The efEects of gamma radiosurgery on 1060ut of l50 cases of skull base meningiomas which had been treated by gamma knife and followed − up for more than 3 years （ mean of 48 ． 2 months ）have been evaluated ． Overall results showed that partial resonse （ PR ） was found in 44 cases ， minor response （ MR ） in 9， no change （ NC ＞in 42 and progression （ PG ）in 11 ， Another words ， response rate was 41． 5％， control rate was 89． 6％ and progression rate was 10． 4％ ・ There found difEerences of the response among different locations；the response rate of C − P angle and CS − P ・・a ・ellar m ・ni・ gi ・mas sh ・ w ・ d high・ ・ th・n ・thers， ・b ・t ・・nt ・・ 1・at ・ w ・ ・ high・・ i ・ C − P ・ngle and t・ ・ t・ 「 i・l m ・n − i。 gi ・ m ・ ． P ・・ 9 ・essi ・n w ・・ f・・nd ・nly i ・ CS − P ・・a・ell・・ a・d p ・t… li ・・l m ・ni・ gi ・m ・・ Th ・ p ・・ gressi ・n ・at・ h・・ changed from O％ at less than 3 years of follow − up ， 10 ． 4 ％ at more than 3 years and 18． 2 ％ at more than 5 years ． The factors related to the progression are the tumor size ， the radiation dosis ， the locations and the tumor pathol − ogy Side ef 〔 ects were found in 4 cases （ 4． 6％ ） − that is radiation induced edema in one ， hearing deterioration in two and visual deterioration in one case within 2 years of treatment． （

An infrared based frameless stereotactic navigation device (Easy Guide Neuro) was investigated for its clinical applicability, registration/application accuracy and limitations in a standard operating room set-up. In a five-month period 40 frameless stereotactic procedures (23 female, 17 male, mean age 46.4, yrs range 10-83) including 36 craniotomies and 4 spinal surgery procedures were performed. Image registration, data transfer and operation planning using skin fixed fiducials (between 5-10, mean 6.6) and CCT in 12 patients/MRI in 28 patients, generally was done the day before surgery. Clinical applicability was proven in all procedures with an additional time for pre-operative imaging and system application in the OR of 50 min mean (35-120 range). A useful registration was achieved in 39/40 patients (97.5%) with a registration accuracy of 3.4 mm (range 1.8-6.7) for brain surgery cases and 14.4 mm (6.8-25) for spine cases. This resulted in intra-operative application accuracy values for brain surgery of 4.2 mm mean (range 1-12). Enhanced registration/application accuracy values over the test period from 4.2/3.8 mm mean (Cases 1-20) up to 3.2/2 mm mean (Cases 21-40) was observed. In spinal surgery an application accuracy of 11.3 mm mean (range 5-20) was found. An intra-operative re-calibration because of system-head drift was necessary in none of the patients, nevertheless, application accuracy degradation due to brain shift was detected in every case. In conclusion, the system allowed a time sufficient accurate frameless intra-operative localisation guidance in cavernoma, meningioma, glioma, and brain metastasis surgery. In spinal surgery, the application accuracy exceeded clinical usefulness due to high registration inaccuracy using skin markers.

Background Corticosteroid therapy (CST) prior to biopsy may hinder histopathological diagnosis in primary central nervous system lymphoma (PCNSL). Therefore, preoperative CST in patients with suspected PCNSL should be avoided if clinically possible. The aim of this study was thus to analyze the difference in the rate of diagnostic surgeries in PCNSL patients with and without preoperative CST. Methods A multicenter retrospective study including all immunocompetent patients diagnosed with PCNSL between 1/2004 and 9/2018 at four neurosurgical centers in Austria was conducted and the results were compared to literature. Results A total of 143 patients were included in this study. All patients showed visible contrast enhancement on preoperative MRI. There was no statistically significant difference in the rate of diagnostic surgeries with and without preoperative CST with 97.1% (68/70) and 97.3% (71/73), respectively (p = 1.0). Tapering and pause of CST did not influence the diagnostic rate. Including our study, there are 788 PCNSL patients described in literature with an odds ratio for inconclusive surgeries after CST of 3.3 (CI 1.7–6.4). Conclusions Preoperative CST should be avoided as it seems to diminish the diagnostic rate of biopsy in PCNSL patients. Yet, if CST has been administered preoperatively and there is still a contrast enhancing lesion to target for biopsy, surgeons should try to keep the diagnostic delay to a minimum as the likelihood for acquiring diagnostic tissue seems sufficiently high.

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