Ladislau Steiner

Prediction of Obliteration after Gamma Knife Surgery for Cerebral Arteriovenous Malformations

OBJECTIVE:To define the factors of importance for the obliteration of cerebral arteriovenous malformations (AVMs), thus making a prediction of the probability for obliteration possible.METHODS:In 945 AVMs of a series of 1319 patients treated with the gamma knife during 1970 to 1990, the relationship

A multicenter, prospective pilot study of gamma knife radiosurgery for mesial temporal lobe epilepsy: Seizure response, adverse events, and verbal memory

The safety, efficacy, and morbidity of radiosurgery (RS) must be established before it can be offered as an alternative to open surgery for unilateral mesial temporal lobe epilepsy. We report the 3‐year outcomes of a multicenter, prospective pilot study of RS.

Long-term results of radiosurgery for arteriovenous malformation: Neurodiagnostic imaging and histological studies of angiographically confirmed nidus obliteration

Detailed follow-up results for 25 patients treated for cerebral arteriovenous malformation (AVM) with a gamma unit are presented. Complete nidus obliteration was angiographically confirmed in 16 (73%) of 22 cases receiving full-dose irradiation. There were no radiation- or AVM-related mortalities. However, we did experience one case of radiation-related morbidity and one of angiography-related mortality, the autopsy findings of which are discussed. Computed tomography scan and magnetic resonance imaging follow-up studies of radiosurgically treated AVMs indicated that increased enhancement of the nidus after contrast or gadolinium administration could persist even after obliteration of the AVM was angiographically confirmed.

Gammathalamotomy in intractable pain

SummaryThalamotomy aiming at the CM-Pf complex and using stereotactic gamma irradiation has been performed in a series of 52 patients with severe pain due to malignancy. Lesions were produced either contra- or ipsilaterally to the side of the pain as well as bilaterally. Eight patients experienced good pain relief, 18 had moderate relief, and in 24 the operation did not significantly influence the pain. A second operation following recurrence of pain was rarely of value. There was a tendency towards more efficient relief of pain located in the face or in the arm and shoulder than of pain in the lower part of the body. Although contralateral lesions seem to be most effective, ipsilateral operations may also give some relief. The best results were obtained when the lesions were placed close to the wall of the third ventricle and at the level of the posterior commissure. Postmortem examination of 21 brains disclosed that the mean error in the placing of the lesions was about 1 mm. It is concluded that medial thalamotomy may be tried as a last resort in the treatment of cancer pain in selected patients with a short life expectancy.

Gamma knife radiosurgery for acromegaly: outcomes after failed transsphenoidal surgery.

OBJECTIVE This study evaluates the safety and efficacy of gamma knife radiosurgery (GKRS) in patients with a growth hormone-secreting adenoma. METHODS A retrospective review of data collected from a prospective database of GKRS patients between January 1988 and September 2006 was performed in patients with acromegaly. Successful endocrine outcome was defined as normalization of the insulin-like growth factor level. Tumor volume was also assessed. At least 18 months of follow-up was available in 95 patients who received radiosurgery during the study period. Mean endocrine follow-up was 57 months (range, 18-168 mo). RESULTS Normal insulin-like growth factor levels were achieved in 50 patients (53%) at an average time of 29.8 months after radiosurgery (median, 23.5 mo). A decrease in tumor volume control was achieved in 83 (92%) of 90 patients. Five patients (6%) had no change in tumor volume, and two patients (2%) had an increase in tumor volume. New endocrine deficiencies developed in 32 patients (34%). Four patients developed new-onset partial visual acuity deficits; three of these patients had received previous conventional fractionated radiation therapy. CONCLUSION GKRS is a complementary treatment for recurrent or residual growth hormone-secreting pituitary adenomas. Although infrequent, tumor growth, new-onset pituitary hormone deficiency, recurrence, and neurological dysfunction require careful clinical, radiological, and endocrinological follow-up.

Gamma Knife surgery for pituitary adenomas: factors related to radiological and endocrine outcomes

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.

Gamma knife surgery for previously irradiated arteriovenous malformations.

OBJECTIVE The goal was to report the treatment results after a second gamma knife treatment and to compare them with the results obtained after a first gamma knife treatment, as well as to investigate whether the models to predict the results after a first treatment are also applicable after gamma knife treatment of previously irradiated arteriovenous malformations. METHODS The number of complications and the posttreatment hemorrhage rate were recorded for 112 patients in the study, and the number of obliterations was recorded for the 101 patients for whom conclusive angiograms were obtained. The results were compared with the expected results after a first gamma knife treatment. RESULTS The observed number of obliterations was 62, which is not significantly different from the predicted number of 65. There were 14 observed and 5 predicted complications. When the risk from the preceding radiation treatment was added, the observed number of complications was similar to the predicted number. Six hemorrhages were observed after the second treatment. Of the 5 patients with unchanged arteriovenous malformation size after both the first and second treatments, 2 experienced hemorrhages after the second treatment, compared with none among the 81 patients for whom the malformation was obliterated or significantly decreased in size after the second treatment. CONCLUSIONS The obliteration rate after gamma knife surgery for previously irradiated arteriovenous malformations is similar to that after primary gamma knife treatment. The complication rate increases with the amount of radiation previously given. The incidence of posttreatment hemorrhages is lower in the latency period if the malformation is affected by the radiation.

Gamma knife radiosurgery for medically and surgically refractory prolactinomas

OBJECTIVE:Experience with gamma knife radiosurgery (GKRS) for prolactinomas is limited because of the efficacy of medical and surgical intervention. Patients who are refractory to medical and/or surgical therapy may be treated with GKRS. We characterize the efficacy of GKRS for medically and surgically refractory prolactinomas. METHODS:We reviewed our series of patients with prolactinomas who were treated with GKRS after failing medical and surgical intervention who had at least 1 year of follow-up. RESULTS:Twenty-three patients were included in analysis of endocrine outcomes (median and average follow-up of 55 and 58 mo, respectively) and 28 patients were included in analysis of imaging outcomes (median and average follow-up of 48 and 52 mo, respectively). Twenty-six percent of patients achieved a normal serum prolactin (remission) with an average time of 24.5 months. Remission was significantly associated with being off of a dopamine agonist at the time of GKRS and a tumor volume less than 3.0 cm3 (P < 0.05 for both). Long-term image-based volumetric control was achieved in 89% of patients. Complications included new pituitary hormone deficiencies in 28% of patients and cranial nerve palsy in two patients (7%). CONCLUSION:Clinical remission in 26% of treated patients is a modest result. However, because the GKRS treated tumors were refractory to other therapies and because complication rates were low, GKRS should be part of the armamentarium for treating refractory prolactinomas. Patients with tumors smaller than 3.0 cm3 and who are not receiving dopamine agonist at the time of treatment will likely benefit most.

Stereotactic Radiosurgical Treatment of Arteriovenous Malformations

Stereotactic radiosurgery for arteriovenous malformations (AVM) of the brain was introduced by Steiner in 1970 at the Karolinska Institute. However, the concept of radio-surgery was coined by Leksell in 1951, when he first described his technique for the irradiation of a sharply delimited intracranial target with stereotactically directed narrow beams of ionizing radiation [7]. Today, radio-surgery can be defined as single-session irradiation of a predetermined target volume, causing destruction or a desired biological effect in this tissue volume without damage to surrounding tissue.

Histological changes in the normal rat brain after gamma irradiation

SummaryRadiation-induced changes in the parietal cortex of Wistar rats were observed at various time points after gamma surgery. Maximum dosages of 50, 75, and 120 Gy were given at the iso-center of the radiation using a 4-mm collimator. Conventional histochemical and immunocytochemical analyses, and computer-assisted videomicroscopy were utilized to examine perfusion-fixed brain tissue.Irradiation at a dosage of 50 Gy elicited morphological changes of astrocytes in the parietal cortex at 3 months. Vasodilatation became obvious at 12 months; fibrin deposition was observed in the dilated capillary wall. Neither leakage of Evans Blue from the vasculature into the tissue nor necrosis was observed across the 12 month observation period.Irradiation at a dosage of 75 Gy resulted in morphological changes of astrocytes within 1 month. Dilatation of vessels and capillary thickening were observed at 3 months. Evans Blue leakage and necrosis were observed at 4 months after 75 Gy irradiation. At this time, the walls of arterioles became thickened by subintimal accumulation of fibrin and hyaline substance; this sometimes resulted in occlusion of the lumen. Significant hemispheric swelling was observed at 4 months.Irradiation at a dosage of 120 Gy elicited changes in astrocytic morphology within 3 days. Evans Blue leakage into the tissue was observed by 3 weeks. Vasodilatation became marked at this time point and rarefaction was observed in the irradiated cortex. Necrosis was observed at 4 weeks, however, no significant swelling was observed.Taken together, these findings demonstrate time-dependent and dosage-dependent changes in normal cerebral tissue after Gamma Knife irradiation. These results provide a basis for gauging the impact of gamma surgery in regions of eloquent tissue. An enhanced understanding of the cellular responses to radiosurgery will contribute to developing and evaluating future applications for gamma surgery.