Long-term outcome of Gamma Knife stereotactic radiosurgery for arteriovenous malformations graded by the Spetzler-Martin classification.

OBJECT: The object of this study was to assess outcomes in patients with arteriovenous malformations (AVMs) treated by Gamma Knife stereotactic radiosurgery (SRS); lesions were stratified by size, symptomatology, and Spetzler-Martin (S-M) grade. METHODS: The authors performed a retrospective analysis of 102 patients treated for an AVM with single-dose or staged-dose SRS between 1993 and 2004. Lesions were grouped by S-M grade, as hemorrhagic or nonhemorrhagic, and as small (< 3 cm) or large (≥ 3 cm). Outcomes included death, morbidity (new neurological deficit, new-onset seizure, or hemorrhage/rehemorrhage), nidus obliteration, and Karnofsky Performance Scale score. RESULTS: The mean follow-up was 8.5 years (range 5-16 years). Overall nidus obliteration (achieved in 75% of patients) and morbidity (19%) correlated with lesion size and S-M grade. For S-M Grade I-III AVMs, nonhemorrhagic and hemorrhagic combined, treatment yielded obliteration rates of 100%, 89%, and 86%, respectively; high functional status (Karnofsky Performance Scale Score ≥ 80); and 1% mortality. For S-M Grade IV and V AVMs, outcomes were less favorable, with obliteration rates of 54% and 0%, respectively. The AVMs that were not obliterated had a mean reduction in nidus volume of 69% (range 35%-96%). On long-term follow-up, 10% of patients experienced hemorrhage/rehemorrhage (6% mortality rate), which correlated with lesion size and S-M grade; the mean interval to hemorrhage was 81 months. CONCLUSIONS: For patients with S-M Grade I-III AVMs, SRS offers outcomes that are favorable and that, except for the timing of obliteration, appear to be comparable to surgical outcomes reported for the same S-M grades. Staged-dose SRS results in lesion obliteration in half of patients with S-M Grade IV lesions.

Kepler-16: a transiting circumbinary planet.

We report the detection of a planet whose orbit surrounds a pair of low-mass stars. Data from the Kepler spacecraft reveal transits of the planet across both stars, in addition to the mutual eclipses of the stars, giving precise constraints on the absolute dimensions of all three bodies. The planet is comparable to Saturn in mass and size and is on a nearly circular 229-day orbit around its two parent stars. The eclipsing stars are 20 and 69% as massive as the Sun and have an eccentric 41-day orbit. The motions of all three bodies are confined to within 0.5° of a single plane, suggesting that the planet formed within a circumbinary disk.

Efficacy and quality of life outcomes in patients with atypical trigeminal neuralgia treated with gamma-knife radiosurgery.

PURPOSE: To assess efficacy and quality of life (QOL) outcomes associated with gamma-knife radiosurgery (GK-RS) in treating atypical trigeminal neuralgia (ATN) compared with classic trigeminal neuralgia (CTN). METHODS AND MATERIALS: Between September 1996 and September 2004, 35 cases of ATN were treated with GK-RS. Patients were categorized into two groups: Group I comprised patients presenting with ATN (57%); Group II consisted of patients presenting with CTN then progressing to ATN (43%). Median prescription dose 75 Gy (range, 70-80 Gy) was delivered to trigeminal nerve root entry zone. Treatment efficacy and QOL improvements were assessed with a standardized questionnaire. RESULTS: With median follow-up of 29 months (range, 3-74 months), 72% reported excellent/good outcomes, with mean time to relief of 5.8 weeks (range, 0-24 weeks) and mean duration of relief of 62 weeks (range, 1-163 weeks). This rate of pain relief is similar to rate achieved in our previously reported experience treating CTN with GK-RS (p = 0.36). There was a trend toward longer time to relief (p = 0.059), and shorter duration of relief (p = 0.067) in patients with ATN. There was no difference in rate of, time to, or duration of pain relief between Groups I and II. Of the patients with ATN, 88% discontinued or decreased the use of pain medications. Among the patients with sustained pain relief, QOL improved an average of 85%. CONCLUSION: This is the largest reported GK-RS experience for the treatment of ATN. Patients with ATN can achieve rates of pain relief similar to those in patients with CTN. Further follow-up is necessary to assess adequately the durability of response.

Concomitant boost of stratified target area with gamma knife radiosurgery: a treatment planning study.

Conventional Gamma Knife Stereotactic Radiosurgery (GKSRS) has been focused on delivering a single peripheral dose to the gross target volume based on the anatomic information derived from the magnetic resonance or computed tomography (CT) studies. In this study, we developed a treatment planning approach that allows a boost dose to be delivered concomitantly to the desired subtarget area while maintaining the peripheral isodose coverage of the target volume. The subtarget area is defined as the high-risk or the tumor burden areas based on the functional imaging information such as the magnetic resonance spectroscopy (MRS) studies or the physician's clinical diagnosis. Treatment plan comparisons were carried out between the concomitant boost plans and the conventional treatment plans using dose volume histogram (DVH), tissue volume ratio (TVR), and the maximum dose to the peripheral dose ratio (MD/PD) analysis. Using the concomitant boost approach, more conformal and higher dose was delivered to the desired subtarget area while maintaining the peripheral isodose coverage of the gross target volume (GTV). Additionally, the dose to the normal brain tissue was found to be equivalent between the concomitant boost plans and the conventional plans. As a result, we conclude that concomitant boost of a stratified target area is feasible for GKSRS.