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Gregory J. Zipfel and Ralph G. Dacey

Over the past decade, several factors have led to a dramatic change in the manner in which patients with unruptured intracranial aneurysms are diagnosed and treated. These factors include the increased use of noninvasive imaging modalities for the diagnosis of intracranial aneurysms, publication of new natural history data detailing the hemorrhage risks associated with unruptured intracranial aneurysms, and the broad application of endovascular therapy for their treatment. With these new technologies and new natural history data has come considerable uncertainty about the optimal treatment strategy for patients with unruptured intracranial aneurysms. In this light, it seems prudent to review periodically and examine critically all recent data pertaining to the natural history and treatment of unruptured intracranial aneurysms, in an effort to provide a scientific update on which management recommendations can be based. This review article represents the authors' attempt at such an update, and it is their hope that members of the community of neurovascular surgeons might find this information helpful during their continuing efforts to provide optimal care for their patients with unruptured intracranial aneurysms.

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Eric J. Arias and Gregory J. Zipfel

Giant cerebral aneurysms may be treated through a variety of options, including aneurysm trapping with concurrent bypass. This video describes the case of a large, recurrent, left middle cerebral artery aneurysm that was treated using a high flow, radial artery bypass graft, from the external carotid artery to the left temporal M2 branch. A step-by-step operative description, with emphasis on proper microsurgical technique, is included.

The video can be found here:

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Gregory J. Zipfel, Patrick Bradshaw, Frank J. Bova, and William A. Friedman

Object. The authors sought to determine which morphological features of arteriovenous malformations (AVMs) are statistically predictive of preradiosurgical hemorrhage, postradiosurgical hemorrhage, and neuroimaging-defined failure of radiosurgical treatment. In addition, correlation between computerized tomography (CT) scanning and angiography for the identification of AVM structures was investigated.

Methods. Archived CT dosimetry and available angiographic and clinical data for 268 patients in whom AVMs were treated with linear accelerator radiosurgery were retrospectively reviewed. Many of the morphological features of AVMs, including location, volume, compact or diffuse nidus, neovascularity, ease of nidus identification, number of feeding arteries, location (deep or superficial) of feeding arteries, number of draining veins, deep or superficial venous drainage, venous stenoses, venous ectasias, and the presence of intranidal aneurysms, were analyzed. In addition, a number of patient and treatment factors, including patient age, presenting symptoms, radiation dose, repeated treatment, and radiological outcome, were subjected to multivariate analyses.

Two hundred twenty-seven patients were treated with radiosurgery for the first time and 41 patients underwent repeated radiosurgery. Eighty-one patients presented with a history of AVM hemorrhage and 91 patients had AVMs in a periventricular location. Twenty-six patients (10%) experienced a hemorrhage following radiosurgery. Of the 268 patients, 81 (30%) experienced angiographically defined cures, and 37 (14%) experienced MR imaging-defined cures. Eighty-six patients (32%) experienced neuroimaging-defined treatment failure, and 64 underwent insufficiently long follow up.

A larger AVM volume (odds ratio [OR] 0.349; p = 0.004) was associated with a decreased rate of pretreatment hemorrhage, whereas periventricular location (OR 6.358; p = 0.000) was associated with an increased rate of pretreatment hemorrhage. None of the analyzed factors was predictive of hemorrhage following radiosurgery. A higher radiosurgical dose was strongly correlated with neuroimaging-defined success (OR 3.743; p = 0.006), whereas a diffuse nidus structure (OR 0.246; p = 0.008) and associated neovascularity (OR 0.428; p = 0.048) were each associated with a lower neuroimaging-defined cure rate. A strong correlation between CT scanning and angiography was noted for both nidus structure (p = 0.000; Fisher exact test) and neovascularity (p = 0.002; Fisher exact test).

Conclusions. Patients presenting with AVMs that are small or periventricular were at higher risk for experiencing hemorrhage. A higher radiosurgical dose correlated strongly with neuroimaging-defined success. Patients in whom the AVM had a diffuse structure or associated neovascularity were at higher risk for neuroimaging-defined failure of radiosurgery. A strong correlation between CT scanning and angiography in the assessment of AVM structure was demonstrated.

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Matthew R. Reynolds, Spiros L. Blackburn, and Gregory J. Zipfel

Perimesencephalic nonaneurysmal subarachnoid hemorrhage (PNSAH) is a benign variant of SAH defined by clinical symptoms of SAH, a characteristic pattern of extravasated blood on noncontrast CT, and negative findings on cerebral angiography. This syndrome carries a favorable prognosis with reportedly no risk of recurrent hemorrhage. The authors present the case of a 62-year-old man with no significant medical history who experienced recurrent, spontaneous episodes of PNSAH within the course of 5 months. No precipitating causes were identified, but the patient had been involved in exertional activities preceding both events. To the authors' knowledge, this is the first conclusive report of recurrent, idiopathic PNSAH. The findings suggest that while the risk of recurrent hemorrhage in the setting of PNSAH is far less than that for aneurysmal SAH, rebleeding can still occur. The authors speculate on the etiology of this rare phenomenon.