Human Brain Deuterium Metabolic Imaging at 7 T: Impact of Different [6,6'-2H2]Glucose Doses.

BACKGROUND: Deuterium metabolic imaging (DMI) is an innovative, noninvasive metabolic MR imaging method conducted after administration of 2H-labeled substrates. DMI after [6,6'-2H2]glucose consumption has been used to investigate brain metabolic processes, but the impact of different [6,6'-2H2]glucose doses on DMI brain data is not well known. PURPOSE: To investigate three different [6,6'-2H2]glucose doses for DMI in the human brain at 7 T. STUDY TYPE: Prospective. POPULATION: Six healthy participants (age: 28 ± 8 years, male/female: 3/3). FIELD STRENGTH/SEQUENCE: 7 T, 3D 2H free-induction-decay (FID)-magnetic resonance spectroscopic imaging (MRSI) sequence. ASSESSMENT: Three subjects received two different doses (0.25 g/kg, 0.50 g/kg or 0.75 g/kg body weight) of [6,6'-2H2]glucose on two occasions and underwent consecutive 2H-MRSI scans for 120 minutes. Blood was sampled every 10 minutes during the scan, to determine plasma glucose levels and plasma 2H-Glucose atom percent excess (APE) (part-1). Three subjects underwent the same protocol once after receiving 0.50 g/kg [6,6'-2H2]glucose (part-2). STATISTICAL TEST: Mean plasma 2H-Glucose APE and glucose plasma concentrations were compared using one-way ANOVA. Brain 2H-Glc and brain 2H-Glx (part-1) were analyzed with a two-level Linear Mixed Model. In part-2, a General Linear Model was used to compare brain metabolite signals. Statistical significance was set at P < 0.05. RESULTS: Between 60 and 100 minutes after ingesting [6,6'-2H2]glucose, plasma 2H-Glc APE did not differ between 0.50 g/kg and 0.75 g/kg doses (P = 0.961), but was significantly lower for 0.25 g/kg. Time and doses significantly affected brain 2H-Glucose levels (estimate ± standard error [SE]: 0.89 ± 0.01, 1.09 ± 0.01, and 1.27 ± 0.01, for 0.25 g/kg, 0.50 g/kg, and 0.75 g/kg, respectively) and brain 2H-Glutamate/Glutamine levels (estimate ± SE: 1.91 ± 0.03, 2.27 ± 0.03, and 2.46 ± 0.03, for 0.25 g/kg, 0.50 g/kg, and 0.75 g/kg, respectively). Plasma 2H-Glc APE, brain 2H-Glc, and brain 2H-Glx levels were comparable among subjects receiving 0.50 g/kg [6,6'-2H2]glucose. DATA CONCLUSION: Brain 2H-Glucose and brain 2H-Glutamate/Glutamine showed to be [6,6'-2H2]glucose dose dependent. A dose of 0.50 g/kg demonstrated comparable, and well-detectable, 2H-Glucose and 2H-Glutamate/Glutamine signals in the brain. EVIDENCE LEVEL: 1 TECHNICAL EFFICACY: Stage 2.

Association between cerebral perfusion and paediatric postoperative cerebellar mutism syndrome after posterior fossa surgery-a systematic review.

BACKGROUND: Paediatric postoperative cerebellar mutism syndrome (ppCMS) is a common complication following the resection of a cerebellar tumour in children. It is hypothesized that loss of integrity of the cerebellar output tracts results in a cerebello-cerebral "diaschisis" and reduced function of supratentorial areas of the brain. METHODS: We performed a systematic review of the literature according to the PRISMA guidelines, in order to evaluate the evidence for hypoperfusion or hypofunction in the cerebral hemispheres in patients with ppCMS. Articles were selected based on the predefined eligibility criteria and quality assessment. RESULTS: Five studies were included, consisting of three prospective cohort studies, one retrospective cohort study and one retrospective case control study. Arterial spin labelling (ASL) perfusion MRI, dynamic susceptibility contrast (DSC) perfusion MRI and single photon emission computed tomography (SPECT) were used to measure the cerebral and cerebellar tissue perfusion or metabolic activity. Reduced cerebral perfusion was predominantly demonstrated in the frontal lobe. CONCLUSIONS: This systematic review shows that, after posterior fossa tumour resection, cerebral perfusion is reduced in ppCMS patients compared to patients without ppCMS. Well-powered prospective studies, including preoperative imaging, are needed to ascertain the cause and role of hypoperfusion in the pathophysiology of the syndrome.

Integrated model reference adaptive control to coordinate active front steering and direct yaw moment control.

The paper proposes an integrated adaptive coordination technique for active front steering (AFS) and direct yaw moment control (DYC). The main contribution is to present an integrated multi-input multi-output (MIMO) adaptive control method to manage the variations of vehicle mass and tire-road friction coefficient as parameter uncertainties. The proposed integrated control strategy encompasses two: upper and lower control layers. At the upper control layer, there is a model reference adaptive controller responsible for generating additive steering angle and corrective yaw moment. The coordination between AFS and DYC is realized using a gain scheduling mechanism based on a stability index. At the lower control layer, the desired yaw moment is converted to the brake torque before being applied to the rear wheels. Three critical and important high-speed lane-change maneuvers are considered. The simulation results confirm that the proposed control structure can reduce the sideslip angle and lateral acceleration. Furthermore, the system tracking performance in terms of handling and stability in different maneuvers is improved.

The Cerebellar Cognitive Affective Syndrome-a Meta-analysis.

The cerebellar cognitive affective syndrome (CCAS) was first described by Schmahmann and Sherman in 1998. Despite their clear depiction of the syndrome, it is our experience that the CCAS has not yet found solid ground as a disease entity in routine clinical practice. This made us question the dimension of the CCAS in cerebellar patients. We performed a systematic review of the literature according to the PRISMA guidelines, in order to answer the question whether patients with acquired isolated cerebellar lesions perform significantly worse on neuropsychological testing compared to healthy controls. Studies were selected based on the predefined eligibility criteria and quality assessment. The systematic search resulted in ten studies, mainly observational cohorts consecutively including adult patients with isolated cerebellar lesions. Patients were compared to healthy controls, and neuropsychological investigation was done within one year of diagnosis. Meta-analysis of the twelve tests that were done in two or more studies showed that cerebellar patients perform significantly worse on Phonemic Fluency, Semantic Fluency, Stroop Test (naming, reading and interference), Block Design test and WMS-R visual memory. Cerebellar patients have significant and relevant deficits in the visuospatial, language and executive function domain. This meta-analysis therefore emphasizes the importance of the cerebellar cognitive affective syndrome as described by Schmahmann and Sherman.