Search

M ENINGIOMAS of the eerebellar fossa, although few in number, deserve special s tudy as a group. They show certain characteristic findings leading to an early diagnosis, which is particularly important for a cure. The cramped space in which they occur and their proximity to vital structures make removal hazardous, particularly since they are so vascular and so often attached to the large sinuses within the subtentorial space. Complete removal with far less hazard can therefore be accomplished before the tumor has at tained too great a size. Ten cases of meningiomas of the cerebellar fossa are presented here. These show a ratio of 1 to 5.8 in a total of 58 meningiomas and represent per cent of our intracranial tumor series. In Cushing's series, a there were ~3 cases in a total of ~95 meningiomas, a ratio of 1 to 13 and representing 1.04 per cent of his total. As he noted, the incidence is much less compared to the supratentorial meningiomas than the involved dural area would indicate, for by measuring a normal adult brain he found the subtentorial dural surface to be 166 sq. cm., and the total supratentorial dural surface including the falx to be 754 sq. cm., a ratio of 1 to 4.5. The site of a t tachment of these tumors in our series was found to be chiefly the tentorium and transverse and sigmoid sinuses. One of the tumors perforated the tentorium, and the ventriculograms of 1 other indicated a similar extension. The a t tachment of 3 situated in the angle could not be ascertained. In another in this position the a t tachment was to almost the entire anterior dural surface of the cerebellar fossa on one side with extension beyond the midline. In Cushing's series, similar a t tachments were found with specific mention of 11 tumors arising from the tentorium and the transverse and sigmoid sinuses. Of 7 tumors found in the angle an a t tachment was found of only 1 small one, and this was to the porus acusticus. Sufficient removal could not be accomplished in the others to ascertain the point of origin. I t appears from a study of the findings that the site of a t tachment determines to a large extent the symptomatology. For example, those tha t arose from the tentorium showed early 5th nerve changes while those situated in the angle showed symptoms characteristic of an acoustic neurinoma with early 8th nerve involvement. The most consistent and one of the earliest findings was pain in the back of the head and neck (Fig. 1). This was usually

The microchemical analysis of human inner ear fluid has not only advanced our knowledge of inner ear function in normal and pathological states, but also has added another dimension to our diagnostic armamentarium in inner ear disease. The purpose of this thesis is 1 To review and evaluate all pertinent literature concerning the chemistry of human inner ear fluids. 2 To determine what percentage of inner ear fluids can be collected without contamination by hemolyzed cells (hemoglobin) or erythrocytes. 3 To study the glucose concentrations in human inner ear fluid in various pathological states. 4 To present the data from uncontaminated endolymph samples in Meniere's disease. 5 To study the correlation between the clinical picture of acoustic neurinoma and the results of inner ear fluid analysis. 6 To evaluate the present status of diagnostic labyrinthotomy (labyrinthine tap).

Diagnostic labyrinthotomy is indicated in acoustic neurinoma suspects: (1) when there is a progressive unilateral sensorineural loss and the laminograms of the internal auditory canals show no abnormalities; (2) when the posterior fossa contrast study is equivocal or unsatisfactory; (3) when there is a question of whether the filling defect represents an intracanicular or extra-canicular tumor; (4) to confirm the diagnosis of acoustic tumor following iophendylate study of the posterior fossa; (5) when the patient is allergic to contrast media; and (6) when there is no serviceable hearing in the affected ear.

The correlation between various clinical parameters and MIB-1 (Ki-67) staining indices was evaluated in 58 acoustic neurinomas. The index ranged from 0.37% to 6.61% (mean 1.70%), and did not correlate with age, sex, or initial tumor volume. Sixteen of the 18 tumors removed subtotally or partially showed regrowth, and two showed a volume reduction. The 16 patients with regrowth were divided into two groups according to Ki-67 staining index,2.00% andor = 2.00%. These groups had a significant difference in tumor doubling time (TDT). In addition, there was a significant logarithmic correlation between Ki-67 staining index and TDT. Ki-67 staining index can be used as an index of regrowth rate in partially or subtotally removed acoustic neurinomas. Intraoperative assessment of Ki-67 staining index may be useful for better management planning as well as the estimation of prognosis.

The authors describe the case of a 71-year-old man without signs of phacomatosis with a history of progressive psychomotory lowering and two simultaneous tumors of the olfactory groove and of the cerebellopontine angle, as demonstrated by CT scans. Histologic examinations showed the lesions to be a meningioma and a neurinoma. The rarity and the possible pathogenesis of this association are discussed.

The introduction of the operating microscope has strongly influenced our surgical possibilities for preserving and reconstructing the facial nerve in tumor surgery in the cerebellopontine angle as well as in the internal auditory canal. In 1975, we introduced a new method for facial nerve reconstruction in the cerebellopontine angle. Since then, we have operated upon 20 patients using this technique of intracranial-intratemporal nerve graft; 15 of these have been done directly after the removal of the acoustic neurinoma. Of these patients, 12 have been followed over a period of 9 to 87 months. A sural nerve graft 4 to 5 cm in length was placed between the central stump of facial nerve at the brain stem and the distal end of facial nerve in tympanal or mastoidal course after total removal of the acoustic neurinoma. The results, demonstrated in this paper, are highly encouraging. It is recommended that this operative technique be included in the entire concept of microsurgery in the cerebellopontine angle.

An experimental model for controlled studies of an acoustic neurinoma will be described. The model employs nonhuman primates. It permits chronic experimentation. It is reversible. Essentially, the preparation is based upon the implantation of an inflatable Silastic rubber balloon in the VII and VIII cranial nerves in the internal auditory meatus of the monkey. Prior to and following such preparation, a systematic study of the contralaterally evoked stapedius reflex was performed. Afferent and efferent limbs of the reflex arc were studied. The effects of balloon inflation and deflation were examined. Variables studied included threshold across frequency, dynamic range, habituation, rate of rise, and recovery time. Normative data indicate the characteristics of the monkey stapedius reflex are comparable to man. Implantation reversibly affected all variables except habituation which was permanently affected. Changes in all variables were reversibly influenced by balloon inflation and deflation. The time course and quantitative changes observed will be described. Clinical implications and possible basic mechanisms underlying the effects of the acoustic neurinoma on auditory function will be discussed. [Work supported by NS08181 and RR00166.]

This unusual case, recorded by kind permission of Mr. Joseph Schorstein, the surgeon in charge, presents several features of clinical and radiological interest. The patient was admitted to hospital with suspected chronic intracranial abscess, but was found to have a glioblastoma of one cerebral hemisphere. At post-mortem examination, there was also found to be a left acoustic neurinoma, which had produced considerable erosion of the internal auditory canal, easily identifiable on review of the X-ray films, but which had not given rise to symptoms during life. Audiometry would almost certainly have revealed impaired hearing, but this was not found on ordinary clinical examination. The location of the glioblastoma deep to a tantalum plate which had been seven years in position raises interesting aetiological problems, but may well be pure coincidence. This plate was inserted to cover a bone defect resulting from fracture.

At the Western Section Meeting of the Triological Society, Douglas A. Chen, MD, Frank M. Rizer, MD, and Derald E. Brackmann, MD, reviewed their experience at the Otologic Medical Group, Los Angeles, with radiation therapy for acoustic tumors. They were able to find only five patients in the records of the Otologic Medical Group who had undergone radiation therapy for acoustic neurinoma. They observed that tumor growth had been arrested in four of the five patients, and that one patient required surgery because of progressive tumor growth. Hearing was lost after radiation therapy in two of the five patients. None of these five patients had useful hearing. Two patients also demonstrated multiple cranial nerve neuropathies. The authors concluded that most of the reports favoring radiotherapy for acoustic neuromas currently come from Scandinavia, and that the present available information suggests that surgery remains the treatment of choice for resectable acoustic neuromas.—

Between January 1, 1978, and July 1, 1983, 149 patients underwent acoustic neurinoma removal (151 procedures). Of these, 119 ears (118 patients) had had some degree of hearing on the affected side preoperatively, and in all of them the tumors had been removed by a posterior cranial fossa approach. Fourteen (12%) had measurable hearing preserved postoperatively--serviceable in eight ears and poor in six. The patients with preserved hearing had had their hearing loss for a shorter period, slightly better preoperative hearing levels, and a smaller tumor. The complications, morbidity, and mortality in this group were comparable to those in other series. It is concluded that preservation of hearing is a worthwhile goal that can be achieved without increased risk.

A case of a 3-cm acoustic neurinoma totally excised with preservation of the facial and cochlear nerves is reported. Hearing was not impaired by the operation, but dramatically improved within 2 months. The literature on operations of acoustic tumors with preservation of hearing is reviewed. In patients with some hearing ability, the operation should be conservative, whatever the size of the neurinoma, because there is a fair chance of success.

This article reviews the roentgenographic studies performed in 131 patients who had surgically confirmed acoustic neurinomas. In this 5-year study (1978-1982), all patients had computed tomography (CT) and 82% had petrous apex tomography. Approximately 18% of patients underwent angiography, and 18% had positive contrast rhombencephalography. The diagnostic capability with CT scanning has improved remarkably. There were no false-negative results for scans obtained in 1981 and 1982. At the same time the accuracy of other radiographic and audiometric tests was decreasing. The proportion of small tumors diagnosed has increased 200%, with a corresponding decrease in medium and large tumors. Tumors can be diagnosed at an earlier stage; and, because of this, surgical results have improved. No surgical mortality occurred in this series, preservation of the facial nerve was excellent, and in some patients cochlear function was maintained.

Meningiomas originating within the posterior fossa frequently cause much difficulty in diagnosis, and there are few intracranial tumors so challenging to the neurosurgeon. Whereas meningiomas in their favored locations, such as the olfactory groove, the sphenoid wing, the convexity, and the parasagittal region, give rise to characteristic clinical features, those within the posterior fossa differ widely in their mode of onset and the symptoms they produce. In some cases the development of symptoms may be so insidious and misleading that posterior fossa tumors seem remote from consideration. In other instances the histories and neurological findings are indistinguishable from those of an acoustic neurinoma. Since meningiomas in general offer a favorable prognosis, early diagnosis of the ones within the posterior fossa is particularly important because of their propensity to involve vital structures in or about the brain stem. The incidence of subtentorial meningiomas has been very low. As recently as 1953