Incidence of acoustic neuromas.

The annual incidence of diagnosed acoustic neuromas in Denmark during two 7-year periods from June 1976 to June 1990 was compared, collecting all operated and non-operated tumors from the entire country. During the first period 278 tumors were diagnosed with an annual incidence of 38 tumors or 7.8 tumors per million per year. During the second period the annual incidence rose to 48 tumors and 9.4 tumors per million per year. There was a significant decrease of extrameatal tumor size from 33 to 26 mm and diminishing of giant tumors.     

Imaging of acoustic neuromas.

A negative high-quality, high-resolution, contrast-enhanced MRI scan is excellent evidence that a patient does not have an AN. Most nerve sheath tumors have a characteristic appearance, and when a tumor is detected there is seldom any doubt as to the identity of the lesion. There are other causes of enhancement, however, or of high signal that can be mistaken for an AN, and these must be kept in mind when a case is considered positive. In some cases, it may be appropriate to defer surgery to clarify a questionable finding by obtaining a follow-up scan. CT is still a reliable examination. In addition to evaluating the IAC, valuable information about the architecture of the petrous bone and labyrinth is provided. Improvements in imaging technology are occurring at a rapid rate. Thinner slices and more rapid scan techniques will make MRI even more useful in evaluation of the IAC.     

Spinal proteins in patients with acoustic neuromas

The values of total spinal protein in cerebrospinal fluid (CSF), used as normal material, from 98 persons are presented. These values showed that the previously used reference limits (0.20-0.40 g/l) for total protein in CSF were too low, and consequently the new reference values 0.20-0.85 g/l are used. 77 patients with surgically verified acoustic neuromas had total protein determined in CSF prior to operation, and 63% of patients with tumours less than 25 mm in diameter had normal total protein values, while only 3% of patients with tumours larger than 25 mm had normal values. Since the large tumours can be easily diagnosed by the non-invasive computer tomography, it is concluded that CSF total protein determination is only of limited value in the search for acoustic neuromas. A more quantitated examination of CSF proteins (albumin, alpha 2-macroglobulin, IgA, IgG and IgM) showed significantly increased values among the tumour patients, but the findings were not of any significant clinical value in the diagnosis of tumours.     

Small acoustic neuromas: surgical outcomes versus observation or radiation.

OBJECTIVE: Evaluate factors affecting outcomes of small acoustic neuroma (AN) removal via a middle cranial fossa (MCF) approach, and compare results to published data on observation and radiation therapy. STUDY DESIGN: Retrospective chart review. SETTING: Academic tertiary referral center. METHODS: 162 consecutive patients (ages 19-70) with unilateral AN (0.2-2.5 cm in largest dimension) removed through a MCF approach were reviewed focusing on preservation of hearing, facial nerve function and complications. One hundred thirteen patients had pre-operative word recognition scores (WRS)>70%. RESULTS: Both tumor size and pre-operative WRS were related to post-operative WRS (p<0.01). Overall, at least some hearing was preserved in 94 (60%) of the 156 patients who had hearing before surgery. If the WRS was also >70% (N=113), 56 (50%) maintained WRS>70%. Importantly, WRS for 12 others improved to >70% after surgery. When the patients were stratified by tumor size, the patients with small tumors (2-10 mm) faired better than the overall group. At least some hearing was preserved in 65 (72%) of the 90 patients. If the WRS was also >70% (N=66), 39 (59%) maintained WRS>70%. WRS for eight others improved to >70% after surgery. When the tumor was 1.1-1.4 cm (N=34), the chance of preserving some hearing decreased to 42% (14/33). If the WRS was also >70% (N=23), 9 (39%) maintained WRS>70%. WRS for three others improved to >70% after surgery. When the tumor reached 1.5-2.5 cm (N=35), the hearing preservation rate was 43%. If the WRS was also >70% (N=24), only eight (33%) maintained WRS of 70%, and one other improved to >70%. The addition of intra-operative whole eighth nerve near field monitoring improved results during small tumor (70% WRS in 76% (22/29) of those with >70% pre-operative WRS. Good facial nerve function (HB I-II) was achieved in 97% (86% HB I). When tumor size was 相似文献   

Non-surgical management of acoustic neuromas.

Watchful waiting is one of the options available in the management of acoustic neuromas and this article deals with 13 patients who were so managed. Non-operative management was advised because of age, poor general health, small size of tumour, only hearing ear, or in patients unwilling to undergo surgery for various reasons. This group was followed up at 6-12-monthly intervals and the follow-up period ranged from 1 to 18 years (mean 5.3 years). Ten patients had small tumours and only in 2 of these was increase in tumour size demonstrated on follow-up CT scan. In one this increase was later followed by regression. Two patients required partial removal of tumour because of increasing symptoms after 3 and 7 years of follow-up; one of them died on the twelfth post-operative day. There appears to be a small group of patients for whom delay is worth while rather than to subject all patients with acoustic neuroma to surgery from which full recovery cannot be guaranteed.     

Conservative management of acoustic neuromas.

The results of this study and others document the biologic behavior of acoustic neuromas. In view of the evidence presented, which describes both variable rates of individual tumor growth and spontaneous regression in size, it would seem prudent that before selecting a nonsurgical treatment modality, the growth rate for the particular tumor in question should be established. To date, none of the literature that addresses the use of focused irradiation has attempted to do so. Our study as well as those of others suggests that the growth rate of acoustic neuromas becomes predictable over time. Based on this observation, a conservative (nontumor excision) management strategy is proposed for selected individuals. Patients to whom this management philosophy has been recommended or who themselves have chosen this option are seen twice yearly. Each visit consists of a thorough neurotologic examination as well as high-definition CT or MRI. Careful comparison of the clinical course as well as calculation of the tumor size is carried out in each instance. If the clinical course and rate of tumor growth remain unchanged over a 3-year follow-up, annual assessments are recommended. In the event of tumor enlargement, surgery may or may not be recommended, depending on the rate of growth and the age of the patient. Our experience suggests that a rate of growth equal to or exceeding 0.2 cm per year constitutes an indication for tumor removal.     

Neuro-otological findings in patients with small acoustic neuromas

Summary The method of choice for the diagnosis of even the smallest acoustic neuromas is CT gas cisternography. Lumbar puncture and gas insufflation, however, is an intervention demanding strict indication. Neuro-otological examinations should lead to this indication. The aim of this paper is to demonstrate neuro-otological findings on 19 patients presenting small acoustic neuromas. These neuro-otological findings are not necessarily comparable to earlier reports in the literature dealing with mainly larger tumours at a time when early diagnosis was not so advanced.     

Evoked otoacoustic emissions in patients with acoustic neuromas

Click-evoked otoacoustic emissions were recorded in 28 patients with surgically proven acoustic neuromas and 22 patients with brain stem pathologic disorders. Data collected in acoustic tumor ears were compared with those obtained in 30 nontumor ears demonstrating sensorineural hearing losses. Acoustic emissions were altered (increased detection-threshold or no detectable emissions) in all ears with eighth nerve tumors and were not affected in those with brain stem pathologic conditions that do not involve cochlear function. The properties of acoustic emissions were similar in both tumor and nontumor ears with hearing loss, which suggests that acoustic tumors usually produce a cochlear hearing loss.     

Management of acoustic neuromas in the elderly: retrospective study

The wide availability of gadolinium-enhanced magnetic resonance imaging (MRI-Gd) has led to the discovery of an increasing number of small and less symptomatic acoustic neuromas in elderly patients. We conducted a retrospective study in order to obtain data on outcomes and complications associated with different management strategies that would be useful in establishing a management guideline. We identified 44 patients aged 65 to 77 years with acoustic neuromas who had been managed with either surgery or simple observation with MRI-Gd imaging. Of the entire group, 36 patients had tumors larger than 1 cm, and they underwent surgery (most via the translabyrinthine approach). Complete removal of the tumor was achieved in 34 of these patients (94.4%). At the 1-year follow-up, grade VI facial nerve paralysis was evident in only two of 35 evaluable patients (5.7%). Postsurgical complications occurred in five patients (13.9%), including one death. The remaining eight patients had tumors 1 cm or smaller, and they were managed with periodic MRI-Gd scanning. At the 5-year follow-up, no tumor growth was seen in six of these patients. The other two patients exhibited a tumor growth rate of less than 2 mm per year. No patient in the observation group required surgical intervention.     

Epidemiology of acoustic neuromas

In Denmark one surgical team, during the last 7 years, has performed about 80 per cent of all acoustic neuroma surgery. Because of this centralization, in such a limited population as that of Denmark, we have attempted to make a epidemiological survey of all diagnosed tumours in the period from 1976 to 1983. Systematic and prospective records were made by the authors of all patients with translabyrinthine operations, and data on patients with suboccipital operations were collected retrospectively from the six neurosurgical departments in Denmark. The average annual incidence was 8 tumours per million inhabitants, with the highest incidence of approximately 13 tumours per million occurring in Copenhagen County. The incidence reported in previously published autopsy series is 800-900 times higher and the following may serve as an explanation for this enormous difference: Autopsy series are in all probability based on highly selected cases; they are predominantly based on elderly people and the incidence is not directly applicable to the population at large. Several of the silent tumours from the autopsy series were located in the cochlea or in the labyrinth and not in the internal ear canal. The conclusion from our study is that both the knowledge and data available at present are insufficient to serve as a basis for an actual calculation of incidence and prevalence of acoustic neuromas.(ABSTRACT TRUNCATED AT 250 WORDS)     

Auditory brain-stem response in patients with acoustic neuromas. Wave presence and absence

Auditory brain-stem response (ABR) waveforms from 61 patients with eighth nerve or cerebellopontine angle tumors were analyzed for wave presence or absence. Eighteen patients yielded ABRs lacking any readable waves; 27 patients revealed ABRs in which waves were partially present (ie, one or two waves present); and 16 patients demonstrated ABRs with all waves (I, III, and V) present. In the partially present ABR group, waves I and V were most prevalent. The group lacking waves (absent ABR group) had significantly poorer hearing sensitivity and larger tumors than the partial ABR group. Various additional group comparisons for hearing sensitivity and tumor size did not yield any significant differences among the three groups.     

Quantitated determination of proteins in perilymph in patients with acoustic neuromas

Perilymph, cerebrospinal fluid (CSF) and plasma from 19 patients with acoustic neuromas were examined for albumin, alpha 2-macroglobulin and IgG. Patients with otosclerosis were used as controls. A highly significant increase of the tested proteins was found in perilymph from patients with acoustic neuromas. Determination of the tau-transferrin, which is a specific CNS protein, could neither be demonstrated in plasma nor in perilymph. This is in favour of the assumption that perilymph is plasma-derived and not concentrated CSF. Various causes for the high protein concentrations are discussed, and it is suggested that the increase is caused by a blockage of the neuroaxonal transport mechanisms.     

Electrocochleographic evaluation of hearing loss in acoustic neuromas.

OBJECTIVE: This study aimed to clarify the pathophysiology involved in the cause of hearing impairment due to acoustic neuromas (AN) with electrocochleograph (ECoG). STUDY DESIGN: The study design was a retrospective case study. SETTING: This study was conducted in a tertiary referral center. PATIENT: Thirty-four patients diagnosed as having AN by magnetic resonance imaging between 1988 and 1995. INTERVENTION: Diagnostic. MAIN OUTCOME MEASURES: The authors made a comparison between the patients' ECoG findings and the size of their tumors as determined by magnetic resonance imaging and a pure-tone audiometry (PTA). The disparity between the threshold of PTA and the detective threshold of compound action potential (CAP) or that of the cochlear microphonics (CM) was calculated. When the threshold of the PTA was worse than the detective threshold of the CAP or the CM, the disparity was regarded as indicating a hearing loss of retrocochlear origin. RESULTS: There was no correlation found between tumor size and the detective threshold of CAP or CM. Disparity was found to correlate with tumor size. CONCLUSIONS: These findings seem to indicate that retrocochlear damage in AN increases parallel to the growth of the tumor and that retrocochlear damage can be detected by the ECoG before surgery.     

Audiological findings in 125 cases of acoustic neuromas.

The audiological findings in 125 patients with surgically confirmed acoustic neuromas are presented. Following the classification by Pulec et al. (1971) we found 20 medium-size and 105 large tumours; small tumours were not represented. A clear connection between the degree of hearing loss and tumour size was noted, while there was no correlation between duration of history and tumour size. An attempted evaluation of the different audiological tests (ABLB and Metz recruitment test, speech discrimination scores, tone decay, reflex decay, and Békésy tracings) that were applied to the patients, has been made. Attention is called to some audiological findings which, to our knowledge, have not been described previously. No patient in the entire material had normal hearing; 73 had anacusis, and 52 hearing losses of varying degree. In the presence of a normal contralateral ear, the evaluation of audiological tests at PTA thresholds poorer than 80 dB is rather questionable. Attention was therefore concentrated on 32 patients with a hearing loss of 80 dB or less. The pathophysiological basis for the typical hearing loss in patients with retrocochlear disease is a reduction in the number of active fibers in the acoustic nerve and it was to be expected that abnormal findings would be present especially in those tests that exert the greatest demand on the total transmission capacity of the nerve, in other words with the application of intense and/or prolonged sounds. The Metz test is just such a procedure and it is not surprising that it shows the highest degree of validity between all the tests. No single test suffices to distinguish cochlear from retrocochlear disease and it is necessary to use a battery of tests. Any unexpected variability in the outcome of ordinary routine test results has gradually become one main indication to pursue the diagnosis with more elaborate procedures, ant it has been a great help always to apply the Metz test as a part of our routine clinical examination.