====== Gamma knife radiosurgery for arteriovenous malformation ======

[[Gamma knife radiosurgery]] for [[arteriovenous malformation]] is a safe [[treatment]] method although delayed [[complication]]s may occur. Post-gadolinium enhancement of obliterated nidi may indicate an active post-irradiative process
((Malikova H, Koubska E, Vojtech Z, Weichet J, Syrucek M, Sroubek J, Rulseh A,
Liscak R. Late morphological changes after radiosurgery of brain arteriovenous
malformations: an MRI study. Acta Neurochir (Wien). 2016 Sep;158(9):1683-90. doi:
10.1007/s00701-016-2876-3. Epub 2016 Jul 1. PubMed PMID: 27368701; PubMed Central
PMCID: PMC4980423.
)).


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Enhanced nodular lesion on magnetic resonance imaging and chronic encapsulated expanding haematoma associated with [[cyst formation]] may have common aetiopathology caused by late radiation effects, mainly consisting of dilated capillary vessels with wall damage. Massive protein exudation from such damaged capillary vessels is important in cyst development
((Shuto T, Yagishita S, Matsunaga S. Pathological characteristics of cyst
formation following Gamma knife radiosurgery for arteriovenous malformation. Acta
Neurochir (Wien). 2014 Dec 13. [Epub ahead of print] PubMed PMID: 25503297.
)).




===== Complications =====

see [[Adverse radiation effects]]

Advances in SRS procedures since 1990s have resulted in a lower risk of [[radiation induced complications]] (RICs), but fewer patients had AVM obliteration. Increasing the prescription dose for patients with medium- and large-volume AVMs by using current conformal dose-planning techniques may improve the obliteration rate while maintaining a low risk of RICs
((Pollock BE, Link MJ, Stafford SL, Garces YI, Foote RL. Stereotactic
Radiosurgery for Arteriovenous Malformations: The Effect of Treatment Period on
Patient Outcomes. Neurosurgery. 2016 Apr;78(4):499-509. doi:
10.1227/NEU.0000000000001085. PubMed PMID: 26990410.))

Volume staging remains advantageous over hypofractionation in delivering a higher dose to the target and for better sparing of normal brain tissue in the treatment of large [[cerebral arteriovenous malformation]]s AVMs. More clinical data are needed, however, to justify the clinical superiority of this increased dose when compared with a hypofractionated treatment regimen
((Fogh S, Ma L, Gupta N, Sahgal A, Nakamura JL, Barani I, Sneed PK, McDermott M,
Larson DA. High-precision volume-staged Gamma knife radiosurgery and equivalent
hypofractionation dose schedules for treating large arteriovenous malformations. 
J Neurosurg. 2012 Dec;117 Suppl:115-9. doi: 10.3171/2012.7.GKS121023. PubMed
PMID: 23205798.
)).


Better conformity can favor the [[Cyberknife]] (CK) system for treatment of large AVMs at the cost of higher maximum doses and worse homogeneity. [[Linac]] with a micro-multileaf [[collimator]] (L-mMLC) is superior when shorter treatment time is required. Neither system can assure satisfying dose gradients outside large targets surrounded by numerous critical structures
((Blamek S, Grządziel A, Miszczyk L. Robotic radiosurgery versus micro-multileaf collimator: a dosimetric comparison for large or critically located arteriovenous malformations. Radiat Oncol. 2013 Aug 23;8:205. doi: 10.1186/1748-717X-8-205. PubMed PMID: 23968165; PubMed Central PMCID: PMC3766053.)).