Suboccipital Removal of Acoustic Neuromas: Results of 125 Operations

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.

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.

Osteoma of the internal auditory canal. Case report and literature review

Osteomas of the internal auditory canal are rare lesions, with only 12 reported cases in the world literature. Symptoms are those of eighth nerve compression, and include unilateral hearing loss and vestibular weakness, thus mimicking symptoms of acoustic neuroma. We report a patient with an osteoma of the internal auditory canal, along with a review of the literature. We note age and sex characteristics from the literature, give evidence of localized trauma as a possible etiologic factor for this lesion, and discuss the pitfalls of relying exclusively on magnetic resonance imaging in the workup of suspected retrocochlear lesions.

Intracranial schwannoma as atypical facial pain. Case report

Facial pain is a common complaint that leads those who have it to seek professional help. Often times, the general dentist is the first clinician that a patient consults because of a presumed odontogenic origin of the pain. Occasionally a small number of these patients will be found to have an intracranial tumor. The case reported here is one such patient who was diagnosed and treated for a seventh nerve schwannoma.

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.

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)

Hearing conservation in acoustic tumor surgery: pro's and con's

This article presents an overview of the points to be made both for and against the consideration of hearing conservation in acoustic tumor surgery based on current available data in the literature. Age, general health, tumor size, and hearing - in the tumor ear and in the contralateral ear as well as the interaural relationship - are the presurgical factors discussed. Either the middle fossa or posterior fossa approach may be utilized for hearing conservation. The technical factors relating to surgical anatomy, specific risks, and the probability that hearing may be preserved by these approaches have been abstracted from a review of the literature. Finally, the patient's considerations and his need for the conservation of his hearing are presented, including realistic alternatives to surgical conservation.

Acoustic neuromas (diagnostic value of testing the function of the trigeminal nerve, the cerebellum and optokinetic nystagmus)

The involvement of the trigeminal nerve, cerebellum, and optokinetic nystagmus in patients with acoustic neuromas, as well as the methods of investigation, are described. The corneal and/or facial sensibility was found to be reduced in 29 per cent of the whole series and in 53 per cent of tumors larger than 40 mm. There was a significant correlation between reduced corneal and/or facial sensibility and the findings of pressure at the trigeminal root at operation. Only three patients had a persistent reduction of trigeminal function post-operatively. Cerebellar dysfunction was found in 32 per cent, but significantly more frequently (58 per cent) in patients with tumors larger than 40 mm. Post-operatively, six patients had cerebellar symptoms in the form of gait disturbances; five of these patients had a supplementary suboccipital removal performed, after the initial translabyrinthine approach. A defective optokinetic nystagmus was found pre-operatively in 10 patients, nine of whom had tumors larger than 40 mm in diameter. All patients with a defective optokinetic nystagmus had a large anatomic impression in the pons at operation. In patients suspected of having an acoustic neuroma, symptoms from the trigeminal nerve, the cerebellum and the optokinetic nystagmus predict the presence of a large tumor and subsequent difficulties at operation. The symptoms were completely reversible in the vast majority of cases and post-operative symptoms persisted only in patients in whom tumor removal was difficult and the tumor very large. Testing of the trigeminal nerve, the cerebellum and the optokinetic nystagmus still deserves its place in the diagnostic work-up of patients with unilateral acoustic or vestibular symptoms, especially in cases with severe hearing impairment, which necessitate the use of tests that are independent of acoustic function.

The price of preservation of hearing in acoustic neuroma surgery

Translabyrinthine surgery for acoustic neuroma was introduced in Denmark in 1976, and the results of the first 100 operations are presented. Two deaths occurred, unrelated to the translabyrinthine surgery. Postoperatively, 75% of the patients had normal facial function, while function was reduced in 15% and abolished in 10%. The series represents 85% of all acoustic neuromas operated in Denmark, with 30 new neuromas being diagnosed each year, derived from a population of 5.1 million. The overall postoperative results are compared with the available results from suboccipital removals of acoustic neuromas, and are clearly in favor of the translabyrinthine approach. It is concluded that centralization of acoustic neuroma surgery is necessary, that all acoustic neuromas regardless of size can be removed by the translabyrinthine approach and that the discussion about the hypothetical preservation of hearing by applying the suboccipital approach is being made without solid grounds. To adduce the theoretical chance of preserving hearing in a very small percentage of patients as an argument in favor of the suboccipital approach appears quite irrelevant, and the price of attempting this with the suboccipital approach is too high.

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.

Early, active diagnosis of acoustic neuromas

Since the introduction of the translabyrinthine approach in the treatment of acoustic neuromas in Denmark. 47 patients have been operated on, the series containing 2% small, 60% medium and 38% large tumours. This distribution differs significantly from previously published tumour series, where the large tumours dominated. The paper describes the various diagnostic procedures applied in the present active search for acoustic neuromas, and the reduction in tumour size is ascribed to information on the improved surgical results obtained by the translabyrinthine approach.

Computer tomography of cerebellopontine angle lesions

Computer tomography (CT) was used in 53 consecutive patients with a working diagnosis of cerebellopontine angle tumor. The CT was performed with the 160 X 160 matrix scanner, height of sections was 13 mm. Metrizoate sodium (1.5 ml/kg of body weight) was used for tumor enhancement. Seventeen CT scans revealed tumors; one patient proved at operation to be false-positive. Thirty-six CT scans revealed no tumors; two examinations may prove to be false-negative, but surgical verification has so far not been obtained. The smallest tumor demonstrated by CT extended 7 mm into the angle, while one of the possible false-negative CT scans after iophendylate injection cisternography showed a tumor extending 5 mm into the angle. It is concluded that CT is a harmless, noninvasive neuroradiological procedure, and should precede invasive procedures. It can be used safely in patients with increased intracranial pressure.

Cerebellopontine angle tumours, other than acoustic neuromas. A report on 34 cases. A presentation of 7 bilateral acoustic neuromas

The symptoms, preoperative diagnostic results and histological findings in 34 cerebellopontine angle tumour cases, other than acoustic neuromas, are presented. The meningeomas dominate by far this group of tumours. The symptomatology is much less uniform than that of the acoustic neuromas, where the VIII nerve is dominant. The facial nerve is less involved, whereas the other cranial nerves give symptoms more frequently. One remarkable sign is the presence of severe trigeminal neuralgia, which we have not encountered in acoustic neuromas. Only 35% of the 'non-neuroma' patients had elevated spinal fluid protein, compared with 100% in our acoustic neuroma cases. Furthermore, 7 patients with bilateral acoustic neuromas are presented. The connection with von Recklinghausens disease and multiple meningeomas is discussed.