Synthetic MRI for Stroke: A Qualitative and Quantitative Pilot Study

PurposeSynthetic MR provides quantitative multiparametric data about tissue properties in a fast single-acquisition. We compared synthetic and conventional image quality and investigated synthetic relaxometry of acute and chronic ischemic lesions to support its interest in stroke imaging. MethodsFor this pilot study, we prospectively acquired synthetic and conventional brain MR of 43 consecutive adult patients with suspected stroke. We studied a total of 136 lesions, of which 46 DWI-positive with restricted ADC (DWI+/rADC), 90 white matter T2/FLAIR hyperintensities (WMH), and 430 normal brain regions (NBR). We assessed image quality for lesion definition according to a 3-level score by two readers of different experiences. We compared relaxometry of lesions and regions of interest.Results Synthetic images were superior to their paired conventional images for lesion definition except for sFLAIR (sT1 or sPSIR vs. cT1 and sT2 vs. cT2 for DWI+/rADC and WMH definition; p-values <.001) with substantial to almost perfect inter-rater reliability (κ ranging from 0.711 to 0.932, p-values <.001). We found significant differences in relaxometry between lesions and NBR and between acute and chronic lesions (T1, T2, and PD of DWI+/rADC or WMH vs. mirror NBR; p-values <.001; T1 and PD of DWI+/rADC vs. WMH; p-values of 0.034 and 0.008).Conclusion Synthetic MR may contribute to stroke imaging by fast acquiring consistent relaxometry data and accessible derived images of interest for the study of ischemic lesions.

Sphenoid sinusitis: a rare cause of ischaemic stroke

We present the case of a 61-year-old woman who presented to the accident and emergency department with an ischaemic stroke, on a background of receiving intravenous and oral antibiotics to treat chronic left sphenoid sinusitis. Initially presenting with right-sided weakness and aphasia, a diagnosis of acute ischaemic stroke was made. Antibiotics had been commenced 1 month prior to the ischaemic stroke. Imaging at that time showed changes in keeping with chronic sphenoid sinusitis along with a small dehiscence in the lateral wall of the left sphenoid sinus and thrombosis of the left superior ophthalmic vein. During that admission blood cultures grew Streptococcus constellatus, a member of the Streptococcus milleri group. We discuss the unusual aetiology of this stroke, the emerging evidence associating chronic rhinosinusitis with stroke and the complex multidisciplinary approach required for management in this case.

State of the Art Stroke Imaging: A Current Perspective

Acute stroke is a widespread, debilitating disease. Fortunately, it also has one of the most effective therapeutic options available in medicine, endovascular treatment. Imaging plays a major role in the diagnosis of stroke and aids in appropriate therapy selection. Given the rapid accumulation of evidence for patient subgroups and concurrent broadening of therapeutic options and indications, it is important to recognize the benefits of certain imaging technologies for specific situations. An effective imaging protocol should: 1) be fast, 2) easily implementable, 3) produce reliable results, 4) have few contraindications, and 5) be safe, all with the goal of providing the patient the best chance of achieving a favorable outcome. In the following, we provide a review of the currently available imaging technologies, their advantages and disadvantages, as well as an overview of the future of stroke imaging. Finally, we offer a perspective.

Glass Half Full: Preserved Anatomical Bypasses Predict Variance in Language Functions After Stroke

The severity of post-stroke aphasia is related to damage to white matter connections. However, neural signaling can route not only through direct connections, but also along multi-step network paths. When brain networks are damaged by stroke, paths can bypass around the damage to restore communication. The shortest network paths between regions could be the most efficient routes for mediating bypasses. We examined how shortest-path bypasses after left hemisphere strokes were related to language performance. Regions within and outside of the canonical language network could be important in aphasia recovery. Therefore, we innovated methods to measure the influence of bypasses in the whole brain. Distinguishing bypasses from all residual shortest paths is difficult without pre-stroke imaging. We identified bypasses by finding shortest paths in subjects with stroke that were longer than those observed in the average network of the most reliably observed connections in age-matched controls. We tested whether features of those bypasses predicted scores in four orthogonal dimensions of language performance derived from a factor analysis of a battery of language tasks. The features were the length of each bypass in steps, and how many bypasses overlapped on each individual direct connection. We related these bypass features to language factors using grid-search cross-validated Support Vector Regression, a technique that extracts robust relationships in high-dimensional data analysis. We discovered that the length of bypasses reliably predicted variance in lexical production (R2 = .576) and auditory comprehension scores (R2 = .164). Bypass overlaps reliably predicted variance in Lexical Production scores (R2 = .247). The predictive elongation features revealed that bypass efficiency along the dorsal stream and ventral stream were most related to Lexical Production and Auditory Comprehension, respectively. Among the predictive bypass overlaps, increased bypass routing through the right hemisphere putamen was negatively related to lexical production ability.