Large Acoustic Neurinoma Research Articles

Is “total” tumor resection and facial nerve functional preservation possible in large acoustic neurinoma?

Is “total” tumor resection and facial nerve functional preservation possible in large acoustic neurinoma?

Bilateral acoustic neurinomas

A 20-year-old girl with family history of neurofibromatosis presented with complaints of decreased hearing in both ears, change in voice, headaches and progressive ataxia for the past 1 year. On admission, she was alert, active but dysarthric. There was bilateral horizontal gaze evoked nystagmus. Fundus examination revealed bilateral papilledema. The right corneal reflex was depressed and the sensations over the right side of face were marginally decreased. There was right facial paresis, bilateral sensorineural deafness and severe truncal ataxia. There were marked bilateral cerebellar signs. MR imaging showed large bilateral acoustic neurinomas severely compressing the brainstem [Figures 1 and 2]. It was difficult even to identify the brainstem in certain sequential images. A radical resection of both acoustic neurinomas was performed through bilateral retromastoid craniectomies in two stages at an interval of 3 months. On both sides, a thin sheath of tumor was left behind adjacent to the facial nerves in an attempt to save their function. The patient developed right facial palsy following the first surgery and needed tarsorrhaphy. However, her ataxia improved remarkably. Post-operative MR imaging showed considerable reformation of the brainstem [Figure 3].

Removal of large acoustic neurinomas (vestibular schwannomas) by the retrosigmoid approach with no mortality and minimal morbidity

Objective: To evaluate the safety and efficacy of removing large acoustic neurinomas (⩾3 cm) by the retrosigmoid approach. Methods: Large acoustic neurinomas (mean (SD), 4.1 (0.6) cm) were removed from...

Electrocochleogram after transection of vestibulo-cochlear nerve in a patient with a large acoustic neurinoma

This study reports pre- and post-operative compound action potentials (CAPs) that were recorded from a 27-year-old woman with an acoustic neurinoma. During surgery it was necessary to totally sever her vestibulo-cochlear nerve to excise a large tumor. A pure tone audiogram changed to the scale-out pattern immediately after operation. However, CAP, the waveform of which was broadened, has been recorded 3 years post-operatively with a threshold elevation of 10 dB over the pre-operative threshold. This phenomenon suggests that CAP may originate from the extreme periphery of the auditory nerve within the cochlea. The broadening of the CAP was assumed to result from enhancement of the negative summating potential included in the CAP. We studied the effect of preceding stimulus on CAP using paired click stimuli pre- and post-operatively. A reduction of CAP amplitude in response to the second click of paired clicks was markedly suppressed in the inter-click interval between 3 and 80 ms post-operatively. We speculate that depletion of adaptation induced the abnormal CAP recovery described above and that the lateral efferent nerve system was involved in abnormal CAP adaptation with transection of the vestibulo-cochlear nerve in this case.

口腔症状から発見された聴神経鞘腫の１例

A case of acoustic neurinoma associated with oral symptoms is described. The patient was a 55-year-old woman with discomfort and hypesthesia of the left side of the mandibular gingiva, tongue, and buccal mucosa. She was referred to a neurosurgeon, because her history and symptoms suggested an intracranial neoplasm. The presence of a large acoustic neurinoma was observed in the left cerebellopontine angle on computed tomography and magnetic resonance imaging. The tumor was successfully removed, but the patient died of cardiovascular and respiratory insufficiency. The histological diagnosis was consistent with the clinical diagnosis. Hearing loss, dizziness, ear obstruction, and tinnitus are the major symptoms of this tumor. Thus, it is unfamiliar to oral and maxillofacial surgeons. However, trigeminal and facial nerve symptoms such as hypesthesia of the oral mucosa and facial skin may appear with tumor growth. Therefore, it should be included in the differential diagnosis in patients with symptoms suggesting involvement of the trigeminal and facial nerves.

Preservation of hearing in large acoustic neurinomas following removal via suboccipito-lateral approach.

A consecutive series of 61 patients with pre-operative hearing underwent surgical removal of a large acoustic neurinoma via the lateral suboccipital approach between 1984 and 1996. Brain-stem auditory evoked potentials (BAEP) were present in all cases before surgery and all patients underwent intra-operative monitoring of BAEP. The average tumour size including the portion within the meatus acusticus internus was 30, 5 mm (range 20 mm-49 mm). Complete tumour removal was achieved in all but three cases. In 43.1% of patients with complete tumour removal hearing was preserved initially after surgery. Delayed postoperative hearing loss was observed in 11 patients and hearing recovery in 2 patients leading to 27.5% definite hearing preservation. Hearing preservation was achieved in 37% of cases with tumour size between 20 mm-29 mm and in 23.5% of case with tumour size larger than 30 mm. These results indicate that even in large neurinoms hearing preservation should be attempted in all patients with documented pre-operative hearing and BAEP.

P-5-653 - The treatment of large acoustic neurinomas: Microsurgery, prophylaxis of ischemic complications

In the present study, we examined the cranial nerve foramina of Risso's dolphin (Grampus griseus). There were two distinguishable characters in the cranial nerve foramina compared with terrestrial mammals. One was that the foramen infraorbitale was composed of several holes, but not a single hole. They should therefore be termed foramina infraorbitales. The infraorbital nerves ran through these foramina, went into the ‘melon’ and then branched in a complicated fashion. The facial nerve innervated the muscles surrounding the melon. A welldeveloped infraorbital and facial nerve complex may control the melon. Another was the presence of a porus acusticus internus and independent tympano-periotic bone. The separate ear bone forced the vestibulocochlear and facial nerves to exit from the cranial cavity through the porus acusticus internus. The independent ear bone structure may shut off the noise from the cranial bone to the periotic bone with a true receptor of hearing. It may be an adaptation for an acute sense of hearing. Compared with other dolphins, the cranial foramina of Risso's dolphin are definitely separate. The structure of the foramina is similar to that of pilot whales, but not to dolphins, so that Grampus may be closely allied to pilot whales.

Long-term follow-up of the residual intracanalicular tumours after subtotal removal of acoustic neurinomas.

We examined growth potential of residual intracanalicular tumours left from subtotal removal of large acoustic neurinomas. Eleven patients were followed-up by magnetic resonance (MR) imaging. The interval between surgery and MR study ranged from 12 to 29 years (median, 16 years). MR images of two patients showed no evidence of tumour remnant, and in six a small tumour was localized in the internal auditory canal. The other three showed an intracanalicular tumour protruding slightly towards the intracranial portion. This result suggests that the intracanalicular residual tumours have less risk of regrowth after subtotal removal of acoustic neurinomas. It is advisable to choose intracapsular, subtotal removal without opening the internal auditory canal in the treatment of acoustic neurinoma, if it is large in size and there is a high risk of nerve injury.

Hemihypoglossal—facial nerve anastomosis in treating unilateral facial palsy after acoustic neurinoma resection

Eight patients underwent hemihypoglossal-facial nerve anastomosis (anastomosis of a split hypoglossal nerve to the facial nerve) for treatment of unilateral facial palsy. All patients previously had undergone resection of a large acoustic neurinoma and the facial nerve had been resected at that time. The interval between tumor resection and hemihypoglossal-facial nerve anastomosis ranged from 1 to 6 months, with an average of 2.1 months. Postoperative recovery of facial movement was good in all cases during an average follow-up period of 4.2 years. In all eight patients, the degree of hypoglossal nerve atrophy on the operated side was graded mild or moderate, but not severe. It was concluded that hemihypoglossal-facial nerve anastomosis results in good facial reanimation as long as the procedure is performed early after the onset of facial palsy and that this procedure may reduce the degree of hemiglossal atrophy in comparison with classic hypoglossal-facial nerve anastomosis.

Full recovery from deafness after removal of a large acoustic neurinoma associated with neurofibromatosis 2: Case report

The first case of full recovery from deafness after radical intracapsular removal of a large acoustic neurinoma, more than 4 cm in diameter, is reported. The patient, a 17-year-old woman, had multiple intracranial and intraspinal tumors in addition to bilateral acoustic neurinomas. Radical intracapsular removal is a useful technique to preserve nerves in patients with large acoustic neurinoma. When identifiable evoked potentials are preserved in brain stem auditory evoked potential, hearing preservation should be tried despite preoperative hearing level.

Interface between the facial nerve and large acoustic neurinomas. Immunohistochemical study of the cleavage plane in NF2 and non-NF2 cases.

In acoustic neurinoma surgery, the surgeon is required to find a cleavage plane between the facial nerve and the tumor, and with the aid of the operating microscope this is usually achieved by fine dissection. A histological specimen of the nerve-tumor interface is available only if the facial nerve was hopelessly adherent to the tumor (usually a large or giant neoplasm) and the surgeon decided to sever the nerve to obtain a complete removal. The authors have examined immunohistochemically the nerve-tumor interface of 20 such facial nerves (six cases of neurofibromatosis 2 (NF2) and 14 of non-NF2) in a series of 351 acoustic neurinomas. The largest extrameatal dimension of the 20 tumors ranged from 20 to 51 mm (median 39 mm). In all of these 20 instances the nerve-tumor contact area was at least partially devoid of a clear-cut histological cleavage plane. Where the facial nerve trunk was attached to the surface of the tumor, nerve fibers of the contact areas either abutted directly against tumor cells or nerve fibers were seen to penetrate into the tumor tissue. Frank embedding of nerve fibers was more frequent in NF2.

Delayed Hearing Loss after Surgery for Acoustic Neurinomas: Clinical and Electrophysiological Observations

Abstract In a series of 26 patients with medium-sized and large acoustic neurinomas and documented hearing before surgery, 7 patients had preservation of hearing initially after the procedure but then developed delayed hearing loss. The most prominent intraoperative electrophysiological finding in these cases was a gradual deterioration of brain stem auditory evoked potentials (BAEP);, especially of Wave V. Four additional patients with a similar gradual intraoperative loss of BAEP and severe postoperative hearing deterioration received vasoactive treatment after surgery (low-molecular weight dextran);. In all 4 patients, including 1 patient with documented total deafness after surgery, hearing was preserved. Initial preservation of cochlear nerve function after the removal of an acoustic neurinoma does not guarantee postoperative hearing. Intraoperative BAEP help to identify patients at risk for delayed postoperative hearing loss. The pathophysiological mechanism can be attributed to disturbances of the microcirculation in endoneurial vasa nervorum caused by the mechanical manipulation of the cochlear nerve.

Delayed hearing loss after surgery for acoustic neurinomas

In a series of 26 patients with medium-sized and large acoustic neurinomas and documented hearing before surgery, 7 patients had preservation of hearing initially after the procedure but then developed delayed hearing loss. The most prominent intraoperative electrophysiological finding in these cases was a gradual deterioration of brain stem auditory evoked potentials (BAEP), especially of Wave V. Four additional patients with a similar gradual intraoperative loss of BAEP and severe postoperative hearing deterioration received vasoactive treatment after surgery (low-molecular weight dextran). In all 4 patients, including 1 patient with documented total deafness after surgery, hearing was preserved. Initial preservation of cochlear nerve function after the removal of an acoustic neurinoma does not guarantee postoperative hearing. Intraoperative BAEP help to identify patients at risk for delayed postoperative hearing loss. The pathophysiological mechanism can be attributed to disturbances of the microcirculation in endoneurial vasa nervorum caused by the mechanical manipulation of the cochlear nerve.

Radical intracapsular removal of acoustic neurinomas

Historically, the neurosurgical treatment of large acoustic neurinomas has developed with two principal goals: complete tumor removal and preservation of facial nerve function. A recent goal for small tumors is the preservation of hearing. Out of a personal series of 124 acoustic neurinomas treated over the past 35 years, the senior author has undertaken a radical intracapsular approach in 12 patients with large tumors (greater than 3 cm in diameter). Surgical indications for intracapsular removal included advanced age (five cases), the patient's wish to avoid any risk of facial paralysis (six cases), contralateral facial palsy (one case), and contralateral deafness (one case). Eleven of these 12 patients were available for follow-up review. Tumor recurrence developed in two patients (18%) at 2 and 3 years postoperatively; there were no late recurrences. Four patients died of unrelated causes, 10 to 19 years after surgery. The remaining five patients have survived a mean of 12 years since surgery without recurrence (range 3 to 22 years). Facial function was preserved in nine patients (82%). The results suggest that radical intracapsular removal may be the procedure of choice under certain circumstances and may offer an alternative to focused high-energy radiation.

Temporal Bone Pathology of Acoustic Neurinoma (Unilateral and Bilateral) in Relation to the Internal Auditory Canal Surgery

Temporal bone pathology of 3 cases with large unilateral acoustic neurinoma (AN) and 2 cases with large bilateral AN (neurofibromatosis 2; NF2) were studied. One case with unilateral AN was diagnosed as neurofibromatosis 1 (NF1). Unilateral AN had distinct borderlines at the fundus in 5 of 12 examination points between tumor tissues and nerve fibers, but only 1 of 12 was distinct around the porus acousticus. Bilateral AN showed no distinct borderlines at the fundus and around the porus acousticus. These findings suggest that clear separation of the VIIth or VIIIth nerve from large tumors is very difficult, especially in cases of bilateral AN. Geniculate ganglion cells of tumor origin on ears were fairly well preserved in 2 cases with unilateral AN and 1 case with bilateral AN. Well preserved geniculate ganglion cells could be dependent on blood supply not from the internal auditory artery.

Case report: Acoustic neuroma presenting as a cyst with fluid level

A rare case of large cystic acoustic neurinoma with fluid level is described. The pathogenesis of the lesion and its differential diagnosis, particularly from meningioma, are briefly discussed.

Neuroradiology of intracranial neuromas

A rare case of large cystic acoustic neurinoma with fluid level is described. The pathogenesis of the lesion and its differential diagnosis, particularly from meningioma, are briefly discussed.

Technical and instrumental improvements in the surgical treatment of acoustic neurinomas.

Microsurgical removal of large acoustic neurinomas, more than 3 cm in diameter, has been performed by the lateral suboccipital transmeatal approach with the patient in the lateral position in 68 cases in the past 5 years. sixty-two patients (92%) returned to their former occupations and two died: one in the immediate postoperative period and the other 16 months later. The postoperative follow-up examination showed satisfactory facial nerve function in 70% of the patients. Hearing was preserved in six of 14 patients who had preoperatively retained their auditory function. The authors emphasize the usefulness of bipolar forceps for intraoperative stimulation of the facial nerve and for facial muscle monitoring. The value of the four-pronged hook and the multipurpose head-frame in this procedure is also discussed.

Diagnostic significance of brainstem auditory evoked responses in acoustic neurinomas and other posterior fossa lesions.

Brainstem auditory evoked responses (BER) have been studied in 67 supratentorial lesions, 10 midbrain lesions, 23 intrinsic pontine lesions and 27 extrinsic compressions of the pons, including 15 acoustic neurinomas. BER in supratentorial lesions showed completely normal records. In midbrain lesions wave V was specifically altered. As wave I is a far field reflection of the VIII nerve potential and wave V the midbrain potential, waves II to IV can be inferred to originate in the central auditory pathway between the peripheral VIII nerve and the midbrain. Alterations of these waves correlated well with the location and nature of brainstem lesions. The BER in large acoustic neurinomas showed no response to clicks on the affected side and waves of delayed latencies with stimulation on the normal side. In small to medium-sized tumors with preservation of hearing, wave I of normal or delayed latency was recorded and subsequent components were absent in the majority of cases. These alterations of BER are closely related to the size and location of the tumors.

Surgery for acoustic neurinoma.

This presentation is concerned with the one-stage translabyrinthine operation of small acoustic neurinomas and a combined translabyrinthine suboccipital staged operation for removal of large acoustic neurinomas. The technique for the translabyrinthine approach to the cerebellopontine angle is described in detail and demonstrated by photographs of the dissection as it progresses. The technique includes both a one-staged translabyrinthine operation for removal of small acoustic neurinomas and preparation of the involved field when the second stage suboccipital operation is necessary. The first 75 consecutive cases are reviewed. Total removal of tumor was accomplished in 43 of these patients by the translabyrinthine route with incidence of 12% permanent facial nerve paralysis. Twenty-seven patients required a second stage suboccipital operation. Total removal was accomplished in 16 of these patients. Only three of the 11 patients with subtotal removal of tumor have required additional surgery. There was an incidence of permanent facial nerve paralysis in eight of these patients. Five of 75 patients underwent a translabyrinthine operation with subtotal removal of tumor. A second stage suboccipital operation was not performed in these patients because of advanced age or refusal. One of these five patients has a permanent facial paralysis and none have required further surgery to date. There was an incidence of 18% permanent facial paralysis among the entire 75 cases. The author prefers the hypoglossal facial nerve anastomosis procedure for rehabilitation for those patients with facial nerve paralysis. There has been no operative mortality in this entire series and 94% of the patients have been able to resume their previous level of work and activity. There was only one transient episode of cerebrospinal fluid otorhinorrhea among the 75 patients.