Analysis of Cerebral Aneurysm Wall Tension and Enhancement Using Finite Element Analysis and High-Resolution Vessel Wall Imaging.

Biomechanical computational simulation of intracranial aneurysms has become a promising method for predicting features of instability leading to aneurysm growth and rupture. Hemodynamic analysis of aneurysm behavior has helped investigate the complex relationship between features of aneurysm shape, morphology, flow patterns, and the proliferation or degradation of the aneurysm wall. Finite element analysis paired with high-resolution vessel wall imaging can provide more insight into how exactly aneurysm morphology relates to wall behavior, and whether wall enhancement can describe this phenomenon. In a retrospective analysis of 23 unruptured aneurysms, finite element analysis was conducted using an isotropic, homogenous third order polynomial material model. Aneurysm wall enhancement was quantified on 2D multiplanar views, with 14 aneurysms classified as enhancing (CRstalk≥0.6) and nine classified as non-enhancing. Enhancing aneurysms had a significantly higher 95th percentile wall tension (µ = 0.77 N/cm) compared to non-enhancing aneurysms (µ = 0.42 N/cm, p < 0.001). Wall enhancement remained a significant predictor of wall tension while accounting for the effects of aneurysm size (p = 0.046). In a qualitative comparison, low wall tension areas concentrated around aneurysm blebs. Aneurysms with irregular morphologies may show increased areas of low wall tension. The biological implications of finite element analysis in intracranial aneurysms are still unclear but may provide further insights into the complex process of bleb formation and aneurysm rupture.

Reversible bilateral optic tract edema following pipeline-assisted coiling of a large ophthalmic aneurysm: A case report.

Edema coursing the optic apparatus has traditionally been associated with sellar and para-sellar tumors. However, postoperative aneurysmal volume expansion following endovascular treatment has been reported to induce cranial neuropathies, such as vision loss in rare instances. Here, we present a case report of worsening optic tract edema associated with bilateral visual acuity deficit following treatment of a large left paraophthalmic aneurysm with pipeline-assisted coiling. Rapid resolution of visual deficit was observed following administration of corticosteroids. A 42-year-old female with a 6-month history of worsening left eye vision and sentinel headache presented with left visual field cut and decreased left visual acuity. She was found to have a large paraophthalmic aneurysm which was treated with pipeline-assisted coiling. Within one week post-treatment, the patient presented to the emergency department with worsening right visual complaints. On magnetic resonance imaging, T2 hyperintensities coursing the right posterior optic nerve, optic chiasm, and bilateral optic tracts were noted. Angiography demonstrated an expanding neck remnant. The patient was treated with oral corticosteroids and repeat pipeline stenting. At four week follow up, she demonstrated significant improvement of symptoms and reduced T2 hyperintensities. With the advancement in endovascular technique for the treatment of large aneurysms, more patients are electing endovascular treatment over microsurgical clipping. Given the possibility of continued growth following endovascular treatment, patient counseling regarding risks and side effects is paramount.

Tirofiban Protocol Protects Against Delayed Cerebral Ischemia: A Case-Series Study.

BACKGROUND: There has not been any effective prophylaxis for delayed cerebral ischemia delayed cerebral ischemia (DCI) since the introduction of nimodipine. Platelet inhibition may reduce the risk by preventing the formation of microthrombi. Tirofiban has been used as a single monotherapy bridge given its safety profile and controlled platelet inhibition. OBJECTIVE: To assess the risk of DCI in aneurysmal subarachnoid hemorrhages (aSAH) patients treated with the tirofiban protocol. METHODS: aSAH patients between December 2010 and March 2019 who were treated with stent assisted coiling or flow-diverting device were started on a continuous tirofiban infusion protocol and were compared with patients who underwent coil embolization without antiplatelet therapy. Safety analysis was performed to assess DCI, hemorrhagic, and ischemic events. RESULTS: A total of 21 patients were included in the tirofiban series and 81 in the control group. There was no statistical difference in age, gender, Hunt-Hess grade, and Fisher scale between the 2 groups except for a higher Fisher grade II in the tirofiban group. Multivariate analysis revealed tirofiban to reduce the risk of vasospasm by 72 percent (OR .28, P = .03), without affecting the risk of hemorrhagic complications (OR = 0.50, P = .26). Tirofiban reduced the risk of symptomatic stroke endovascular procedure but it did not reach significance (P = .06). DCI, older age, and postprocedural symptomatic stroke were significant predictors of mortality. Tirofiban reduced the mortality risk, but this association was not statistically significant. CONCLUSION: The tirofiban protocol in aSAH patients reduces the risk of DCI without conferring additional risks. This supports previous findings were antiplatelet therapy reduced DCI in human and animal models.

Quantitative Susceptibility Mapping and Vessel Wall Imaging as Screening Tools to Detect Microbleed in Sentinel Headache.

BACKGROUND: MR-quantitative susceptibility mapping (QSM) can identify microbleeds (MBs) in intracranial aneurysm (IA) wall associated with sentinel headache (SH) preceding subarachnoid hemorrhage. However, its use is limited, due to associated skull base bonny and air artifact. MR-vessel wall imaging (VWI) is not limited by such artifact and therefore could be an alternative to QSM. The purpose of this study was to investigate the correlation between QSM and VWI in detecting MBs and to help develop a diagnostic strategy for SH. METHODS: We performed a prospective study of subjects with one or more unruptured IAs in our hospital. All subjects underwent evaluation using 3T-MRI for MR angiography (MRA), QSM, and pre- and post-contrast VWI of the IAs. Presence/absence of MBs detected by QSM was correlated with aneurysm wall enhancement (AWE) on VWI. RESULTS: A total of 40 subjects harboring 51 unruptured IAs were enrolled in the study. MBs evident on the QSM sequence was detected in 12 (23.5%) IAs of 11 subjects. All these subjects had a history of severe headache suggestive of SH. AWE was detected in 22 (43.1%) IAs. Using positive QSM as a surrogate for MBs, the sensitivity, specificity, positive predictive value, and negative predictive value of AWE on VWI for detecting MBs were 91.7%, 71.8%, 50%, and 96.6%, respectively. CONCLUSIONS: Positive QSM findings strongly suggested the presence of MBs with SH, whereas, the lack of AWE on VWI can rule it out with a probability of 96.6%. If proven in a larger cohort, combining QSM and VWI could be an adjunctive tool to help diagnose SH, especially in cases with negative or non-diagnostic CT and lumbar puncture.

Objective quantification of contrast enhancement of unruptured intracranial aneurysms: a high-resolution vessel wall imaging validation study.

OBJECTIVE: High-resolution vessel wall imaging (HR-VWI) has emerged as a valuable tool in assessing unruptured intracranial aneurysms (UIAs). There is no standardized method to quantify contrast enhancement of the aneurysm wall. Contrast enhancement can be objectively measured as signal intensity (SI) or subjectively adjudicated. In this study, the authors compared the different methods to quantify wall enhancement of UIAs and determined the sensitivity and specificity of each method as a surrogate of aneurysm instability. They also compared SI quantification between scanners from different manufacturers. METHODS: The University of Iowa HR-VWI Project database was analyzed. This database compiles patients with UIAs who prospectively underwent HR-VWI using a 3T MRI scanner. The mean and maximal SI values of the aneurysm wall, pituitary stalk, and genu of the corpus callosum were used to compare 3 different measurement methods: 1) aneurysm enhancement ratio AER = (SIwall post - SIwall pre)/SIwall pre; 2) aneurysm-to-pituitary stalk contrast ratio CRstalk = SIwall post/SIstalk post; and 3) aneurysm enhancement index AEI = ([SIwall post/SIbrain post] - [SIwall pre/SIbrain pre])/(SIwall pre/SIbrain pre) (where "pre" indicates precontrast images and "post" indicates postcontrast images). Size ≥ 7 mm was used as a surrogate of aneurysm instability for receiver operating characteristic (ROC) curve analysis. To determine if the objective quantification of SI varies among scanners from different manufacturers, 9 UIAs underwent the same HR-VWI protocol using a 3T General Electric (GE) scanner and a 3T Siemens scanner. Three UIAs also underwent a third scanning procedure on a unit with a different magnet strength (7T GE). RESULTS: Eighty patients with 102 UIAs were included in the study. The mean age was 64.5 ± 12.2 years, and 64 (80%) patients were women. UIAs ≥ 7 mm had significantly higher SIs than smaller UIAs (< 7 mm): AER = 0.82 vs 0.49, p < 0.001; CRstalk = 0.84 vs 0.61, p < 0.001; and AEI = 0.81 vs 0.48, p < 0.001. ROC curves demonstrated optimal sensitivity of 81.5% for CRstalk ≥ 0.60, 75.9% for AEI ≥ 0.50, and 74.1% for AER ≥ 0.49. Intermanufacturer correlation between 3T GE and 3T Siemens MRI scanners for CRstalk using mean and maximal SI values was excellent (Pearson coefficients > 0.80, p < 0.001). A similar correlation was identified among the 3 UIAs that underwent 7T imaging. CONCLUSIONS: CRstalk using maximal SI values was the most reliable objective method to quantify enhancement of UIAs on HR-VWI. The same ratios were obtained between different manufacturers and on scans obtained using magnets of different strengths.

Single surgeon experience with minimally invasive supraorbital craniotomy versus bifrontal craniotomy for anterior skull base meningiomas.

BACKGROUND: Anterior skull base meningiomas (ASBMs) account for about 10% of meningiomas. Bifrontal craniotomy (BFC) represents the traditional transcranial approach to accessing meningiomas in these locations. Supraorbital craniotomy (SOC) provides a minimally invasive subfrontal corridor in select patients. Here, we present our series of ASBM accessed by SOC and BFC by a single surgeon to review decision-making and compare outcomes in both techniques. METHODS: Thirty-three patients were identified with ASBM. Age, tumor characteristics, presenting symptoms, postoperative complications, and outcomes were analyzed. RESULTS: Bifrontal and SOC were performed in 13 and 20 patients, respectively. Mean follow-up time was 98.4 months. Patients undergoing SOC had smaller tumor size, located farther from the posterior table of frontal sinus, had less peritumoral edema, and decreased length of stay compared to patients undergoing BFC. Extent of resection was slightly better with BFC (99.8%) compared to SOC (91.8%), although this difference did not reach statistical significance. Recurrence-free survival and rate of re-do surgeries were not different between two groups. BFC was associated with higher rates of postoperative encephalomalacia. CONCLUSION: SOC provides an excellent surgical option for ASBMs providing comparable extent of resection, minimal manipulation of brain, and excellent cosmetic outcomes for patients. The patient selection is key to maximize the benefits from this approach.