Supratentorial arachnoid cysts in adults. A discussion of two cases from a pathophysiologic and surgical perspective.

Large congenital arachnoid cysts are a rare cause of increased intracranial pressure and progressive neurologic deficits in adult life. We describe two patients, diagnosed by computerized axial tomography and surgically treated. The pertinent medical literature was reviewed. The outer cyst membranes were excised, and a communication between cyst and subarachnoid space was established. When possible, the membranes and fluid content of these lesions should be studied. This fluid is best obtained by aspiration prior to dural incision. At present, three etiologic mechanisms of cyst enlargement appear tenable: (1) secretion of fluid by ependymal cells, (2) fluid ingress due to an osmotic gradient, and finally, (3) trapping of fluid by a ball-valve mechanism. Regardless of the reasons why these lesions enlarge, drainage of cyst content into the venous system warrants a clinical consideration.

Stereotactic biopsy and brachytherapy of brain tumours.

This paper discusses 98 patients who had their cerebral lesions stereotactically biopsied. Modified Riechert-Mundinger instrumentation was employed. Of the 98 patients, eight received only biopsy and 90 were then interstitially radiated with iridium-192 (192Ir) custom stacked in afterloading catheters. The vast majority of brachytherapeutically treated lesions were anaplastic or malignant astrocytomas. There were some metastatic lesions, and in two instances the tumour occupied the infratentorial compartment. Two-thirds of the patients had received prior teletherapy; in the remainder, stereotaxis provided the initial diagnosis and brachytherapy the principal treatment. The survival data suggest reasons for optimism. Eighty percent of patients with anaplastic astrocytoma were alive 2 yr later, compared with 55% for those harbouring malignant astrocytomas. Since this is the largest database on this topic in the U.S.A., we are in the process of a more critical review. Complication rate is low. Diagnostic tissue was obtained in all instances. Delayed radionecrosis at the site of implant may aggravate neurological deficits when lesions involve functionally sensitive cortex or their pertinent underlying structures. Such reactions may appear 4-18 mnth after brachytherapy and are more likely to occur in patients who were previously radiated.

Salivary gland choristoma of the middle ear.

Salivary gland choristoma (ectopic salivary gland tissue) is an unusual condition that occurs in various locations within the middle ear. It is a distinct histopathologic entity that should be differentiated from other epithelial lesions of the middle ear. Since the lesion commonly involves the facial nerve, its recognition is particularly critical to avoid unnecessary severing of the nerve.

Salivary gland choristoma of the middle ear.

We discuss the eighth reported case of a benign salivary gland tumor in the middle ear. The lesion was a smooth lobulated mass and was found to be intimately associated with the tympanic portion of the facial nerve. Recommended treatment is biopsy without attempting removal. This concept of management is supported by a report of a similar case with a 15-year follow-up.

Cholesterol granuloma of the petrous apex: CT diagnosis.

Cholesterol granuloma of the petrous apex is a readily recognizable and treatable entity that is more common than previously realized. Cholesterol granuloma grows slowly in the petrous apex as a mass lesion until it produces hearing loss, tinnitus, vertigo, and facial twitching. Twelve cases of cholesterol granuloma of the petrous apex are illustrated; ten of these are analyzed in detail, especially with respect to CT findings. A sharply and smoothly marginated expansile lesion in the petrous apex, isodense with brain and nonenhancing on CT, is in all probability a cholesterol granuloma. Cholesterol granuloma and cholesteatoma of the petrous apex are different lesions and treated differently. Cholesterol granuloma can be treated simply and effectively by drainage and permanent fistulization. Preoperative recognition by CT is important for planning proper treatment.

CT-compatible system for stereotactic biopsy and brachytherapy of infratentorial tumors.

Teletherapy of nonresectable radiosensitive brain tumors is the mainstay of adjunctive treatment. In the past two decades brachytherapy has begun to play an ever-increasing role, particularly on the European continent. Yet this attention has been addressed almost exclusively to lesions of the supratentorial space. This article describes modifications of the Riechert-Mundinger stereotactic system which were made by one of us (P.D.) to allow an unencumbered yet precisely computerized stereotactic approach to posterior fossa lesions for biopsy and interstitial radiation with iridium 192. A case report is described to illustrate the technical details involved in such an undertaking.

Computer-aided, CT-guided biopsy and brachytherapy of brain tumors.

The authors present the principles of computer-aided, CT-guided stereotaxis as it applies to the modified Riechert-Mundinger equipment. A preliminary report on 20 prospectively biopsied and interstitially radiated patients with cerebral mass lesions is discussed. 192Ir served as the interstitial isotope exclusively. To date the results are encouraging and complement the European experience. However, a great deal of improvement is possible, particularly in the sophistication of interstitial radiation of brain tumors; all well within presently available technology.