Invasive freshwater snails form novel microbial relationships

Resident microbes (microbiota) can shape host organismal function and adaptation in the face of environmental change. Invasion of new habitats exposes hosts to novel selection pressures, but little is known about the impact on microbiota and the host-microbiome relationship (e.g., how rapidly new microbial associations are formed, whether microbes influence invasion success). We used high-throughput 16S rRNA sequencing of New Zealand (native) and European (invasive) populations of the freshwater snail Potamopyrgus antipodarum and found that while invaders do carry over some core microbial taxa from New Zealand, their microbial community is largely distinct. This finding highlights that invasions can result in the formation of novel host-microbiome relationships. We further show that the native microbiome is composed of fewer core microbes than the microbiome of invasive snails, suggesting that the microbiota is streamlined to a narrower set of core members. Furthermore, native snails exhibit relatively low alpha diversity but high inter-individual variation, whereas invasive snails have higher alpha diversity but are relatively similar to each other. Together, our findings demonstrate that microbiota comparisons across native and invasive populations can reveal the impact of a long coevolutionary history and specialization of microbes in the native host range, as well as new associations occurring after invasion. We lay essential groundwork for understanding how microbial relationships affect invasion success and how microbes may be utilized in the control of invasive hosts.

TP1-11 MS-STAT2: a phase 3 trial of high dose simvastatin in secondary progressive multiple sclerosis

Objectives

Disease modifying treatment for secondary progressive multiple sclerosis (SPMS) represents a major unmet need. We outline here the rationale for the MS-STAT2 trial – a phase 3 study of simvastatin in decreasing clinical progression in SPMS. MS-STAT2 will be a landmark study not only for patients with SPMS, but also for the area of drug repurposing and academically led clinical trials as a whole.

Design

Multicentre, double blind, parallel group randomised placebo-controlled trial. It follows the positive outcome from the phase 2 MS-STAT1 trial, which demonstrated a 43% reduction in the annualised rate of brain atrophy compared to placebo.1

Subjects

1180 patients with SPMS with an expanded disability status scale (EDSS) score of 4.0–6.5. Patients need to show evidence of disease progression over the preceding 2 years.

Methods

Subject will be recruited at 28 sites across the UK, and randomised to simvastatin 80 mg or matched placebo and assessed every 6 months over the 3 year trial.

Results

The primary outcome measure is time to 6 month confirmed disability progression, based on change in Expanded Disability Status Scale (EDSS) scores compared to baseline. Secondary outcomes include assessments of cognition, walking, upper limb function and vision. Sub-studies will include advanced imaging outcomes, ocular coherence tomography and fluid biomarkers.

Conclusions

MS-STAT2 is set to be a pivotal trial for SPMS. Recruitment has now commenced and further sites are welcome.

Reference

Chataway J, et al. MS-STAT. Lancet2014;383:2213–21.

A Type 1 Diabetes Genetic Risk Score Predicts Progression of Islet Autoimmunity and Development of Type 1 Diabetes in Individuals at Risk

OBJECTIVE

We tested the ability of a type 1 diabetes (T1D) genetic risk score (GRS) to predict progression of islet autoimmunity and T1D in at-risk individuals.

RESEARCH DESIGN AND METHODS

We studied the 1,244 TrialNet Pathway to Prevention study participants (T1D patients' relatives without diabetes and with one or more positive autoantibodies) who were genotyped with Illumina ImmunoChip (median [range] age at initial autoantibody determination 11.1 years [1.2-51.8], 48% male, 80.5% non-Hispanic white, median follow-up 5.4 years). Of 291 participants with a single positive autoantibody at screening, 157 converted to multiple autoantibody positivity and 55 developed diabetes. Of 953 participants with multiple positive autoantibodies at screening, 419 developed diabetes. We calculated the T1D GRS from 30 T1D-associated single nucleotide polymorphisms. We used multivariable Cox regression models, time-dependent receiver operating characteristic curves, and area under the curve (AUC) measures to evaluate prognostic utility of T1D GRS, age, sex, Diabetes Prevention Trial-Type 1 (DPT-1) Risk Score, positive autoantibody number or type, HLA DR3/DR4-DQ8 status, and race/ethnicity. We used recursive partitioning analyses to identify cut points in continuous variables.

RESULTS

Higher T1D GRS significantly increased the rate of progression to T1D adjusting for DPT-1 Risk Score, age, number of positive autoantibodies, sex, and ethnicity (hazard ratio [HR] 1.29 for a 0.05 increase, 95% CI 1.06-1.6; P = 0.011). Progression to T1D was best predicted by a combined model with GRS, number of positive autoantibodies, DPT-1 Risk Score, and age (7-year time-integrated AUC = 0.79, 5-year AUC = 0.73). Higher GRS was significantly associated with increased progression rate from single to multiple positive autoantibodies after adjusting for age, autoantibody type, ethnicity, and sex (HR 2.27 for GRS >0.295, 95% CI 1.47-3.51; P = 0.0002).

CONCLUSIONS

The T1D GRS independently predicts progression to T1D and improves prediction along T1D stages in autoantibody-positive relatives.

Reversal of apixaban anticoagulation by four-factor prothrombin complex concentrates in healthy subjects: a randomized three-period crossover study

Essentials Prothrombin complex concentrates (PCCs) may reverse the effect of factor Xa (FXa) inhibitors. We conducted an open-label, randomized, placebo-controlled, three-period crossover study in 15 subjects. Both PCCs rapidly reversed apixaban-mediated decreases in mean endogenous thrombin potential. Four-factor PCC administration had no effect on apixaban pharmacokinetics or anti-FXa activity.

SUMMARY

Background Currently, there is no approved reversal agent for direct activated factor Xa (FXa) inhibitors; however, several agents are under investigation, including prothrombin complex concentrates (PCCs). Objective This open-label, randomized, placebo-controlled, three-period crossover study assessed the effect of two four-factor PCCs on apixaban pharmacodynamics and pharmacokinetics in 15 healthy subjects. Methods Subjects received apixaban 10 mg twice daily for 3 days. On day 4, 3 h after apixaban, subjects received a 30-min infusion of 50 IU kg-1 Cofact, Beriplex P/N (Beriplex), or saline. Change in endogenous thrombin potential (ETP), measured with a thrombin generation assay (TGA), was the primary endpoint. Secondary endpoints included changes in other TGA parameters, prothrombin time (PT), International Normalized Ratio (INR), activated partial thromboplastin time, anti-FXa activity, apixaban pharmacokinetics, and safety. Results Apixaban-related changes in ETP and several other pharmacodynamic measures occurred following apixaban administration. Both PCCs reversed apixaban's effect on ETP; the differences in adjusted mean change from pre-PCC baseline to end of infusion were 425 nm min (95% confidence interval [CI] 219.8-630.7 nm min; P < 0.001) for Cofact, and 91 nm min (95% CI - 31.3 to 212.4 nm min; P > 0.05) for Beriplex. Both PCCs returned ETP to pre-apixaban baseline levels 4 h after PCC infusion, versus 45 h for placebo. For both PCCs, mean ETP peaked 21 h after PCC initiation, and then slowly decreased over the following 48 h. Both PCCs reversed apixaban's effect on TGA peak height, PT, and INR. Apixaban pharmacokinetic and anti-FXa profiles were consistent across treatments. Conclusions Cofact and Beriplex reversed apixaban's steady-state effects on several coagulation assessments.

Population Pharmacokinetics, Pharmacodynamics, and Exploratory Exposure-Response Analyses of Apixaban in Subjects Treated for Venous Thromboembolism

Apixaban is approved for treatment of venous thromboembolism (VTE) and prevention of recurrence. Population pharmacokinetics, pharmacokinetics-pharmacodynamics (anti-FXa activity), and exposure-response (binary bleeding and thromboembolic endpoints) of apixaban in VTE treatment subjects were characterized using data from phase I-III studies. Apixaban pharmacokinetics were adequately characterized by a two-compartment model with first-order absorption and elimination. Age, sex, and Asian race had less than 25% impact on exposure, while subjects with severe renal impairment were predicted to have 56% higher exposure than the reference subject (60-year-old non-Asian male weighing 85 kg with creatinine clearance of 100 mL/min). The relationship between apixaban concentration and anti-FXa activity was described by a linear model with a slope estimate of 0.0159 IU/ng. The number of subjects with either a bleeding or thromboembolic event was small, and no statistically significant relationship between apixaban exposure and clinical endpoints could be discerned with a logistic regression analysis.

Tulbaghia violacea Harv. plant extract affects cell wall synthesis in Aspergillus flavus

AIMS

This study investigates the effect that aqueous extracts of Tulbaghia violacea Harv. harbouring plant saponins, phenolics and tannins have on Aspergillus flavus β-(1,3) glucan and chitin synthesis.

METHODS AND RESULTS

Aspergillus flavus was treated with various subinhibitory concentrations of an aqueous T. violacea plant extract and the β-(1,3) glucan and chitin content was determined together with glucan synthase and chitin synthase production respectively.

CONCLUSIONS

The aqueous extract caused a significant decline (P < 0·05) in β-glucan production in A. flavus in a dose-dependent manner when compared to the untreated sample. Further investigations showed a decrease in β-glucan synthase production as the concentration of the plant extract was increased. A significant reduction in total chitin content corresponding to a decrease in chitin synthase production in the presence of the plant extract was also found.

SIGNIFICANCE AND IMPACT OF THE STUDY

The broad spectrum activity and the efficacy of aqueous T. violacea plant extract on both β-glucan and chitin synthesis may limit the potential of the fungus developing resistance towards it and therefore the extract is an ideal candidate for use as a potential antifungal agent.

The accuracy of interpretation of emergency abdominal CT in adult patients who present with non-traumatic abdominal pain: results of a UK national audit

AIM

To evaluate major/minor discrepancy rates for provisional (initial) and addendum (supplementary senior review) emergency computed tomography (CT) reports in patients presenting with non-traumatic abdominal pain.

MATERIALS AND METHODS

Ethical approval for this type of study is not required in the UK. All radiology departments with an approved lead for audit registered with the Royal College of Radiologists were invited to participate in this retrospective audit. The first 50 consecutive patients (25 surgical, 25 non-surgical) who underwent emergency abdominal CT for non-traumatic abdominal pain in 2013 were included. Statistical analyses were performed to identify organisational and report/patient-related variables that might be associated with major discrepancy.

RESULTS

One hundred and nine (58%) of 188 departments supplied data to the study with a total of 4,931 patients (2,568 surgical, 2,363 non-surgical). The audit standard for provisional report major discrepancy was achieved for registrars (target <10%, achieved 4.6%), for on-site consultants (target <5%, achieved 3.1%) and consultant addendum (target <5%, achieved 2.9%). Off-site reporters failed to meet the standard target (<5%, achieved 8.7% overall and 12.7% in surgical patients). The standard for patients coming to harm was not met in the surgical group (target <1%, achieved 1.5%) and was narrowly missed overall (target <1%, achieved 1%).

CONCLUSION

This study should be used to provide impetus to improve aspects of out-of-hours CT reporting. Clear benefits of CT interpretation/review by on-site and more senior (consultant) radiologists have been demonstrated.

Model-based exposure-response analysis of apixaban to quantify bleeding risk in special populations of subjects undergoing orthopedic surgery

Population pharmacokinetic (PK) and exposure-response analyses of apixaban were performed using data from phase I-III studies to predict bleeding risks for patients receiving apixaban 2.5 mg b.i.d. after total knee or hip replacement (TKR, THR) surgery (N = 5,510). Renal function, age, gender, and body weight impacted apixaban exposure. Bleeding risk increased as a function of exposure. Predicted bleeding frequencies for TKR and THR populations at risk for high apixaban exposure (female, age > 75 years, calculated creatinine clearance (cCrCL) < 30 ml/min, body weight < 50 kg) (6.85 and 10.3%, respectively) were comparable to the reference population (male/female, age 65-75 years, cCrCL ≥ 80 ml/min, body weight 65-85 kg) (6.18 and 9.32%, respectively). A 100% increase in apixaban exposure is expected to raise bleeding frequencies to 7.25% (TKR) and 10.9% (THR), whereas a 200% increase would raise them to 8.49 and 12.7%. Coexistence of combined patient risk factors or doubling of exposure is not likely to result in a substantial, clinically relevant increase in bleeding risk with 2.5 mg b.i.d. apixaban.

Staging cancer of the uterus: a national audit of MRI accuracy

AIM

To report the results of a nationwide audit of the accuracy of magnetic resonance imaging (MRI) staging in uterine body cancer when staging myometrial invasion, cervical extension, and lymph node spread.

MATERIALS AND METHODS

All UK radiology departments were invited to participate using a web-based tool for submitting anonymized data for a 12 month period. MRI staging was compared with histopathological staging using target accuracies of 85, 86, and 70% respectively.

RESULTS

Of the departments performing MRI staging of endometrial cancer, 37/87 departments contributed. Targets for MRI staging were achieved for two of the three standards nationally with diagnostic accuracy for depth of myometrial invasion, 82%; for cervical extension, 90%; and for pelvic nodal involvement, 94%; the latter two being well above the targets. However, only 13/37 (35%) of individual centres met the target for assessing depth of myometrial invasion, 31/36 (86%) for cervical extension and 31/34 (91%) for pelvic nodal involvement. Statistical analysis demonstrated no significant difference for the use of intravenous contrast medium, but did show some evidence of increasing accuracy in assessment of depth of myometrial invasion with increasing caseload.

CONCLUSION

Overall performance in the UK was good, with only the target for assessment of depth of myometrial invasion not being met. Inter-departmental variation was seen. One factor that may improve performance in assessment of myometrial invasion is a higher caseload. No other clear factor to improve performance were identified.

Memory complaints and increased rates of brain atrophy: risk factors for mild cognitive impairment and Alzheimer's disease

AIM

To determine rates of cerebral atrophy in individuals with symptoms of memory loss but no objective cognitive impairment (SNCI) and their association with future cognitive decline.

METHODS

Thirty-two SNCI subjects, 16 with mild cognitive impairment (MCI) and 27 control subjects had clinical assessment and magnetic resonance imaging at baseline and 1 year later. Rates of whole brain atrophy (WBA), hippocampal atrophy (HA) and ventricular enlargement (VE) were measured. Our outcome was clinical diagnosis at 2 years after entry into the study.

RESULTS

The MCI group had greater rates of WBA, HA and VE than both controls and SNCI subjects. As a group SNCI subjects did not have significantly greater rates of atrophy than the controls. However, SNCI subjects who progressed to MCI or dementia had increased rates of atrophy compared with those who remained stable.

DISCUSSION

Individuals with memory complaints but no objective memory deficits, who progress to MCI or dementia, have increased rates of cerebral atrophy.

Onset and progression of pathologic atrophy in Huntington disease: a longitudinal MR imaging study

BACKGROUND AND PURPOSE

Longitudinal MR imaging measures provide an opportunity to track progression in HD before the emergence of clinical symptoms. This may prove useful in assessing disease-modifying treatments. We investigated how caudate and global volumes change as HD progresses from premanifest to early disease.

MATERIALS AND METHODS

Forty HD gene-positive individuals and 19 controls underwent serial volumetric MR imaging (baseline, 12 and 27 months; 2 or 3 scans per person). At baseline, 3 patients with HD were premanifest but developed overt motor features during the study, and 37 had early HD. All had dates of motor onset recorded. Caudates, lateral ventricles, and TIVs were measured using semiautomated procedures. Linear mixed models were used to investigate differences between HD and controls in relation to motor onset, controlling for TIV, sex, and age.

RESULTS

Extrapolating backwards in time, we found that differences in caudate and ventricular volumes between patients with HD and controls were evident 14 and 5 years, respectively, before motor onset (P < .05). At onset, caudate volume was 2.58 mL smaller than that in controls (P < .0001); ventricular volume was 9.27 mL larger (P < .0001). HD caudate atrophy rates were linear, showed low variability between subjects, and were approximately 10-fold higher than those in controls (P < .001). HD ventricular enlargement rates were variable between subjects, were approximately 4-fold higher than those in controls at onset (P < .001), and accelerated with disease duration (P = .02).

CONCLUSIONS

We provide evidence of acceleration of global atrophy in HD with disproportionate caudate involvement. Both caudate and global measures may be of use as early markers of HD pathology.

Acceleration of cortical thinning in familial Alzheimer's disease

BACKGROUND

MRI in presymptomatic autosomal dominant Alzheimer's disease mutation carriers (MC) provides an opportunity to detect changes that pre-date symptoms or clinical diagnosis. We used automated cortical thickness (CTh) measurement to compare the grey matter of such a group with cognitively normal controls.

METHODS

9 presymptomatic mutation carriers (4 PSEN1, 5 APP) and 25 healthy, age and sex-matched controls underwent longitudinal volumetric MRI brain imaging. CTh measurement was performed across the whole brain using a validated, automated technique. Four regions of interest (ROI) (entorhinal cortex (ERC), parahippocampal gyrus (PHG), posterior cingulate cortex and precuneus) and two control regions (paracentral and pericalcarine) were selected on the basis of imaging data in existing Alzheimer's disease (AD) literature. Linear mixed models were used to describe normal ageing in controls and the extent to which mean CTh in cases differed from controls according to time since clinical diagnosis, adjusting for normal ageing.

RESULTS

An accelerating decline in CTh was observed across all ROI in the MC group. No such decline was demonstrated in the control regions for the MC group. Relative to controls, and adjusting for normal ageing, there was evidence (p=0.05, one-sided test) of lower CTh in the posterior cingulate up to 1.8 years prior to diagnosis and in the precuneus up to 4.1 years prior to diagnosis in the MC group.

DISCUSSION

Automated CTh analysis is a relatively practical, rapid and effective technique for assessing subtle structural change in AD. There is evidence that cortical thickness is reduced in mutation carriers a number of years prior to clinical diagnosis.

The synthesis and anticancer activity of selected diketopiperazines

Six selected diketopiperazines, cyclo(Gly-Val), cyclo(Gly-D-Val), cyclo(Gly-Leu), cyclo(Gly-Ile), cyclo(Phe-Cys) and cyclo(Tyr-Cys), were synthesized via various synthetic routes. Their potential to inhibit cancer cell growth in HT-29, HeLa and MCF-7 cells was determined. Cyclo(Tyr-Cys) caused the greatest inhibition in cervical carcinoma cells with near equivalent activity against HT-29 and MCF-7 cells. The other cyclic dipeptides tested were effective in the inhibition of colon, cervical and breast carcinoma cells, respectively, but the percentage inhibition was lower than for cyclo(Tyr-Cys).

Combined coronary artery bypass grafting and phaeochromocytoma excision

We report two patients who had successful combined coronary artery bypass grafting and excision of phaeochromocytoma. These cases represent the first reports of combined coronary artery bypass grafting and laparoscopic adrenalectomy for phaeochromocytoma and of combined coronary artery bypass grafting and excision of extra-adrenal phaeochromocytoma. With careful peri- and intra-operative management, especially in regard to haemostasis, combined operations for coronary artery disease and phaeochromocytoma are both feasible and safe.

Magnetization transfer ratio in Alzheimer disease: comparison with volumetric measurements

BACKGROUND AND PURPOSE

Alzheimer disease (AD) is accompanied by macroscopic atrophy on volumetric MR imaging. A few studies have also demonstrated reduction in magnetization transfer ratio (MTR), suggesting microstructural changes in remaining brain tissue. This study assessed the value of measuring MTR in addition to volumetric MR in differentiating patients with AD from control subjects.

MATERIALS AND METHODS

Volumetric T1-weighted images and 3D MTR maps were obtained from 18 patients with AD and 18 age-matched control subjects. Whole-brain (WB) and total hippocampal (Hc) volumes were measured using semiautomated techniques and adjusted for total intracranial volume. Mean MTR was obtained for WB and in the Hc region. Histogram analysis was performed for WB MTR. Among patients, associations between volumetric and MTR parameters and the Mini-Mental State Examination (MMSE) were explored.

RESULTS

Patients with AD had significantly reduced WB volume (P<.0001) and mean WB MTR (P=.002) and Hc volume (P<.0001) and Hc mean MTR (P<.0001) compared with control subjects. Histogram analysis of WB MTR revealed significant reduction in the 25th percentile point in patients with AD (P=.03). Both WB volume and mean MTR were independently associated with case-control status after adjusting for the other using linear regression models. However, measuring Hc mean MTR added no statistically significant discriminatory value over and above Hc volume measurement alone. Of all MR imaging parameters, only WB volume was significantly correlated with MMSE (r=0.47, P=.048).

CONCLUSIONS

This study demonstrates the independent reduction of WB volume and mean MTR in AD. This suggests that the 2 parameters reflect complementary aspects of the AD pathologic lesion at macrostructural and microstructural levels.

Increased hippocampal atrophy rates in AD over 6 months using serial MR imaging

We measured hippocampi on baseline-, 6- and 12-month scans in a group of AD (n=36) and control subjects (n=20). We found that mean annualised atrophy rates using 6-month intervals were comparable at a group level to those generated from a 12-month interval. Higher variance was seen using shorter intervals, although this was only significant in the control group. This has implications where shorter inter-scan intervals may be advantageous, such as rapid diagnosis, and tracking of disease progression including in a clinical trial.

Improved reliability of hippocampal atrophy rate measurement in mild cognitive impairment using fluid registration

MRI-derived rates of hippocampal atrophy may serve as surrogate markers of disease progression in mild cognitive impairment (MCI). Manual delineation is the gold standard in hippocampal volumetry; however, this technique is time-consuming and subject to errors. We aimed to compare regional non-linear (fluid) registration measurement of hippocampal atrophy rates against manual delineation in MCI. Hippocampi of 18 subjects were manually outlined twice on MRI scan-pairs (interval+/-SD: 2.01+/-0.11 years), and volumes were subtracted to calculate change over time. Following global affine and local rigid registration, regional fluid registration was performed from which atrophy rates were derived from the Jacobian determinants over the hippocampal region. Atrophy rates as derived by fluid registration were computed using both forward (repeat onto baseline) and backward (baseline onto repeat) registration. Reliability for both methods and agreement between methods was assessed. Mean+/-SD hippocampal atrophy rates (%/year) derived by manual delineation were: left: 2.13+/-1.62; right: 2.36+/-1.78 and for regional fluid registration: forward: left: 2.39+/-1.68; right: 2.49+/-1.52 and backward: left: 2.21+/-1.51; right: 2.42+/-1.49. Mean hippocampal atrophy rates did not differ between both methods. Reliability for manual hippocampal volume measurements (cross-sectional) was high (intraclass correlation coefficient (ICC): baseline and follow-up, left and right, >0.99). However, the resulting ICC for manual measurements of hippocampal volume change (longitudinal) was considerably lower (left: 0.798; right: 0.850) compared with regional fluid registration (forward: left: 0.985; right: 0.988 and backward: left: 0.975; right: 0.989). We conclude that regional fluid registration is more reliable than manual delineation in assessing hippocampal atrophy rates, without sacrificing sensitivity to change. This method may be useful to quantify hippocampal volume change, given the reduction in operator time and improved precision.

Do symptoms of memory impairment correspond to cognitive impairment: a cross sectional study of a clinical cohort

BACKGROUND

Symptoms of memory loss are a common complaint within the general population and a frequent reason for seeking medical advice. However, the clinical relevance of these symptoms to future development of neurodegenerative disease is uncertain. The aim of this study is to characterise a cohort of individuals with symptoms of memory loss and varying memory impairment, who will be followed longitudinally with serial neuropsychology and neuroimaging to evaluate the clinical relevance of symptoms of memory loss.

METHOD

Fifty-eight subjects with symptoms of memory loss were recruited from the National Hospital for Neurology and Neurosurgery. All subjects underwent clinical assessment, APOE4 genotyping, neuroimaging and neuropsychological tests.

RESULTS

Those with mild cognitive impairment (MCI) had an increased prevalence of the APOE4 allele, impaired performance on tests of memory, measures of IQ and naming compared to controls. Baseline brain volumes were decreased and ventricular size increased. Those with symptoms of memory loss but no cognitive impairment (SNCI) performed significantly worse on tests of memory than the control group.

CONCLUSIONS

The MCI represent a group with multiple risk factors for progression to AD. The SNCI group may represent a heterogeneous group with some individuals in the early stages of AD whilst others' memory complaints are more likely linked to anxiety or personality traits.

Combining short interval MRI in Alzheimer's disease: Implications for therapeutic trials

Cerebral atrophy calculated from serial MRI is a marker of Alzheimer's disease (AD) progression, and a potential outcome measure for therapeutic trials. Reducing within-subject variability in cerebral atrophy rates by acquiring more than two serial scans could allow for shorter clinical trials requiring smaller patient numbers. Forty-six patients with AD and 23 controls each had up to 10 serial MR brain scans over two years. Whole brain atrophy was calculated for each subject from every scan-pair. 708 volumetric MRI scans were acquired: 2199 measures of atrophy were made for patients, and 1182 for controls. A linear mixed model was used to characterise between and within-individual variability. These results were used to investigate the power of combining multiple serial scans in treatment trials of varying lengths. In AD, the mean whole brain atrophy rate was 2.23%/year (95% CI: 1.90-2.56%/year). The linear mixed model was shown to fit the data well and led to a formula (0.99(2) + (0.82/t)2) for the variance of atrophy rates calculated from two scans "t" years apart. Utilising five optimally timed scans with repeat scans at each visit reduced the component of atrophy rate variance attributable to within-subject variability by approximately 56%, equating to a approximately 40% sample size reduction (228 vs 387 patients per arm to detect 20% reduction in atrophy rate) in a six-month placebo-controlled trial. This benefit in terms of sample size is relatively reduced in longer trials, although adding extra scanning visits may have benefits when patient drop-outs are accounted for. We conclude that sample sizes required in short interval therapeutic trials using cerebral atrophy as an outcome measure may be reduced if multiple serial MRI is performed.

Increased rate of whole-brain atrophy over 6 months in early Huntington disease

The authors measured the rate of whole-brain atrophy over 6 months in 13 patients with early Huntington disease (HD) and seven matched controls. Patients with early HD had significantly increased rates of whole-brain atrophy vs controls (mean [SD] HD, 1.10 [0.88]%/year; controls, 0.26 [0.54]%/year). The measurement of cerebral change over short time periods (e.g., 6 months) may be relevant for trials designed to assess effects on neurodegeneration or atrophy.

Automatic calculation of hippocampal atrophy rates using a hippocampal template and the boundary shift integral

We describe a method of automatically calculating hippocampal atrophy rates on T1-weighted MR images without manual delineation of hippocampi. This method was applied to a group of Alzheimer's disease (AD) (n=36) and control (n=19) subjects and compared with manual methods (manual segmentation of baseline and repeat-image hippocampi) and semi-automated methods (manual segmentation of baseline hippocampi only). In controls, mean (S.D.) atrophy rates for manual, semi-automated, and automated methods were 18.1 (53.5), 15.3 (50.2) and 11.3 (50.4) mm3 loss per year, respectively. In AD patients these rates were 174.6 (106.5) 159.4 (101.2) and 172.1 (123.1) mm3 loss per year, respectively. The automated method was a significant predictor of disease (p=0.001) and gave similar group discrimination compared with both semi-automated and manual methods. The automated hippocampal analysis in this small study took approximately 20 min per hippocampal pair on a 3.4 GHz Intel Xeon server, whereas manual delineation of each hippocampal pair took approximately 90 min of operator-intensive labour. This method may be useful diagnostically or in studies where analysis of many scans may be required.

MRS shows abnormalities before symptoms in familial Alzheimer disease

BACKGROUND

Pathologic change in Alzheimer disease (AD) begins some years before symptoms. MRS has the potential to detect metabolic abnormalities reflecting this early pathologic change. Presenilin 1 (PS1) and amyloid precursor protein (APP) mutation carriers have a nearly 100% risk of developing AD and may be studied prior to symptom onset.

METHODS

Short echo time proton MR spectra were acquired from a midline posterior cingulate voxel in presymptomatic carriers of PS1 or APP mutations ("presymptomatic mutation carriers" [PMCs]; n = 7) and age- and sex-matched control subjects (n = 6). Ratios of N-acetyl aspartate (NAA), myo-inositol (MI), and choline-containing compounds (Cho) to creatine (Cr) were measured and NAA/MI calculated. Regression analyses and t tests were performed after log transformation.

RESULTS

PMC and control subjects were matched for age and sex. PMC subjects were 1.7 to 21.6 years (mean 9.8 years) before expected symptom onset, predicted from family-specific mean age at onset. Age did not significantly affect metabolite ratios. Geometric mean ratios in control subjects were as follows: NAA/Cr = 1.75, MI/Cr = 0.59, and NAA/MI = 2.95. NAA/Cr and NAA/MI were significantly reduced in PMC relative to controls (NAA/Cr mean decrease 10% [95% CI 2 to 18%]; NAA/MI mean decrease 25% [95% CI 3 to 44%]). MI/Cr was increased in PMC, but the differences did not achieve significance (19% increase [95% CI 1% decrease to 41% increase]; p = 0.07)). In PMCs, reduction in NAA/MI (p = 0.001) and MI/Cr (p = 0.002) were related to proximity of expected age at onset.

CONCLUSIONS

Metabolic changes are detectable in presymptomatic mutation carriers years before expected onset of Alzheimer disease. Their magnitude is related to proximity of expected age at onset.