Phillip V. Parry

Stereotactic radiosurgery for arteriovenous malformations, Part 6: multistaged volumetric management of large arteriovenous malformations

OBJECT The object of this study was to define the long-term outcomes and risks of arteriovenous malformation (AVM) management using 2 or more stages of stereotactic radiosurgery (SRS) for symptomatic large-volume lesions unsuitable for surgery. METHODS In 1992, the authors prospectively began to stage the treatment of anatomical components to deliver higher single doses to AVMs with a volume of more than 10 cm(3). Forty-seven patients with such AVMs underwent volume-staged SRS. In this series, 18 patients (38%) had a prior hemorrhage and 21 patients (45%) underwent prior embolization. The median interval between the first-stage SRS and the second-stage SRS was 4.9 months (range 2.8-13.8 months). The median target volume was 11.5 cm(3) (range 4.0-26 cm(3)) in the first-stage SRS and 9.5 cm(3) in the second-stage SRS. The median margin dose was 16 Gy (range 13-18 Gy) for both stages. RESULTS In 17 patients, AVM obliteration was confirmed after 2-4 SRS procedures at a median follow-up of 87 months (range 0.4-209 months). Five patients had near-total obliteration (volume reduction > 75% but residual AVM). The actuarial rates of total obliteration after 2-stage SRS were 7%, 20%, 28%, and 36% at 3, 4, 5, and 10 years, respectively. The 5-year total obliteration rate after the initial staged volumetric SRS with a margin dose of 17 Gy or more was 62% (p = 0.001). Sixteen patients underwent additional SRS at a median interval of 61 months (range 33-113 months) after the initial 2-stage SRS. The overall rates of total obliteration after staged and repeat SRS were 18%, 45%, and 56% at 5, 7, and 10 years, respectively. Ten patients sustained hemorrhage after staged SRS, and 5 of these patients died. Three of 16 patients who underwent repeat SRS sustained hemorrhage after the procedure and died. Based on Kaplan-Meier analysis (excluding the second hemorrhage in the patient who had 2 hemorrhages), the cumulative rates of AVM hemorrhage after SRS were 4.3%, 8.6%, 13.5%, and 36.0% at 1, 2, 5, and 10 years, respectively. This corresponded to annual hemorrhage risks of 4.3%, 2.3%, and 5.6% for Years 0-1, 1-5, and 5-10 after SRS. Multiple hemorrhages before SRS correlated with a significantly higher risk of hemorrhage after SRS. Symptomatic adverse radiation effects were detected in 13% of patients, but no patient died as a result of an adverse radiation effect. Delayed cyst formation did not occur in any patient after SRS. CONCLUSIONS Prospective volume-staged SRS for large AVMs unsuitable for surgery has potential benefit but often requires more than 2 procedures to complete the obliteration process. To have a reasonable chance of benefit, the minimum margin dose should be 17 Gy or greater, depending on the AVM location. In the future, prospective volume-staged SRS followed by embolization (to reduce flow, obliterate fistulas, and occlude associated aneurysms) may improve obliteration results and further reduce the risk of hemorrhage after SRS.

Long-term outcomes after gamma knife stereotactic radiosurgery for nonfunctional pituitary adenomas.

BACKGROUND Nonfunctional pituitary adenomas (NFPAs) represent approximately 50% of all pituitary tumors. OBJECTIVE To evaluate the long-term outcomes of stereotactic radiosurgery for NFPAs. METHODS We evaluated the management outcomes of Gamma Knife radiosurgery in 125 patients with NFPAs over an interval of 22 years. The median patient age was 54 years (range, 16-88 years). One hundred ten patients (88%) had residual or recurrent tumors after ≥ 1 surgical procedures, and 17 (14%) had undergone prior fractionated radiation therapy. The median target volume was 3.5 cm3 (range, 0.4-28.1 cm3), and the median tumor margin dose was 13.0 Gy (range, 10-25 Gy). RESULTS Tumor volume decreased in 66 patients (53%), remained stable in 46 (37%), and increased in 13 (10.4%) during a median of 62 months (maximum, 19 years) of imaging follow-up. The actuarial tumor control rates at 1, 5, and 10 years were 99%, 94%, and 76%, respectively. Factors associated with a reduced progression-free survival included larger tumor volume (≥ 4.5 cm3) and ≥ 2 prior recurrences. Of 88 patients with residual pituitary function, 21 (24%) suffered new hormonal deficits at a median of 24 months (range, 3-114 months). Prior radiation therapy increased the risk of developing new pituitary hormonal deficits. One patient (0.8%) had a decline in visual function, and 2 (1.6%) developed new cranial neuropathies without tumor progression. CONCLUSION Stereotactic radiosurgery can provide effective management for patients with newly diagnosed NFPAs and for those after prior resection and/or radiation therapy.

Leukoencephalopathy after whole-brain radiation therapy plus radiosurgery versus radiosurgery alone for metastatic lung cancer

As systemic therapies improve and patients live longer, concerns mount about the toxicity of whole‐brain radiation therapy (WBRT) for treatment of brain metastases. Development of delayed white matter abnormalities indicative of leukoencephalopathy have been correlated with cognitive dysfunction. This study assesses the risk of imaging‐defined leukoencephalopathy in patients whose management included WBRT in addition to stereotactic radiosurgery (SRS). This risk is compared to patients who only underwent SRS.

Image-guided frameless stereotactic needle biopsy in awake patients without the use of rigid head fixation

OBJECT Image-guided frameless stereotactic techniques provide an alternative to traditional head-frame fixation in the performance of fine-needle biopsies. However, these techniques still require rigid head fixation, usually in the form of a head holder. The authors report on a series of fine-needle biopsies and brain abscess aspirations in which a frameless technique was used with a patients head supported on a horseshoe headholder. To validate this technique, they performed an in vitro accuracy study. METHODS Forty-eight patients underwent fine-needle biopsy of intracranial lesions that ranged in size from 0.9 to more than 107.7 ml; a fiducial-less, frameless, image-guided technique was used without rigid head fixation. In 1 of the 48 patients a cerebral abscess was drained. The accuracy study was performed with a skull phantom that was imaged with a CT scanner and tracked with a registration mask containing light-emitting diodes. The objective was a skin fiducial marker with a 4-mm circular target to accommodate the 2.5-mm biopsy needle. A series of 50 trials was conducted. RESULTS Diagnostic tissue was obtained on the first attempt in 47 of 48 brain biopsy cases. In 2 cases small hemorrhages at the biopsy site were noted as a complication on the postoperative CT scan. One of these hemorrhages resulted in hand and arm weakness. The accuracy study demonstrated a 98% success rate of the biopsy needle passing through the 4-mm circular target using the registration mask as the registration and tracking device. This demonstrates a ± 0.75-mm tolerance on the targeting method. CONCLUSIONS The accuracy study demonstrated the ability of the mask to actively track the target and allow navigation to a 4-mm-diameter circular target with a 98% success rate. The frameless, pinless, fiducial-less technique described herein will likely be another safe, fast alternative to frame-based stereotactic techniques for fine-needle biopsy that avoids the potential morbidity of rigid head-pin fixation. Furthermore, it should lend itself to other image-guided applications such as the placement of ventricular catheters for shunting or Ommaya reservoirs.

Multistaged volumetric management of large arteriovenous malformations.

We sought to define the long-term outcomes and risks of arteriovenous malformation (AVM) management using 2 or more stages of stereotactic radiosurgery (SRS) for symptomatic large-volume AVMs unsuitable for surgery. Two decades ago, we prospectively began to stage anatomical components in order to deliver higher single doses to AVMs>10 cm3 in volume. Forty-seven patients with large AVMs underwent volume-staged SRS. The median interval between the two SRS procedures was 4.9 months (range, 3-14 months). The median nidus volume was 11.5 cm3 (range, 4.0-26 cm3) in the first stage of SRS and 9.5 cm3 in the second. The median margin dose was 16 Gy (range, 13-18 Gy) for both SRS stages. The actuarial rates of total obliteration after 2-staged SRS were 7, 20, 28 and 36% at 3, 4, 5 and 10 years, respectively. Sixteen patients needed additional SRS at a median interval of 61 months (range, 33-113 months) after the 2-staged SRS. After repeat procedure(s), the eventual obliteration rate was 66% at 10 years. The cumulative rates of AVM hemorrhage after SRS were 4.3, 8.6, 13.5 and 36.0% at 1, 2, 5 and 10 years, respectively. Symptomatic adverse radiation effects were detected in 13% of patients. Successful prospective volume-staged SRS for large AVMs unsuitable for surgery requires 2 or more procedures to complete the obliteration process. Patients remain at risk for hemorrhage if the AVM persists.

Importance of the C1 anterior tubercle depth and lateral mass geometry when placing C1 lateral mass screws.

OBJECTIVEWe measured the variability in the size of the anterior tubercle of C1 and the optimal depth and angle of placement of C1 lateral mass screws using axial and sagittal reconstructed computed tomographic scans to determine the utility of these parameters for preoperative planning and intraoperative guidance. METHODSOne hundred consecutive cervical spine computed tomographic scans were reviewed (mean patient age, 44.6 years; age range, 7–96 years). The size of the anterior tubercle of C1, bilateral depths of optimal screw placement in the axial and sagittal planes, and optimal angles of placement in the axial and sagittal planes were measured in a standardized manner using the measuring tool included in our radiology server software. These measurements were correlated with age and sex. RESULTSThe mean depth of the C1 tubercle was 6.9 mm (range, 2.7–11.2 mm; standard deviation, 1.7 mm). The depth of the C1 tubercle tended to increase with age, but the relationship was not significant. The optimal screw depth in the sagittal plane was significantly greater than in the axial plane (right 2.09 versus 1.93 cm; left 2.07 versus 1.91 cm). The depth of the right lateral mass increased significantly with age. No other relationships reached significance. CONCLUSIONThe depth of the anterior tubercle of C1 varies considerably and should be studied carefully before using lateral fluoroscopy of this structure to guide depth of C1 lateral mass screw placement. Optimal angles and depths of placement of C1 lateral mass screws vary widely and should be examined preoperatively to plan appropriate depth and trajectory.

Future Perspectives on Brain Metastasis Management

Brain metastases are the most common intracranial tumors encountered by physicians. Historically, the mainstays of therapy were limited to surgery and whole brain radiation. Surgery is typically reserved for safely accessible and symptomatic tumors in patients well enough to tolerate a procedure. Whole-brain radiation therapy has proven to have limited efficacy and concerns have arisen regarding its toxicity. Advances in the treatment of systemic cancers have yielded improved long-term survival and quality of life for patients. To parallel these efforts in systemic treatment, continual improvement of the treatment of brain metastases is a must. The last two decades have seen a paradigm shift in the thinking about metastatic brain tumor treatment as a result of the advent of stereotactic radiosurgery. Radiosurgery has proven to be an efficacious, minimally invasive, and highly selective treatment for metastatic brain tumors. In this review, we discuss the evolution of metastatic brain tumor management, the appropriately diminished role for reflexive whole brain radiation, and the growing importance of stereotactic radiosurgery as an upfront treatment modality in conjunction with surgery and subsequent salvage radiosurgery.

A novel route of revascularization in basilar artery occlusion and review of the literature

Ischemia of the basilar artery is one of the most devastating types of arterial occlusive disease. Despite treatment of basilar artery occlusions (BAO) with intravenous tissue plasminogen activator, antiplatelet agents, intra-arterial therapy or a combination, fatality rates remain high. Aggressive recanalization with mechanical thrombectomy is therefore often necessary to preserve life. When direct access to the basilar trunk is not possible, exploration of chronically occluded vessels through collaterals with angioplasty and stenting creates access for manual aspiration. We describe the first report of retrograde vertebral artery (VA) revascularization using thyrocervical collaterals for anterograde mechanical aspiration of a BAO followed by stenting of the chronically occluded VA origin. Our novel retrograde–anterograde approach resulted in resolution of the patients clinical stroke syndrome.

Solitaire salvage: a stent retriever-assisted catheter reduction technical report

The endovascular management of giant aneurysms often proves difficult with standard techniques. Obtaining distal access to allow catheter reduction is often key to approaching these aneurysms, but several anatomic challenges make this task unsafe and not feasible. Obtaining distal anchor points and performing catheter reduction maneuvers using adjunctive devices is not a novel concept, however using the Solitaire in order to do so may have some distinct advantages compared with previously described methods. Here we describe our novel Solitaire salvage technique, which allowed successful reduction of a looped catheter within an aneurysm in three cases. While this technique is expensive and therefore best performed after standard maneuvers have failed, in our experience it was effective, safe, and more efficient than other methods.

148 Preinjury Antithrombotic Therapy and the Elderly TBI Patient

Methods We performed a retrospective analysis of elderly TBI patients (>=65 years) with evidence of brain hemorrhage on computed tomography (CT) scan at our institution from 2006-2010. Patient demographics, injury severity, clinical course, length of stay, and disposition were collected. Statistical analyses were performed to compare groups and identify predictors of mortality, complication, infection, neurosurgical intervention, and hemorrhage progression. Results 1552 patients were identified with 543 aspirin only (AO), 97 clopidogrel only (CO), 218 warfarin only (WO), 193 clopidogrel/aspirin (CA), and 501 patients on no antithrombotic medication (NAT). Significant differences existed in abbreviated injury score (AIS) (p=0.012), Glasgow Coma Scale (GCS) score (p=0.013), and Marshall score (p<0.001) at time of presentation. Blood products were administered to reverse coagulopathy in 77.3% of patients. After adjusting for covariates, including medication reversal, antithrombotic use was associated with increased mortality (p=0.03); WO use conferred greater odds of mortality than preinjury use of antiplatelet agents (OR 2.53, p=0.003), which did not influence mortality (p=0.622). Rates of neurosurgical interventions (p=0.677) did not differ between groups. Survivor subset analysis demonstrated that CT-identified hemorrhage progression was not associated with preinjury antithrombotic therapy, nor were rates of complication or infection development, hospital/ICU LOS, ventilator days, or discharge disposition. When stratifying for severe and moderate TBI only, use of antithrombotics did not affect outcomes. Conclusions Preinjury use of warfarin, but not antiplatelet medications, influences survival in elderly patients admitted with TBI. Hemorrhage progression, neurosurgical interventions, and morbidity are not affected. The importance of antithrombotic therapy seems to lie in its impact on initial injury severity, which, in turn, is predictive of increased morbidity and mortality. Learning Objectives By the conclusion of this session, participants should be able to: 1) describe the importance of particular risk factors for poor outcomes amongst elderly TBI patients, 2) discuss, in small groups, potential options for identifying particular at-risk subsegments of this demographic and optimizing their care, and 3) identify strategies to limit wasteful healthcare expenditures in this population.