplasms. Twenty cases underwent three-dimensional Fourier-transformation (3DFT) constructive interference in steady state and contrast-enhanced 3DFT-fast low angled shot MR imaging and surgery. Seventeen cases underwent caloric test. MR diagnosis on the origin of intracanalicular neoplasms was compared with surgical results. For MR diagnosis, the origin of intracanalicular neoplasms was predicted according to the location of the tumor in the internal auditory canal (IAC) in two ways, i.e., determining (1) a single specific nerve of origin and (2) whether the tumor originated from the superior or inferior aspect of the IAC. Surgery could determine the nerve of origin in 16 cases (14 inferior and 2 superior vestibular schwannomas), but it was indeterminate in 4. Comparison between MR prediction and surgical results on a single nerve origin revealed exact agreement in five, but inconsistent in three. Regarding whether the tumor was derived from superior or inferior aspect of the IAC, agreement was found in 10 of the 16 cases (62.5%). Caloric test was abnormal in all patients examined but one with superior vestibular schwannoma. 3DFT-MR imaging was not particularly useful in predicting a precise nerve of origin of intracanalicular neoplasms. The prediction on whether the tumor originated in the superior or inferior aspect of the IAC was superior to caloric test, which might have clinical significance in treatment planning especially for hearing preservation surgery.

Frequency specific hearing improvement in microvascular decompression of the cochlear nerve

BACKGROUND

Microvascular compressions of the cochlear nerve can lead to hearing loss. Due to the tonotopic organization of the cochlear nerve any focal compression of the cochlear nerve will result in a frequency specific hearing loss. Decompressing the cochlear nerve could result in a frequency specific hearing improvement, without improving overall hearing.

METHOD

Thirty one patients underwent microvascular decompression operations of the vestibulocochlear nerve for vertigo or tinnitus. Preoperative audiograms were substracted from postoperative audiograms obtained 2 years after microvascular decompression. The frequencies of maximal hearing improvement postoperatively were determined.

FINDINGS

Of the 31 patients studied, 19 had improvements of 5 dB or more at one or more frequencies postoperatively, and 15 patients had improvements of 10 dB or more. Three patients had improvements of 25 dB or more postoperatively. The postoperative hearing improvement was frequency-specific and related to the anatomical location of the vascular contact on the auditory nerve. The improvement of hearing becomes diluted when the difference between pre- and postoperative hearing thresholds are averaged over all audiometric frequencies. We therefore present results for each frequency that was tested.

CONCLUSIONS

Microvascular decompression of the cochlear nerve can improve hearing in selected patients. The improvement seems too small to justify decompressive surgery for the sole purpose of hearing improvement, but it could be considered if associated short vertigo spells, ipsilateral tinnitus, otalgia and cryptogenic hemifacial spasm are present. Decompression should be performed early, before BAEP changes become noticeable. 3D-MRI could become a valuable tool for selecting good surgical candidates.

[Auditory neuropathy--new disease]

Auditory neuropathy, a disorder of neural synchrony, is a retrocochlear hearing disorder identified by absence of auditory brainstem responses (ABR) and presence of evoked acoustic otoemissions (EOA). Registration of emissions shows normal function of external cilliary cells. Patients with auditory neuropathy have difficulties to understand speech especially in presence of beckground noise. Normal conversation requires the support of orofacial reading. The authors presents electrophysiological and behavioral tests useful in diagnostic process. An option in treatment of auditory neuropathy is cochlear implantation. Such treatment is indicated when conventional hearing aids doe not help to improve speech understanding.

Cochlear implantation in an adult patient with auditory neuropathy

We present a case report of effective cochlear implantation for an adult patient with auditory neuropathy. A 34-year-old man developed bilateral hearing loss at approximately 10 years of age. His speech discrimination score was very severe despite only moderate sensorineural hearing loss. Absence of auditory brainstem responses (ABR) and preservation of distortion product otoacoustic emissions (DPOAE) were confirmed by our audiological examinations. After cochlear implantation, good responses for electrically evoked compound action potential (EAP) and electrically evoked ABR (EABR) were observed. Postoperatively, his audiological performance was significantly improved. We conclude that cochlear implantation can be a valid option for patients with auditory neuropathy.

Vascular malformation (so-called hemangioma) of Scarpa's ganglion

Vascular malformations of the cerebello-pontine angle (CPA) arising from the capillary plexus surrounding Scarpa's ganglion are rare tumors. We report a case of so-called "hemangioma" of the CPA which was operated on via a trans-labyrinthine approach based on a preoperative diagnosis of vestibular schwannoma. Although there are some differences between these tumors in terms of the clinical, biological and especially MRI findings, surgery is usually performed based on an assumption of vestibular schwannoma. Surgery is the treatment of choice for these lesions as early intervention ensures better postoperative facial function. It is important to make the differential diagnosis if conservative management of vestibular schwannoma is adopted.

Galvanic-induced body sway in vestibular schwannoma patients: evidence for stimulation of the central vestibular system

OBJECTIVE

To investigate the various possible sites of excitation by galvanic stimulation by comparing the galvanic-induced body sway (GBS) in vestibular schwannoma (VS) patients with that in healthy subjects.

MATERIAL AND METHODS

This was a prospective experimental study conducted in a tertiary referral centre. In a previous study we developed a standardized procedure for reproducible quantification of GBS using a monaural continuous 1-cosinusoidal stimulus (0.5 Hz; 2 mA). In this study, 23 VS patients were tested before and 12 VS patients were also tested after surgical intervention (extirpation of tumour with concomitant vestibular neurectomy) and the results were compared with those obtained in 47 healthy subjects.

RESULTS

There were no significant differences in mean total GBS gain between VS patients and healthy subjects (p>0.05) before surgical intervention. After vestibular neurectomy a significant difference in the mean total GBS gain was observed, but GBS was still present after surgery.

CONCLUSION

These results prove that galvanic vestibular stimulation excites the central vestibular system even when conduction via the vestibular nerve is hampered.

Epithelioid schwannoma of the vestibular nerve

Epithelioid schwannomas are rarely encountered intracranially, with only four cases involving the eighth nerve reported in the literature. Histological behaviour ranging from benign to aggressive has been described. We report a 45-year-old woman who presented with right-sided tinnitus and hearing impairment. Magnetic resonance imaging revealed a tumour in the right cerebellopontine angle with intracanalicular extension. The patient underwent retromastoid craniectomy with near-total tumour excision. Microscopical examination confirmed the diagnosis of epithelioid schwannoma of the vestibular nerve. Intraoperative findings of sharp circumscription, bland histological appearance, low proliferative activity, coupled with the indolent clinical course, point to the quiescent nature of the lesion in this case.

Cochlear implants: indications in groups of patients with borderline indications. A review

Cochlear implants (CI) represent the current treatment for patients affected by profound sensorineural hearing loss (SNHL). Initially only deaf adult patients were considered to be candidates for a CI; however, the development of technology and matured experience have expanded the indications for cochlear implantation. Today, CIs are implanted in adults and children and broader indications are followed. There are, however, a number of patients who do not completely fulfill the current indications and who are potential candidates for CI. The duration of deafness and residual hearing represent prognostic indicators for CI performance; however, the candidacy of children with residual hearing and prelingually deafened adults are still under debate. Anatomical variants such as cochlear ossification, cochlear malformation and chronic otitis media represented and still represent for some surgeons a contraindication to CI. The otological experience of CI surgeons and the advent of auditory brainstem implants have changed the approach to these patients, who may still benefit from hearing rehabilitation. This paper briefly analyses and reviews the results obtained in these groups of patients, who were not, at least initially, considered to be candidates for cochlear implantation.

Internal auditory canal metastasis

This report deals with 3 cases of internal auditory canal metastasis, an extremely rare lesion, few cases having been reported in the international literature. Since pre-operative diagnosis is fundamental in the planning of a correct therapeutic strategy, it is important that the neurotologist be aware of the possibility of their occurrence in this particular area. Metastasis can occur unilaterally as well as bilaterally; the latter being the case in 1 of the patients described herein. Correct pre-operative diagnosis is particularly difficult in patients in whom the primary tumour has not been detected at the time of identification of the lesion in the internal auditory canal. The only characteristic, specific of metastasis, is the presence of multifocal cerebral lesions. However, these were detected in only 1 of the present cases. On the contrary, in cases of a single metastasis, both magnetic resonance imaging and computed tomography usually fail to show any distinctive feature when compared to the most common tumours of the internal auditory canal (vestibular schwannomas and meningiomas). Bilateral metastases can also be misdiagnosed as neurofibromatosis type 2. Clinical data that should alert the clinician are: rapidly progressive sensorineural hearing loss, followed by onset of progressive facial nerve weakness. Radiotherapy and/or chemotherapy are the two main treatment modalities, while surgical removal is reserved for selected cases of a single metastasis. Albeit, due to the paucity of specific radiological and clinical characteristics, surgical removal is often necessary to reach the correct diagnosis, as occurred in 2 of the present patients.

Endoscope-assisted Microsurgery for Microvascular Compression Syndromes

OBJECTIVE

To discuss the results of endoscope-assisted surgery in microvascular decompression (MVD) of Cranial Nerves (CNs) V, VII, and VIII.

METHODS

Neuroendoscopy was used as an adjunct to the surgical microscope in the MVD of the trigeminal (17 patients), facial (10 patients), and vestibulocochlear (1 patient) nerves in a series of 28 consecutive patients. After a standard microsurgical approach to CNs V, VII, and VIII, the endoscope was used to inspect all aspects of neural anatomy, to assess vascular compression, and to check the results of the decompression. Endoscope use was graded in four categories: Grade I, used but no definite role; Grade II, visualization assisted; Grade III, procedure assisted; and Grade IV, primary role. The usefulness of the endoscope was evaluated in each case.

RESULTS

The endoscope was useful in visualizing the anatomy in all cases. It was especially useful in establishing trigeminal vein compression of CN V in Meckel's cave; observing multiple sources of vascular compression; ensuring adequate decompression after cauterization of vein, insertion of the Teflon felt, or a pexy procedure; and permitting observation of the compression of CN VII at the root exit zone by small arteries and veins. In six patients with trigeminal neuralgia, the trigeminal vein was cauterized and divided by using endoscopic vision only because the venous compression was not completely visualized with the microscope. During a follow-up period of 6 to 52 months (mean, 29 mo; median, 40 mo), all patients were asymptomatic and receiving no medication.

CONCLUSION

The endoscope is a useful adjunct to MVD in the treatment of trigeminal neuralgia, hemifacial spasm, and disabling positional vertigo or tinnitus.

[Assessment of the state of water sectors in neurosurgical profile patients in the pre-, intra- and postoperative periods]

The state of water sectors has been analyzed at the stages of preparation to and performing anesthesia as well as in the early postoperative period in neurosurgical patients in connection with planned surgical procedures (37 cases). The impedance method of control of the hydration degree before operation allowed to find out a risk group--hypohydrated patients. In most cases the detected disturbances of the water-electrolytic balance could not be diagnosed clinically. Despite a relative stability of traditionally analyzed indices of circulation during anesthesia, the reactions of central hemodynamics were more pronounced than could be considered undesirable. The analysis performed makes a foundation for optimization of infusion and cardiotropic therapy both during anesthesiological maintenance of neurosurgical procedures and at the postoperative period.

[Are we sectioning the cochlear efferent system during vestibular neurotomy?]

INTRODUCTION

In addition to sensory neurons which transmit information from the inner ear to the brain, there is a system of efferent feedback fibers, called the olivocochlear system, carrying signals from the brain to the ear. Over the past half-century, the efferent system has been extensively studied in animals and results provided theories as to the functional significance of these efferents: to improve signal-to-noise ratio in the auditory periphery, to mediate selective attention, and to protect the inner ear from acoustic overexposure. The results of several studies conducted in man rely on the study of patients who have undergone a vestibular neurectomy. Indeed, anatomical data show that olivocochlear efferents could travel along or inside the vestibular part of the auditory nerve before reaching the organ of Corti. Therefore, these patients may be considered as an experimental model of unilaterally de-efferented subjects. However, to date, none has reported the existence of olivocohlear efferents in the vestibular section following neurectomy.

MATERIALS AND RESULTS

In this study, we present the histological results from 18 vestibular sections and show the absence of olivocochlear efferents.

CONCLUSION

These results provide a reason to reconsider the results of previous experiments conducted in similar patients and ask for further studies on the olivocochlear efferents pathways.

Cochlear implantation in patients with auditory neuropathy of varied etiologies

OBJECTIVES/HYPOTHESIS

Auditory neuropathy is a relatively recently described pattern of hearing loss characterized by preservation of outer hair cell function despite absent brainstem auditory evoked responses. Intact outer hair cell function is demonstrated by the presence of otoacoustic emissions and/or a measurable cochlear microphonic on electrocochleography, whereas no synchronous neural activity (absent action potentials) is seen on acoustically evoked brainstem auditory evoked response testing. The study reviews the authors' experience with six patients diagnosed with auditory neuropathy, four of whom have undergone cochlear implantation.

MATERIALS AND METHODS

A retrospective review of all medical and audiological charts at the University of Virginia Hospitals (Charlottesville, VA) was performed to identify patients who have undergone cochlear implantation or have been diagnosed with auditory neuropathy, or both.

RESULTS

Six patients with hearing loss attributable to auditory neuropathy were identified, four of whom have undergone cochlear implantation. Causes varied, including congenital, infectious, and idiopathic origins. Adults demonstrated subjective auditory perception on promontory stimulation, whereas no repeatable brainstem auditory evoked response waveforms could be demonstrated on pediatric promontory stimulation testing. Patients with implants demonstrated implant-evoked brainstem auditory evoked responses and improved audiological performance.

CONCLUSIONS

The six cases presented in the study represent varied causes and, probably, varied sites of lesions of auditory neuropathy. Promontory stimulation has been valuable, particularly in adults. Cochlear implantation allows the opportunity to provide a supraphysiological electrical stimulation to the auditory nerve, with the hope of reintroducing synchronous neural activity. Greater confidence and enthusiasm for cochlear implantation in appropriately selected patients with auditory neuropathy are gained through experience with such diverse cases.

Aggressive vestibular schwannomas with postoperative rapid growth: clinicopathological analysis of 15 cases

OBJECTIVE

Vestibular schwannomas (VSs) are known to be relatively slow-growing tumors. Some VSs, however, rapidly regrow or recur after surgical resection. Our objective was to investigate the clinicopathological characteristics of these tumors and to elucidate factors that can predict rapid regrowth or recurrence after surgical resection.

METHODS

Between 1978 and 2000, 29 patients with VS underwent reoperation for regrowth or recurrence at the Department of Neurosurgery in Seoul National University Hospital. Among these patients, 15 experienced rapid VS regrowth or recurrence (annual growth rate, >15 mm/yr). The clinical, radiological, operative, and pathological findings were reviewed. For a comparison of the morphology and proliferative activity, 15 cases of VS were randomly selected as a control group from among the consecutive operative cases with tumor size larger than 4 cm treated between 1991 and 1999. Pathological parameters consisting of cellularity, pleomorphism, mitosis, necrosis, invasion to adjacent tissue, and microvascular proliferation were analyzed. Proliferative indices (e.g., Ki-67 index) also were evaluated. Statistical analyses were performed using Fisher's exact test and the analysis of variance test.

RESULTS

The differences in clinical features between the aggressive VS group and the control VS group were nonspecific. The mean ages at diagnosis were 40.6 years (range, 21-63 yr) and 49.7 years (range, 35-67 yr) (P = 0.438), and the male-to-female ratios were 7:7 and 5:10 (P = 0.462), respectively. The clinical symptoms and signs were similar between the two groups. Radiologically, aggressive tumors at initial presentation had more lobulating contours than those in the control group (7 of 13 cases versus 3 of 15 cases; P = 0.001). In pathological findings, cellularity and pleomorphism were significantly higher than those in the control group (P = 0.001). However, mitosis, necrosis, invasion to adjacent tissue, and microvascular proliferation were not different between the two groups. The proliferative index (Ki-67 index) was higher in the aggressive group than in the control group (2.28 [range, 0.1-8.6] versus 0.59 [range, 0-1.5]; P = 0.034).

CONCLUSION

VSs presenting with lobulating contour, high proliferative index (Ki-67 index), and high cellularity or pleomorphism require frequent radiological investigation during follow-up to facilitate early detection of regrowth or recurrence.

Outcome of cochlear implantation in pediatric auditory neuropathy

OBJECTIVE

Auditory neuropathy, characterized by absence or abnormality of auditory brainstem responses and normal otoacoustic emissions, is often associated with particularly poor response to amplification. Outcome data from four such pediatric patients who received cochlear implants are discussed.

STUDY DESIGN

Four patients from the Carolina Children's Communicative Disorders Program were identified as having received a diagnosis of auditory neuropathy before implantation with a Clarion cochlear implant. Speech data collected after implantation were compared with data from control pediatric implant patients, matched for age at implantation and duration of implant use. Electrically evoked auditory brainstem response data and electrically evoked acoustic reflex data were also obtained.

METHODS

Routine clinical procedures were used to obtain speech outcome data. A 75-micros biphasic 21.1-Hz pulse train served as the eliciting stimulus for both evoked auditory brainstem responses and reflex measures, which were obtained contralateral to the implant.

RESULTS

Speech data were comparable with those obtained from the general population of pediatric patients receiving cochlear implants at this center. Identifiable evoked auditory brainstem response data were obtained in all subjects on at least two of the three electrodes tested, and variability was comparable with that observed in other children with implants. A robust electrically evoked acoustic reflex with no decay was observed at estimated M-level in all children.

CONCLUSION

The data gathered to date suggest that the outcome of cochlear implantation in these four patients is not significantly different from that in other pediatric implant patients. Physiologic data suggest that the implant was able to overcome the desynchronization hypothesized to underlie auditory neuropathy.

Neuromuscular hamartoma of the cochlear nerve: a rare occurrence in the internal auditory meatus

The authors present a case of neuromuscular hamartoma of the cochlear nerve, an unusual occurrence in the internal auditory meatus (IAM). A review of the literature shows no previous report of neuromuscular hamartoma of the cochlear nerve. This tumour was clinically and radiologically difficult to distinguish from acoustic neuroma. It is important to consider the diagnosis of these rare small tumours pre-operatively, as it may be appropriate to manage this conservatively.

A case of multiple schwannomas of the trigeminal nerves, acoustic nerves, lower cranial nerves, brachial plexuses and spinal canal: schwannomatosis or neurofibromatosis?

In most cases, while schwannoma is sporadically manifested as a single benign neoplasm, the presence of multiple schwannomas in one patient is usually indicative of neurofibromatosis 2. However, several recent reports have suggested that schwannomatosis itself may also be a distinct clinical entity. This study examines an extremely rare case of probable schwannomatosis associated with intracranial, intraspinal and peripheral involvements. A 63-year-old woman presented with a seven-year history of palpable lumps on both sides of the supraclavicular area and hearing impairment in both ears. On physical examination, no skin manifestations were evident. Facial sensory change, deafness in the left ear and decreased gag reflex were revealed by neurological examination. Magnetic resonance imaging revealed multiple lesions of the trigeminal nerves, acoustic nerves, lower cranial nerves, spinal accessory nerve, brachial plexuses, and spinal nerves. Pathological examination of tumors from the bilateral brachial plexuses, the spinal nerve in the T8 spinal position and the neck mass revealed benign schwannomas. Following is this patient case report of multiple schwannomas presenting with no skin manifestations of neurofibromatosis.

Implementation of a clinical pathway in management of the postoperative vestibular schwannoma patient

OBJECTIVE

The purpose of the study was to evaluate the effectiveness of a new clinical pathway in management of patients with postoperative vestibular schwannoma. The impact on duration of hospitalization and quality of care was evaluated.

STUDY DESIGN

The study was a retrospective review of 59 consecutive patients undergoing surgical intervention for vestibular schwannoma between January 1995 and July 1999.

METHODS

A new clinical pathway for management of postoperative vestibular schwannoma patients was implemented at The California Ear Institute at Stanford (Palo Alto, CA) in January 1995. All patients undergoing surgical intervention subsequent to initiation of the pathway were included in the study. Data including surgical approach, patient age, sex, and tumor size were included. Duration of hospitalization and postoperative complications were recorded. During the same time period, data for patients undergoing radiation therapy for vestibular schwannomas were evaluated for length of hospital stay and in-hospital complications. Data were compared with norms recorded in the literature for duration of hospitalization and complications following surgical intervention.

RESULTS

Fifty-nine patients underwent 35 middle fossa approaches and 24 translabyrinthine approaches to their tumors. The average patient age was 53 years; there were 34 female and 25 male patients. The average length of hospital stay was 3.83 days (SD = 1.4 days) with a range from 2 to 10 days. Postoperative complications were observed in 19% of patients, including eight (13%) cerebrospinal fluid (CSF) leaks, two requiring lumbar drains (3.4%); one hematoma (1.6%), one postoperative fever (1.6%), and one dural tear with associated hyponatremia (1.6%). These results compared favorably with previously recorded average hospital stays of 5.95 to 9.5 days 1,5-7 and CSF leak complication rates of 7% to 15%.9,10

CONCLUSIONS

Implementation of a clinical pathway for management of the patient with postoperative vestibular schwannoma improves efficiency of patient care, allowing decreased duration of hospitalization. This goal is achieved without increasing complication rates and, in our experience, actually improving the quality of clinical care. The cost-effectiveness of clinical pathways may become increasingly important in a managed care-driven environment.

Hearing habilitation with auditory brainstem implantation in two children with cochlear nerve aplasia

Patients with aplasia and hypoplasia of the cochlear nerve have no chance of having their hearing restored by stimulating the periphery of the auditory system using the traditional cochlear implant. A possible approach to auditory rehabilitation may be direct electrical stimulation of the cochlear nuclei with an auditory brainstem implant (ABI). Recently, two children, aged 4 and 3 years, respectively, with bilateral severe cochlear malformations and cochlear nerve aplasia received an ABI. The present paper reports the technique and the preliminary results of this experience. The classic retrosigmoid approach was used. The correct position of the electrodes was estimated with the aid of EABRs and neural response telemetry (NRT). No postoperative complications were observed. High-resolution CT scans with a bone algorithm reconstruction technique were taken postoperatively to evaluate electrode placement before discharge. The ABI was activated 30 days after implantation in both patients. To date 16 and 13 electrodes, respectively, have been activated in the two children. Three months after activation the first patient had achieved good environmental sound awareness, good speech detection and some speech discrimination. The second child, 1 month after activation, had achieved good environmental sound awareness and moderate speech detection. To the best of our knowledge this is the first report of patients with hypoplasia of the cochlea and aplasia of the cochlear nerve, aged below 5 years and treated with an ABI.

Vestibular neurectomy

A brief history of the vestibular neurectomy is given. This treatment modality was introduced in Denmark by us, using the experiences obtained by the use of translabyrinthine treatment modality for vestibular schwannoma surgery. This paper presents our experiences with this type of surgery (translabyrinthine, retrolabyrinthine and retrosigmoid vestibular nerve section) from 1980 to 1996, including 43 operations in 42 patients. The patients had all been treated with conventional methods without success and were all severely handicapped by their attacks of vertigo. The mean age was 51 years, postoperative observation time between 2 and 15 years, with a mean of 6.4 years. The vertigo was controlled in 88% of the patients, while postoperative imbalance occurred in 14 patients, mainly due to the ablation of the vestibular labyrinth and not by episodic vertigo. A total of 39 patients indicated that they were satisfied with the operation. Six patients were deaf before surgery and 92% of the remaining patients retained their preoperative hearing. Postoperative complications were few, including two re-operations for CSF leaks, one patient with a slight transient facial nerve paresis and one transient VI nerve paresis. The results compare favorably with results from other authors. Retrosigmoid vestibular nerve section is an effective treatment modality to be offered to patients in whom other modalities have failed. Information about the efficacy and leniency of the treatment should be given to the patient's organization in order to diminish the fear of an intracranial intervention. Surgical experience is necessary in order obtain good results, the number of patients needing the operation is small and centralization of the treatment is mandatory.

Microvascular decompression for cochlear symptoms

OBJECT

The object of this study was to evaluate the efficacy of a new neurovascular decompression technique in relieving symptoms of cochlear nerve dysfunction.

METHODS

Nineteen patients with slowly progressive hearing loss, low-frequency fluctuating hearing loss, and high-pitched tinnitus due to neurovascular compression (NVC) of the eighth cranial nerve in a triangular space between the seventh and eighth cranial nerves (the VII-VIII triangle) of the cerebellopontine angle (CPA) were treated using a new technique for microvascular decompression that was developed by anatomical study in 24 cadaver specimens of the CPA. In 12 of 19 patients the anterior inferior cerebellar artery (AICA) was observed to cause compression in the VII-VIII triangle and this vessel was easily mobilized medially for placement of a silicone sponge or Teflon cushion between the compressing artery and nerve. Postoperatively, hearing loss of 20 dB or more that was present in 11 of the 19 patients with NVC improved by more than 5 dB in seven (64%), including the patient with the most severe hearing loss. Of 18 patients presenting with tinnitus preoperatively, eight (44%) had no tinnitus and an additional nine (for a total of 94%) had good improvement in tinnitus after surgery and at long-term follow up.

CONCLUSIONS

The microvascular decompression technique described is highly successful in treating symptoms due to direct or indirect compression of the cochlear nerve, with minimal risk of complications. Recordings of auditory brainstem responses confirmed the clinical diagnosis of NVC of the eighth cranial nerve and correlated with clinical results after microvascular decompression of the cochlear nerve.

Gamma surgery for vestibular schwannoma

OBJECT

The goal of this study was to assess the results of gamma surgery (GS) for vestibular schwannoma (VS) in 200 cases treated over the last 10 years and to review the role of this neurosurgical procedure in the management of VS.

METHODS

Follow-up reviews ranging from 1 to 10 years were available in 153 of these patients. Follow-up images in these cases were analyzed using computer software that we developed to obtain volume measurements for the tumors, and the clinical condition of the patients was assessed using questionnaires. Gamma surgery was the primary treatment modality in 96 cases and followed microsurgery in 57 cases. Tumors ranged in volume from 0.02 to 18.3 cm(3). In the group in which GS was the primary treatment, a decrease in volume was observed in 78 cases (81%), no change in 12 (12%), and an increase in volume in six cases (6%). The decrease was more than 75% in seven cases. In the group treated following microsurgery, a decrease in volume was observed in 37 cases (65%), no change in 14 (25%), and an increase in volume in six (11%). The decrease was more than 75% in eight cases. Five patients experienced trigeminal dysfunction; in three cases this was transient and in the other two it was persistent, although there has been improvement. Three patients had facial paresis (in one case this was transient, lasting 6 weeks; in one case there was 80% recovery at 18 months posttreatment; and in one case surgery was performed after the onset of facial paresis for presumed increase in tumor size). Over a 6-year period, hearing deteriorated in 60% of the patients. Three patients showed an improvement in hearing. No hearing deterioration was observed during the first 2 years of follow-up review.

CONCLUSIONS

Gamma surgery should be used to treat postoperative residual tumors as well as tumors in patients with medical conditions that preclude surgery. Microsurgery should be performed whenever a surgeon is confident of extirpating the tumor with a risk-benefit ratio superior to that presented in this study.

Management of intrameatal vestibular schwannoma

The growth of purely intrameatal vestibular schwannoma (VS) was investigated, in the period 1973-96 in a series of 40 patients with 40 unilateral VS. In the present study, the material was analysed and updated. By the end of the observation period (mean 3.6 years), 27 tumours (67.5%) revealed growth and 13 tumours (32%) had no measurable growth. Four growth patterns were observed: (A) 15 tumours (37.5%) exhibited constant growth; (B) 13 tumours (32.5%) had no measurable growth; (C) 8 tumours (20%) revealed growth subsequent to a no-growth period; and (D) 4 tumours (10%) showed different growth patterns during the observation period. The annual diameter growth rate ranged between 00 mm/year and 6.5 mm/year and the mean diameter growth per year was 3.2 mm. The findings of the present study, especially those for group B (the non-growing tumours) and C (tumour growth subsequent to a silent period) bring into question the reliability of the results achieved by radiosurgery, as without any intervention it may be that no tumour growth occurs.

[Vascular origin of cerebellopontine angle syndrome]

INTRODUCTION

The seventh and eighth cranial nerves course toward the internal auditory canal within the cerebellopontine angle. Lesions in this region are usually related to malfunctions of these cranial nerves. Although an acoustic schwannoma is one of the main etiologies of cerebellopontine angle pathology, various inflammatory processes and vascular anomalies even though rare must be considered.

PATIENTS/METHODS

We describe 5 cases with vascular loops of the basilar or vertebral arteries as a possible cause for hearing loss, vertigo and pulsatile tinnitus. In two cases the vascular lesion was confirmed at surgery, in which a decompression procedure was performed. The work-up for each patient included an auditory test battery and electronystagmography. Imaging studies included MRI and angiography in two cases.

RESULTS/CONCLUSIONS

Our experiences show that while the cerebellopontine angle syndrome is mostly caused by benign tumors an abnormal vascular loop has to be considered in any differential diagnosis.