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Jason P. Sheehan, Nader Pouratian, Ladislau Steiner, Edward R. Laws and Mary Lee Vance

Object

Gamma Knife surgery (GKS) is a common treatment for recurrent or residual pituitary adenomas. This study evaluates a large cohort of patients with a pituitary adenoma to characterize factors related to endocrine remission, control of tumor growth, and development of pituitary deficiency.

Methods

A total of 418 patients who underwent GKS with a minimum follow-up of 6 months (median 31 months) and for whom there was complete follow-up were evaluated. Statistical analysis was performed to evaluate for significant factors (p < 0.05) related to treatment outcomes.

Results

In patients with a secretory pituitary adenoma, the median time to endocrine remission was 48.9 months. The tumor margin radiation dose was inversely correlated with time to endocrine remission. Smaller adenoma volume correlated with improved endocrine remission in those with secretory adenomas. Cessation of pituitary suppressive medications at the time of GKS had a trend toward statistical significance in regard to influencing endocrine remission. In 90.3% of patients there was tumor control. A higher margin radiation dose significantly affected control of adenoma growth.

New onset of a pituitary hormone deficiency following GKS was seen in 24.4% of patients. Treatment with pituitary hormone suppressive medication at the time of GKS, a prior craniotomy, and larger adenoma volume at the time of radiosurgery were significantly related to loss of pituitary function.

Conclusions

Smaller adenoma volume improves the probability of endocrine remission and lowers the risk of new pituitary hormone deficiency with GKS. A higher margin dose offers a greater chance of endocrine remission and control of tumor growth.

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Oral Presentations

2010 AANS Annual Meeting Philadelphia, Pennsylvania May 1–5, 2010

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Editorial

Radiosurgery in cavernous malformations: anatomy of a controversy

Ladislau Steiner, Bengt Karlsson, Chun-Po Yen, James C. Torner, Christer Lindquist and David Schlesinger

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Ayhan Kanat

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Chun Po Yen, Jason Sheehan, Greg Patterson and Ladislau Steiner

Object

Although considered benign tumors, neurocytomas have various biological behaviors, histological patterns, and clinical courses. In the last 15 years, fractionated radiotherapy and radiosurgery in addition to microsurgery have been used in their management. In this study, the authors present their experience using Gamma Knife surgery (GKS) in the treatment of these tumors.

Methods

Between 1989 and 2004, the authors performed GKS in seven patients with a total of nine neurocytomas. Three patients harbored five recurrent tumors after a gross-total resection, three had progression of previous partially resected tumors, and one had undergone a tumor biopsy only. The mean tumor volume at the time of GKS ranged from 1.4 to 19.8 cm3 (mean 6.0 cm3). A mean peripheral dose of 16 Gy was prescribed to the tumor margin with the median isodose configuration of 32.5%.

Results

After a mean follow-up period of 60 months, four of the nine tumors treated disappeared and four shrank significantly. Because of secondary hemorrhage, an accurate tumor volume could not be determined in one. Four patients were asymptomatic during the follow-up period, and the condition of the patient who had residual hemiparesis from a previous transcortical resection of the tumor was stable. Additionally, the patient who experienced tumor hemorrhage required a shunt revision, and another patient died of sepsis due to a shunt infection.

Conclusions

Based on this limited experience, GKS seems to be an appropriate management alternative. It offers control over the tumor with the benefits of minimal invasiveness and low morbidity rates. Recurrence, however, is not unusual following both microsurgery and GKS. Open-ended follow-up imaging is required to detect early recurrence and determine the need for retreatment.

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William J. Mauermann, Jason P. Sheehan, Daniel R. Chernavvsky, Edward R. Laws, Ladislau Steiner and Mary Lee Vance

Object

Patients with adrenocorticotropic hormone (ACTH)–secreting pituitary adenomas may require a bilateral adrenalectomy to treat their Cushing's disease. Approximately one third of these patients, however, will experience progressive enlargement of the residual pituitary adenoma, develop hyperpigmentation, and have an elevated level of serum ACTH. These patients with Nelson's syndrome can be treated with Gamma Knife surgery (GKS).

Methods

The prospectively collected University of Virginia Gamma Knife database of patients with pituitary adenomas was reviewed to identify all individuals with Nelson's syndrome who were treated with GKS. Twenty-three patients with a minimum of 6 months of follow up were identified in the database. These patients were assessed for tumor control (that is, lack of tumor growth over time) with neuroimaging studies (median follow-up duration 22 months) and for biochemical normalization of their ACTH levels (median follow-up duration 50 months). Neuroimaging follow-up studies were available for 22 patients, and endocrine follow up was available for 15 patients in whom elevation of ACTH levels was documented prior to GKS.

In the 22 patients in whom neuroimaging follow-up studies were available, 12 had a decrease in tumor size, eight had no tumor growth, and two had an increase in tumor volume. Ten of 15 patients with elevated ACTH levels prior to GKS showed a decrease in their ACTH levels at last follow up; three of these 10 patients achieved normal ACTH levels (< 50 pg/ml) and the other five patients with initially elevated values had an increase in ACTH levels.

Ten patients were thoroughly evaluated for post-GKS pituitary function; four were found to have new pituitary hormone deficiency and six did not have hypopituitarism after GKS. One patient suffered a permanent third cranial nerve palsy and four patients are now deceased.

Conclusions

Gamma Knife surgery may control the residual pituitary adenoma and decrease ACTH levels in patients with Nelson's syndrome. Delayed hypopituitarism or cranial nerve palsies can occur after GKS. Patients with Nelson's syndrome require continued multidisciplinary follow-up care. Given the difficulties associated with management of Nelson's syndrome, even the modest results of GKS may be helpful for a number of patients.

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Martin H. Weiss and William T. Couldwell

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Jay Jagannathan, Jason P. Sheehan, Nader Pouratian, Edward R. Laws, Ladislau Steiner and Mary Lee Vance

Object

In this study the authors address the efficacy and safety of Gamma Knife surgery (GKS) in patients with adrenocorticotropic hormone–secreting pituitary adenomas.

Methods

A review of data collected from a prospective GKS database between January 1990 and March 2005 was performed in patients with Cushing's disease. All but one patient underwent resection for a pituitary tumor, without achieving remission. Successful endocrine outcome after GKS was defined as a normal 24-hour urinary free cortisol (UFC) concentration posttreatment after a minimum of 1 year of follow up. Patient records were also evaluated for changes in tumor volume, development of new hormone deficiencies, visual acuity, cranial nerve neuropathies, and radiation-induced imaging changes. Ninety evaluable patients had undergone GKS, with a mean endocrine follow-up duration of 45 months (range 12–132 months). The mean dose to the tumor margin was 23 Gy (median 25 Gy).

Normal 24-hour UFC levels were achieved in 49 patients (54%), with an average time of 13 months after treatment (range 2–67 months). In the 49 patients in whom a tumor was visible on the planning magnetic resonance (MR) image, a decrease in tumor size occurred in 39 (80%), in seven patients there was no change in size, and tumor growth occurred in three patients. Ten patients (20%) experienced a relapse of Cushing's disease after initial remission; the mean time to recurrence was 27 months (range 6–60 months). Seven of these patients underwent repeated GKS, with three patients achieving a second remission. New hormone deficiencies developed in 20 patients (22%), with hypothyroidism being the most common endocrinopathy after GKS. Five patients experienced new visual deficits or third, fourth, or sixth cranial nerve deficits; two of these patients had undergone prior conventional fractionated radiation therapy, and four of them had received previous GKS. Radiation-induced changes were observed on MR images in three patients; one had symptoms attributable to these changes.

Conclusions

Gamma Knife surgery is an effective treatment for persistent Cushing's disease. Adenomas with cavernous sinus invasion that are not amenable to resection are treatable with the Gamma Knife. A second GKS treatment appears to increase the risk of cranial nerve damage. These results demonstrate the value of combining two neurosurgical treatment modalities—microsurgical resection and GKS—in the management of pituitary adenomas.

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Jason Sheehan, Chun Po Yen, Yasser Arkha, David Schlesinger and Ladislau Steiner

Object

Trigeminal schwannomas are rare intracranial tumors. In the past, resection and radiation therapy were the mainstays of their treatment. More recently, neurosurgeons have begun to use radiosurgery in the treatment of trigeminal schwannomas because of its successful use in the treatment of vestibular schwannomas. In this article the authors evaluate the radiological and clinical outcomes in a series of patients in whom Gamma Knife surgery (GKS) was used to treat trigeminal schwannomas.

Methods

Twenty-six patients with trigeminal schwannomas underwent GKS at the University of Virginia Lars Lek-sell Gamma Knife Center between 1989 and 2005. Five of these patients had neurofibromatosis and one patient was lost to follow up. The median tumor volume was 3.96 cm3, and the mean follow-up period was 48.5 months. The median prescription radiation dose was 15 Gy, and the median prescription isodose configuration was 50%. There was clinical improvement in 18 patients (72%), a stable lesion in four patients (16%), and worsening of the disease in three patients (12%). On imaging, the schwannomas shrank in 12 patients (48%), remained stable in 10 patients (40%), and increased in size in three patients (12%). These results were comparable for primary and adjuvant GKSs. No tumor growth following GKS was observed in the patients with neurofibromatosis.

Conclusions

Gamma Knife surgery affords a favorable risk-to-benefit profile for patients harboring trigeminal schwannomas. Larger studies with open-ended follow-up review will be necessary to determine the long-term results and complications of GKS in the treatment of trigeminal schwannomas.

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Peter Varady, Jason Sheehan, Melita Steiner and Ladislau Steiner

Heading : Chun Po Yen

Object

Subtotal obliteration of cerebral arteriovenous malformations (AVMs) after Gamma Knife surgery (GKS) implies a complete angiographic disappearance of the AVM nidus but persistence of an early filling draining vein, indicating that residual shunting is still present; hence, per definition there is still a patent AVM and the risk of bleeding is not eliminated. The aim of this study was to determine the risk of hemorrhage for patients with subtotal obliteration of AVMs.

Methods

After GKS for cerebral AVMs, follow-up angiography demonstrated a subtotally obliterated lesion in 159 patients. Of these, in 16 patients a subtotally obliterated AVM developed after a second GKS was performed for the partially obliterated lesion. The mean age of these patients was 35.2 years at the time of the diagnosis of subtotally obliterated AVMs. The lesion volumes at the time of initial GKS treatment ranged from 0.1 to 11.5 cm3 (mean 2.5 cm3). The mean peripheral dose used in the 175 GKS treatments was 22.5 Gy (median 23 Gy, range 15–31 Gy). To achieve total obliteration of the AVM, 23 patients underwent a new GKS targeting the proximal end of the early filling vein. The mean peripheral dose given in these cases was 23 Gy (median 24, range 18–25 Gy).

The incidence of subtotally obliterated AVMs was 7.6% from a total of 2093 AVMs treated and in which follow-up imaging was available. The diagnosis of subtotally obliterated AVMs was made a mean of 29.4 months (range 4–178 months) after GKS. The number of patient-years at risk (from the time of the diagnosis of subtotally obliterated AVMs until either the confirmation of a total obliteration of the lesion on angiography or the time of the latest follow-up angio-graphic study that still visualized the early filling vein) was a mean of 3.9 years, ranging from 0.5 to 13.5 years, and a total of 601 patient-years. There was no case of bleeding after the diagnosis of subtotally obliterated AVMs. Of 90 patients who did not undergo further treatment and in whom follow-up angiography studies were available, the same early filling veins still filled in 24 (26.7%), and the subtotally obliterated AVMs were subsequently obliterated in 66 patients (73.3%). In 19 patients who underwent repeated GKS for subtotally obliterated AVMs and in whom follow-up angiography studies were available, the AVMs were obliterated in 15 (78.9%) and remained patent in four (21.1%).

Conclusions

The fact that none of the patients with subtotally obliterated AVMs suffered a rupture is not compatible with the assumption of an unchanged risk of hemorrhage for these lesions, and implies that the protection from re-bleeding in patients with subtotal obliteration is significant. Subtotal obliteration does not necessarily seem to be a stage of an ongoing obliteration. At least in some cases it represents an end point of this process, with no subsequent obliteration occurring. This observation requires further confirmation by open-ended follow-up imaging.