Surgery for acoustic neurinoma

Spectrum of 68Ga-DOTA TATE Uptake in Patients With Neuroendocrine Tumors

PURPOSE

To analyze the biodistribution of Ga-DOTA-TATE in the normal tissues and uptake in benign, indeterminate, and malignant lesions in a population of patients with known neuroendocrine tumors (NET) using semiquantitative standardized uptake values (SUV) measurements.

METHODS

One hundred four consecutively scanned patients (51 men and 53 women; mean age, 56.4 years) with confirmed diagnosis of NET underwent PET/CT 1 hour after administration of Ga-DOTA-TATE. SUVmean, and SUVmax were measured in 37 normal anatomical structures for each patient. Abnormal uptake was divided into benign, indeterminate, and malignant categories based on imaging characteristic, clinical follow-up, and pathology.

RESULTS

High physiologic uptake (SUVmax > 7) was observed in spleen, renal parenchyma, adrenal glands, pituitary gland, stomach, and liver (in decreasing order). Moderate uptake (3.5-7) was present in the prostate, jejunum, pancreas, ileum, and salivary glands. Mild uptake (2-3.5) was present in the uterus, colon, thyroid, rectum, and skeleton. A total of 678 lesions (limited to 5 lesions with highest uptake per organ) were included in the analysis, including 127 benign and 54 indeterminate lesions. Uptake was significantly higher in malignant lesions than in benign lesions, but an overlap was noted between the groups.

CONCLUSIONS

Ga-DOTA TATE uptake in normal and abnormal structures is highly variable in patients with NET. SUV is a useful measure for characterizing benign versus malignant lesions. Anatomical and clinical correlation may be necessary to characterize foci of intermediate uptake.

Causes of facial nerve paresis after translabyrinthine surgery for acoustic neuroma

Forty-six consecutive video-recorded translabyrinthine operations at Gentofte Hospital, for tumors of 5 to 25 mm, were investigated for possible damage to the facial nerve from cauterization, suction, stretching, pushing, and other instrumental trauma at the following regions: fundus, internal meatus, porus, cerebellopontine angle, and brain stem. House-Brackmann grading of the postoperative facial nerve function was determined from the patient records for the 1st, 3rd, and 10th days and 3 months and 6 months postoperatively, as well as the final status. Suction on the nerve seems to be the most important factor for perioperative facial nerve damage. The most common site of damage was the porus region. This investigation shows thermic drilling lesions to be very relevant. There was no correlation between the degree and character of damage and the postoperative facial nerve function. In eight patients we cannot explain the postoperative facial palsy.

Cerebrospinal fluid leaks and meningitis in acoustic neuroma surgery

Cerebrospinal fluid leaks and associated meningitis are the most common life-threatening complications of surgery for acoustic neuromas. This retrospective study reviews 319 patients who had surgery for 321 acoustic tumors at the Sunnybrook Health Sciences Center, University of Toronto, from April 1975 to March 1990. Cerebrospinal fluid leaks occurred after 13.4% of primary tumor operations. Surgical repair was required in 6.2% of all patients; 4.4% needed more than one operation. Meningitis occurred in 5.3% of all patients. These complications were more common in larger tumors and after the combined translabyrinthine middle fossa approach. Transnasopharyngeal eustachian tube obliteration was used to stop recurrent cerebrospinal fluid leaks in two patients.

The translabyrinthine approach for the removal of large acoustic neuromas

The results and the sequelae are reported from a series of consecutive 400 translabyrinthine removals of acoustic neuromas comprising almost all such tumors in Denmark during a 12-year period from 1976 to 1988. There were two intrameatal, 137 median-sized, 112 large and 149 advanced tumors, the latter having a diameter exceeding 40 mm. The mortality rate in the overall series was 2%. The incidence of cerebrospinal fluid leak occurred in 11%, and persisted for more than 2 weeks in 4%. Facial nerve function was completely normal in 67% of the patients, while only 5% required a nerve anastomosis.

Anatomy of the cerebello-pontine angle visualized through the translabyrinthine approach

The anatomical situations of the cerebello-pontine angle were studied in cadavers via the translabyrinthine approach. A series of black and white photographs are presented showing the exit zones and intracranial courses of the IV-XI cranial nerves, as seen observed through the translabyrinthine approach in different directions. In order to popularize this procedure and to publish the technical details involved, it is necessary that the anatomy and patho-anatomy of the cerebello-pontine angle and its surroundings are studied systematically as they appear through the translabyrinthine approach.

A modified extended middle cranial fossa approach for acoustic nerve tumors. Results of 125 operations

During the past 10 years, 125 operations for acoustic nerve tumors were performed on 114 patients at the authors' institution using a modified extended middle cranial fossa approach. This approach is based on a combination of King and Morrison's translabyrinthine-transtentorial approach and on the extended approach through the middle cranial fossa described by Bochenek and Kukwa. There were two hospital deaths (operative mortality 1.6%). In 102 operations on the initial tumor, total removal was performed in 89 cases (87%), and in 71 (80%) of these the facial nerve was anatomically preserved. Intracranial end-to-end anastomosis was performed on five of the 18 sacrificed facial nerves; a facial-hypoglossal anastomosis was carried out in the remaining 13 patients and in five (7%) of the 71 patients whose anatomically preserved facial nerve functioned poorly. In seven (39%) of the 18 patients in whom an attempt to preserve hearing was made, postoperative hearing was saved. In 23 operations on 17 patients for recurrent tumors, most of which had previously been removed subtotally via the suboccipital approach, total removal was accomplished in 13 (57% of the 23 reoperations and 76% of the 17 patients). At reoperation, the facial nerve was preserved in six (55%) of the 11 patients in whom the facial nerve had not been sacrificed. Postoperative leakage of cerebrospinal fluid occurred in 11 cases (8.8%), with rhinorrhea in 10 cases and otorrhea in one. Five of the fistulas were corrected by surgery and the rest healed spontaneously. Other complications were not significant.

Is preservation of hearing in acoustic neuroma worthwhile?

In a series of 300 translabyrinthine removals of acoustic neuromas, comprising almost all tumours operated on in Denmark during a period of 10 years, the preoperative hearing in the tumour ear and in the contralateral ear was analysed in 72 patients with tumours smaller than 2 cm in extrameatal diameter. These patients constitute likely candidates for a hearing preserving operation via the suboccipital approach. In the tumour ear in 4 patients there was a pure-tone average (PTA) of 0-20 dB and a discrimination score (DS) of 81-100%. Applying this criterion to the whole series, 1% of the patients would be candidates for a hearing preserving procedure. Changing the criterion to a PTA of 0-40 dB and a DS of 61-100%, the number of candidates would increase to 8 patients (3%), and with a PTA of 0-50 dB and a DS of 51-100% 14 candidates (5%) would have been found. In all of these patients, contralateral hearing was normal (SRT 0-20 dB, DS 95-100%). Since preservation of hearing would be achieved in only half of those subjected to suboccipital removal and since the hearing retained in patients with successful operations is generally poorer than the preoperative level, the number of patients obtaining serviceable hearing is so modest that preservation of hearing cannot be considered an argument in favour of suboccipital tumour removal. It should be borne in mind that contralateral hearing is normal in these patients and that, according to most reports, the mortality rate is higher and paralysis of the facial nerve more frequent with the suboccipital approach than with the translabyrinthine procedure.

Surgery for acoustic neurinomas: a proposal

Surgery for resection of acoustic neurinomas (vestibular schwannomas) has been performed by way of the middle fossa craniotomy, suboccipital route, and translabyrinthine operation. The author has preferred the translabyrinthine operation for small tumors (less than 2 cm) for patients with poor hearing and the suboccipital approach for large tumors and for small tumors when attempting to preserve hearing. This paper proposes an operation designed for better tumor removal results, an improved technique for preservation of hearing, and fewer complications. During the first part of the operation, the posterior fossa dura posterior to the labyrinth, and also bound by the superior petrosal and sigmoid venous sinuses, is exposed by the mastoidectomy route. The mastoid is obliterated with adipose tissue. The suboccipital route is then used to resect large tumors and small tumors when attempting to preserve hearing. This operation would 1) facilitate dissection of the internal auditory meatus, 2) reduce chance for injury to the labyrinth with a resulting total hearing loss, and 3) eliminate the rather frequent (less than 10%) incidence of postoperative CSF otorhinorrhea and its complications.

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.

Translabyrinthine surgery of acoustic neurinoma

In translabyrinthine and translabyrinthine-suboccipital removal of 47 acoustic tumours, the mortality rate was 2.1%; among 18 large tumours, 5.6%. The facial nerve was preserved in 89%, and 80% had normal facial nerve function. 98% of the tumours were removed in toto, including 17% where the tumour remnant was removed by the suboccipital approach one week after the translabyrinthine operation.

Intermedius nerve involvement and testing in acoustic neuromas

The clinical findings in 125 patients with surgically confirmed acoustic neuromas are presented, with special regard to the involvement of the intermedius nerve in the diagnosis. In assessing the function of the intermedius nerve the examination of the nasolacrimal reflex and the sensation of taste on the anterior two-thirds of the tongue are used. The methods of investigation are described in detail. The material consisted of 20 medium-sized and 105 large tumours; no intracanalicular tumor was found. Hearing loss was the initial symptom in 85% of the patients, 10% had tinitus and 4% vertigo as the first symptom. Apart from the VIII cranial nerve symptoms, a defective nasolacrimal reflex was the most significant evidence of cerebellopontine angle pathology. The test was positive in 65% of the medium-sized tumours, in the entire material, 85%. The figures are higher than the incidence of trigeminal nerve symptoms. This in contrast to the reports of most authors. The tests described are simple and quick to perform, and it is emphasized that they should be applied to all patients with unilateral hearing loss of unknown origin.

Facial nerve function after suboccipital removal of acoustic neurinoma

The recovery of facial nerve function after suboccipital removal of 91 acoustic neurinomas is presented. The results after anatomical preservation of the nerve (60 cases), direct anastomosis of the nerve (7 cases), nerve grafting (16 cases), and facial hypoglossal anastomosis (8 cases) are presented after a follow-up period of 31.2 months. A simplified classification was used to describe motor function. The results are compared to those in the literature.