Progressive Neurochemical Abnormalities in Cognitive and Motor Subgroups of Amyotrophic Lateral Sclerosis: A Prospective Multicenter Study

OBJECTIVE

To evaluate progressive cerebral degeneration in amyotrophic lateral sclerosis (ALS) by assessing alterations in N-acetylaspartate (NAA) ratios in the motor and prefrontal cortex within clinical subgroups of ALS.

METHODS

Seventy-six patients with ALS and 59 healthy controls were enrolled in a prospective, longitudinal, multicenter study in the Canadian ALS Neuroimaging Consortium. Participants underwent serial clinical evaluations and magnetic resonance spectroscopy at baseline and 4 and 8 months using a harmonized protocol across 5 centers. NAA ratios were quantified in the motor cortex and prefrontal cortex. Patients were stratified into subgroups based on disease progression rate, upper motor neuron (UMN) signs, and cognitive status. Linear mixed models were used for baseline and longitudinal comparisons of NAA metabolite ratios.

RESULTS

Patients with ALS had reduced NAA ratios in the motor cortex at baseline (p < 0.001). Ratios were lower in those with more rapid disease progression and greater UMN signs (p < 0.05). A longitudinal decline in NAA ratios was observed in the motor cortex in the rapidly progressing (p < 0.01) and high UMN burden (p < 0.01) cohorts. The severity of UMN signs did not change significantly over time. NAA ratios were reduced in the prefrontal cortex only in cognitively impaired patients (p < 0.05); prefrontal cortex metabolites did not change over time.

CONCLUSIONS

Progressive degeneration of the motor cortex in ALS is associated with more aggressive clinical presentations. These findings provide biological evidence of variable spatial and temporal cerebral degeneration linked to the disease heterogeneity of ALS. The use of standardized imaging protocols may have a role in clinical trials for patient selection or subgrouping.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that MRS NAA metabolite ratios of the motor cortex are associated with more rapid disease progression and greater UMN signs in patients with ALS.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov Identifier: NCT02405182.

Identifying the translational complexity of magnetic resonance spectroscopy in neonates and infants

Little attention has been paid to relating MRS outputs of vendor-supplied platforms to those from research software. This comparison is crucial to advance MRS as a clinical prognostic tool for disease or injury, recovery, and outcome. The work presented here investigates the agreement between metabolic ratios reported from vendor-provided and LCModel fitting algorithms using MRS data obtained on Siemens 3 T TIM Trio and 3 T Skyra MRI scanners in a total of 55 premature infants and term neonates with hypoxic ischemic encephalopathy (HIE). We compared peak area ratios in single voxels placed in basal ganglia (BG) and frontal white matter (WM) using standard PRESS (TE = 30 ms and 270 ms) and STEAM (TE = 20 ms) MRS sequences at multiple times after birth from 5 to 60 days. A total of 74 scans met quality standards for inclusion, reflecting a spectrum of neonatal disease and several months of early infant development. For the long TE PRESS sequence, N-acetylaspartate (NAA) and Choline (Cho) ratios to Creatine (Cr) correlated strongly between LCModel and vendor-supplied software in the BG. For shorter TEs, the ratios of NAA/Cr and Cho/Cr were more closely related using STEAM at TE = 20 ms in BG and WM, which was significantly better than using PRESS at TE = 30 ms in the BG of HIE infants. At short TEs, however, it is still unclear which MRS sequence, STEAM or PRESS, is superior and thus more work is required in this regard for translating research-generated MRS ratios to clinical diagnosis and prognostication, and unlocking the potential of MRS for in vivo metabolomics. MRS at both long and short TEs is desirable for standard metabolites such as NAA, Cho and Cr, along with important lower concentration metabolites such as myo-inositol and glutathione.

Magnetic resonance spectroscopy and brain volumetry in mild cognitive impairment. A prospective study

OBJECTIVE

To assess the accuracy of magnetic resonance spectroscopy (1H-MRS) and brain volumetry in mild cognitive impairment (MCI) to predict conversion to probable Alzheimer's disease (AD).

METHODS

Forty-eight patients fulfilling the criteria of amnestic MCI who underwent a conventional magnetic resonance imaging (MRI) followed by MRS, and T1-3D on 1.5 Tesla MR unit. At baseline the patients underwent neuropsychological examination. 1H-MRS of the brain was carried out by exploring the left medial occipital lobe and ventral posterior cingulated cortex (vPCC) using the LCModel software. A high resolution T1-3D sequence was acquired to carry out the volumetric measurement. A cortical and subcortical parcellation strategy was used to obtain the volumes of each area within the brain. The patients were followed up to detect conversion to probable AD.

RESULTS

After a 3-year follow-up, 15 (31.2%) patients converted to AD. The myo-inositol in the occipital cortex and glutamate+glutamine (Glx) in the posterior cingulate cortex predicted conversion to probable AD at 46.1% sensitivity and 90.6% specificity. The positive predictive value was 66.7%, and the negative predictive value was 80.6%, with an overall cross-validated classification accuracy of 77.8%. The volume of the third ventricle, the total white matter and entorhinal cortex predict conversion to probable AD at 46.7% sensitivity and 90.9% specificity. The positive predictive value was 70%, and the negative predictive value was 78.9%, with an overall cross-validated classification accuracy of 77.1%. Combining volumetric measures in addition to the MRS measures the prediction to probable AD has a 38.5% sensitivity and 87.5% specificity, with a positive predictive value of 55.6%, a negative predictive value of 77.8% and an overall accuracy of 73.3%.

CONCLUSION

Either MRS or brain volumetric measures are markers separately of cognitive decline and may serve as a noninvasive tool to monitor cognitive changes and progression to dementia in patients with amnestic MCI, but the results do not support the routine use in the clinical settings.

Cortical and subcortical glutathione levels in adults with autism spectrum disorder

Increased oxidative stress has been postulated to contribute to the pathogenesis of autism spectrum disorder (ASD). However, reports of alterations in oxidation markers including glutathione (GSH), the major endogenous antioxidant, are indirect, coming from blood plasma level measurements and postmortem studies. Therefore we used in-vivo 3 Tesla proton magnetic resonance spectroscopy ([1H]MRS) to directly measure GSH concentrations in the basal ganglia (BG) and the dorsomedial prefrontal cortex of 21 normally intelligent adult males with ASD and 29 controls who did not differ in age or IQ. There was no difference in brain GSH between patients and controls in either brain area; neither did GSH levels correlate with measures of clinical severity in patients. Thus [1H]MRS measures of cortical and subcortical GSH are not a biomarker for ASD in intellectually able adult men.

Early Alzheimer's disease neuropathology detected by proton MR spectroscopy

Proton magnetic resonance spectroscopy ((1)H-MRS) is sensitive to early neurodegenerative processes associated with Alzheimer's disease (AD). Although (1)H-MRS metabolite ratios of N-acetyl aspartate (NAA)/creatine (Cr), NAA/myoinositol (mI), and mI/Cr measured in the posterior cingulate gyrus reveal evidence of disease progression in AD, pathologic underpinnings of the (1)H-MRS metabolite changes in AD are unknown. Pathologically diagnosed human cases ranging from no likelihood to high likelihood AD (n = 41, 16 females and 25 males) who underwent antemortem (1)H-MRS of the posterior cingulate gyrus at 3 tesla were included in this study. Immunohistochemical evaluation was performed on the posterior cingulate gyrus using antibodies to synaptic vesicles, hyperphosphorylated tau (pTau), neurofibrillary tangle conformational-epitope (cNFT), amyloid-β, astrocytes, and microglia. The slides were digitally analyzed using Aperio software, which allows neuropathologic quantification in the posterior cingulate gray matter. MRS and pathology associations were adjusted for time from scan to death. Significant associations across AD and control subjects were found between reduced synaptic immunoreactivity and both NAA/Cr and NAA/mI in the posterior cingulate gyrus. Higher pTau burden was associated with lower NAA/Cr and NAA/mI. Higher amyloid-β burden was associated with elevated mI/Cr and lower NAA/mI ratios, but not with NAA/Cr. (1)H-MRS metabolite levels reveal early neurodegenerative changes associated with AD pathology. Our findings support the hypothesis that a decrease in NAA/Cr is associated with loss of synapses and early pTau pathology, but not with amyloid-β or later accumulation of cNFT pathology in the posterior cingulate gyrus. In addition, elevation of mI/Cr is associated with the occurrence of amyloid-β plaques in AD.

Higher glutamate+glutamine and reduction of N-acetylaspartate in posterior cingulate according to age range in patients with cognitive impairment and/or pain

RATIONALE AND OBJECTIVES

The aim of the study was to analyze 1) whether the metabolite levels in the posterior cingulate cortex (PCC) are different in healthy individuals compared to a group of patients with cognitive impairment and/or pain and 2) whether there exists a correlation between brain metabolites and the age of a patient.

MATERIALS AND METHODS

Two hundred seven patients with cognitive impairment and/or pain (66 mild cognitive impairment, 54 fibromyalgia, 36 Alzheimer disease, 33 interictal migraine, 10 somatization disorder, and 8 after trigeminal neuralgia, and 193 healthy participants adjusted for gender and age. Proton magnetic resonance spectroscopy (MRS) of the brain was performed with the voxel placed in the ventral PCC and postprocessed with LCModel (Stephen Provencher, Oakville, Ontario, Canada).

RESULTS

Using linear regression and adjusting for gender and age, mean brain metabolite values for the pathological group, when compared to healthy controls, were significantly lower in N-acetylaspartate (P=.003) and N-acetylaspartate/creatine (P=.015) and significantly greater in glutamate+glutamine (P<.001) and glutamate+glutamine/creatine (P<.000). All metabolites were significantly correlated with age: glutamate, glutamate+glutamine, N-acetylaspartate, and their creatine ratios exhibited a negative correlation, whereas myoinositol and choline exhibited a positive correlation.

CONCLUSIONS

Although the number of patients is relatively small with heterogeneous state of disease, MRS in PCC may serve as a useful noninvasive tool for diagnostic of patients with cognitive impairment and pain.

Magnetic Resonance Spectroscopy Study of Amnestic Mild Cognitive Impairment and Vascular Cognitive Impairment With No Dementia

Amnestic mild cognitive impairment (aMCI) and vascular cognitive impairment with no dementia (VCIND) are highly predictive of Alzheimer's disease and vascular dementia. In this study, a 2-dimensional magnetic resonance spectroscopy was performed in 25 patients with aMCI, 28 patients with VCIND, and 32 normal controls (NCs). The concentrations of N-acetyl aspartate (NAA), choline (Cho), myoinositol (MI), and creatine (Cr) were measured, and their ratios were calculated. The patients with aMCI displayed significantly lower NAA/MI bilaterally in the posterior cingulate gyrus (PCG) and white matter of occipital lobe (OLWM) than NC participants or patients with VCIND , whereas patients with VCIND displayed markedly lower NAA/Cho bilaterally in the white matter of frontal lobe (FLWM) and left OLWM, and right dorsal thalamus (DT) than patients with NC or aMCI. Compared with the controls, patients with aMCI displayed lower NAA and NAA/Cr in bilateral PCG, left precuneus, and DT, whereas patients with VCIND displayed lower NAA/Cr in bilateral DT and FLWM. In addition, increased MI in right PCG of patients with aMCI and increased Cho in left FLWM of patients with VCIND were also observed. The results might help guide a clinical differentiation between the 2 disorders.

The evolving role of neurological imaging in neuro-oncology

Neuroimaging has played a critical role in the management of patients with neurological disease, since the first ventriculogram was performed in 1918 by Walter Dandy (Mezger et al. Langenbecks Arch Surg 398(4):501-514, 2013). Over the last century, technology has evolved significantly, and within the last decade, the role of imaging in the management of patients with neuro-oncologic disease has shifted from a tool for gross identification of intracranial pathology, to an integral part of real-time neurological surgery. Current neurological imaging provides detailed information about anatomical structure, neurological function, and metabolic and metabolism-important characteristics that help clinicians and surgeons non-invasively manage patients with brain tumors. It is valuable to review the evolution of neurological imaging over the past several decades, focusing on its role in the management of patients with intracranial tumors. Novel neuro-imaging tools and developing technology with the potential to further transform clinical practice will be discussed, as will the key role neurological imaging plays in neurosurgical planning and intraoperative navigation. With increasingly complex imaging modalities creating growing amounts of raw data, validation of techniques, data analysis, and integrating various pieces of imaging data into individual patient management plans, remain significant challenges for clinicians. We thus suggest mechanisms that might ultimately allow for evidence based integration of imaging in the management of patients with neuro-oncologic disease.

Relative metabolite concentrations and ratios determined by use of 3-T region-specific proton magnetic resonance spectroscopy of the brain of healthy Beagles

OBJECTIVE

To determine relative concentrations of selected major brain tissue metabolites and their ratios and lobar variations by use of 3-T proton (hydrogen 1 [(1)H]) magnetic resonance spectroscopy (MRS) of the brain of healthy dogs.

ANIMALS

10 healthy Beagles.

PROCEDURES

3-T (1)H MRS at echo times of 144 and 35 milliseconds was performed on 5 transverse slices and 1 sagittal slice of representative brain lobe regions. Intravoxel parenchyma was classified as white matter, gray matter, or mixed (gray and white) and analyzed for relative concentrations (in arbitrary units) of N-acetylaspartate (NAA), choline, and creatine (ie, height at position of peak on MRS graph) as well as their ratios (NAA-to-choline, NAA-to-creatine, and choline-to-creatine ratios). Peak heights for metabolites were compared between echo times. Peak heights for metabolites and their ratios were correlated and evaluated among matter types. Yield was calculated as interpretable voxels divided by available lobar voxels.

RESULTS

Reference ranges of the metabolite concentration ratios were determined at an echo time of 35 milliseconds (NAA-to-choline ratio, 1.055 to 2.224; NAA-to-creatine ratio, 1.103 to 2.161; choline-to-creatine ratio, 0.759 to 1.332) and 144 milliseconds (NAA-to-choline ratio, 0.687 to 1.788; NAA-to-creatine ratio, 0.984 to 2.044; choline-to-creatine ratio, 0.828 to 1.853). Metabolite concentration ratios were greater in white matter than in gray matter. Voxel yields ranged from 43% for the temporal lobe to 100% for the thalamus.

CONCLUSIONS AND CLINICAL RELEVANCE

Metabolite concentrations and concentration ratios determined with 3-T (1)H MRS were not identical to those in humans and were determined for clinical and research investigations of canine brain disease.

Dopamine reduction in the substantia nigra of Parkinson's disease patients confirmed by in vivo magnetic resonance spectroscopic imaging

OBJECTIVES

Metabolic changes in the substantia nigra of patients with Parkinson's disease were previously investigated in different molecular-pathological examinations. The aim of our study was the in vivo measurement of these alterations using three-dimensional magnetic resonance spectroscopic imaging.

METHODS

21 patients with Parkinson's disease and 24 controls were examined using magnetic resonance spectroscopic imaging at 3 Tesla. The spectra of rostral and caudal substantia nigra regions were analyzed using LCModel. For spectral fitting, an adjusted basis data set with pathology-specific metabolites and macromolecules was used to better reproduce the in vivo spectra. To assess differences between both groups more accurately, especially in metabolites at lower concentrations, group-averaged spectra were evaluated in addition to the analysis of individual data.

RESULTS

We found significantly decreased N-acetylaspartate, choline, creatine, myo-inositol, glutathione and dopamine concentrations in patients with Parkinson's disease compared to controls, whereas glutamine+glutamate, γ-aminobutyric acid, and homovanillic acid were slightly increased. According to anatomical features, clear differences in the biochemical profiles were found between rostral and caudal substantia nigra voxels in both groups.

CONCLUSIONS

Reduced N-acetylaspartate and dopamine concentrations result from progressive degeneration of dopamine-producing neurons within the substantia nigra pars compacta. Decreased creatine levels can be interpreted as impaired energy metabolism due to mitochondrial dysfunction. Lower glutathione concentrations might be a cause or consequence of oxidative stress. Furthermore, slightly increased glutamine+glutamate and γ-aminobutyric acid levels are expected based on post mortem data in Parkinson's disease. To the best of our knowledge, this is the first non-invasive confirmation of these metabolic changes.

Neurochemical changes within human early blind occipital cortex

Early blindness results in occipital cortex neurons responding to a wide range of auditory and tactile stimuli. These changes in tuning properties are accompanied by an extensive reorganization of the occipital cortex that includes alterations in anatomical structure, neurochemical and metabolic pathways. Although it has been established in animal models that neurochemical pathways are heavily affected by early visual deprivation, the effects of blindness on these pathways in humans is still not well characterized. Here, using (1)H magnetic resonance spectroscopy in nine early blind and normally sighted subjects, we find that early blindness is associated with higher levels of creatine, choline and myo-Inositol and indications of lower levels of GABA within the occipital cortex. These results suggest that the cross-modal responses associated with early blindness may, at least in part, be driven by changes within occipital biochemical pathways.

Brain changes in long-term zen meditators using proton magnetic resonance spectroscopy and diffusion tensor imaging: a controlled study

Introduction

This work aimed to determine whether ¹H magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) are correlated with years of meditation and psychological variables in long-term Zen meditators compared to healthy non-meditator controls.

Materials and Methods

Design. Controlled, cross-sectional study. Sample. Meditators were recruited from a Zen Buddhist monastery. The control group was recruited from hospital staff. Meditators were administered questionnaires on anxiety, depression, cognitive impairment and mindfulness. ¹H-MRS (1.5 T) of the brain was carried out by exploring four areas: both thalami, both hippocampi, the posterior superior parietal lobule (PSPL) and posterior cingulate gyrus. Predefined areas of the brain were measured for diffusivity (ADC) and fractional anisotropy (FA) by MR-DTI.

Results

Myo-inositol (mI) was increased in the posterior cingulate gyrus and Glutamate (Glu), N-acetyl-aspartate (NAA) and N-acetyl-aspartate/Creatine (NAA/Cr) was reduced in the left thalamus in meditators. We found a significant positive correlation between mI in the posterior cingulate and years of meditation (r = 0.518; p = .019). We also found significant negative correlations between Glu (r = −0.452; p = .045), NAA (r = −0.617; p = .003) and NAA/Cr (r = −0.448; P = .047) in the left thalamus and years of meditation. Meditators showed a lower Apparent Diffusion Coefficient (ADC) in the left posterior parietal white matter than did controls, and the ADC was negatively correlated with years of meditation (r = −0.4850, p = .0066).

Conclusions

The results are consistent with the view that mI, Glu and NAA are the most important altered metabolites. This study provides evidence of subtle abnormalities in neuronal function in regions of the white matter in meditators.

Longitudinal magnetic resonance spectroscopy as marker of cognitive deterioration in mild cognitive impairment

OBJECTIVE

Amnestic mild cognitive impairment (MCI) is highly predictive of Alzheimer's disease but the pace of deterioration varies across patients. We hypothesize that magnetic resonance spectroscopy (MRS) could be a useful surrogate marker to monitor progression of cognitive impairment in patients with amnestic MCI.

METHODS

A cohort of patients with amnestic MCI underwent single-voxel (1)H-MRS at baseline and at 2-year follow-up. We included 16 patients who converted to dementia of Alzheimer type and other 16 who did not. Changes in cognitive function were compared with the changes in the metabolite levels assessed in vivo.

RESULTS

At baseline the converters had lower mean N-acetyl-aspartate (NAA)/creatine (Cr) ratios in the posteromedial parietal cortex (1.41) than nonconverters (1.47). Most patients tended to lose points in the Mini-Mental test after 2-year follow-up in parallel with decreases in NAA levels (r = .53; P = .002) in the posteromedial parietal cortex as well. The converters showed significant decreases in NAA levels and Cr ratios, whereas the nonconverters did not (P = .001 and .02, respectively) in this area.

CONCLUSION

We conclude that MRS is a technique sensitive enough to monitor cognitive changes and progression to dementia in patients with amnestic MCI.

Quantitative proton magnetic resonance spectroscopy and spectroscopic imaging of the brain: a didactic review

This article presents background information related to methodology for estimating brain metabolite concentration from magnetic resonance spectroscopy (MRS) and magnetic resonance spectroscopic imaging measurements of living human brain tissue. It reviews progress related to this methodology, with emphasis placed on progress reported during the past 10 years. It is written for a target audience composed of radiologists and magnetic resonance imaging technologists. It describes in general terms the relationship between MRS signal amplitude and concentration. It then presents an overview of the many practical problems associated with deriving concentration solely from absolute measured signal amplitudes and demonstrates how a various signal calibration approaches can be successfully used. The concept of integrated signal amplitude is presented with examples that are helpful for qualitative reading of MRS data as well as for understanding the methodology used for quantitative measurements. The problems associated with the accurate measurement of individual signal amplitudes in brain spectra having overlapping signals from other metabolites and overlapping nuisance signals from water and lipid are presented. Current approaches to obtaining accurate amplitude estimates with least-squares fitting software are summarized.

Brain glutamate levels are decreased in Alzheimer's disease: a magnetic resonance spectroscopy study

Glutamate (Glu) is the most abundant excitatory neurotransmitter in the central nervous system (CNS) and is involved in the pathophysiology of Alzheimer's disease (AD) in which there is an increased excitotoxicity. Biochemical composition of living tissues including the levels of Glu was analyzed by magnetic resonance spectroscopy (MRS). Previous reports point to decreased levels of Glu in AD. As Glu plays an important role in memory, we hypothesize that Glu levels are decreased in patients with AD when compared with controls. A consecutive sample of 30 patients with mild-to-moderate AD underwent H-MRS with the voxel placed in the bilateral posterior cingulate gyrus. For comparison purposes, we carried out the same technique in 68 patients with mild cognitive impairment (MCI) and in 26 controls. The healthy controls had higher metabolite levels of N-acetyl-aspartate (NAA) than patients with MCI and AD. In turn, patients with MCI and the controls had higher levels of Glu than in patients with AD. The differences were significant in the analysis of variance (ANOVA) test model corrected for age. In the post hoc analysis, the most remarkable differences were seen between patients with AD and the rest (patients with MCI and the controls). In AD, the levels of Glu and NAA are decreased in comparison with MCI and normality, which reflects loss of neurons.

Three-dimensional magnetic resonance spectroscopic imaging in the substantia nigra of healthy controls and patients with Parkinson's disease

OBJECTIVES

To investigate the substantia nigra in patients with Parkinson's disease three-dimensional magnetic resonance spectroscopic imaging with high spatial resolution at 3 Tesla was performed. Regional variations of spectroscopic data between the rostral and caudal regions of the substantia nigra as well as the midbrain tegmentum areas were evaluated in healthy controls and patients with Parkinson's disease.

METHODS

Nine patients with Parkinson's disease and eight age- and gender-matched healthy controls were included in this study. Data were acquired by using three-dimensional magnetic resonance spectroscopic imaging measurements. The ratios between rostral and caudal voxels of the substantia nigra as well as the midbrain tegmentum areas were calculated for the main-metabolites N-acetyl aspartate, creatine, choline, and myo-inositol. Additionally, the metabolite/creatine ratios were calculated.

RESULTS

In all subjects spectra of acceptable quality could be obtained with a nominal voxel size of 0.252 ml. The calculated rostral-to-caudal ratios of the metabolites as well as of the metabolite/creatine ratios showed with exception of choline/creatine ratio significant differences between healthy controls and patients with Parkinson's disease.

CONCLUSIONS

The findings from this study indicate that regional variations in N-acetyl aspartate/creatine ratios in the regions of the substantia nigra may differentiate patients with Parkinson's disease and healthy controls.

Magnetic resonance spectroscopy in the prediction of early conversion from amnestic mild cognitive impairment to dementia: a prospective cohort study

BACKGROUND

Mild cognitive impairment (MCI) of an amnestic type is a common condition in older people and highly predictive of Alzheimer's disease (AD). To date, there is no clear consensus regarding the best antecedent biomarker to predict early conversion to AD.

OBJECTIVE

The aim of the study is to demonstrate that (1)H magnetic resonance spectroscopy (MRS) of the brain in MCI patients may predict early conversion to dementia within the 2-year period after baseline assessment.

METHODS

A cohort of patients fulfilling the criteria of amnestic MCI were enrolled consecutively. At baseline the patients underwent neuropsychological examination, standard blood tests and APOE genotype. (1)H-MRS (1.5 T) of the brain was carried out by exploring two areas: the posteromedial bilateral parietal lobe and left medial occipital lobe. The patients were followed up to detect conversion to probable AD according to the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association group criteria.

RESULTS

After a 2-year follow-up, 27 (38%) patients converted to AD. The mean N-acetyl-aspartate/creatine (NAA/Cr) ratio in the posteromedial bilateral parietal cortex was 1.38 in converters versus 1.49 in non-converters (p<0.0001). An NAA/Cr ratio equal to or lower than 1.43 in this area predicted conversion to probable AD at 74.1% sensitivity and 83.7% specificity (area under the curve: 0.84; 95% CI 0.73 to 0.92). The cross-validated accuracy of classification was 82%, which reaches 85% when the APOE4 genotype and memory test are included in the analysis. In the left medial occipital lobe, the predictive value was somewhat lower with 85.2% sensitivity and 61.4% specificity (area under the curve: 0.8; 95% CI 0.69 to 0.89). Neither the APOE4 genotype nor leuco-araiosis was predictive of conversion to dementia.

CONCLUSION

MRS is a valuable biomarker to predict early conversion to dementia in patients with amnestic MCI.

Correlation of findings in advanced MRI techniques with global severity scales in patients with Parkinson disease

RATIONALE AND OBJECTIVES

This work is aimed at determining whether magnetic resonance spectroscopy (MRS) and diffusion tensor imaging (DTI) may correlate with disease severity in a series of Parkinson disease (PD) patients.

MATERIALS AND METHODS

We recruited a consecutive sample of 39 PD patients in several stages of the disease according to Hoehn and Yahr scale. There were 22 men, and the mean age was 74.5 years (SD 7.5). Disease severity was measured with the Unified Parkinson Disease Rating Scale (UPDRS). All of them underwent ¹H MRS in basal ganglia and the anterior cingulate area, as well as DTI in bilateral substantia nigra. Correlation was made between radiological findings and UPDRS.

RESULTS

We found significant negative correlation between UPDRS scores and the Glx (glutamate+glutamine) levels in the right (r = -0.35; P = .03) and the left (r = -0.44; P = .006) lentiform nucleus; as well as with glutamate (r = -0.43; P = .008), the Glx/Cr ratio in the right (r = -0.41; P = .01), and in the left lentiform nucleus (r = -0.36; P = .02). We also found positive correlation between UPDRS scores and DTI in right rostral substantia nigra (r = 0.36; P = .02). Glx was increased in lentiform nucleus and fractional anisotropy was reduced in the rostral SN of subjects with PD in early stages.

CONCLUSIONS

The results are consistent with the view that more than half the dopaminergic neurons in the nigrostriatal projection are lost before the onset of PD.

Clinical and Radiological Differences in Alzheimer's Disease with and without a History of Mild Cognitive Impairment

We assessed the influence of a history of amnesic mild cognitive impairment (MCI) in patients with Alzheimer's disease (AD) at presentation from a clinical and radiological point of view. A consecutive sample of patients fulfilling the criteria of probable Alzheimer's disease according to the NINCDS-ADRDA work group not previously diagnosed nor treated underwent neuropsychological assessment including mini-mental test, Blessed dementia rating scale (BDRS), ADAS-Cog, neuropsychiatric inventory (NPI), and a daily living activities scale (DAD). Radiological evaluation consisted of magnetic resonance imaging, left hippocampal volumetry and magnetic resonance spectroscopy (MRS) of the brain. We divided the patients into two groups according to positive/negative history of MCI for a period longer than one year. The AD patients with a history of MCI were more likely to have a history of depression (OR: 5.5; 95% CI: 1.12-26) and have more depressive symptoms at presentation in the NPI than those without a history of MCI. They also had a history of hypertension more frequently than the remainder. The presence/absence of ApoE4 alleles did not have influence in the clinical course. With regard to radiological findings the patients with previous MCI showed lower values of N-acetyl-aspartate (NAA) in parietal (p=0.0001) temporal (p=0.08) and occipital (p=0.00001) lobes than the other group, as well as a smaller left hippocampus although the difference was not statistically significant. A history of MCI in AD patients represents a form of the disease with slower progression from clinical and radiological viewpoints. These patients present with more depressive symptoms and a history of depression than the remainder. The lower NAA levels on MRS are compatible with a longer disease duration when AD is preceded by amnesic MCI.

Localized 1H-NMR spectroscopy in patients with fibromyalgia: a controlled study of changes in cerebral glutamate/glutamine, inositol, choline, and N-acetylaspartate

INTRODUCTION

The purpose of this study was to investigate whether single-voxel (SV) proton magnetic resonance spectroscopy (MRS), diffusion-weighted imaging (DWI), and diffusion tensor imaging (DTI) detected differences between fibromyalgia (FM) patients and healthy controls. We also searched for correlations between neuroimaging abnormalities and neuropsychological variables.

METHODS

Ten patients with FM and 10 gender- and age-matched control subjects were studied. A neuropsychological examination, DWI, DTI, and proton MRS were performed on the brain areas known to be associated with pain processing.

RESULTS

Compared with healthy controls, FM patients had significantly higher levels of glutamate + glutamine (Glx) (mean ± SD, 10.71 ± 0.50 arbitrary institutional units versus 9.89 ± 1.04; P = 0.049) and higher glutamate + glutamine/creatine (Glx/Cr) ratios (1.90 ± 0.12 versus 1.72 ± 0.23; P = 0.034) in the posterior gyrus. Myoinositol (Ins) levels of the right and left hippocampi were significantly lower in FM patients (4.49 ± 0.74 versus 5.17 ± 0.62; P = 0.008 and 4.91 ± 0.85 versus 6.09 ± 0.78; P = 0.004, respectively). In FM patients, decreased myoinositol/creatine (Ins/Cr) ratios were found in the left sensorimotor area (P = 0.05) and the left hippocampus (P = 0.002) and lower levels of choline (P = 0.019) and N-acetyl aspartate + N-acetyl aspartyl glutamate (NAA + NAG) (P = 0.034) in the left hippocampus. Significant correlations between depression, pain, and global function and the posterior gyrus Glx levels and Glx/Cr ratios were observed.

CONCLUSIONS

Glx within the posterior gyrus could be a pathologic factor in FM. Hippocampal dysfunction may be partially responsible for the depressive symptoms of FM. Additional studies with larger samples are required to confirm these preliminary data.