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Leland Rogers, Peixin Zhang, Michael A. Vogelbaum, Minesh P. Mehta and on behalf of the authors

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Amr M. N. El-Shehaby, Wael A. Reda, Khaled M. Abdel Karim, Ahmed M. Nabeel, Reem M. Emad Eldin and Sameh R. Tawadros

OBJECTIVE

The objective of this study was to assess hearing function after Gamma Knife treatment of cerebellopontine angle (CPA) meningiomas and assess factors affecting hearing outcome. Additionally, the authors opted to compare these results with those after Gamma Knife treatment of vestibular schwannomas (VSs), because most of the information on hearing outcome after stereotactic radiosurgery (SRS) comes from reports on VS treatment. Hearing preservation, to the best of the authors’ knowledge, has never been separately addressed in studies involving Gamma Knife radiosurgery (GKRS) for CPA meningiomas.

METHODS

This study included all patients who underwent a single session of GKRS between 2002 and 2014. The patients were divided into two groups. Group A included 66 patients with CPA meningiomas with serviceable hearing and tumor extension into the region centered on the internal auditory meatus. Group B included 144 patients with VSs with serviceable hearing. All patients had serviceable hearing before treatment (Gardner-Robertson [GR] Grades I and II). The median prescription dose was 12 Gy (range 10–12 Gy) in both groups. The median follow-up of groups A and B was 42 months (range 6–149 months) and 49 months (range 6–149 months), respectively.

RESULTS

At the last follow-up, the tumor control rate was 97% and 94% in groups A and B, respectively. Hearing preservation was defined as maintained serviceable hearing according to GR hearing score. The hearing preservation rate was 98% and 66% and the 7-year actuarial serviceable hearing preservation rate was 75% and 56%, respectively, between both groups. In group A, the median maximum cochlear dose in the patients with stable and worsened hearing grade was 6.3 Gy and 5.5 Gy, respectively. In group B, factors affecting hearing preservation were cochlear dose ≤ 7 Gy, follow-up duration, and tumor control. The only determinant of hearing preservation between both groups was tumor type.

CONCLUSIONS

GKRS for CPA meningiomas provides excellent hearing preservation in addition to high tumor control rate. Hearing outcome is better with CPA meningiomas than with VSs. Further long-term prospective studies on determinants of hearing outcome after GKRS for CPA meningiomas should be conducted.

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Ji Woong Oh, Kyoung Su Sung, Ju Hyung Moon, Eui Hyun Kim, Won Seok Chang, Hyun Ho Jung, Jin Woo Chang, Yong Gou Park, Sun Ho Kim and Jong Hee Chang

OBJECTIVE

This study investigated long-term follow-up data on the combined pituitary function test (CPFT) in patients who had undergone transsphenoidal surgery (TSS) for nonfunctioning pituitary adenoma (NFPA) to determine the clinical parameters indicative of hypopituitarism following postoperative Gamma Knife surgery (GKS).

METHODS

Between 2001 and 2015, a total of 971 NFPA patients underwent TSS, and 76 of them (7.8%) underwent postoperative GKS. All 76 patients were evaluated with a CPFT before and after GKS. The hormonal states were analyzed based on the following parameters: relevant factors before GKS (age, sex, extent of resection, pre-GKS hormonal states, time interval between TSS and GKS), GKS-related factors (tumor volume; radiation dose to tumor, pituitary stalk, and normal gland; distance between tumor and stalk), and clinical outcomes (tumor control rate, changes in hormonal states, need for hormone-related medication due to hormonal changes).

RESULTS

Of the 971 NFPA patients, 797 had gross-total resection (GTR) and 174 had subtotal resection (STR). Twenty-five GTR patients (3.1%) and 51 STR patients (29.3%) underwent GKS. The average follow-up period after GKS was 53.5 ± 35.5 months, and the tumor control rate was 96%. Of the 76 patients who underwent GKS, 23 were excluded due to pre-GKS panhypopituitarism (22) or loss to follow-up (1). Hypopituitarism developed in 13 (24.5%) of the remaining 53 patients after GKS. A higher incidence of post-GKS hypopituitarism occurred in the patients with normal pre-GKS hormonal states (41.7%, 10/24) than in the patients with abnormal pre-GKS hormonal states (10.3%, 3/29; p = 0.024). Target tumor volume (4.7 ± 3.9 cm3), distance between tumor and pituitary stalk (2.0 ± 2.2 mm), stalk dose (cutoffs: mean dose 7.56 Gy, maximal dose 12.3 Gy), and normal gland dose (cutoffs: maximal dose 13.9 Gy, minimal dose 5.25 Gy) were factors predictive of post-GKS hypopituitarism (p < 0.05).

CONCLUSIONS

This study analyzed the long-term follow-up CPFT data on hormonal changes in NFPA patients who underwent GKS after TSS. The authors propose a cutoff value for the radiation dose to the pituitary stalk and normal gland for the prevention of post-GKS hypopituitarism.

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Richard Menger, Benjamin F. Mundell, J. Will Robbins, Peter Letarte, Randy Bell and in conjunction with Council of State Neurosurgical Societies and AANS/CNS Joint Committee of Military Neurosurgeons

OBJECTIVE

Papers from 2002 to 2017 have highlighted consistent unique socioeconomic challenges and opportunities facing military neurosurgeons. Here, the authors focus on the reserve military neurosurgeon who carries the dual mission of both civilian and military responsibilities.

METHODS

Survey solicitation of current active duty and reserve military neurosurgeons was performed in conjunction with the AANS/CNS Joint Committee of Military Neurosurgeons and the Council of State Neurosurgical Societies. Demographic, qualitative, and quantitative data points were compared between reserve and active duty military neurosurgeons. Civilian neurosurgical provider data were taken from the 2016 NERVES (Neurosurgery Executives Resource Value and Education Society) Socio-Economic Survey. Economic modeling was done to forecast the impact of deployment or mobilization on the reserve neurosurgeon, neurosurgery practice, and the community.

RESULTS

Seventy-five percent (12/16) of current reserve neurosurgeons reported that they are satisfied with their military service. Reserve neurosurgeons make significant contributions to the military’s neurosurgical capabilities, with 75% (12/16) having been deployed during their career. No statistically significant demographic differences were found between those serving on active duty and those in the reserve service. However, those who served in the reserves were more likely to desire opportunities for improvement in the military workflow requirements compared with their active duty counterparts (p = 0.04); 92.9% (13/14) of current reserve neurosurgeons desired more flexible military drill programs specific to the needs of practicing physicians. The risk of reserve deployment is also borne by the practices, hospitals, and communities in which the neurosurgeon serves in civilian practice. This can result in fewer new patient encounters, decreased collections, decreased work relative value unit generation, increased operating costs per neurosurgeon, and intangible limitations on practice development. However, through modeling, the authors have illustrated that reserve physicians joining a larger group practice can significantly mitigate this risk. What remains astonishing is that 91.7% of those reserve neurosurgeons who were deployed noted the experience to be rewarding despite seeing a 20% reduction in income, on average, during the fiscal year of a 6-month deployment.

CONCLUSIONS

Reserve neurosurgeons are satisfied with their military service while making substantial contributions to the military’s neurosurgical capabilities, with the overwhelming majority of current military reservists having been deployed or mobilized during their reserve commitments. Through the authors’ modeling, the impact of deployment on the military neurosurgeon, neurosurgeon’s practice, and the local community can be significantly mitigated by a larger practice environment.

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Hirotaka Hasegawa, Shunya Hanakita, Masahiro Shin, Mariko Kawashima, Taichi Kin, Wataru Takahashi, Yuichi Suzuki, Yuki Shinya, Hideaki Ono, Masaaki Shojima, Hirofumi Nakatomi and Nobuhito Saito

OBJECTIVE

In Gamma Knife radiosurgery (GKS) for arteriovenous malformations (AVMs), CT angiography (CTA), MRI, and digital subtraction angiography (DSA) are generally used to define the nidus. Although the AVM angioarchitecture can be visualized with superior resolution using rotational angiography (RA), the efficacy of integrating RA into the GKS treatment planning process has not been elucidated.

METHODS

Using data collected from 25 consecutive patients with AVMs who were treated with GKS at the authors’ institution, two neurosurgeons independently created treatment plans for each patient before and after RA integration. For all patients, MR angiography, contrasted T1 imaging, CTA, DSA, and RA were performed before treatment. The prescription isodose volume before (PIVB) and after (PIVA) RA integration was measured. For reference purposes, a reference target volume (RTV) for each nidus was determined by two other physicians independent of the planning surgeons, and the RTV covered by the PIV (RTVPIV) was established. The undertreated volume ratio (UVR), overtreated volume ratio (OVR), and Paddick’s conformal index (CI), which were calculated as RTVPIV/RTV, RTVPIV/PIV, and (RTVPIV)2/(RTV × PIV), respectively, were measured by each neurosurgeon before and after RA integration, and the surgeons’ values at each point were averaged. Wilcoxon signed-rank tests were used to compare the values obtained before and after RA integration. The percentage change from before to after RA integration was calculated for the average UVR (%ΔUVRave), OVR (%ΔOVRave), and CI (%ΔCIave) in each patient, as ([value after RA integration]/[value before RA integration] − 1) × 100. The relationships between prior histories and these percentage change values were examined using Wilcoxon signed-rank tests.

RESULTS

The average values obtained by the two surgeons for the median UVR, OVR, and CI were 0.854, 0.445, and 0.367 before RA integration and 0.882, 0.478, and 0.463 after RA integration, respectively. All variables significantly improved after compared with before RA integration (UVR, p = 0.009; OVR, p < 0.001; CI, p < 0.001). Prior hemorrhage was significantly associated with larger %ΔOVRave (median 20.8% vs 7.2%; p = 0.023) and %ΔCIave (median 33.9% vs 13.8%; p = 0.014), but not %ΔUVRave (median 4.7% vs 4.0%; p = 0.449).

CONCLUSIONS

Integrating RA into GKS treatment planning may permit better dose planning owing to clearer visualization of the nidus and, as such, may reduce undertreatment and waste irradiation. Further studies examining whether the observed RA-related improvement in dose planning also improves the radiosurgical outcome are needed.

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Randy S. Bell, Chris J. Neal and Randall McCafferty

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José Pedro Lavrador, Shami Acharya, Anastasios Giamouriadis, Francesco Vergani, Keyoumars Ashkan and Ranjeev Bhangoo

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Seyed Amir Javadi and Mehdi Zeinalizadeh