Evaluation and surgical treatment of acoustic neuroma

Gamma Knife Radiosurgery for Large Vestibular Schwannoma More Than 10 cm3: A Single-Center Indian Study

Introduction Gamma Knife radiosurgery (GKRS) is an effective treatment for benign vestibular schwannomas (VSs). The established cutoffs have recently been challenged, as recent literature expanded the horizon of GKRS to larger tumors. Even though microsurgery remains the primary option for large VS, GKRS can provide reasonable tumor control and is more likely to avoid cranial neuropathies associated with open surgery.

Methods We analyzed patients with VS with volume exceeding 10 cm3 who underwent GKRS at our center from January 2006 to December 2016. Clinicoradiological and radiosurgical data were collected from medical records for statistical analysis. Follow-up was performed every 6 months with a clinical assessment along with magnetic resonance imaging (MRI) of the brain and audiometric evaluation in patients with serviceable hearing.

Results The study included 34 patients (18 males and 16 females) with an average age of 45.5 years. The mean tumor volume was 10.9 cm3 (standard deviation [SD], ± 0.83), with a median tumor dose of 12 Gy (interquartile range, 11.5–12) and a mean follow-up of 34.7 months (SD, ± 23.8). Tumor response was graded as regression in 50%, stable in 44.1%, and increase or GKRS failure in 2 cases (5.8%). Treatment failure was noted in five cases (14.7%), requiring microsurgical excision and a ventriculoperitoneal shunt post-GKRS. The tumor control rate for the cohort is 85.3%, with a facial preservation rate of 96% (24/25) and hearing loss in all (5/5), while three patients developed new-onset hypoesthesia. We noted that gait ataxia and involvement of cranial nerve V or VII at initial presentation were associated with GKRS failure in univariate analysis.

Conclusion Microsurgery should remain the first-choice treatment option for large VSs. GKRS is a viable alternative with good tumor control and improved or stabilized cranial neuropathies with a low complication rate.

A Retrospective Clinicoradiologic Study of 126 Cerebellopontine Angle Tumors to Predict the Outcome of House–Brackmann Status to Prognosticate Them: A Single-Center Tertiary Care Perspective

Introduction House–Brackmann (HB) grading had been described to quantify the facial nerve involvement in cerebellopontine angle (CPA) tumors, a very common tumor in neurosurgical practice. Very few studies have specifically looked into the factors predicting the facial nerve morbidity and its severity. Here, we try finding these while going through the clinicoradiologic factors and its natural course to help us prognosticate the patients.

Objective To analyze the size of tumor and duration of symptoms to predict the severity of HB status of facial nerve presentation and outcome, and to study the course of the disease to help prognosticate the patients with respect to facial nerve status.

Materials and Methods This was a retrospective analysis of 126 operated CPA tumors, where we studied the natural course of HB status with respect to size and duration of symptoms of patients at our institute between December 2016 to February 2020.

Results Average duration of symptoms were 33.8 days with increasing risk of HB outcome after 36 days of symptoms. All patients improved to their preoperative facial nerve status at 3 months and only 18 maintained the worsened HB status. Average size of tumor was 3.53 cm, and size higher than 3.8 cm was associated with poorer HB outcome.

Conclusion Although there can be a significant deterioration of HB status in immediate postoperative period, it improves to preoperative status in due time. Tumor larger than 3.8 cm and symptom duration more than 36 days are two important factors predicting poorer HB outcome.

Evolving Role of Non-Total Resection in Management of Acoustic Neuroma in the Gamma Knife Era

OBJECTIVE

To examine patients with residual tumor after vestibular schwannoma (VS) resection with focus on need for further therapy, including stereotactic radiosurgery (SRS) and revision surgery.

STUDY DESIGN AND SETTING

Retrospective review at two tertiary otology referral centers.

PATIENTS AND INTERVENTION

Patients undergoing primary surgery for VS from 2007 to 2017.

MAIN OUTCOME MEASURE

Degree of resection and need for further treatment.

RESULTS

Of 289 patients undergoing surgery, 38 (13.1%) underwent subtotal resections (<95% of tumor resected) and 77 (26.6%) underwent near-total resections (≥95% but <100%). Patients with any residual tumor had larger tumors preoperatively (mean estimated volume 6.3 cm versus 2.1 cm, p < 0.0005) but were otherwise clinically and demographically similar to the population as a whole. Further treatment (surgery or SRS) was needed in 4.6, 14.3, and 50.0% of patients after gross total, near-total, and subtotal resections, respectively (p < 0.0005). Patients undergoing additional therapy had larger residual tumors (median post- to preoperative estimated volume ratio 0.09 versus 0.01, p < 0.0005). Patients undergoing subtotal and near-total resections had poorer facial function at ultimate follow up than those undergoing gross total resections (p = 0.001), likely due to larger tumors and more difficult resections. Literature review revealed higher rates of gross total resection as well as facial palsy in the pre-SRS era.

CONCLUSION

Residual tumor following VS resection is more common today than in the pre-SRS era. Availability of SRS may encourage leaving residual tumor intraoperatively to preserve neural structures. Current surgical strategies decrease surgical morbidity but necessitate further treatment in over 10% of cases.

Stereotactic radiosurgery for recurrent vestibular schwannoma after previous resection

OBJECTIVE

The goal of this retrospective cohort study was to assess long-term outcomes in patients with vestibular schwannoma (VS) who underwent stereotactic radiosurgery (SRS) after initial microsurgical resection.

METHODS

From the authors' database of 1770 patients with VS, the authors retrospectively analyzed data from 173 Gamma Knife SRS procedures for VS after 1 (128 procedures) or multiple (45 procedures) microsurgical resections. The median length of the interval between the last resection and SRS was 42 months (range 2–329 months). The median length of clinical follow-up was 74 months (range 6–285 months). Progression-free survival after SRS was determined with Kaplan-Meier analysis.

RESULTS

At the time of SRS, the hearing of 161 patients (93%) was Gardner-Robertson Class V, and 81 patients (47%) had facial neuropathy (i.e., facial function with House-Brackmann [HB] grades of III–VI), 87 (50%) had trigeminal neuropathy, and 71 (41%) reported imbalance or disequilibrium disorders. The median tumor volume was 2.7 cm3 (range 0.2–21.6 cm3), and the median dose to the tumor margin was 13 Gy (range 11–20 Gy). Radiosurgery controlled growth of 163 (94%) tumors. Progression-free survival after SRS was 97% at 3 years, 95% at 5 years, and 90% at 10 years. Four patients with delayed tumor progression underwent repeat SRS at a median of 35 months (range 23–64 months) after the first SRS. Four patients (2.3%) with tumor progression underwent repeat resection at a median of 25 months (range 19–33 months). Among the patients with any facial dysfunction (indicated by HB grades of II–VI), 19% had improvement in this condition after SRS, and 5.5% with some facial function (indicated by HB grades of I–V) developed more facial weakness. Among patients with trigeminal neuropathy, 20% had improvement in this condition, and 5.8% developed or had worsened trigeminal neuropathy after SRS.

CONCLUSIONS

Stereotactic radiosurgery offered a safe and effective long-term management strategy for VS patients whose tumors remained or recurred after initial microsurgery.

Hearing disorders in brainstem lesions

Auditory processing can be disrupted by brainstem lesions. It is estimated that approximately 57% of brainstem lesions are associated with auditory disorders. However diseases of the brainstem usually involve many structures, producing a plethora of other neurologic deficits, often relegating "auditory symptoms in the background." Lesions below or within the cochlear nuclei result in ipsilateral auditory-processing abnormalities detected in routine testing; disorders rostral to the cochlear nuclei may result in bilateral abnormalities or may be silent. Lesions in the superior olivary complex and trapezoid body show a mixture of ipsilateral, contralateral, and bilateral abnormalities, whereas lesions of the lateral lemniscus, inferior colliculus, and medial geniculate body do not affect peripheral auditory processing and result in predominantly subtle contralateral abnormalities that may be missed by routine auditory testing. In these cases psychophysical methods developed for the evaluation of central auditory function should be employed (e.g., dichotic listening, interaural time perception, sound localization). The extensive connections of the auditory brainstem nuclei not only are responsible for binaural interaction but also assure redundancy in the system. This redundancy may explain why small brainstem lesions are sometimes clinically silent. Any disorder of the brainstem (e.g., neoplasms, vascular disorders, infections, trauma, demyelinating disorders, neurodegenerative diseases, malformations) that involves the auditory pathways and/or centers may produce hearing abnormalities.

Pediatric cerebellopontine angle and internal auditory canal tumors: clinical article

OBJECT

The aim in this study was to describe the clinical presentation, differential diagnosis, and risk for neurofibromatosis Type 2 (NF2) in pediatric patients presenting with cerebellopontine angle (CPA) and internal auditory canal (IAC) tumors.

METHODS

The authors conducted a retrospective study at a tertiary care academic referral center. All patients with an age ≤ 18 years who had presented with an extraaxial CPA or IAC tumor between 1987 and 2012 were included in the study cohort. Data regarding symptoms, diagnosis, tumor characteristics, and NF2 status were collected and analyzed.

RESULTS

Sixty patients (55% female, 45% male) harboring 87 tumors were identified. The mean age at diagnosis was 12.8 years (median 14.0 years, range 0.9-18.9 years). Schwannomas were the most commonly identified lesions (57 of 87 tumors, including 52 vestibular, 3 facial, and 2 trigeminal schwannomas), followed by meningiomas (5 of 87) and epidermoid cysts (4 of 87). Six malignant tumors were diagnosed, including small-cell sarcoma, squamous cell carcinoma, malignant meningioma, atypical rhabdoid-teratoid tumor, endolymphatic sac tumor, and malignant ganglioglioma. Headache, followed by hearing loss and imbalance, was the most common presenting symptom, whereas dysphagia, otalgia, and facial pain were uncommon. Neurofibromatosis Type 2 was diagnosed in 20 (61%) of 33 patients with vestibular schwannoma (VS), while the other 13 patients (39%) had sporadic tumors. Nineteen of the 20 patients with NF2 met the diagnostic criteria for that disorder on initial presentation, and 15 of them presented with bilateral VS. At the last follow-up, 19 of the 20 patients subsequently diagnosed with NF2 demonstrated bilateral VSs, whereas 1 patient with a unilateral VS and multiple other NF2-associated tumors has yet to demonstrate a contralateral VS to date. Only 1 patient presenting with an isolated unilateral VS and no family history of NF2 demonstrated a contralateral VS on subsequent radiological screening.

CONCLUSIONS

Cerebellopontine angle and IAC tumors in the pediatric population are rare. There are several noteworthy differences between the adult and pediatric populations harboring these lesions. While VS is the most common pathology in both age groups, the lesion was found in only 60% of the pediatric patients in the present study. Unlike in adults, VSs in the pediatric population were associated with NF2 in over one-half of all cases. The majority of pediatric patients with NF2 fulfilled the diagnostic criteria at initial presentation; however, approximately 7% of patients presenting with a seemingly sporadic (no family history of NF2) unilateral VS will meet the criteria for NF2 later in life. Finally, malignancies account for a significantly higher percentage (10%) of cases among pediatric patients. These findings underscore the importance of early screening and close radiological follow-up and may be helpful in patient counseling.

Fractionated Conformal Radiotherapy in Vestibular Schwannoma: Early Results from a Single Centre

AIMS

To assess the local control and cranial nerve toxicity in vestibular schwannoma patients treated with fractionated conformal radiotherapy delivered using a linear accelerator.

MATERIALS AND METHODS

Ninety-five patients were referred for consultation to the Oncology Department in Addenbrookes Hospital between 1996 and 2005. The 42 cases who received fractionated conformal radiotherapy are the subject of this analysis. All patients had radiological or symptomatic progression. Conformal radiotherapy was prescribed at 50Gy in 30 fractions over 6 weeks, delivered using a linear accelerator. Patients were immobilised using either a beam direction shell or a Gill Thomas Cosman relocatable stereotactic head frame.

RESULTS

The median age was 63 years (range 28-81) with 57% men. The average tumour size was 21.5mm on magnetic resonance imaging. Before treatment, 20 (48%) patients were deemed to have useful hearing on the affected side. The median follow-up was 18.6 months (range 0.3-6.5 years) and the actuarial local control rate at 2.5 years was 96.9% (one patient progressed after treatment). In previously hearing patients, the actuarial rate of useful hearing preservation was 100%, and the rate of mild hearing loss was 20% at 1 year and 26.7% at 2.5 years of follow-up. There were five neurofibromatosis type 2 patients treated, two of whom had useful hearing before radiotherapy. In one patient this was affected, with a 20dB loss, although he still has useful hearing. In those with normal facial nerve function before radiotherapy (n=40), this was preserved in 96.8% at 2.5 years. Trigeminal nerve function was preserved in all patients (n=38) who had normal nerve function before radiotherapy.

CONCLUSION

Although follow-up was relatively short in this single institution series, fractionated linear accelerator radiotherapy gave excellent local control, useful hearing preservation and retained cranial nerve function in vestibular schwannoma.

A clinical, genetic and audiological study of patients and families with unilateral vestibular schwannomas. II. Audiological findings in 93 patients with unilateral vestibular schwannomas

Ninety-three patients with histolofically or radiolofically confiemd unilateral vestibular schwannomas were recruited. Audiological testing for retrocochelar pathology was undertaken. Patients' hospital records were examined for previous audiological and radiological results.

The audiometric configuration was designated as one of the following normal, sloping, low frequency, peak, through or falt. A sloping sensorneural audiometric configuration was present in 68 pec cent of cases. No significant correlation was found between tumour size and average pure tone threshold 500 HZ to 4000 HZ, optimum discrimination score or interaural differences for wave V. Ninety-one per cent of cases had abnoramalities on auditory evoked potential; 92 per cent of cases showed abnormalities on stapedial reflex testing.

The limitations of audiologica testing in the investigation of patients with suspected unilateral vestibular schwannomas are discussed. A protocol for the investigation of such patients is presented.

Solitary metastasis from occult follicular carcinoma of the thyroid mimicking trigeminal neurinoma--case report

A 50-year-old woman presented with an extremely uncommon case of solitary metastasis from follicular carcinoma of the thyroid, which presented clinically as trigeminal neurinoma. Neuroimaging detected a tumor in the right petrous apex, which was removed surgically. Histological examination showed metastatic follicular carcinoma of the thyroid. However, no primary tumor was detected by various investigations. The tumor recurred twice, and was treated surgically both times. The patient finally agreed to adjuvant therapy for the suspected primary. Radiotherapy was performed followed by complete thyroidectomy. Examination of the gross specimen found the tumor nodule. Clinically significant metastasis can arise from histologically benign and silent follicular thyroid neoplasms.

Retrosigmoid approach to acoustic neuroma (vestibular schwannoma)

The retrosigmoid approach for the microsurgical removal of an acoustic neuroma (vestibular schwannoma) is described, and perioperative medical management of the patient is discussed. The techniques for monitoring facial and cochlear nerve function are presented. The supine-oblique position, skin incision, bone removal, dural opening, and initial exposure are outlined. Important points in the technique for removing acoustic neuromas and preserving hearing, when possible, are described and illustrated.

Results of linear accelerator-based stereotactic radiosurgery for recurrent and newly diagnosed acoustic neuromas

Stereotactic radiosurgery (SRS) is used to treat acoustic neuromas, but additional information is needed to firmly establish its safety and efficacy. We review our experience over 7 years treating 29 consecutive patients with a modified linear accelerator (linac) SRS system. Between August 1989 and October 1995, 29 patients with a median age of 67 years (range 26 to 83) underwent linac SRS treatment. Twenty-five patients had unilateral acoustic neuromas, and four patients with neurofibromatosis type II had bilateral vestibular schwannoma. Eligibility criteria for SRS were recurrent tumors (n = 9), age >65 (n = 16), or patient preference (n = 6). Follow-up magnetic resonance imaging scans were performed on all patients. The most common presenting symptoms were hearing impairment (18 patients) and gait difficulties (17 patients). Ten patients were deaf in the affected ear prior to treatment. Doses to the periphery of the tumor ranged from 800 to 2,400 cGy (median 1, 600 cGy) prescribed to the 50% to 80% isodose line (median 80%). After a median radiographic follow-up of 49 months (range 4 to 110 months), 11 tumors were smaller, 17 were stable, and one had evidence of progression (at 41 months). The 5-year local disease control rate (Kaplan-Meier estimate) was 94%. Acute complications were minimal, with only two patients experiencing nausea and vomiting after the procedure. Long-term complications included new or progressive trigeminal and facial nerve deficits with estimated 5-year incidences of 15% and 32%, respectively. Subjective hearing reduction or loss occurred in 14 (74%) of the 19 patients who had useful hearing prior to treatment. Five patients died from unrelated causes. These results suggest that linac SRS provides excellent short-term tumor control rates. Since there was a high risk of cranial nerve neuropathy, we do not recommend using only computed tomography-based planning and high prescription doses. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 145-151 (2000).

Fractionated stereotactic radiation therapy and single high-dose radiosurgery for acoustic neuroma: early results of a prospective clinical study

PURPOSE

To prospectively assess the local control and toxicity rate in acoustic neuroma patients treated with linear accelerator-based radiosurgery and fractionated stereotactic radiation therapy.

METHODS AND MATERIALS

We evaluated 37 consecutive patients treated with stereotactic radiation therapy for acoustic neuroma. All patients had progressive tumors, progressive symptoms, or both. Mean tumor diameter was 2.3 cm (range 0.8-3.3) on magnetic resonance (MR) scan. Dentate patients were given a dose of 5x4 Gy or 5x5 Gy and edentate patients were given a dose of 1x10 Gy or 1x12.50 Gy prescribed to the 80% isodose. All patients were treated with a single isocenter.

RESULTS

With a mean follow-up period of 25 months (range 12-61), the actuarial local control rate at 5 years was 91% (only 1 patient failed). The actuarial rate of hearing preservation at 5 years was 66% in previously-hearing patients. The actuarial rate of freedom from trigeminal nerve toxicity was 97% at 5 years. No patient developed facial nerve toxicity or other complications.

CONCLUSION

In this unselected series, fractionated stereotactic radiation therapy and linear accelerator-based radiosurgery give excellent local control in acoustic neuroma. It combines a high rate of preservation of hearing with a very low rate of other toxicity, although follow-up is relatively short.

Fractionated stereotactic radiotherapy for the treatment of acoustic neuromas: preliminary results

PURPOSE

To evaluate the efficacy and toxicity of fractionated, stereotactic radiotherapy (SRT) for acoustic neuromas.

METHODS AND MATERIALS

Twelve patients with acoustic neuroma were treated with SRT between June 1992 and October 1994. Follow-up ranged from 16-44 months. Patient age ranged from 27-70 (median: 45). Eight patients were treated with primary SRT and four patients were treated after primary surgical intervention for recurrent [3] or persistent [1] disease. Tumor volumes were 1.2-18.4 cm3 (median: 10.1 cm3). Collimator sizes ranged from 30-50 mm (median: 37.5). Tumors received 1.8 Gy/day normalized to the 95% isodose line. Patients received a minimum prescribed dose of 54 Gy in 27-30 fractions over a 6-week period.

RESULTS

After a median follow-up of 26.5 months, local control was obtained in 12 out of 12 lesions. Tumor regression was noted in three patients, and tumor stabilization was found in the remaining nine patients. No patient developed a new cranial nerve deficit. One patients developed worsening of preexisting Vth cranial neuropathy and another experienced a decrease in hearing. However, all nine patients with useful hearing prior to SRT maintained useful hearing at last follow-up.

CONCLUSIONS

Stereotactic radiotherapy provided excellent local control without new cranial nerve deficits. These results must be viewed as tentative in nature because of the small number of patients and the short median follow-up period.

Acoustic cellular schwannoma invading the petrous bone: case report

Cellular schwannoma, a variant of benign schwannomas characterized by a high pseudosarcomatous cellularity, rarely involves the cranial nerves. In this report, we present the case of a 74-year-old woman with a cellular schwannoma of the VIIIth cranial nerve, which recurred from an ordinary schwannoma resected 9 years before. The tumor has been controlled for 35 months by a simple re-excision, indicating the benign nature of this tumor, although the tumor showed bone destruction and a high MiB-1 labeling ratio.

Acoustic neuroma: correlation among tumor size, symptoms, and patient age

Due to improved diagnostic techniques, acoustic neuromas more frequently are detected at an early stage. Subsequent treatment depends on such factors as expected tumor growth rate, tumor size, and patient age. The natural history of acoustic neuromas is still uncertain: This study was performed to examine possible correlations among tumor size, patient age, signs and symptoms, and duration of symptoms. The study included 164 patients with an acoustic neuroma who were treated at University Hospital Nijmegen, The Netherlands, over a period of 13 years. Comparisons were made between the findings of this study and the reports in the literature. No support was found for any of the correlations mentioned in other studies, and no relationships could be demonstrated between the parameters evaluated in this study. The authors therefore recommend that treatment policies be based only on well-established correlations.

Complications of translabyrinthine vs. suboccipital approach for acoustic tumor surgery

This study presents the operative results of surgeons with experience in both the translabyrinthine and suboccipital approaches to acoustic tumor removal for the purpose of resolving some of the controversy among centers favoring one approach over the other. The subjects were 171 patients with acoustic tumors who were treated at Virginia Mason Clinic from 1975 to 1986. The translabyrinthine approach was used in 64% of cases, the suboccipital approach in 35%, and the middle fossa approach in 1%. There were minor differences in morbidity and mortality between approaches. These data did not favor one approach over another. In an exploratory analysis, we found that the morbidity with a planned two-stage translabyrinthine-suboccipital removal was greater than the morbidity with a one-stage removal.

Radiation therapy for the treatment of non-eight nerve intracranial neurilemmoma

The records of 19 patients treated for intracranial neurilemmomas, other than of the eighth nerve, at the University of California, San Francisco from 1945 through 1983 were reviewed. One patient who died within 30 days following surgery was excluded from the analysis. The 5th and the 9/10/11th nerve complex were the most common sites of tumor origin. Patients were classified by the extent of surgical resection: total (90-99% resection, NTR), subtotal (less than 90% resection, STR) and biopsy. Five patients had total excision of their tumor without post-operative irradiation and none had recurred. One of the 2 patients who had STR and did not receive post-operative irradiation recurred, while 2 of the 3 patients who received post-operative irradiation following STR recurred. One of the 2 patients who had NTR and did not receive post-operative irradiation recurred, while 1 of the 3 patients who received post-operative irradiation following NTR recurred. Two patients were treated with post-operative irradiation following biopsy and one recurred. One patient was treated with planned preoperative irradiation to reduce tumor vascularity, followed by total resection. Because of the small number of patients, no firm conclusion regarding the efficacy of irradiation for non-eighth nerve intracranial neurilemmoma can be made.

Efficacy of irradiation for incompletely excised acoustic neurilemomas

The records of 124 patients treated for acoustic neurilemoma at the University of California, San Francisco, from 1945 through 1983 were reviewed. Patients were classified by the extent of surgical resection: total, nearly total (90% to 99% resection), subtotal (less than 90% resection), or biopsy. Thirty-one patients received irradiation as part of their primary treatment. Total resection of tumor, without irradiation, was associated with a 3% chance of local recurrence. One of 15 patients who had nearly total resection of their tumor and did not receive postoperative irradiation suffered a recurrence, compared with neither of the two patients who received postoperative irradiation (greater than 45 Gy) following nearly total resection. Postoperative irradiation (greater than 45 Gy) decreased the recurrence rate after subtotal resection from 46% (six of 13 cases without irradiation) to 6% (one of 17 cases: p = 0.01). All three patients treated by biopsy alone received postoperative irradiation (greater than 45 Gy), and none had a recurrence. Six patients were treated with preoperative irradiation because of excessive tumor vascularity; four are without evidence of disease 12 to 23 years later. Only three of seven patients treated with irradiation for tumor recurrence after surgical resection survived. It is concluded that postoperative irradiation significantly decreased the chance for local tumor progression following subtotal resection of acoustic neurilemoma, and that postoperative irradiation may be effective therapy following treatment by biopsy. Patients with total or nearly total resection appeared not to benefit from postoperative irradiation.

An extended middle fossa approach combined with a suboccipital craniectomy to the base of the skull in the posterior fossa

A new approach to the base of the skull in the posterior fossa is described. This approach involves removing the petrous bone without any injury to the labyrinth, and dividing the superior petrosal sinus and tentorium cerebelli. A combined suboccipital craniectomy is used for excision of the portion of tumors that extended inferiorly. Total or subtotal removal of tumors was performed in 11 patients and partial removal in 3 patients, without any operative mortality. The facial nerve was preserved in all patients and hearing was retained in 9 of 12 patients. This approach is useful for large tumors located around the clivus.

Spontaneous massive haemorrhage into acoustic neuroma during anticoagulation therapy

We report the case of a 58-year old man who bled into an undiagnosed acoustic neuroma while on long-term anticoagulation therapy which was commenced following aortic valve replacement. The patient presented with multiple cranial nerve-paralysis of sudden onset. The tumour was subtotally removed but died 5 days postoperatively from recurrent haemorrhage into the tumour bed.

Use of intraoperative auditory evoked potentials to preserve hearing in unilateral acoustic neuroma removal

Twenty-two patients with unilateral acoustic neuromas and preoperative speech discrimination scores of 35% or more had intraoperative monitoring of the electrocochleogram (ECoG) using a transtympanic electrode, and of the brain-stem auditory evoked potentials (BAEP's) using scalp electrodes. Rapid feedback was provided about the status of the cochlear microphonics from the hair cells of the inner ear (CM of the ECoG), the compound action potential of the auditory nerve (N-1 of the ECoG or Wave I of the BAEP's) and the potentials from the lower brain stem (Wave V of the BAEP's). All patients had total removal of the tumor. In 21, the cochlear nerve was anatomically preserved, and 20 had good postoperative facial nerve function. Correlation of tumor size with postoperative hearing was as follows: discrimination scores of more than 35% in three of four patients with 1-cm tumors, two of eight with 1.5-cm tumors, two of six with 2- to 2.5-cm tumors, and one of four with tumors of 3 cm or more. Two other patients with 1.5-cm tumors had discrimination scores of less than 35%, and one patient with a 2-cm tumor had only sound perception. In two patients, the discrimination scores improved. At the end of the operation, all patients with hearing had a detectable N-1, and, when recorded, CM. All but one patient with no hearing had lost N-1, and CM was absent or reduced. Unless Wave V was unchanged, it was a poor predictor of postoperative hearing, and its absence did not preclude preservation of good hearing. The electrophysiological changes during each stage of the operation were analyzed and correlated with events during surgery. Areas in which there was an increased risk of loss of the potentials were determined. In some patients monitoring was unnecessary, because either there were no significant changes or the changes were abrupt and no recovery occurred. However, in other patients, monitoring alerted the surgeon to a possible problem and the method of dissection was altered. Possible mechanisms of hearing loss were suggested from the changes in the recordings.

Sudden hemorrhage in an acoustic neuroma. Case report

The authors present a case of acoustic neuroma associated with spontaneous hemorrhage. The sudden onset of new symptoms was noted and appears to be common to all such cases. The computerized tomography appearance of the mass underwent changes consistent with the clinical, surgical, and pathological findings.

Acoustic neuroma surgery. Translabyrinthine-transtentorial approach via the middle cranial fossa

In our approach for acoustic tumors, the method of Morrison and King and that of Bochenek and Kukwa have been modified into one method. This modified method is basically a neuro-otological-neurosurgical team approach, extending the operative field by drilling the temporal bone and cutting the superior petrosal sinus, tentorium, and posterior fossa dura according to the size of the tumor. Therefore, for tumors slightly protruding into the posterior fossa from the prous of the internal auditory canal, only the bone adjacent to it is removed (Bochenek et al's method). For larger tumors, labyrinthectomy and mastoidectomy with the separation of the superior petrosal sinus and the tentorium and posterior fossa dura are also performed. In Morrison et al.'s method, the translabyrinthine approach is done first and the middle cranial fossa approach is performed thereafter. In contrast, in the modified method, drilling the bone from the middle cranial fossa to the tip of the mastoid--labyrinthectomy and mastoidectomy--is the first thing done after elevating the temporal lobe and revealing the middle cranial fossa, and the internal auditory canal is opened thereafter. Thirty-five cases of acoustic tumors and other cerebello-pontine angle tumors were operated on during the past 3.5 years through the middle cranial fossa. Among 30 cases of acoustic tumors, eight cases in which the tumors were confined to the internal auditory canal were operated on through the middle cranial fossa. In four cases, Bochenek et al's method was performed in which bones adjacent to the internal auditory canal and a part of the labyrinth are removed without cutting the superior petrosal sinus. In 23 cases including five cerebellopontine angle tumors, the modified translabyrinthine-transtentorial approach through the middle cranial fossa was done. This modification has the advantage that severe postoperative complications are less frequent. The surgical technique and the results are discussed.

Cerebrospinal fluid otorrhea

Cerebrospinal fluid (CSF) otorrhea is a dangerous and potentially life threatening occurrence for which the otolaryngologist is often consulted. CSF otorrhea occurs on the basis of skull fracture, tumor, infections, congenital anomalies, and operative trauma. Forty-three patients with CSF otorrhea of varied etiology are reviewed in this paper. Eight cases are of congenital or labyrinthine origin confirming at surgery the probable connection between the subarachnoid and perilymphatic spaces. Eleven cases had spinal fluid otorrhea due to infection. All cases presented with symptoms of chronic infection: 4 cases had a history of previous surgery for chronic ear disease; 7 cases had temporal lobe abscess; 1 case had a cerebellar abscess; 8 had tegmen defects secondary to cholesteatoma; in 1 case the tegmen defect was due to previous surgery for chronic infection. Nine of 11 cases have serviceable hearing postoperatively. Fourteen cases of spinal fluid otorrhea resulted from trauma: 1 case was due to traumatic stapes footplate fracture in a congenitally malformed ear; 4 were due to transverse temporal bone fracture; and 9 were due to longitudinal temporal bone fractures. All transverse fractures resulted in nonhearing ears. Three cases were due to a combination of temporal bone fracture and infection. In 2 of these cases chronic infection preceded the fracture; in 1 case the fracture led to chronic ear disease with spinal fluid leakage. One patient required 1 surgical procedure for closure of the otorrhea, 1 patient 2 procedures, and 1 patient 3 procedures. Ten cases are due to translabyrinthine acoustic neuroma removal: 7 cases had resolution of the spinal fluid leakage after conservative nonsurgical treatment; and 3 required surgical intervention using muscle, fat and fascia obliteration of the spinal fluid pathway.

Total one-stage suboccipital microsurgical removal of acoustic neuromas of all sizes: with emphasis on arachnoid planes and on saving the facial nerve

Clinical suspicion is essential for early diagnosis of acoustic neuroma. No absolutely characteristic pattern of hearing loss occurs, and atypical presentations are the rule. The diagnosis of acoustic neuroma is possible by tests that can be performed on an outpatient basis. A hearing loss for high tones with impaired speech discrimination is frequently seen. Testing of the acoustic reflexes and particularly the brain stem auditory-evoked responses (BAER) are becoming the most reliable methods of defining hearing loss in patients suspected of having an acoustic neuroma. High-resolution, thin-sectioning, overlapping-cut CT scanning including CT pneumography when necessary and polytomography of the internal auditory meatus are the mainstays of radiologic evaluation. Complete removal of the tumor at one operation is usually possible by the suboccipital retromastoid route with preservation or restoration of normal brain stem function and preservation of facial nerve function. Preservation of hearing has occasionally been accomplished, and the potential occasionally exists for restoration of hearing in patients with favorable smaller tumors, which have not acquired extensive arterial supply in common with the cochlea. The two factors that most influence results are early diagnosis and gentleness of surgical manipulation of the tissues that is made possible by magnification and illumination with the operating microscope.

Translabyrinthine and transtentorial removal of acoustic nerve tumors. Results in 150 cases

The translabyrinthine route or an extension of it was used to remove 150 acoustic nerve tumors. The mortality was 2% and the morbidity low. Preservation of the facial nerve was achieved in 100% of the small and 80% of the medium-sized tumors, but in only 20% of the large growths. The complications encountered are discussed.

The two-stage excision of huge acoustic neurinomas

Total removal of huge acoustic neurinomas was carried out in 23 patients by means of a two-stage suboccipital transmeatal approach with microsurgical technique. There was no operative mortality. Good results were obtained in 18 (78%) of the patients who have returned to normal activities or full-time employment. Five patients (22%) have residual preoperative neurological deficits causing a reduced level of activity. All of these, except one, are able to care for themselves. None of the patients has had any further significant neurological deficit caused by the operative procedures. Anatomical integrity of the facial nerve was maintained in 17 patients (74%). Surgical technique, operative morbidity, and results are thoroughly discussed. The potential advantages of this technique are stressed.

CSF total protein: normal values. A re-appraisal and discussion of its value in diagnosis of acoustic neuromas

A reference material of total cerebrospinal fluid protein (CSF protein) from 53 men and 45 women is presented. Lowry's Folin-phenol method for determining CSF protein has been used unchanged in this laboratory since 1964, with normal values ranging from 0.2 to 0.4 g/l. In this new reference material higher values were found with the 0.05--0.95 fractile interval for normal CSF protein determined to 0.29--0.88 g/l. This implies that the value of determining CSF protein in diagnosis of acoustic neuromas is most questionable. Among the medium sized tumours there were statistically significant increased values, but no clinical significance. The large tumours showed both statistically as well as clinically significant increased protein, but these tumours can be easily diagnosed by other means. A more detailed determination of CSF protein is discussed.

Computed tomography for small acoustic neuromas

The minimal size of acoustic neuromas detectable by computered tomography (CT) is, according to the available literature, 1.5 to 2 cm. The new otoneurosurgical technic using the transtemporal and translabyrinthine approach necessitates an early diagnosis of neuromas protruding 1 cm or less into the cerebellopontine angle cistern. This seemed impossible with the available CT equipment. Eight proven acoustic neuromas 1 cm or less in diameter, detected with CT, are reported. Diagnostic criteria are elaborated. The study shows that small cerebellopontine angle tumors can be detected by use of CT machines of the newer generation which perform scanning with thin and overlapping slices.

Limitations of computed tomography in the investigation of acoustic neuromas

Seventy percent of 80 surgically proven acoustic neuromas were visualized on preoperative computed tomography (CT) scans. Many more tumors were seen on contrast enhanced scans than on unenhanced scans (55 vs 25). No intracanalicular tumors and only one of 15 tumors less than 2 cm in size were visualized on CT scan. Most medium size tumors (2.0-3.0 cm) and all large tumors (greater than 3.0 cm) were visualized on CT scan when optimal technique was used. Positive CT scans often replace more invasive diagnostic studies in the investigation of acoustic neuromas. Negative scans do not rule out tumors as intracanalicular, and small tumors are usually not visualized with current techniques. If there is clinical suspicion of an acoustic neuroma, positive contrast posterior fossa cisternography should be done when the CT scan is negative.

Suboccipital removal of acoustic neuromas. Results of 125 operations

The surgical results obtained in 125 patients with acoustic neuromas, using the suboccipital approach, are reported. These results do not differ from those obtained in other neurosurgical materials, with the same distribution of tumour size, and the same surgical approach. The material consists of 20 medium size tumours, and 105 large. However, the results, regarding both mortality, postoperative facial paralysis as well as post-operative condition in general are unsatisfactory. A historical review of the development of the surgical treatment of acoustic neuromas is given, and the necessity of a closer neurosurgical-otologic cooperation is stressed, both with regard to diagnosis of the neuromas as well as the surgical treatment.

Prosthetic support for unilateral facial paralysis

Removable prostheses were used to determine that esthetics and speech could be improved for patients with permanent unilateral facial paralysis. Esthetics had to be compromised somewhat to obtain the maximum benefit for intelligible speech. This procedure can be beneficial in helping patients who are high surgical risks or for whom surgery, for various reasons, is unacceptable.

Suboccipital microsurgical removal of acoustic neurinomas of all sizes

This report discusses a combined neurosurgical-otologic team approach to the management of 16 consecutive suspected VIII nerve neurinomas, all operated via the suboccipital route. A suboccipital craniectomy is done with the patient in the prone position. Dissection for all size tumors began with exposure of the internal auditory canal to the transverse crest with dissection of the neurinoma from the VII and VIII cranial nerves beginning in the lateral most posterior portion of the internal auditory canal. There was one death and one cerebrospinal fluid (CSF) leak. Total tumor removal was accomplished in 14 of 15 acoustic neurinoma patients. Facial nerve function was preserved in 12 of 15 patients and preoperative hearing maintained in 5 of 15 patients.

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.

The translabyrinthine removal of acoustic and other cerebellopontine angle tumors

This paper reviews the history of acoustic tumor surgery and sets forth the technique of translabyrinthine surgery. Thirty-five patients with 36 tumors are presented and the results explained in detail. A plea is made for standardization of reporting results and some of the controversy concerning surgical technique is discussed briefly.