Efficacy Of Radiosurgery On Indirect Carotid-cavernous Sinus Dural Arteriovenous Fistulae: Gamma Knife Compared With X Knife

Keywords: arteriovenous fistula, linear accelerator, gamma knife, cavernous sinus, dural arteriovenous fistula

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     The emergence of modern technology made radiosurgery possible to be one of multiple disciplinary modalities in treating indirect carotid-cavernous sinus dural arteriovenous fistulae(indrirect C-C fistulae) . Based on the imaging fusion technique of cerebral angiogram with MRI or CT during the treatment procedure, Gamma knife and X knife was the most popular radiosurgical instruments in the treatment of indirect C-C fistulae.
     In this study, we compared the efficacy, neurological results, and possible complication of these two treatment modalities on indirect C-C fistulae.
     Forty one patients (X knife=14, Gamma knife=27) with indirect C-C fistulae were retrieved from the radiosurgical data bank from March 2001 to August 2008. Among these patients, at least two consecutive MRI imaging after radiosurgery was available for determination of the obliteration of the fistula. All patients received regular follow up to evaluate the neurological and ophthmalogical function with the interval of 1-3 months.
     The symptomatology, obliteration rate, radiation dose, instrument accuracy and adverse effect were determined as well as compared between two groups. The data was analyzed by using the Student’s t test.
     The median age of the patients was 63 with M/F of 9/32. The median follow up period was 63 (at least 14) months. Thirty-five of 40 patients with chemosis and proptosis of eyes were resolved after treatment (3 with residual fistula, 2 with arterializations of sclera). Five of 5 patients with glaucoma were cures. Five of 10 patients with cranial nerve palsy were cure. The laterization of the fistula included 16 over right side, 12 over left side and 13 over bilateral side. There was one patient with optic neuritis (treated by GK), one intracranial hemorrhage (X knife), one brain stem edema(X knife), and four temporal lobe radiation edema(X knife). Significant discrepancy existed between X knife and GK groups such as radiation volume (5.68±1.72 vs.1.69±0.27) ml, conformity index (3.08± 0.26 vs.1.61±0.12), number of isocenter (3.2±0.46 vs.7.57±0.73), instrument accuracy (0.56 ±0.04 vs. 0.146 ±0.009 )mm, maximum dosage (27±1.44 vs. 33.7±0.47) Gy with corresponding isodose line in peripheral (65±3.3 vs.55±1.6) %. Significant radiation dosage difference occurred over Rt /Lt lens (0.96±0.07 vs.0.51±0.07/0.89±0.09 vs.0.48±0.06), Rt /Lt optic nerve ( 6.28±0.38 vs.3.9±0.35 /6.5±0.24 vs.3.23 ±0.3) , chiasma ( 5.9±0.33 vs.2.8 ±0.24), and brain stem (10.1±0.39 vs.7.2 ±0.6). Ten Gy volumes in temporal and brain stem also showed the same trends.
     This is a retrospective study.
     Gamma knife and X knife showed the very similar efficacy in the obliteration of indirect C-C fistulae.
     Higher incidence of radiation edema occurred in X knife group which paralleled unnecessary irradiation dosage delivered to the normal brain tissue.


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