Laurens J.L. De Cocker

High-Resolution Postcontrast Time-of-Flight MR Angiography of Intracranial Perforators at 7.0 Tesla

Background and Purpose Different studies already demonstrated the benefits of 7T for precontrast TOF-MRA in the visualization of intracranial small vessels. The aim of this study was to assess the performance of high-resolution 7T TOF-MRA after the administration of a gadolinium-based contrast agent in visualizing intracranial perforating arteries. Materials and Methods Ten consecutive patients (7 male; mean age, 50.4 ± 9.9 years) who received TOF-MRA at 7T after contrast administration were retrospectively included in this study. Intracranial perforating arteries, branching from the parent arteries of the circle of Willis, were identified on all TOF-MRA images. Provided a TOF-MRA before contrast administration was present, a direct comparison between pre- and postcontrast TOF-MRA was made. Results It was possible to visualize intracranial perforating arteries branching off from the entire circle of Willis, and their proximal branches. The posterior cerebral artery (P1 and proximal segment of P2) appeared to have the largest number of visible perforating branches (mean of 5.1 in each patient, with a range of 2–7). The basilar artery and middle cerebral artery (M1 and proximal segment M2) followed with a mean number of 5.0 and 3.5 visible perforating branches (range of 1–9 and 1–8, respectively). Venous contamination in the postcontrast scans sometimes made it difficult to discern the arterial or venous nature of a vessel. Conclusion High-resolution postcontrast TOF-MRA at 7T was able to visualize multiple intracranial perforators branching off from various parts of the circle of Willis and proximal intracranial arteries. Although confirmation in a larger study is needed, the administration of a contrast agent for high-resolution TOF-MRA at 7T seems to enable a better visualization of the distal segment of certain intracranial perforators.

In vivo visualization of the PICA perfusion territory with super-selective pseudo-continuous arterial spin labeling MRI

In this work a method is described to discern the perfusion territories in the cerebellum that are exclusively supplied by either or both vertebral arteries. In normal vascular anatomy the posterior inferior cerebellar artery (PICA) is supplied exclusively by its ipsilateral vertebral artery. The perfusion territories of the vertebral arteries were determined in 14 healthy subjects by means of a super-selective pseudo-continuous ASL sequence on a 3T MRI scanner. Data is presented to show the feasibility of determining the PICA perfusion territory. In 10 subjects it was possible to accurately determine both PICA perfusion territories. In two subjects it was possible to determine the perfusion territory of one PICA. Examples in which it was not possible to accurately determine the PICA territory are also given. Additionally, the high variability of the extent of the PICA territory is illustrated using a statistical map. The posterior surface of the cerebellum is entirely supplied by the PICA in six subjects. The most posterior part of the superior surface is supplied by the PICA in eight subjects, and the inferior half of the anterior surface in six subjects. The inferior part of the vermis is supplied by the PICA in all subjects. Two subjects were found with interhemispheric blood flow to both tonsils from one PICA without contribution from the contralateral PICA. With the method as presented, clinicians may in the future accurately classify cerebellar infarcts according to affected perfusion territories, which might be helpful in the decision whether a stenosis should be considered symptomatic.

Cerebellar infarct patterns: The SMART-Medea study

Objective Previous studies on cerebellar infarcts have been largely restricted to acute infarcts in patients with clinical symptoms, and cerebellar infarcts have been evaluated with the almost exclusive use of transversal MR images. We aimed to document the occurrence and 3D-imaging patterns of cerebellar infarcts presenting as an incidental finding on MRI. Methods We analysed the 1.5 Tesla MRI, including 3D T1-weighted datasets, of 636 patients (mean age 62 ± 9 years, 81% male) from the SMART-Medea study. Cerebellar infarct analyses included an assessment of size, cavitation and gliosis, of grey and white matter involvement, and of infarct topography. Results One or more cerebellar infarcts (mean 1.97; range 1–11) were detected in 70 out of 636 patients (11%), with a total amount of 138 infarcts identified, 135 of which showed evidence of cavitation. The average mean axial diameter was 7 mm (range 2–54 mm), and 131 infarcts (95%) were smaller than 20 mm. Hundred-thirty-four infarcts (97%) involved the cortex, of which 12 in combination with subcortical white matter. No infarcts were restricted to subcortical branches of white matter. Small cortical infarcts involved the apex of a deep (pattern 1) or shallow fissure (pattern 2), or occurred alongside one (pattern 3) or opposite sides (pattern 4) of a fissure. Most (87%) cerebellar infarcts were situated in the posterior lobe. Conclusions Small cerebellar infarcts proved to be much more common than larger infarcts, and preferentially involved the cortex. Small cortical infarcts predominantly involved the posterior lobes, showed sparing of subcortical white matter and occurred in characteristic topographic patterns.

Misinterpretation of ischaemic infarct location in relationship to the cerebrovascular territories

Purpose Cerebral perfusion territories are known to vary widely among individuals. This may lead to misinterpretation of the symptomatic artery in patients with ischaemic stroke to a wrong assumption of the underlying aetiology being thromboembolic or hypoperfusion. The aim of the present study was to investigate such potential misinterpretation with territorial arterial spin labelling (T-ASL) by correlating infarct location with imaging of the perfusion territory of the carotid arteries or basilar artery. Materials and methods 223 patients with subacute stroke underwent MRI including structural imaging scans to determine infarct location, time-of-flight MR angiography (MRA) to determine the morphology of the circle of Willis and T-ASL to identify the perfusion territories of the internal carotid arteries, and basilar artery. Infarct location and the perfusion territory of its feeding artery were classified with standard MRI and MRA according to a perfusion atlas, and were compared to the classification made according to T-ASL. Results A total of 149 infarctions were detected in 87 of 223 patients. 15 out of 149 (10%) infarcts were erroneously attributed to a single perfusion territory; these infarcts were partly located in the originally determined perfusion territory but proved to be localised in the border zone with the adjacent perfusion territory instead. 12 out of 149 (8%) infarcts were misclassified with standard assessments and were not located in the original perfusion territory. Conclusions T-ASL with territorial perfusion imaging may provide important additional information for classifying the symptomatic brain-feeding artery when compared to expert evaluation with MRI and MRA.

Cerebellar Cortical Infarct Cavities Correlation With Risk Factors and MRI Markers of Cerebrovascular Disease

Background and Purpose— Small cerebellar infarct cavities have been recently found on magnetic resonance imaging (MRI) to preferentially involve the cerebellar cortex, but epidemiological studies are lacking. We aimed to determine the prevalence and risk factor profiles of cerebellar cortical infarct cavities (⩽1.5 cm) as well as their association with MRI markers of cerebrovascular disease and functioning. Methods— We analyzed the 1.5 Tesla MRI of 636 patients (mean age, 62±9 years; 81% men) from the Second Manifestations of Arterial Disease-Memory, Depression and Aging (SMART-Medea) study. Logistic regression analyses were performed to estimate the associations of age, sex, vascular risk factors, MRI markers of cerebrovascular disease, and functioning with cerebellar cortical cavities, adjusted for age and sex. Results— Cerebellar cortical infarct cavities occurred on MRI in 10% of patients and were significantly associated with age, intima-media thickness (odds ratio [OR], 2.0; 95% confidence interval [CI], 1.1–3.7), high levels of homocysteinemia (OR, 1.8; 95% CI, 1.0–3.3), cortical infarcts (OR, 2.9; 95% CI, 1.6–5.4), gray matter lacunes of presumed vascular origin (OR, 3.0; 95% CI, 1.6–5.8), brain stem infarcts (OR, 5.1; 95% CI, 1.9–13.6), and decreased brain parenchymal fraction (OR, 0.84; 95% CI, 0.74–0.94), but not with white matter hyperintensities (OR, 1.2; 95% CI, 0.8–1.8) or white matter lacunes of presumed vascular origin (OR, 1.1; 95% CI, 0.5–2.5). They were also associated with worse physical functioning (OR 0.96; 95% CI, 0.94 to 0.99) but not with mental functioning. Conclusions— Cerebellar cortical infarct cavities are far more common than previously assumed based on symptomatic case series and are associated with markers of atherothromboembolic cerebrovascular disease.

Clinical vascular imaging in the brain at 7 T

ABSTRACT Stroke and related cerebrovascular diseases are a major cause of mortality and disability. Even at standard‐field‐strengths (1.5 T), MRI is by far the most sensitive imaging technique to detect acute brain infarctions and to characterize incidental cerebrovascular lesions, such as white matter hyperintensities, lacunes and microbleeds. Arterial time‐of‐flight (TOF) MR angiography (MRA) can depict luminal narrowing or occlusion of the major brain feeding arteries, and this without the need for contrast administration. Compared to 1.5 T MRA, the use of high‐field strength (3 T) and even more so ultra‐high‐field strengths (7 T), enables the visualization of the lumen of much smaller intracranial vessels, while adding a contrast agent to TOF MRA at 7 T may enable the visualization of even more distal arteries in addition to veins and venules. Moreover, with 3 T and 7 T, the arterial vessel walls beyond the circle of Willis become visible with high‐resolution vessel wall imaging. In addition, with 7 T MRI, the brain parenchyma can now be visualized on a submillimeter scale. As a result, high‐resolution imaging studies of the brain and its blood supply at 7 T have generated new concepts of different cerebrovascular diseases. In the current article, we will discuss emerging clinical applications and future directions of vascular imaging in the brain at 7 T MRI. HIGHLIGHTSClinically feasible stroke imaging protocols at 7 T have been developed.DWI still limits the use of 7 T MRI in acute stroke patients.Submillimeter cerebrovascular lesions have come within the detection limit of 7 T.7 T allows to study the healthy and diseased intracranial arterial vessel walls.Evaluation of cerebral aneurysms and AVMs may benefit from 7 T MRI.

MRI of Cerebellar Infarction

Background: MRI is the imaging modality of choice for diagnosing brain infarction. Because of few or atypical clinical symptoms and a relatively low sensitivity of CT scans, many cerebellar infarctions may be detected only with MRI. With adequate recognition of cerebellar infarction on MRI and prompt initiation or optimisation of preventive therapeutic measures, more dramatic strokes may be avoided in selected cases. Summary: We first briefly review the clinical presentation of cerebellar infarctions, followed by a short refresher on cerebellar anatomy and pathophysiological mechanisms of cerebellar infarcts. Then, we review the arterial cerebellar perfusion territories recently made visible with territorial arterial spin labeling (ASL), followed by a discussion and illustration of the MRI appearance of cerebellar infarcts in different stages. Similar to large cerebellar infarcts, recent studies investigating volumetric MRI datasets have now shown that small cerebellar infarcts occur in typical spatial patterns, knowledge of which may help in the diagnosis of even the smallest of cerebellar infarcts on MRI. Key Messages: MRI is the modality of choice for diagnosing cerebellar infarction. The posterior inferior cerebellar artery (PICA)-territories can be visualised with super-selective territorial ASL MRI. The PICA supplies at least the medial part of the posterior cerebellar surface. Anterior inferior cerebellar artery-infarcts can be mistaken for lateral PICA-infarcts. Small infarcts typically affect the cortex and often present as incidental cavities. Subacute cerebellar infarcts may be missed on imaging due to a phenomenon called “fogging.”

Multinodular and vacuolating neuronal tumor in an adolescent with Klinefelter syndrome

Dear Editor-in-Chief, With great interest, we read the article by R. Alsufayan et al. on the ‘Natural history of lesions with the MR imaging appearance of multinodular and vacuolating neuronal tumor’ [1–3]. Since February 2016, we have been following a patient with genetically confirmed Klinefelter syndrome (XXY) with a brain lesion. The patient, born in March 2000, was diagnosed with XXY syndrome in the beginning of 2016 due to small testicles. A brain MRI was made for endocrinological reasons and revealed a lesion in the left occipital lobe (Fig. 1); after which, the patient was referred to us by the endocrinologist out of concerns for an intracranial germ cell tumor, which is more common in patients with XXY. Because of the MR imaging features of the lesion, however, we made the tentative diagnosis of a dysembryoplastic neuroepithelial tumor (DNET) [4]. Nevertheless, the lesion did not fulfil the typical imaging features of a DNET. In addition, the patient did not have epilepsy nor other neurological symptoms or signs. Upon reading the article in Neuroradiology on multinodular and vacuolating neuronal tumor (MVNT) and its differential diagnosis [1], the presumptive diagnosis of the tumor in our patient was changed to MVNT. As is characteristic for this recently recognised tumor, the lesion shows clusters of discrete ‘bubbly’ T2 FLAIR hyperintensities in the superficial subcortical white matter, without cystic changes nor enhancement and with an otherwise normal-appearing cortex. The tumor with the typical MR imaging features of MVNT in our patient with XXY has remained unchanged between the original MRI in February 2016 and the last MRI follow-up in August 2017.