Intracavernous aneurysm. Superior demonstration by magnetic resonance angiography

A Systematic Review and Meta-Analysis of 3-Dimensional Morphometric Parameters for Cerebral Aneurysms

BACKGROUND

Imaging modalities with increased spatial resolution have allowed for more precise quantification of cerebral aneurysm shape in 3-dimensional (3D) space. We conducted a systematic review and meta-analysis to assess the correlation of individual 3D morphometric measures with cerebral aneurysm rupture status.

METHODS

Two independent reviewers performed a PRISMA (preferred reporting items of systematic reviews and meta-analysis)-guided literature search to identify articles reporting the association between 3D morphometric measures of intracranial aneurysms and rupture status.

RESULTS

A total of 15,122 articles were identified. After screening, 39 studies were included. We identified 17 3D morphometric measures, with 11 eligible for the meta-analysis. The meta-analysis showed a significant association with rupture status for the following measures: nonsphericity index (standardized mean difference [SMD], 0.66; 95% confidence interval [CI], 0.53-0.79; P < 0.0001; I2 = 55.2%), undulation index (SMD, 0.55; 95% CI, 0.26-0.85; P = 0.0017; I2 = 68.1%), ellipticity index (SMD, 0.53; 95% CI, 0.29-0.77; P = 0.0005; I2 = 70.8%), volume (SMD, 0.18; 95% CI, 0.02-0.35; P = 0.0320; I2 = 82.3%), volume/ostium ratio (SMD, 0.43; 95% CI, 0.16-0.71; P = 0.0075; I2 = 90.4%), elongation (SMD, -0.94; 95% CI, -1.12 to -0.76; P = 0.0005; I2 = 0%), flatness (SMD, -0.87; 95% CI, -1.04 to -0.71; P = 0.0005; I2 = 0%), and sphericity (SMD, -0.62; 95% CI, -1.06 to -0.17; P = 0.0215; I2 = 67.9%). A significant risk of publication bias was estimated for the ellipticity index (P = 0.0360) and volume (P = 0.0030).

CONCLUSIONS

Based on the results of a meta-analysis containing 39 studies, the nonsphericity index, undulation index, elongation, flatness, and sphericity demonstrated the most consistent correlation with rupture status.

The new proposed magnetic resonance areas of the cavernous sinus and their relation to the neurosurgical triangles

MRI appears to be the best contemporary method with which to evaluate cavernous sinus anatomy. Based on anatomic landmarks that are easily detectable in the standard MRI examination, the cavernous sinus is divided into six areas. Each of the newly defined areas corresponds to the previously described neuroanatomic triangles. Evaluation of the newly defined areas in a plane perpendicular to these triangles on a MRI scan permits expansion of these two-dimensional areas into three-dimensional spaces; thus, the neurosurgical approach can be observed and their anatomic and pathologic content examined. Radiologic and surgical evaluation of the cavernous sinus is presented.

Negative MRI versus real disease

A 76-year-old diabetic woman presented with progressive binocular vertical diplopia and right eye pain. Examination revealed a pupil-involving partial right third cranial nerve palsy, with development of anisocoria over the course of several hours. MRI of the brain showed no mass lesion. MRA, even with retrospective review of the images, failed to clearly identify a 1 cm right posterior communicating artery aneurysm detected by subsequent conventional cerebral angiography. While MRA has been reported to be highly sensitive in cerebral aneurysm detection at some centers, other investigators have indicated less favorable data. Standardized protocols for data acquisition and meticulous attention to proper post-processing and image interpretation are essential if MRA is to supplant invasive arteriography. Currently, conventional (x-ray) angiography remains the gold standard for aneurysm detection, while MRA possesses excellent potential in this regard.

Clinical utility of three-dimensional time-of-flight magnetic resonance angiography for the evaluation of intracranial aneurysms

Magnetic resonance (MR) angiographic studies of 14 patients with intracranial aneurysms (AN) were analyzed retrospectively as compared with contrast angiographic studies. Eighteen of 19 (95%) lesions were detected, and the relation between AN and their parent vessels was precisely assessed. The diameter of the smallest aneurysm detected in our case was 3 mm. However, small vessels around AN were not visualized. Therefore, MR angiography (MRA) is definitely not a substitute for preoperative contrast angiography. MRA is a useful screening tool for nonruptured AN, but further refinement is required to evaluate emergency ruptured AN.

Magnetic resonance angiography of vascular lesions causing neuro-ophthalmic deficits

Magnetic resonance angiography (MRA) is a noninvasive, rapidly evolving technique for imaging the intra- and extracranial carotid and vertebrobasilar circulations. It may in some circumstances obviate conventional angiography and the accompanying risks associated with catheterization and contrast injection. MRA exploits the different physical properties between moving protons and stationary tissue to yield flow sensitive data in the form of anatomic images or velocity and flow measurements. Since patients with various vascular disorders may present exclusively with ophthalmologic signs and symptoms, it is expected that MRA will become more frequently utilized by ophthalmologists. The exact role of MRA in the workup of vascular disorders remains to be more precisely defined, pending the performance of additional well-controlled standardized studies. At present, MRA is utilized to complement the conventional spin-echo studies of patients with arterial and venous occlusion, vascular malformations, intracranial aneurysms, and neoplastic vascular invasion. With further refinements, it is expected that MRA will become a standard diagnostic tool for the evaluation of patients with vascular disorders.