Huston, John

Intracranial aneurysms are heterogeneous in histopathology and imaging appearance. The biological behavior of different types of aneurysms is now known to depend on the structure and physiology of the aneurysm wall itself in addition to intraluminal flow and other luminal features. Aneurysm wall structure and imaging markers of physiology such as aneurysm wall enhancement have been assessed in many prior investigations using conventional-resolution MRI. Recently, high-resolution vessel wall imaging (HR-VWI) techniques with MRI have been introduced. Reports of findings on high-resolution imaging have already emerged for many types of aneurysms demonstrating detailed characterization of wall enhancement, thickness, and components, but many questions remain unexplored. This review discusses the key HR-VWI literature to date. Aneurysm wall findings on conventional-resolution MRI are also discussed as these may help one understand the potential utility and findings on HR-VWI for various aneurysm types. The authors have illustrated these points with several examples demonstrating both features already described in the literature and novel cases demonstrating the potential for future clinical and research applications.

PurposeTo investigate the feasibility of utilizing brain stiffness as a potential biomarker for behavioral variant frontotemporal dementia (bvFTD) patients. Magnetic resonance elastography (MRE) is a noninvasive technique for evaluating the mechanical properties of brain tissue in vivo. MRE has demonstrated decreased brain stiffness in patients with Alzheimer's disease.Materials and MethodsWe examined five male subjects with bvFTD and nine cognitively normal age‐matched male controls (NC) with brain 3T MRE. Stiffness was calculated in nine regions of interest (ROIs): whole brain (entire cerebrum excluding cerebellum), frontal lobes, occipital lobes, parietal lobes, temporal lobes, deep gray matter / white matter (GM/WM; insula, deep gray nuclei and white matter tracts), cerebellum, sensorimotor cortex (pre‐ and postcentral gyri), and a composite region labeled FT (frontal and temporal lobes excluding the pre‐ and postcentral gyri).ResultsSignificantly lower stiffness values were observed in the whole brain (P = 0.007), frontal lobe (P = 0.001), and temporal lobes (P = 0.005) of bvFTD patients compared to NC. No significant stiffness differences were observed in any other ROIs of bvFTD patients compared to NC (P > 0.05). These results demonstrate that statistically significant brain softening occurs in the frontal and temporal lobes of bvFTD patients, which corresponds to the expected pathophysiology of bvFTD.ConclusionFuture studies evaluating the feasibility of brain MRE for early disease detection and monitoring disease progression could shed new insights into understanding the mechanisms involved in bvFTD. J. Magn. Reson. Imaging 2016;43:474–478.

Object Investigators conducting the International Study of Unruptured Intracranial Aneurysms, sponsored by the National Institutes of Health, sought to evaluate predictors of future hemorrhage in patients who had unruptured mirror aneurysms. These paired aneurysms in bilateral arterial positions mirror each other; their natural history is unknown. Methods Centers in the US, Canada, and Europe enrolled patients for prospective assessment of unruptured intracranial aneurysms. Central radiological review confirmed the presence or absence of mirror aneurysms in patients without a history of prior subarachnoid hemorrhage (SAH) (Group 1). Outcome at 1 and 5 years and aneurysm characteristics are compared. Results Of 3120 patients with aneurysms treated in 61 centers, 376 (12%) had mirror aneurysms, which are more common in women than men (82% [n = 308] vs 73% [n = 1992], respectively; p <0.001) and in patients with a family history of aneurysm or SAH (p <0.001). Compared with patients with nonmirror saccular aneurysms, a greater percentage of patients with mirror aneurysms had larger (>10 mm) aneurysms (mean maximum diameter 11.7 vs 10.4 mm, respectively; p <0.001). The most common distribution for mirror aneurysms was the middle cerebral artery (34% [126 patients]) followed by noncavernous internal carotid artery (32% [121]), posterior communicating artery (16% [60]), cavernous internal carotid artery (13% [48]), anterior cerebral artery/anterior communicating artery (3% [13]), and vertebrobasilar circulation (2% [8]). When these patients were compared with patients without mirror aneurysms, no statistically significant differences were found in age (mean age 54 years in both groups), blood pressure, smoking history, or cardiac disease. Aneurysm rupture rates were similar (3.0% for patients with mirror aneurysms vs 2.8% for those without). Conclusions Overall, patients with mirror aneurysms were more likely to be women, to report a family history of aneurysmal SAH, and to have larger aneurysms. The presence of a mirror aneurysm was not an independent predictor of future SAHs.

Objective. To highlight the clinical profiles and angiographic findings of two patients with recurrent thunderclap headache (TCH) without subarachnoid hemorrhage (SAH) and to present modified diagnostic criteria for this unusual syndrome. Background. TCH may be a benign recurrent headache disorder or it may represent a serious underlying process such as SAH or venous sinus thrombosis. The pathophysiology of this disorder in the absence of underlying pathology is not well understood and its potential angiographic features are not well appreciated. Methods. Two case descriptions with illustrative angiography. Results. Both cases demonstrated the potential for reversible intracranial vasospasm without intracranial aneurysm or SAH and a benign clinical outcome. Conclusions. Primary TCH has a distinctive clinical and angiographic profile and must be distinguished from central nervous system vasculitis and SAH.