Acoustic tumors

Surgical management for large vestibular schwannomas: a systematic review, meta-analysis, and consensus statement on behalf of the EANS skull base section

BACKGROUND AND OBJECTIVE

The optimal management of large vestibular schwannomas continues to be debated. We constituted a task force comprising the members of the EANS skull base committee along with international experts to derive recommendations for the management of this problem from a European perspective.

MATERIAL AND METHODS

A systematic review of MEDLINE database, in compliance with the PRISMA guidelines, was performed. A subgroup analysis screening all surgical series published within the last 20 years (January 2000 to March 2020) was performed. Weighted summary rates for tumor resection, oncological control, and facial nerve preservation were determined using meta-analysis models. This data along with contemporary practice patterns were discussed within the task force to generate consensual recommendations regarding preoperative evaluations, optimal surgical strategy, and follow-up management.

RESULTS

Tumor classification grades should be systematically used in the perioperative management of patients, with large vestibular schwannomas (VS) defined as > 30 mm in the largest extrameatal diameter. Grading scales for pre- and postoperative hearing (AAO-HNS or GR) and facial nerve function (HB) are to be used for reporting functional outcome. There is a lack of consensus to support the superiority of any surgical strategy with respect to extent of resection and use of adjuvant radiosurgery. Intraoperative neuromonitoring needs to be routinely used to preserve neural function. Recommendations for postoperative clinico-radiological evaluations have been elucidated based on the surgical strategy employed.

CONCLUSION

The main goal of management of large vestibular schwannomas should focus on maintaining/improving quality of life (QoL), making every attempt at facial/cochlear nerve functional preservation while ensuring optimal oncological control, thereby allowing to meet patient expectations. Despite the fact that this analysis yielded only a few Class B evidences and mostly expert opinions, it will guide practitioners to manage these patients and form the basis for future clinical trials.

Translabyrinthine microsurgical resection of small vestibular schwannomas

OBJECTIVE

Translabyrinthine resection is one of a number of treatment options available to patients with vestibular schwannomas. Though this procedure is hearing destructive, the authors have noted excellent clinical outcomes for patients with small tumors. The authors review their experience at a tertiary acoustic neuroma referral center in using the translabyrinthine approach to resect small vestibular schwannomas. All operations were performed by a surgical team consisting of a single neurosurgeon and 1 of 7 neurotologists.

METHODS

Data from a prospectively maintained clinical database were extracted and reviewed. Consecutive patients with a preoperative diagnosis of vestibular schwannoma that had less than 1 cm of extension into the cerebellopontine angle, operated on between 2008 and 2013, were included. Patents with neurofibromatosis Type 2, previous treatment, or preexisting facial weakness were excluded. In total, 107 patients were identified, 74.7% of whom had poor hearing preoperatively.

RESULTS

Pathologically, 6.5% of patients were found to have a tumor other than vestibular schwannoma. Excluding two malignancies, the tumor control rates were 98.7%, as defined by absence of radiographic disease, and 99.0%, as defined by no need for additional treatment. Facial nerve outcome was normal (House-Brackmann Grade I) in 97.2% of patients and good (House-Brackmann Grade I–II) in 99.1%. Complications were cerebrospinal fluid leak (4.7%) and sigmoid sinus thrombosis (0.9%), none of which led to long-term sequelae.

CONCLUSIONS

Translabyrinthine resection of small vestibular schwannomas provides excellent results in terms of complication avoidance, tumor control, and facial nerve outcomes. This is a hearing-destructive operation that is advocated for selected patients.

ABR Results in Patients with Posterior Fossa Tumors and Normal Pure-Tone Hearing

Sixteen patients with confirmed mass lesions of the posterior fossa and normal hearing sensitivity for pure tones were studied. Patients' main symptoms, auditory brainstem response (ABR), and lesion size were analyzed. All patients manifested neurologic and/ or ofoneurologic symptoms or complained of hearing difficulty disproportionate to their pure-tone findings. Interestingly, the patients in this select group were younger (mean = 34 years) than the typical patient with a posterior fossa tumor. ABR results were abnormal in 15 of the patients, although several indices—including absolute and interwave latencies, interaural latency difference, and wave presence/absence—were employed to achieve this sensitivity. Lesion size varied considerably and failed to correlate with ABR or pure-tone results.

[Role of radiosurgery and stereotactic radiotherapy in the management of vestibular schwannomas]

PURPOSE OF THE STUDY

In order to investigate the role of radiosurgery and stereotactic radiotherapy in the management of vestibular schwannomas, we have reviewed our own prospective cohort and the main series of the modern literature.

PATIENTS AND METHODS

Between July 14th 1992 and June 1st 2011, 2991 vestibular schwannomas were operated on the Stereotactic and Functional Neurosurgery Department of Timone University Hospital. All the patients have been evaluated prospectively, with a follow up longer than 3 years for 2336 patients, excluding patients suffering from type 2 neurofibromatosis (148 patients). In 7% of the patients, the vestibular schwannoma had previously been resected. According to Koos classification, in 17.6% of the patients, vestibular schwannomas were stage I, 51.8% stage II, 27% stage III and 3.6% stage IV. The mean tumour volume was 2.63 cm(3). According to Garner Robertson classification, the hearing was still functional at the time of radiosurgery in 46% and subnormal in 20.9% of the patients.

RESULTS

Long term tumour control was achieved in 97.5% of the patients. A transient facial palsy was observed in 0.5% of the cases. The rate of trigeminal injury was 0.5%. Useful hearing was preserved at 3 years in 78%. This rate reached 95% in patients with no past history of sudden hearing loss. Other predictors of functional hearing preservation are the young age, the small size of the lesion and a dose to the modiulus of the cochlea lower than 4Gy. We observed no radio-induced tumour. Only large, Koos IV vestibular schwannomas are contraindicated for upfront radiosurgery. In these patients, we propose a combined approach with a deliberately partial microsurgical removal, followed by a radiosurgery of the residue.

CONCLUSION

This cohort is unique by the size of the population and the length of the follow up and results demonstrate the efficacy of radiosurgery and its safety, especially its high rate of hearing preservation.

Residual and recurrent acoustic neuroma in hearing preservation procedures: neuroradiologic and surgical findings

Magnetic resonance imaging with gadolinium DTPA is currently the most accurate method for detecting small intracanalicular yestibular schwannomas. This imaging modality is not nearly as clear in diagnosis of a small residual or recurrent neuroma after a hearing preservation procedure. This study looked for gadolinium-enhanced MRI images mimicking recurrent lesions in 104 consecutive cases of unilateral acoustic neuroma removed with a hearing preservation technique by the retrosigmoid transmeatal approach. A number of cases with enhancing MRI images in the internal anditory canal were reoperated, permitting the histologic examination of the enhancing tissue. Criteria for the MRI diagnosis of residual-recurrent acoustic neuroma are presented, along with the short-to mid-term rate of "residual-recurrent" tumor.

Acoustic Neuroma in a Private Neurotology Practice: Trends in Demographics and Practice Patterns

OBJECTIVES/HYPOTHESIS

To determine whether changes in demographics and management of patients with acoustic neuromas occurred between the years 1990 and 2005.

STUDY DESIGN

Retrospective chart review.

METHODS

Charts of all 614 patients with a diagnosis of acoustic neuroma, excluding neurofibromatosis-2, from 1990 through 2005 were reviewed. Age at diagnosis, tumor size, hearing, and initial therapy (observation, stereotactic radiation, or surgical excision) were obtained. Patients were grouped by time period (1990-1994, 1995-2000, 2001-2005).

RESULTS

Mean age at diagnosis increased slightly from the middle period (53.4 yr) to the most recent (56.9 yr) (P < or = .025). The proportion of patients 65 years or older increased from 21% to 29% to 32%, respectively, but the change was not significant. Average tumor size decreased from 1.7 cm initially to 1.4 cm most recently (P < or = .039). There were no significant changes in hearing. Although surgical excision remains our most common treatment (58.5% in 2001-2005), it is becoming less frequent (>80% in earlier periods) (P < or = .001). Observation with serial imaging was recommended in 37.3% in 2001 to 2005 as compared with 18.3% and 11.6% in the previous two time periods (P < or = .001). These changes in initial treatment choices occurred for all age groups and primarily for small tumors. Use of radiation has increased only slightly, to 4.2% in the recent period.

CONCLUSION

: Patients with acoustic neuroma are presenting with increased age and smaller tumors compared with 16 years ago. However, these changes cannot totally account for the large change in treatment trends. Technology and demographics are influential in these changes, but other difficult to measure forces, such as patient influence and patient use of the Internet, are also factors.

Natural history of acoustic neuromas

OBJECTIVES/HYPOTHESIS

1) Develop a computerized technique to accurately compare acoustic neuroma size on routine computed tomography and magnetic resonance imaging (MRI) scans; 2) use this technique to determine the growth pattern in a large series of patients with acoustic neuroma who were conservatively managed; 3) describe the natural history of patients with acoustic neuromas who did not receive surgical intervention and those who underwent subtotal resection; 4) correlate the size and growth rate of acoustic neuromas to clinical presentation and auditory and vestibular testing; and 5) recommend guidelines for the management of patients with acoustic neuromas.

STUDY DESIGN

A retrospective study from 1974 to 1999 of patients with unilateral acoustic neuromas who had conservative treatment by serial imaging studies (80 patients) or subtotal resection (49 patients).

METHODS

All patient charts were evaluated for presenting symptoms, reasons for the type of management given, and clinical outcome. Charts were also reviewed with respect to serial audiological assessment, electronystagmography, and brainstem auditory evoked response. Imaging studies were analyzed using a computer technique so that serial studies could be compared to determine growth rates.

RESULTS

Rigorous computer analysis of tumor size and growth rate was statistically the same as the radiologist's description of the tumor size and growth rate. Of 70 patients who were older than 65 years of age old at the time their tumor was discovered, 4 (5.7%) required intervention and 18 (26%) were dead of unrelated causes. These patients had a mean follow-up of 4.8 years (range, 0.01-17.2 y). Overall, growth rate for nonsurgical patients was 0.91 mm per year. Nonsurgical tumors did not grow or regressed in 42%. Overall postoperative growth rate for surgical subtotal resection patients was 0.35 mm per year. Surgical tumors did not grow or regressed after subtotal resection of acoustic neuroma in 68.5% of patients. Three patients (6.1%) required revision surgery because of tumor growth or the development of symptoms. Neither auditory nor vestibular testing was a reliable measure for determining tumor growth.

CONCLUSION

Measurement of the maximal tumor diameter on MRI scans is a reliable method for following acoustic neuroma growth. There is no need to perform a rigorous analysis of tumor size to determine whether the tumor is growing significantly. The vast majority of patients older than 65 years with acoustic neuromas do not require intervention. The indications for intervention should be based on a combination of rapid tumor growth with the development of symptoms.

[Radiosurgery or microsurgery of vestibular schwannomas?]

PURPOSE

Microsurgical excision is the reference treatment of vestibular schwannomas. Yet, morbidity and functional risk of this surgery is significant, as Pellet et al have demonstrated in their study. In order to define the role of gamma knife surgery we have designed a prospective study concerning effectiveness and tolerance of this treatment.

PATIENTS AND METHODS

Between July 14, 1992 and August, 1997, 400 patients were included. All the treatments were carried out according to a homogeneous methodology, with multiisocentric planning. We use low marginal doses dependent mainly on the treatment volume: 14 Gy for small stade II tumors, 12 Gy or less for larger tumors and 16 Gy for intracanalicular tumors. The evaluation protocol included preoperative examination with clinical examination, House grading, Shirmer's test, tonal and vocal audiometry, brain stem electrical response audiometry (BERA), vestibular caloric and pendular tests, magnetic resonance imaging (MRI) or computerized tomography (CT) scan; control at 6 months, 1 year and 2 years with clinical examination, tonal audiometry and MRI and/or CT scan; at 3 years the preoperative examination was repeated and a questionnaire based on Pellet's concerning functional results was completed.

RESULTS

Among the 400 treatments, 80% were first intended treatment of unilateral vestibular schwannoma. At the time of the analysis, 100 consecutive patients with unilateral schwannoma (treated in first intention) had a 3 year follow-up (results concerned these 100 patients). Average age was 61 years (17-82 years). According to Portmann's classification, five patients presented a stade 1 tumor, 60 a stade 2 tumor, 33 a stade 3, and two a stade 4 tumor. According to House's grading at preoperative examination, there was 86 (86%) grade 1 tumors, 12 grade 2, two grade 3, and at 3 year follow-up: 77 (94%) grade 1 and five grade 2 (17 patients had no House grading). At preoperative examination, three patients presented an hemispasm; at 3 years this had disappeared for all patients. Two others patients presented a transient hemispasm at 8 and 11 months, respectively. At preoperative examination, four patients presented with facial numbness and 14 with hypoesthesia. At 3 year follow-up, trigeminal function was normal for all patients but one, for whom this had only improved. Seven others patients presented a transient numbness or hypoesthesia. At preoperative examination, five patients presented hydrocephalus without cerebro spinal fluid (CSF) shunting. At 3 year follow-up, seven patients presented CSF shunting: three presented a preoperative hydrocephalus, three a hydrocephalus after treatment and one a hydrocephalus secondary to tumor growth. Average age for these six patients was 71 years. Audiological classification was based on Gardner-Robertson's. Seventy percent of patients with normal hearing maintained useful hearing, and 50% of patients with useful hearing maintained serviceable hearing. Three (3%) patients (two with stade 2 tumors and one with a stade 3) had microsurgical excision at 16, 35 and 36 months, respectively. During microsurgical excision no unusual difficulty was encountered. Seventeen questionnaires investigating functional outcome and quality of life were completed: 100% (63% in Pellet's study) of the patients answered they had no facial motion disturbance, 49% (17% in Pellet's study) had no ocular problems, 20% (in Pellet's study 55%) had subjective trigeminal problems, 8% (in Pellet's study 13%) had deglutition problems, none (16% in Pellet's study) had other eating problems, 91% (61% in Pellet's study) had no change in their life. Mean hospitalization stay was 3 days (for 23 days in Pellet's study). All the patients who worked, except one, had the same professional activity (66% in Pellet's study). Mean work cessation was 7 days (130 days in Pellet's study). (ABSTRACT TRUNCATED)

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.

Hearing preservation in vestibular schwannoma surgery: what factors influence outcome?

The goals in the management of patients with vestibular schwannomas have changed drastically over the past few decades, with preservation of useful hearing representing the newest challenge. The true incidence of preserved useful hearing, however, has become clouded by a lack of uniformity in reporting results. The authors have analyzed 56 consecutive cases, in which directed attempts were made to preserve hearing on the involved side, to understand what factors play a major role in postoperative hearing preservation. Of the 56 cases reviewed, there were 46 patients who had "good" preoperative hearing (pure tone average < 50 dB; speech discrimination score > 50%). We found that, in this group of patients, if the tumor was less than 2 cm in diameter from pons to petrous, there was a 52% (16 of 31 patients) chance of preserving good hearing and if the tumor was 1 cm or less, the chances increased to 83%. Factors such as preoperative hearing status, tumor size and location, tumor consistency, and preoperative and intraoperative brainstem auditory evoked potentials are discussed in detail as they relate to postoperative outcome.

Subcutaneous growth of human acoustic schwannomas in athymic nude mice

In order to develop an in vivo model for growth of acoustic schwannomas, we studied tumor specimens from 10 patients, transplanted into a subcutaneous pocket of 67 nude mice. The number of tumors which survived or grew was 63 (94%). Obvious macroscopic growth was observed in 22 (33%), status quo in 28 (42%), and regression of tumor size in 13 (19%). The tumor disappeared in 4 cases (6%). Serial implantation was not possible due to the small amount of neuroma tissue in the surviving tumors. In animals with obvious macroscopic growth, neovascularization was clearly demonstrated. The presence of Schwann cells in the implants was confirmed immunohistochemically. The proliferative activity in the original and implanted tumors was evaluated by the proliferating cell nuclear antigen (PCNA) and Ki-67 nuclear antigen stainings and showed good correlation between primary tumors and implants. This in vivo tumor model will open new opportunities to study the biology of acoustic tumors and to test different therapeutic modalities.

Facial myokymia due to acoustic neurinoma

The case of a 62-year-old female patient who presented with facial myokymia is reported. The patient had a 13-year history of progressive left-sided hearing loss. In further course, involuntary, wormlike, rippling movements of the left facial muscles developed. Computed tomography revealed a tumor located in the left cerebellopontine angle. Electrophysiologic examinations confirmed the diagnosis of facial myokymia. The tumor, which evolved from the eighth cranial nerve, was totally removed microsurgically. The tumor was histologically verified to be an acoustic neurinoma. Postoperatively, the patient had a facial nerve paralysis, and the facial myokymia was no longer present. The present case provides further evidence that facial myokymia may be triggered by alterations at one of various sites along the course of the motor axons of the facial nerve.

Cystic vestibular schwannomas: neuroimaging and growth rate

In a series of 571 vestibular schwannomas (VS) operated on in the period 1976-1992, via the translabyrinthine approach, 23 tumours (4 per cent) from 23 patients were radiologically, peroperatively and histologically identified as cystic VS. Neuroimaging examinations (CT and MRI) revealed 15 tumours (2.6 per cent) with extracystic formations and in eight cases (1.4 per cent) intratumoural cysts. In 15 cases (65 per cent), tumours were located extracanalicularly with no involvement of the internal auditory canal (IAC). The extracanalicular tumour extension including the cystic elements ranged between 10 and 60 mm with a mean of 45 mm. In eight cases out of 23 (35 per cent) other diagnostic possibilities such as trigeminal schwannoma, epidermoid cyst and meningioma were proposed at the primary evaluation. Deformation, displacement and/or impression of the fourth ventricle was demonstrated in 17 cases (74 per cent). Three patients (13 per cent) had obstructive hydrocephalus which demanded shunt insertion. Residual tumour was detected in two patients (9 per cent). Growth rate in four cases was more than 10 times higher when compared to the annual growth rate of noncystic VS. The results of this study provide data on cystic VS attenuation demonstrated by CT or MRI which may be valuable in neuroradiological diagnosis of these cystic lesions and emphasizes that the wait-and-see policy should not be applied to the cystic variant of VS.

Growth rate of acoustic neuroma expressed by Ki-67 nuclear antigen versus symptom duration

The growth rate of acoustic tumors varies widely. An immunohistochemical study with Ki-67 monoclonal antibody was performed on a random sample of 21 acoustic neuromas. The tumors belonged to 2 well-defined groups: 1 with a short duration of preoperative symptoms (< 1 year) and 1 with a long duration of preoperative symptoms (> 5 years). The tumors were of small to medium size (7 to 27 mm), and no large, cystic, or Recklinghausen tumors were included. The tumor proliferative fraction expressed by monoclonal antibody Ki-67 was determined. The results revealed a significant relation between the tumor proliferative fraction and symptom duration. Tumors with a high proliferative status had a short preoperative symptom duration, while tumors with a low proliferative status had a long symptom duration. The clinical implications of these results are discussed.

A comparison of growth rates of acoustic neuromas: nonsurgical patients vs. subtotal resection

A conservative approach to the management of acoustic neuromas in elderly patients has been used since 1971. Elderly patients without symptoms of brain stem compression are initially treated by observation and yearly radiographic imaging. A translabyrinthine radical-subtotal resection is performed if brain stem compression is present or if tumor is growing rapidly. Twenty-three patients, ages 65 to 86 years, had initial nonsurgical management of their tumors. Growth rates could be determined for 16 patients. Thirteen patients not requiring surgery had an average tumor growth rate of 0.6 mm/yr. Three patients with an average growth rate of 6.8 mm/yr eventually required surgery. No patient whose tumor was < 15 mm at initial evaluation has experienced brain stem symptoms or demonstrated rapid tumor growth. Twenty-four patients ages 65 to 86 years underwent planned subtotal tumor excision. Eighteen patients followed postoperatively for more than 1 year demonstrated an average rate of regrowth of tumor of 0.7 mm/yr.

Radical Removal of a Large Glossopharyngeal Neurinoma with Preservation of Cranial Nerve Functions

A 51-year-old man is reported who was suffering from an extensive right-sided glossopharyngeal neurinoma (4.6×3.4 cm). The patient was admitted with a history of headache for six to seven years and vomiting for two years accompanied by a progressive hearing loss, tinnitus and dizziness during the last year. Audiometry indicated a perceptive deafness in the whole frequency range up to 70 dB HL, while electronystagmography (ENG) showed a loss of vestibular function of the right side, but there were no signs of a jugular foramen syndrome. Magnetic resonance imaging (MRI) revealed a large tumor portion in the right cerebello-pontine angle with only a small part in the jugular foramen. The neurinoma was completely removed by microsurgery through a suboccipital approach with preservation of nerves VII–XII. The postoperative course was uneventful and normal function of facial and caudal cranial nerves (Nn IX–XII) were proven by electromyography and magnetic stimulation, with exception of a transitory hypesthesia in the palatine region which completely normalized within a few months. The right-sided hearing loss was unchanged, but vertigo improved. In comparison with literature review the lack of temporary or permanent postoperative dysfunctions of caudal cranial nerves as well as of the facial nerve was extraordinary in the reported case.

The preservation of hearing and facial nerve function in a consecutive series of unilateral vestibular nerve schwannoma surgical patients (acoustic neuroma)

Between January 1981 and February 1992, 102 non-NF-2 patients underwent removal of a unilateral vesitbular schwannoma. There were 54 women and 48 men. Eighty-six percent of patients with normal facial function preoperatively retained normal function (House score 1 or 2) postoperatively. Of the 64 patients with a functional cochlear nerve preoperatively, five had normal hearing (PTA < 25 dB, SB > 70%), five had near normal hearing (PTA < 45 dB, SD > 70%), four patients had preserved hearing (PTA < 50 dB, SD > 50%), and three patients had preserved cochlear nerve function (PTA > 50 dB, SD < 50%) after surgery. Hearing preservation was obtained in patients whose tumors were larger than 3 cm. Radiological follow-up revealed 10 patients with recurrent tumor, all but one asymptomatic.

Repair of facial nerve after removal of cerebellopontine angle tumors: a comparative study

The results of repair of 18 facial nerves were examined by means of a modified House-Brackmann grading system. Six were repaired by end-to-end anastomosis and 12 by nerve graft. The reliability of the simplified House-Brackmann grading system was also assessed, using the kappa statistic to analyze the agreement between pairs of observers who examined the function of 40 nerves in 37 patients. Facial nerves studied had been either preserved, repaired or grafted, or divided and treated by faciohypoglossal nerve anastomosis. One nerve was not treated. The grading system proved to be somewhat unreliable, with complete agreement between observers in only 25% of cases. Facial nerve repair produced a fair return of function in just under two-thirds of the cases. The ability of an examiner ignorant of the patient's history to assess from the end result how the nerve had been managed was also estimated. Observers showed little ability to decide correctly on the previous treatment of the nerve when the patient showed moderate dysfunction postoperatively. The implications of these findings for grading systems and for management of the facial nerve in acoustic nerve tumor surgery are discussed.

An algorithm for the management of acoustic neuromas regarding age, hearing, tumor size, and symptoms

An algorithm has evolved for the management of patients with acoustic neuroma. Decisions as to surgery vs. observation, surgical approach, and whether hearing preservation should be attempted depend on age, patient symptoms, size of the tumor, residual hearing, and degree of facial nerve involvement at the time of surgery. Conservative management is used for patients over 65 years of age. This consists of observation or subtotal resection through a translabyrinthine approach, depending on the absence or presence of brainstem signs or symptoms. In patients under 65 years of age, hearing preservation is attempted through the retrosigmoid approach in tumors 1.5 cm or less if pure-tone average is less than 30 dB and the discrimination score is greater than 70%. The translabyrinthine approach is our preferred approach for tumors of any size when hearing is not serviceable. A near-total excision is performed when the facial nerve cannot be separated from the tumor. The rationale for this algorithm in the management of 130 cases of acoustic neuroma over the past 17 years is presented.

Herbert Olivecrona: founder of Swedish neurosurgery

Herbert Olivecrona (1891-1980) singlehandedly founded Swedish neurosurgery. At the International Congress in Neurology in Bern in August, 1931, Harvey Cushing invited the cream of the world's medical society to a private banquet. Among the 28 specially invited guests was Herbert Olivecrona. At 40 years old, Olivecrona took his seat with pioneers such as Otfrid Foerster, Percival Bailey, Hugh Cairns, Geoffrey Jefferson, and Sir Charles Sherrington. This suggests that Cushing was impressed by the Swedish aristocrat's didactic deeds when he visited the Serafimer Hospital in Stockholm 2 years earlier. During the mid-1920's, the radiologist Erik Lysholm greatly improved the technique of ventriculography and, challenged by Olivecrona, his diagnostic neuroradiology became of superior quality. In the early 1930's, utilizing technical innovations of his own, Lysholm became a master at demonstrating and localizing posterior fossa tumors, which Olivecrona then operated on. Olivecrona's clinic became the mecca to which many scholars, thirsting for more knowledge, went on a pilgrimage. The international reputation of the clinic was founded, not on epoch-making discoveries, but by the resolute and practical application of methods already launched elsewhere and the exemplary organization that Olivecrona had established in collaboration with Lysholm. In spite of hardships and primitive working conditions, the clinic at the Serafimer Hospital gradually developed into the ideal prototype for a modern neurosurgical department. Olivecrona trained many colorful personalities who later were to lay the foundation for neurosurgery in their home countries; these included Wilhelm Tönnis of Germany, Edvard Busch of Denmark, and Aarno Snellman of Finland. Olivecrona was a true pioneer who made major contributions in practically all fields of conventional neurosurgery.

Hypoglossal-facial nerve anastomosis for facial nerve palsy following surgery for cerebellopontine angle tumors

Hypoglossal-facial nerve anastomosis is one of the procedures frequently performed to restore function after facial palsy secondary to surgery for removal of cerebellopontine angle tumors. The published results of hypoglossal-facial nerve anastomosis have been variable, and there are still questions about the indications, timing, and surgical techniques for this procedure. The goals of the present retrospective analysis of 22 cases of hypoglossal-facial nerve anastomosis were to assess the extent of the functional recovery and to analyze the factors affecting this recovery. The 22 cases of complete facial palsy were gleaned from a series of 245 cases of cerebellopontine angle tumors treated surgically by one of the authors. Twenty patients had an acoustic neuroma (average size 3.5 cm), one patient had a petrous meningioma, and one patient had a facial neuroma. The average age of the patients was 47.3 years (range 19 to 69 years). The average interval from tumor surgery to hypoglossal-facial nerve anastomosis was 6.4 months (range 12 days to 17 months), and the average follow-up period after the procedure was 65 months. The results were graded as good, fair, poor, or failure according to a new method of classifying facial nerve function after hypoglossal-facial nerve anastomosis. The results were good in 14 cases (63.6%), fair in three (13.6%), and poor in four (18.2%); one (4.5%) was a failure. Good and fair results occurred with higher frequency in younger patients who were operated on within shorter intervals, although these relationships were not statistically significant. There were no surgical complications. Good or fair results were achieved in 17 (77.3%) of the 22 cases, and thus hypoglossal-facial nerve anastomosis is considered an effective procedure for most patients with facial palsy after surgery for cerebellopontine angle tumors.

The fate of tumour rests following removal of acoustic neuromas: an MRI Gd-DTPA study

The fate of capsular fragments left attached to vital structures at the time of otherwise total tumour removal was studied in 14 of 21 such patients who underwent acoustic neuroma surgery. Imaging using magnetic resonance Gd-DTPA at post-operative intervals of 6 months-12 years (mean 70 months) showed evidence of persistent tumour in half the patients. None of the patients had developed new symptoms and computed tomography had failed to demonstrate tumour recurrence. Persistence of the tumour was more likely if the residual fragments were not cauterized at the time of operation. Four of the seven persisting tumour rests showed evidence of gradual enlargement. The implications for patient management, particularly if an attempt is made to preserve hearing, are discussed.

Cystic acoustic schwannomas

Three cases with large space-occupying cysts in the cerebellopontine angle are reported. CT and MRI findings were not typical for acoustic schwannomas but at operation, besides the large cysts, small acoustic schwannomas could be detected and removed. The clinical and neuroradiological features of this unusual variety and the CT and MRI differential diagnosis of cerebellopontine angle lesions are discussed.

Facial nerve monitoring by monopolar low constant current stimulation during acoustic neurinoma surgery

Electrophysiological characteristics of monopolar low constant current stimulation, and evoked facial muscle responses to such stimulation, were evaluated in 34 cases of acoustic neurinoma. Our study, using stimulus parameters of 0.1-ms-duration pulse wave with 0.5-0.6 mA intensity, revealed that extent of spreading current depends on the current intensity, being about 1 mm from the electrode with 0.5-0.6 mA, and insulation of the electrode prevented the current from spreading through the cerebrospinal fluid, giving a reliable amount of current to the tissue. Evoked facial muscle responses to facial nerve stimulation in the internal auditory meatus and over the pons were analyzed and revealed the following: (1) The responses to stimulation in the internal auditory meatus showed no amplitude attenuation throughout the operation. (2) The responses to stimulation over the pons gradually decreased in amplitude as tumor dissection from the nerve proceeded, especially in large tumors. (3) Anatomical continuity of the nerve was obtained in 100% of small, 91.7% of medium, and 88.2% of large tumors. Our data show that monopolar low constant current stimulation is effective in obtaining the precise anatomical orientation of the facial nerve during tumor removal.

Operative management of acoustic neuromas: the priority of neurologic function over complete resection

The objective of surgical management of acoustic tumors is to remove them entirely and preserve facial nerve function and hearing when possible. A dilemma arises when it is not possible to remove the entire tumor without incurring additional neurologic deficits. Twenty patients who underwent intentional incomplete surgical removal of an acoustic neuroma to avoid further neurologic deficit were retrospectively reviewed. They were divided into a subtotal group (resection of less than 95% of tumor) and a near-total group (resection of 95% or more of tumor) and were followed yearly with either computed tomography or magnetic resonance imaging. The subtotal group was planned and consisted of elderly patients (mean age, 68.5 years) with large tumors (mean, 3.1 cm). The near-total group consisted of younger patients (mean age, 45.8 years) and smaller tumors (mean, 2.3 cm). The mean length of followup for all patients was 5.0 years. Ninety percent of patients had House grade I or II facial function post-operatively. Radiologically detectable tumor regrowth occurred in only one patient, who was in the subtotal resection group. Near-total resection of acoustic tumor was not associated with radiologic evidence of regrowth of tumor for the period of observation. Within the limits of the follow-up period of this study, subtotal resection of acoustic neuroma in elderly patients was not associated with clinically significant recurrence in most patients and produced highly satisfactory rates of facial preservation with low surgical morbidity.

The impact of continuous electrophysiological monitoring on preservation of the facial nerve during acoustic tumour surgery

Continuous electromyographic (EMG) activity and responses to electrical stimulation of the facial nerve were monitored intraoperatively in 35 patients undergoing primary removal of acoustic neuroma. The rate of anatomical and immediate functional preservation of the facial nerve of these patients was compared with a matched population where a facial nerve stimulator and monitoring of facial muscle contraction by the anaesthetist only was employed. Overall, 94% (n = 33) of facial nerves were preserved anatomically in patients with continuous EMG monitoring, compared with 64% (n = 89) of patients (n = 139) without continuous monitoring. Amongst the 33 cases with anatomical facial nerve preservation, 64% (n = 21) had immediate functional preservation. Immediate functional preservation was only achieved in 39% (n = 35) of anatomically preserved facial nerves (n = 89) where conventional monitoring was used.

Surgical management of acoustic neuromas during the last five years. Part I

A consecutive series of 94 patients with acoustic neuromas, who were treated in the years 1980-1984, was reviewed. Hearing loss was the most common presenting symptom. During 1980-1984, all acoustic neuromas were treated surgically; 93 cases had a total excision and only one case had a subtotal excision. Mortality and morbidity were low and patients who had a fair to poor outcome rating had large tumors. Overall, cranial nerve VII was preserved in 64.1% of cases, while cranial nerves VII and VIII were anatomically preserved in 27% of cases.

Surgical management of acoustic neuromas during the last five years. Part II: Results for facial and cochlear nerve function

Postoperative facial and cochlear nerve function in 83 consecutive patients with acoustic neuromas, who were undergoing their initial surgical procedure during 1980-1984, have been examined. The facial nerve was preserved in anatomic continuity in 71% of cases. Various nerve grafting procedures were used when the facial nerve was divided; the most common of these was a faciohypoglossal anastomosis, which was performed in 20 cases. The facial and cochlear nerves were anatomically preserved in 30.1% of all patients having their initial surgical procedure. Good speech discrimination was preserved in four patients, whereas more crude hearing was preserved in six other patients.

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.

Acoustic nerve tumor surgery before and since the laser: comparison of results

A random computer selection of 21 patients who underwent 28 operations for acoustic neurinoma between 1974 and 1980 using conventional methods, including the operating microscope and microtechnique, was compared with a cohort of 22 patients who underwent 25 operations between 1980 and 1984 utilizing a carbon dioxide laser. Completeness of tumor removal, anatomical and functional preservation of the facial nerve, preservation of hearing, morbidity and mortality, average hospital stay, and eventual outcome were used as markers and were compared. Utilizing P values, the study demonstrated a significantly superior outcome, and as a result a better life quality, in patients who were operated on utilizing a CO2 laser in addition to conventional microsurgical technique.

ABR results in patients with posterior fossa tumors and normal pure-tone hearing

Sixteen patients with confirmed mass lesions of the posterior fossa and normal hearing sensitivity for pure tones were studied. Patients' main symptoms, auditory brain-stem response (ABR), and lesion size were analyzed. All patients manifested neurologic and/or otoneurologic symptoms or complained of hearing difficulty disproportionate to their pure-tone findings. Interestingly, the patients in this select group were younger (mean = 34 years) than the typical patient with a posterior fossa tumor. ABR results were abnormal in 15 of the patients, although several indices--including absolute and interwave latencies, interaural latency difference, and wave presence/absence--were employed to achieve this sensitivity. Lesion size varied considerably and failed to correlate with ABR or pure-tone results.

Intracranial repair of interrupted facial nerve in course of operation for acoustic neurinoma by microsurgical technique

The microsurgical refinement of the lateral suboccipital approach is, in our opinion, the most satisfactory operative technique for achieving total removal of acoustic neurinomas of all sizes. In this series of 164 operated cases, large or very large tumours accounted for 64% of the cases (105 patients). The facial nerve was sacrificed in about 19% of the cases. In 81% of the cases the facial nerve was respected (65%) or repaired (16%) by direct intracranial suture performed immediately after tumour removal. Good or fair functional results were obtained in about 65% of the cases by this last procedure, which has to be considered as the treatment of choice for facial nerve repair. The results are compared with those of other series and with those obtained by different nerve substitution procedures.

Does intravascular coagulation contribute to the operative mortality for large acoustic neuromas?

Three cases of abnormal bleeding during suboccipital excision of large acoustic neuroma are reported. The possible role of limited operative intravascular coagulation is discussed.

Preoperative and postoperative growth rates in acoustic neuromas documented with CT scanning

Sequential computerized tomography (CT) allows us to determine the growth rate of acoustic neuromas. Prior to CT scanning, a variability in tumor growth rates was recognized on the basis of clinical signs. After incomplete tumor removal, some patients experienced rapid recurrence, whereas others lived many years without recurrence. We used CT scanning to study tumor growth rates in a heterogeneous group of 21 patients. Thirteen elderly patients were given annual scans after incomplete tumor removal, while eight patients who had not had surgery are likewise being followed up. Early detection and complete tumor removal with preservation of hearing and facial function remain the goal in vigorous and healthy patients. However, a large number of older, infirm patients with acoustic neuromas may not require surgery or be candidates for incomplete tumor removal. Because rapid tumor growth may necessitate total tumor removal even in older patients, a better understanding of the growth rates may permit us to take a more scientific approach in planning these patients' management.

[Results of 110 microsurgical acoustic neuroma operations]

We report our experiences in 110 cases of microsurgical removal of acoustic neurinomas. The historic development, the chances of preservation of the facial nerve and hearing function and the mortality risks are described in detail, hereby stressing the advantages of the lateral suboccipital approach in microneurosurgery.