Hearing preservation in patients with vestibular schwannomas with sudden sensorineural hearing loss.

OBJECTIVE: We evaluated hearing outcomes in patients with sudden hearing loss and vestibular schwannoma who underwent a hearing preservation operation for tumor resection in an effort to determine whether a history of sudden sensorineural hearing loss has an impact on subsequent hearing preservation surgery. METHODS: Retrospective chart review of 45 patients operated between 1990 and 1998. Patients were divided into "Recovery" (n = 22) and "No Recovery" (n = 23) groups based on preoperative hearing recovery. Hearing preservation was assessed using the AAO-HNS hearing classification system. RESULTS: Measurable hearing was preserved in 73% of patients, with 47% having good postoperative hearing (AAO-HNS Classes A-B). There was no significant difference in hearing outcome from patients presenting with progressive hearing loss (45% Classes A-B). There was also no difference in postoperative hearing between the "Recovery" and "No Recovery" groups. CONCLUSIONS: Patients with sudden hearing loss and vestibular schwannoma have the same chance of hearing preservation after tumor removal as those with progressive loss. Preoperative recovery of hearing is not predictive of hearing preservation. Available data support the nerve compression theory as the mechanism of sudden hearing loss in patients with vestibular schwannoma.

Early proactive management of vestibular schwannomas in neurofibromatosis type 2.

OBJECTIVE: The treatment of patients with neurofibromatosis Type 2 has always been challenging for neurosurgeons and neurotologists. Guidelines for appropriate management of this devastating disease are controversial. METHODS: A retrospective study of 28 patients with neurofibromatosis Type 2 who underwent 40 middle fossa craniotomies for excision of their acoustic tumors is reported. Eleven patients underwent bilateral procedures. The study focused on hearing preservation and facial nerve results for this group of patients. The 16 male patients and 12 female patients ranged in age (at the time of surgery) from 10 to 70 years, with a mean age of 22.6 years. The mean tumor size was 1.1 cm (range, 0.5-3.2 cm), and the majority of tumors were less than 1.5 cm. RESULTS: Measurable hearing was preserved in 28 ears (70%), with 42.5% being within 15 dB pure-tone average and 15% speech discrimination score of preoperative levels. In 55% of cases there was no change in the hearing class, as defined by the American Academy of Otolaryngology-Head and Neck Surgery. Of the 11 patients who underwent bilateral operations, 9 (82%) retained some hearing bilaterally. After 1-year follow-up periods (mean, 12.8 mo), 87.5% of patients exhibited normal facial nerve function (House-Brackmann Grade I). CONCLUSION: Early surgical intervention to treat acoustic tumors among patients with neurofibromatosis Type 2 is a feasible treatment strategy, with high rates of hearing and facial nerve function preservation.

Brainstem electronic implants for bilateral anacusis following surgical removal of cerebello pontine angle lesions.

The multichannel auditory brainstem implant (ABI) has been used successfully to treat deafness in individuals with neurofibromatosis type II. The device has been implanted in nearly 150 recipients worldwide, and clinical trials with the device are approaching completion. The implantation and fitting of the multichannel ABI differ significantly from cochlear implantation, and the processes are illustrated in a series of case studies. Performance data also are included from recipients with up to 7 years experience.

Twenty-year report of the first auditory brain stem nucleus implant.

We present the 20-year case report of an auditory implant placed on the dorsal cochlear nucleus with long-term electrical stimulation in a patient with neurofibromatosis 2. The patient has continued to use her implant daily for 20 years, and it has greatly enhanced her quality of life. There have been no adverse sequelae.

Restoration of hearing with an auditory brainstem implant in a patient with neurofibromatosis type 2--case report.

A 25-year-old male with neurofibromatosis type 2 had hearing restored with an auditory brainstem implant (ABI) after removal of an acoustic schwannoma. The ABI allows the patient to discern many different environment sounds and is a significant adjunct to lip-reading, enabling conversation with people who have clear pronunciation without the necessity for writing.

Prognostic factors for hearing preservation in vestibular schwannoma surgery.

OBJECTIVE: To determine whether prognostic indicators for hearing preservation could be identified in patients with vestibular schwannoma undergoing middle fossa craniotomy resection. STUDY DESIGN: Prospective case review. SETTING: Private practice tertiary referral center. PATIENTS: 333 patients with serviceable hearing and vestibular schwannoma resected by middle fossa craniotomy from 1992 to 1998. MAIN OUTCOME MEASURES: Potential prognostic indicators, including tumor size and nerve of origin, preoperative pure-tone average, speech discrimination, distortion product otoacoustic emission testing, age, auditory brainstem response (ABR), and electronystagmography. RESULTS: Postoperative hearing near preoperative levels was attained in 167 patients (50%), with an American Academy of Otolaryngology-Head and Neck Surgery Class A hearing result in 33% and a Class B result in 26%. Comparison of potential prognostic indicators between groups with hearing preserved and the group with no measurable hearing revealed significant differences in preoperative hearing, ABR, and tumor origin data. Better preoperative hearing, shorter intraaural wave V latency, shorter absolute wave V latency, and superior vestibular nerve origin were associated with higher rates of hearing preservation. CONCLUSIONS: Preoperative hearing status, ABR, and intraoperative tumor origin data were shown to be of value as prognostic indicators.

Coexpression of neurotrophic growth factors and their receptors in human facial motor neurons.

Neuronal development and maintenance of facial motor neurons is believed to be regulated by neurotrophic growth factors. Using celloidin-embedded sections, we evaluated immunoreactivity of 11 neurotrophic factors and their receptors in facial nuclei of human brain stems (4 normal cases, and 1 from a patient with facial palsy and synkinesis). In the normal subjects, positive immunoreactivity of the growth factor neurotrophin-4 and acidic fibroblast growth factor (aFGF) was observed in facial motor neurons, as was positive immunoreactivity against ret, the receptor shared by glial cell line-derived neurotrophic factor and neurturin. Immunoreactivity was moderate for the receptor trkB and strong for trkC. In the case of partial facial palsy, surviving cells failed to show immunoreactivity against neurotrophins. However, immunoreactivity of aFGF was up-regulated in both neuronal and non-neuronal cells in this patient. Results suggest that these trophic growth factors and their receptors may protect facial neurons from secondary degeneration and promote regrowth of the facial nerve after axotomy or injury.

Report of 190 consecutive cases of large acoustic tumors (vestibular schwannoma) removed via the translabyrinthine approach.

OBJECT: The choice of approach for surgical removal of large acoustic neuromas is still controversial. The authors reviewed the results in a series of patients who underwent removal of large tumors via the translabyrinthine approach. METHODS: The authors conducted a database analysis of 190 patients (89 men and 101 women) with acoustic neuromas 3 cm or greater in size. The mean age of these patients was 46.1+/-15.6 years. One hundred seventy-eight patients underwent primary translabyrinthine surgical removal and 12 underwent surgery for residual tumor. Total tumor removal was accomplished in 183 cases (96.3%). The tumor was adherent to the facial nerve to some degree in 64% of the cases, but the facial nerve was preserved anatomically in 178 (93.7%) of the patients. Divided nerves were repaired by primary attachment or cable graft. Facial nerve function was assessed immediately after surgery, at the time of discharge, and at 3 to 4 weeks and 1 year after discharge. Excellent function (House-Brackmann facial nerve Grade I or II) was present in 55%, 33.9%, 38.8%, and 52.6% of the patients for each time interval, respectively, with acceptable function (Grades I-IV) in 81% at 1 year. Cerebrospinal fluid leakage that required surgical repair occurred in only 1.1% of the patients and meningitis in 3.7%. There were no deaths. CONCLUSIONS: Use of the translabyrinthine approach for removal of large tumors resulted in good anatomical and functional preservation of the facial nerve, with minimum incidence of morbidity and no incidence of mortality. The authors continue to recommend use of this approach for acoustic tumors larger than 3 cm and for smaller tumors when hearing preservation is not an issue.

The multichannel auditory brain stem implant: performance in twenty patients.

The auditory brain stem implant has been used effectively to provide hearing sensations to individuals deafened by bilateral auditory nerve tumors (neurofibromatosis type 2). During tumor removal, the auditory brain stem implant is implanted into the lateral recess of the fourth ventricle by a translabyrinthine approach and is intended to stimulate auditory neurons of the cochlear nucleus complex. A new eight-electrode multichannel auditory brain stem implant was developed and evaluated in 20 patients who had at least 3 months' experience with the device. Mild nonauditory sensations (primarily tingling in the head or torso) were encountered in some instances but could be managed by changing the stimulus characteristics or excluding electrodes. Testing of perceptual performance indicated significant benefit from the device for communication purposes, including sound-only sentence recognition scores in three patients ranging from 49% to 58% and ability to converse on the telephone. These results indicate that significant auditory benefit can be derived from direct multichannel electrical stimulation of the auditory portion of the human brain stem.

Primary lymphoma of the internal auditory canal. Case report and review of the literature.

We report a rare case of a primary intracranial B cell lymphoma originating in the internal auditory canal. The clinical manifestations were indistinguishable from those of other, more common tumors of the same region. We achieved total gross tumor removal with preservation of the facial nerve. A detailed histologic examination and a systemic workup confirmed the primary nature of this tumor. To our knowledge, this is the second case reported in the literature of a primary malignant lymphoma originating in the internal auditory canal. This is the first instance that includes immunohistochemical and cytometric studies of fresh tissue. We discuss the management of primary lymphomas of the central nervous system, with special emphasis on their association with acquired immunodeficiency syndrome and other immune system diseases. Awareness of primary central nervous system lymphomas is important, since a greater occurrence of these rare tumors in the cerebellopontine angle is probable in the future.

Management of the contracted mastoid in the translabyrinthine removal of acoustic neuroma.

Several approaches to the internal auditory canal and cerebellopontine angle for acoustic neuroma removal have been described. We prefer the translabyrinthine approach in patients with tumors larger than 2 cm or poor preoperative hearing, since both factors predict poor hearing preservation. Many surgeons perceive this approach as confining and consider it contraindicated in large tumors or contracted mastoids. We have recently described the utility of the translabyrinthine approach for the removal of large (> 4 cm) acoustic neuromas. In more than 5000 tumor excisions performed by the senior author (W.E.H.), no cases required a modification of the approach because of anatomic constraints within the mastoid. We describe our techniques for the management of the low-lying tegmen, the anterior sigmoid sinus, and the high jugular bulb, alone or in combination, during translabyrinthine removal of acoustic neuromas.

Direct cochlear nerve action potentials as an aid to hearing preservation in middle fossa acoustic neuroma resection.

A new application of auditory evoked potentials using direct cochlear nerve action potentials (CNAPs) for monitoring middle fossa acoustic neuroma resection with attempted hearing preservation is described. Twenty patients have been studied to date. With this technique, a monitoring electrode is secured between the floor of the internal auditory canal and the dura adjacent to the cochlear nerve in an extradural location. Standard auditory evoked potential techniques with click stimuli and microelectrical recording allow observation of nearfield waveforms in seconds versus several minutes required for farfield potentials recorded from the scalp. Advantages of this technique over auditory brainstem response monitoring may include nearly real time measurement of potentials, improved surgeon learning curve and possibly higher rates of hearing preservation, and applicability to all patients undergoing hearing-preservation surgery independent of presence or absence of ABR tracing. Immediate changes in amplitude and latency of waveforms appear to compare with reversible and irreversible intraoperative auditory system damage, thereby guiding surgical maneuvers.

Acoustic neuroma recurrence after suboccipital resection: management with translabyrinthine resection.

Thirty-five patients with recurrent acoustic tumors have been studied before, during, and after revision surgery. Each had their original surgery via a suboccipital approach. Six patients had undergone multiple suboccipital surgeries. Revision surgery was accomplished using a translabyrinthine approach in all patients. Total tumor removal was possible in 33 patients. No second recurrences have occurred to date among the patients with total tumor removal. Anatomic facial nerve integrity was maintained in 24 patients. All recurrent tumors were present in the lateral internal auditory canal. Direct tumor access in this area is not possible with the suboccipital approach without entering the vestibular labyrinth. The suboccipital approach to acoustic neuromas is contraindicated if tumor extends to the fundus of the internal auditory canal. Translabyrinthine resection is the treatment of choice for recurrence of acoustic neuroma after primary suboccipital resection.

Modified retrosigmoid approach: use for selected acoustic tumor removal.

The authors have used a modified retrosigmoid (suboccipital) approach for removal of acoustic tumors in selected patients who have good preoperative hearing and whose tumor does not reach the brain stem or extend to the lateral third of the internal auditory canal. This report presents the surgical technique and results for 15 acoustic neuromas removed by members of the House Ear Clinic between 1986 and 1991 using this approach. The technique differs importantly from the standard suboccipital approach. A mastoidectomy with decompression of the sigmoid sinus allows forward retraction of the sigmoid sinus, enabling tumor removal without cerebellar retraction. Also, replacement of the craniotomy flap prevents adherence to the dura of the scalp, which may prevent postoperative headaches. Tumor size ranged from 0.8 cm to 4.0 cm (mean, 1.9 cm). At 1 year or more postoperative, 13 of the 14 patients with follow-up available had a House-Brackmann (H-B) facial nerve grade I, and one patient had H-B grade II. Three patients retained good hearing ( < or = 30 dB SRT and > or = 70% speech discrimination) postoperatively, and 57% retained at least measurable hearing. For a patient with good preoperative hearing and a tumor that is medially based, involving the cerebellopontine angle but not extending to the brain stem or the lateral end or the internal auditory canal, the authors will continue to use the retrosigmoid approach for tumor removal.

Preservation of auditory and vestibular function after surgical removal of bilateral vestibular schwannomas in a patient with neurofibromatosis type 2.

The outcome of acoustic neuroma (vestibular schwannoma) surgery continues to improve rapidly. Advances can be attributed to several fields, but the most important contributions have arisen from the identification of the genes responsible for the dominant inheritance of neurofibromatosis types 1 (NF1) and 2 (NF2) and the development of magnetic resonance imaging with gadolinium enhancement for the early anatomic confirmation of the pathognomonic, bilateral vestibular schwannomas in NF2. These advances enable early diagnosis and treatment when the tumors are small in virtually all subjects at risk for NF2. The authors suggest that advising young NF2 patients to wait until complications develop, especially hearing loss, before diagnosing and operating for bilateral eighth nerve schwannomas may not always be in the best interest of the patient. To the authors' knowledge, this is the first reported case of preservation of both auditory and vestibular function in a patient after bilateral vestibular schwannoma excision.

Acute postoperative hydrocephalus following translabyrinthine craniotomy for acoustic neuroma resection.

Acute mental status changes following craniotomy for acoustic tumors demand prompt evaluation and treatment to avoid serious morbidity and mortality. Two cases of acute obstructive hydrocephalus complicating the postoperative period following translabyrinthine craniotomy are presented. Diagnosis is made with noncontrast computed tomography scanning. Treatment is rendered at the bedside with placement of a ventriculostomy. Diagnosis and management implications for acoustic tumor patients are discussed.

Comprehensive management of bilateral acoustic neuromas. Current perspectives.

Bilateral acoustic neuromas are pathognomonic for neurofibromatosis 2. Patients with neurofibromatosis 2 present complex and challenging management problems, because growth or surgical removal of the acoustic neuroma may result in total hearing loss. Early diagnosis with gadolinium-enhanced magnetic resonance imaging and refinements in hearing preservation surgery have improved our ability to prevent total hearing loss. For patients with larger tumors or no useful hearing, the auditory brain-stem implant allows restoration of some auditory function when the tumor is removed. We describe our management strategy for patients with bilateral acoustic neuromas, and present case reports to show their diversity. We also discuss the newly identified neurofibromatosis 2 tumor suppressor gene.

Technical modifications to the middle fossa craniotomy approach in removal of acoustic neuromas.

With the increased use of gadolinium-enhanced magnetic resonance imaging studies to detect acoustic neuromas, smaller tumors are discovered more frequently. The middle fossa craniotomy approach for removal of small tumors is ideal for hearing preservation. The authors report hearing preserved at or near the preoperative levels in 71 percent of a series of 24 consecutive patients in whom the middle fossa craniotomy approach was employed. Several technical modifications, including more extensive bony exposure medially, tumor dissection in a medial-to-lateral direction, and topical application of papaverine to the cochlear nerve at the modiolus, have enhanced the ability to preserve hearing.

Translabyrinthine removal of large acoustic neuromas.

Several surgical approaches to the cerebellopontine angle and internal auditory canal have been developed for the removal of acoustic neuromas. The choice of an approach may be influenced by hearing levels and tumor size. We reviewed the records of the primary translabyrinthine removal of 167 large (> or = 4 cm) acoustic neuromas performed between 1982 and 1990. Patients ranged in age from 15 to 83 years, with a mean of 43 years (male, 49%; female, 51%). Total removal was achieved in 95%. The facial nerve was preserved anatomically intact in 91%. At follow-up (mean, 2.1 yr), facial nerve function was acceptable (Grades I-IV) in 75% and good (Grades I-II) in 42%. Vascular complications occurred in 4.8%; however, there were no deaths. A cerebrospinal fluid leak occurred in 9.6% of cases, and meningitis occurred in 8.3%. In patients with large tumors where there is little chance to preserve preoperative hearing, we have successfully used the translabyrinthine approach for total tumor removal. The advantages and disadvantages of both the translabyrinthine and suboccipital approaches are discussed.