Paper details:

Hello I am a physician completing a research proposal in Neurosurgery specifically in radiosurgery. I have already done methodology and statistics for the project but some parts like introduction and objectives are really time consuming. Below I have provided some instructions, also I have attached the format should be used to complete my work ( just highlighted parts are required to be written by writer).

Please contact me via email, I am not available on phone.

Regards

Topic) Effect of prior embolization on radiosurgery outcome for interacranial arteriovenous malformations. A case _control study

Cerebral arteriovenous malformations (AVMs) are rare but potentially devastating vascular lesions that often affect young adults. Intracranial hemorrhage occurs at an average annual rate of 2 to 4%. Surgical excision is the mainstay of treatment for Spetzler-Martin (SM) grade I and II AVM. Because of high procedural morbidity rates, surgery is avoided in larger and higher grade AVM, and alternative therapies are often considered for these lesions. For large AVMs, a combined multidisciplinary approach with partial embolization to reduce the size of the nidus followed by microsurgery or radiosurgery of the remaining patent nidus has become a common practice. However, the effectiveness and risk of stereotactic radiosurgery (SRS) in the management of partially embolized intracranial arteriovenous malformations (AVMs) remain controversial. In my report I am going to describe the outcomes of patients with AVMs who
underwent embolization followed by SRS. I will review factors associated with total obliteration, risk of hemorrhage, and complications. In addition, my report compares treatment outcomes in this subset of patients to the outcomes of matched patients who underwent
SRS without prior embolization.

Main objective;

Cerebral arteriovenous malformations (AVMs) are rare congenital vascular malformations that present equally in both sexes and are typically diagnosed by the 3rd decade of life. The combination of embolization and
radiosurgery is often used in the treatment of brain AVMs; however, the effectiveness of this combination remains controversial. Some series have suggested that embolization before radiosurgery was associated with lower obliteration rates and worse outcomes. Several mechanisms have been suggested to explain lower obliteration rates, including recanalization of the nidus after embolization, enhanced angiogenesis after embolization (as demonstrated in animal models), difficulty in delineation of the nidus after embolization, and beam attenuation by the liquid embolization material.

On the other hand, by reducing the size of the by adjuant embolization, endovascular embolization is thought to improve AVM obliteration rates while also minimizing SRS-related complications. Previous series have reported
conflicting results regarding the efficacy of preradiosurgical AVM embolization.

Method

Betwee September 2003 and August 2013, of patients harboring AVMs and underwent single-stage SRS using the Leksell Gamma Knife (Elekta Instruments) at our cente,we included patients who underwent SRS after one or more embolization procedures and patients who underwent AVM resection before SRS are excluded from this study, because our purpose is to analyze outcomes when embolization is performed with the explicit goal of volume reduction in anticipation of subsequent SRS. Patients characteristics ( age, sex, symptoms leading to the AVM diagnosis (hemorrhage, seizures, extraocular movement dysfunction,…), incidental etc. are determined. The AVMs characteristics (location, coexisting arterial aneurysm, varix,…) Spetzler-Martin and modified Pollock-Flickinger SRS AVM grade (were calculated retrospectively) are determined. The equation to calculate the modified Pollock-Flickinger AVM grading score is as follows: Score = (0.1) (volume in cm3) + (0.02) (age in years) + (0.5) (location: basal ganglia, thalamus, or brainstem = 1, others = 0). Outcome data were obtained from review of the patient’s medical records and supplemented by telephone discussions with the patient and/or patient’s family and current treating physicians.

Prior Embolization

The median interval between the last embolization and SRS and number of embolization procedures before SRS, type of embolization agents were used complications developed after embolization procedures (eg hemiparesis, visual field deficit, dysphasia are determined.

Radiosurgery Technique

(I will provide later) Both T1-weighted with contrast and T2-weighted high-resolution MRI sequences were performed during SRS in patients regardless of whether they had undergone pre-SRS embolization. Successfully embolized volumes were not included in the SRS target volume. As part of the propensity-matching algorithm, the target margin dose used was similar to margin dose used in patients who had not undergone embolization. The median target volume, the median maximal diameter of the AVM nidus, the median prescription dose delivered to the nidus margin, the median maximum dose, the median number of isocenters was are determined. Our dose planning tech nique, using both MRI and angiography, was no different for patients who underwent embolization and those who did not. (I will provide complete radiosurgical procedure later)

Patient Follow-Up

After radiosurgery, patients underwent clinical and imaging assessments at 6-, 12-, 24-, and 36-month time periods. If at the end of 3 years MRI suggested complete obliteration, then a repeat angiogram was requested. If the MRI clearly defined a residual nidus, angiography was delayed, and the patient was offered repeat radiosurgery to achieve the final obliteration response. When obliteration of the AVM was suggested by MRI, cerebral angiography was requested to confirm obliteration. Complete angiographic AVM obliteration was defined as disappearance of the nidus and absence of early venous drainage. At any time when a new neurological symptom or sign developed, the patient underwent CT and/or MRI to rule out hemorrhage or AREs.

Case Matching to Patients Harboring AVMs

Patients with AVMs without prior embolization who underwent singlestage SRS between 2003 and 2013 were eligible to serve as potential case-control matches. We use propensity score matching between the study individuals (case cohort) and patients harboring AVMs who did not undergo prior embolization but underwent SRS (control cohort).2 The propensity score is calculated by fitting a logistic regression model using the following 9 variables: sex, age, prior hemorrhage history, maximum nidus diameter, target volume, margin dose, Spetzler-Martin grade, Pollock-Flickinger score, and follow-up duration. We use a 1:1 matching algorithm based on the propensity score. A caliper width of 0.6 times the sample standard deviation of the propensity score is chosen. After propensity score matching, the Mann-Whitney U-test for continuous data and the Fisher exact test for categorical data is used to compare the two groups. Patients with AVMs who underwent prior embolization were matched to patients with AVMs with identical sex (Mann-Whitney U-test), similar age (difference between groups, 5 years or less), similar prior hemorrhage history, similar maximum nidus diameter, similar target volume, similar margin dose, similar Spetzler-Martin grade, similar Pollock-Flickinger score, and similar follow-up duration (difference between groups, 6 months or less) who did not undergo prior embolization. The rates of total obliteration, hemorrhage after SRS, and AREs are assessed in both patient groups.