Jason Sheehan and Chun Po Yen
Relationship between tinnitus and surgical options for vestibular schwannomas
Douglas Kondziolka and Hideyuki Kano
Douglas Kondziolka, L. Dade Lunsford and A. Julio Martinez
✓ Many physicians rely upon neuroimaging studies alone to select therapy for adult patients suspected of having a glial neoplasm, in the belief that certain imaging features accurately characterize the histological diagnosis of low-grade astrocytoma. During a 4-year interval when both computerized tomography and magnetic resonance imaging was available, the authors performed stereotactic biopsies on 20 consecutive adult patients who were suspected of having an astrocytoma. The patients were generally young (mean age 37 years), had seizures (17 cases), and had lobar lesions. An accurate histological diagnosis was obtained, without morbidity, in all 20 patients. Only 10 (50%) in fact had low-grade astrocytomas, whereas nine (45%) had anaplastic astrocytomas and one (5%) had encephalitis. The results of this study indicate that modern high-resolution neuroimaging alone cannot be used as a reliable tool to predict the histological diagnosis of astrocytoma (50% false-positive rate). All patients with supratentorial mass lesions that exhibit the “typical” imaging features of astrocytoma should undergo stereotactic biopsy for confirmation in order that appropriate management may be planned.
Conor Grady, Omar Tanweer, David Zagzag, Jafar J. Jafar, Paul P. Huang and Douglas Kondziolka
Stereotactic radiosurgery is widely used to treat cerebral arteriovenous malformations (AVMs), with the goal of complete angiographic obliteration. A number of case series have challenged the assumption that absence of residual AVM on follow-up angiograms is consistent with elimination of the risk of hemorrhage. The authors describe 3 cases in which patients who had angiographic evidence of AVM occlusion presented with late hemorrhage in the area of their prior lesions. They compare the radiographic, angiographic, and histological features of these patients with those previously described in the literature.
Delayed hemorrhage from the tissue of occluded AVMs has been reported as early as 4 and as late as 11 years after initial stereotactic radiosurgery. In all cases for which data are available, hemorrhage occurred in the area of persistent imaging findings despite negative findings on conventional angiography. The hemorrhagic lesions that were resected demonstrated a number of distinct histological findings.
While rare, delayed hemorrhage from the tissue of occluded AVMs may occur from a number of distinct, angiographically occult postirradiation changes. The hemorrhages in the authors' 3 cases were symptomatic and localized. The correlation of histological and imaging findings in delayed hemorrhage from occluded AVMs is an area requiring further investigation.
Jason P. Sheehan, Douglas Kondziolka, John Flickinger and L. Dade Lunsford
Nonfunctioning pituitary adenomas comprise approximately 30% of all pituitary tumors. The purpose of this retrospective study was to evaluate the efficacy and role of gamma knife surgery (GKS) in the treatment of these lesions.
The authors conducted a review of cases in which GKS was performed at the University of Pittsburgh between 1987 and 2001. Forty-six patients with nonfunctioning pituitary adenomas and with at least 6 months of follow-up data were identified. In 41 of these patients some form of prior treatment such as transsphenoidal resection, craniotomy and resection, or conventional radiation therapy had been conducted. Five patients were deemed ineligible for microsurgery, and GKS served as the primary treatment modality. Endocrinological, ophthalmological, and radiological responses were evaluated. The mean radiation dose to the margin was 16 Gy.
In all patients with microadenomas and 91% of those with macroadenomas tumor control was demonstrated after radiosurgery. Gamma knife surgery had essentially equal efficacy in terms of achieving tumor control in cases of adenomas with cavernous sinus invasion and suprasellar extension. No new endocrinopathies were noted following radiosurgery. In two patients, however, tumor growth and decline in visual function occurred.
Gamma knife surgery is safe and effective in treating nonfunctioning pituitary adenomas. Radiosurgery may serve as a primary treatment modality in some or as a salvage treatment in others. Treatment must be tailored to meet the patient's symptoms, overall health, and tumor morphometry.