Three-dimensional wall-thickness distributions of unruptured intracranial aneurysms characterized by micro-computed tomography.

Aneurysmal rupture is associated with wall thinning, but the mechanism is poorly understood. This study aimed to characterize the three-dimensional wall-thickness distributions of unruptured intracranial aneurysms. Five aneurysmal tissues were investigated using micro-computed tomography. First, the wall thickness was related to the aneurysmal wall appearances during surgery. The median wall thicknesses of the translucent and non-translucent walls were 50.56 and 155.93 µm, respectively (p < 0.05) with significant variation in the non-translucent wall thicknesses (p < 0.05). The three-dimensional observations characterized the spatial variation of wall thicknesses. Thin walls showed a uniform thickness profile ranging from 10 to 40 µm, whereas thick walls presented a peaked thickness profile ranging from 300 to 500 µm. In transition walls, the profile undulated due to the formation of focal thin/thick spots. Overall, the aneurysmal wall thicknesses were strongly site-dependent and spatially varied by 10 to 40 times within individual cases. Aneurysmal walls are exposed to wall stress driven by blood pressure. In theory, the magnitude of wall stress is inversely proportional to wall thickness. Thus, the observed spatial variation of wall thickness may increase the spatial variation of wall stress to a similar extent. The irregular wall thickness may yield stress concentration. The observed thin walls and focal thin spots may be caused by excessive wall stresses at the range of mechanical failure inducing wall injuries, such as microscopic tears, during aneurysmal enlargement. The present results suggested that blood pressure (wall stress) may have a potential of acting as a trigger of aneurysmal wall injury.

Useful Test for Classification of Cerebral Infarction at Hospital Specializing in Neurosurgery.

Background and Purpose: There are many cases of cerebral infarction of unknown etiology in which the embolic sources cannot be identified including atrial fibrillation despite achievement of complete revascularization after thrombectomy. Method: An analysis was conducted for 556 consecutive cases of patients who were hospitalized for cerebral infarction to determine the significance of accurate classification of disease type and investigation into causes of cerebral infarction of unknown cause. Result: According to the Trials of Org 10172 in Acute Stroke Treatment (TOAST) classification, cerebral infarction of other/unknown etiology was observed in 94 cases, of which 22 cases were found to have causes by additional workup. Implantable cardiac monitors were inserted in 15 of 76 cases of cryptogenic cerebral infarction, of which 4 cases (26%) showed detection of paroxysmal atrial fibrillation (PAF) during observation period (223-384 days). Conclusion: Brain natriuretic peptide (BNP) measurement, abdomen-pelvic computed tomography (CT), cardiac monitoring for 1 week, and implantable cardiac monitors (ICM) were useful for the classification of disease type and detection of cryptogenic atrial fibrillation. (This is secondary publication from J Jpn Coll Angiol 2021; 61: 49-55.).