Estimation of brainstem neuronal loss in amyotrophic lateral sclerosis with in vivo proton magnetic resonance spectroscopy

Cortical Excitability across the ALS Clinical Motor Phenotypes

Amyotrophic lateral sclerosis (ALS) is characterized by its marked clinical heterogeneity. Although the coexistence of upper and lower motor neuron signs is a common clinical feature for most patients, there is a wide range of atypical motor presentations and clinical trajectories, implying a heterogeneity of underlying pathogenic mechanisms. Corticomotoneuronal dysfunction is increasingly postulated as the harbinger of clinical disease, and neurophysiological exploration of the motor cortex in vivo using transcranial magnetic stimulation (TMS) has suggested that motor cortical hyperexcitability may be a critical pathogenic factor linked to clinical features and survival. Region-specific selective vulnerability at the level of the motor cortex may drive the observed differences of clinical presentation across the ALS motor phenotypes, and thus, further understanding of phenotypic variability in relation to cortical dysfunction may serve as an important guide to underlying disease mechanisms. This review article analyses the cortical excitability profiles across the clinical motor phenotypes, as assessed using TMS, and explores this relationship to clinical patterns and survival. This understanding will remain essential to unravelling central disease pathophysiology and for the development of specific treatment targets across the ALS clinical motor phenotypes.

Evolution of the neurochemical profiles in the G93A-SOD1 mouse model of amyotrophic lateral sclerosis

In vivo ¹H magnetic resonance spectroscopy (¹H-MRS) investigations of amyotrophic lateral sclerosis (ALS) mouse brain may provide neurochemical profiles and alterations in association with ALS disease progression. We aimed to longitudinally follow neurochemical evolutions of striatum, brainstem and motor cortex of mice transgenic for G93A mutant human superoxide dismutase type-1 (G93A-SOD1), an ALS model. Region-specific neurochemical alterations were detected in asymptomatic G93A-SOD1 mice, particularly in lactate (-19%) and glutamate (+8%) of brainstem, along with γ-amino-butyric acid (-30%), N-acetyl-aspartate (-5%) and ascorbate (+51%) of motor cortex. With disease progression towards the end-stage, increased numbers of metabolic changes of G93A-SOD1 mice were observed (e.g. glutamine levels increased in the brainstem (>+66%) and motor cortex (>+54%)). Through ALS disease progression, an overall increase of glutamine/glutamate in G93A-SOD1 mice was observed in the striatum (p < 0.01) and even more so in two motor neuron enriched regions, the brainstem and motor cortex (p < 0.0001). These ¹H-MRS data underscore a pattern of neurochemical alterations that are specific to brain regions and to disease stages of the G93A-SOD1 mouse model. These neurochemical changes may contribute to early diagnosis and disease monitoring in ALS patients.

Cerebral degeneration in amyotrophic lateral sclerosis: A prospective multicenter magnetic resonance spectroscopy study

Background

We investigated cerebral degeneration and neurochemistry in patients with amyotrophic lateral sclerosis (ALS) using magnetic resonance spectroscopy (MRS).

Methods

We prospectively studied 65 patients and 43 age-matched healthy controls. Participants were recruited from 4 centers as part of a study in the Canadian ALS Neuroimaging Consortium. All participants underwent single-voxel proton MRS using a protocol standardized across all sites. Metabolites reflecting neuronal integrity (total N-acetyl aspartyl moieties [tNAA]) and gliosis (myo-inositol [Ino]), as well as creatine (Cr) and choline (Cho), were quantified in the midline motor cortex and midline prefrontal cortex. Comparisons were made between patients with ALS and healthy controls. Metabolites were correlated with clinical measures of upper motor neuron dysfunction, disease progression rate, and cognitive performance.

Results

In the motor cortex, tNAA/Cr, tNAA/Cho, and tNAA/Ino ratios were reduced in the ALS group compared with controls. Group differences in tNAA/Cr and tNAA/Cho in the prefrontal cortex displayed reduced ratios in ALS patients; however, these were not statistically significant. Reduced motor cortex ratios were associated with slower foot tapping rate, whereas only motor tNAA/Ino was associated with finger tapping rate. Disease progression rate was associated with motor tNAA/Cho. Verbal fluency, semantic fluency, and digit span forwards and backwards were associated with prefrontal tNAA/Cr.

Conclusions

This study demonstrates that cerebral degeneration in ALS is more pronounced in the motor than prefrontal cortex, that multicenter MRS studies are feasible, and that motor tNAA/Ino shows promise as a potential biomarker.

A Systematic Review of Suggested Molecular Strata, Biomarkers and Their Tissue Sources in ALS

Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease, is an incurable neurodegenerative condition, characterized by the loss of upper and lower motor neurons. It affects 1–1.8/100,000 individuals worldwide, and the number of cases is projected to increase as the population ages. Thus, there is an urgent need to identify both therapeutic targets and disease-specific biomarkers–biomarkers that would be useful to diagnose and stratify patients into different sub-groups for therapeutic strategies, as well as biomarkers to follow the efficacy of any treatment tested during clinical trials. There is a lack of knowledge about pathogenesis and many hypotheses. Numerous “omics” studies have been conducted on ALS in the past decade to identify a disease-signature in tissues and circulating biomarkers. The first goal of the present review was to group the molecular pathways that have been implicated in monogenic forms of ALS, to enable the description of patient strata corresponding to each pathway grouping. This strategy allowed us to suggest 14 strata, each potentially targetable by different pharmacological strategies. The second goal of this review was to identify diagnostic/prognostic biomarker candidates consistently observed across the literature. For this purpose, we explore previous biomarker-relevant “omics” studies of ALS and summarize their findings, focusing on potential circulating biomarker candidates. We systematically review 118 papers on biomarkers published during the last decade. Several candidate markers were consistently shared across the results of different studies in either cerebrospinal fluid (CSF) or blood (leukocyte or serum/plasma). Although these candidates still need to be validated in a systematic manner, we suggest the use of combinations of biomarkers that would likely reflect the “health status” of different tissues, including motor neuron health (e.g., pNFH and NF-L, cystatin C, Transthyretin), inflammation status (e.g., MCP-1, miR451), muscle health (miR-338-3p, miR-206) and metabolism (homocysteine, glutamate, cholesterol). In light of these studies and because ALS is increasingly perceived as a multi-system disease, the identification of a panel of biomarkers that accurately reflect features of pathology is a priority, not only for diagnostic purposes but also for prognostic or predictive applications.

Magnetic Resonance Spectroscopy in ALS

Proton magnetic resonance spectroscopy (MRS) provides a means of measuring cerebral metabolites relevant to neurodegeneration in vivo. In amyotrophic lateral sclerosis (ALS), neurochemical changes reflecting neuronal loss or dysfunction (decreased N-actylaspartate [NAA]) is most significant in the motor cortex and corticospinal tracts. Other neurochemical changes observed include increased myo-inositol (mIns), a putative marker of gliosis. MRS confirmation of involvement of non-motor regions such as the frontal lobes, thalamus, basal ganglia, and cingulum are consistent with the multi-system facet of motor neuron disease with ALS being part of a MND-FTD spectrum. MRS-derived markers exhibit an encouraging discriminatory ability to identify patients from healthy controls, however more data is needed to determine its ability to assist with the diagnosis in early stages when upper motor neuron signs are limited, and in distinguishing from disease mimics. Longitudinal change of NAA and mIns do not appear to be reliable in monitoring disease progression. Technological advances in hardware and high field scanning are increasing the number of accessible metabolites available for interrogation.

Motor cortex metabolite alterations in amyotrophic lateral sclerosis assessed in vivo using edited and non-edited magnetic resonance spectroscopy

Previous MRI and proton spectroscopy (¹H-MRS) studies have revealed impaired neuronal integrity and altered neurometabolite concentrations in the motor cortex of patients with amyotrophic lateral sclerosis (ALS). Here, we aim to use MRI with conventional and novel MRS sequences to further investigate neurometabolic changes in the motor cortex of ALS patients and their relation to clinical parameters. We utilized the novel HERMES (Hadamard Encoding and Reconstruction of MEGA-Edited Spectroscopy) MRS sequence to simultaneously quantify the inhibitory neurotransmitter GABA and antioxidant glutathione in ALS patients (n = 7) and healthy controls (n = 7). In addition, we have also quantified other MRS observable neurometabolites using a conventional point-resolved MR spectroscopy (PRESS) sequence in ALS patients (n = 20) and healthy controls (n = 20). We observed a trend towards decreasing glutathione concentrations in the motor cortex of ALS patients (p = 0.0842). In addition, we detected a 11% decrease in N-acetylaspartate (NAA) (p = 0.025), a 15% increase in glutamate + glutamine (Glx) (p = 0.0084) and a 21% increase in myo-inositol (mIns) (p = 0.0051) concentrations for ALS patients compared to healthy controls. Furthermore, significant positive correlations were found between GABA-NAA (p = 0.0480; Rρ = 0.7875) and NAA-mIns (p = 0.0448; Rρ = -0.4651) levels among the patients. NAA levels in the bulbar-onset patient group were found to be significantly (p = 0.0097) lower compared to the limb-onset group. A strong correlation (p < 0.0001; Rρ = -0,8801) for mIns and a weak correlation (p = 0.0066; Rρ = -0,6673) for Glx was found for the disease progression, measured by declining of the ALS Functional Rating Scale-Revised criteria (ALSFRS-R). Concentrations of mIns and Glx also correlated with disease severity measured by forced vital capacity (FVC). Results suggest that mean neurometabolite concentrations detected in the motor cortex may indicate clinical and pathological changes in ALS.

Biomarkers in Motor Neuron Disease: A State of the Art Review

Motor neuron disease can be viewed as an umbrella term describing a heterogeneous group of conditions, all of which are relentlessly progressive and ultimately fatal. The average life expectancy is 2 years, but with a broad range of months to decades. Biomarker research deepens disease understanding through exploration of pathophysiological mechanisms which, in turn, highlights targets for novel therapies. It also allows differentiation of the disease population into sub-groups, which serves two general purposes: (a) provides clinicians with information to better guide their patients in terms of disease progression, and (b) guides clinical trial design so that an intervention may be shown to be effective if population variation is controlled for. Biomarkers also have the potential to provide monitoring during clinical trials to ensure target engagement. This review highlights biomarkers that have emerged from the fields of systemic measurements including biochemistry (blood, cerebrospinal fluid, and urine analysis); imaging and electrophysiology, and gives examples of how a combinatorial approach may yield the best results. We emphasize the importance of systematic sample collection and analysis, and the need to correlate biomarker findings with detailed phenotype and genotype data.

Metabolic abnormality of pontine tegmentum in patients with REM sleep behavior disorder analyzed using magnetic resonance spectroscopy

OBJECTIVES

We aimed to evaluate the metabolism differences in pontine tegmentum among patients with idiopathic RBD (iRBD), secondary RBD (sRBD) and healthy control groups using magnetic resonance spectroscopy ((1)H-MRS) and whether metabolic changes are correlated with age in patients with RBD.

PATIENTS AND METHODS

The iRBD, sRBD, and control groups were composed of 18, 26, and 29 patients, respectively. All participants underwent magnetic resonance imaging (MRI) and (1)H-MRS detection at 17:00 for approximately 15min. All NAA/Cr, Cho/Cr and NAA/Cho ratios were automatically generated using FuncTool and the correlation between metabolism and age was analyzed by Pearson's correlation analysis.

RESULTS

Significant difference in NAA/Cr ratio was found between the sRBD group and the other groups (p<0.05). Significant difference in NAA/Cho ratio was found among all groups (p<0.05). Cho/Cr ratio remarkably increased in the control group (p<0.05) compared with the other groups. NAA/Cr ratio had an adverse correlation with age in the control, iRBD, and sRBD groups (r=-0.822, p=0.000 vs r=-0.663, p=0.003 vs r=-0.583, p=0.002). However, there was no correlation between participants age and Cho/Cr (r=-0.054, p=0.651) or NAA/Cho (r=0.029, p=0.805).

CONCLUSION

Neurons in the sRBD group were lost or damaged; however, this damage was not obvious in the iRBD group. Nevertheless, NAA and Cho levels were reduced in the local nerve cells of both RBD groups; these changes might indicate the sensitive pathogenic areas among patients with RBD.

Assessment of the upper motor neuron in amyotrophic lateral sclerosis

Clinical signs of upper motor neuron (UMN) involvement are an important component in supporting the diagnosis of amyotrophic lateral sclerosis (ALS), but are often not easily appreciated in a limb that is concurrently affected by muscle wasting and lower motor neuron degeneration, particularly in the early symptomatic stages of ALS. Whilst recent criteria have been proposed to facilitate improved detection of lower motor neuron impairment through electrophysiological features that have improved diagnostic sensitivity, assessment of upper motor neuron involvement remains essentially clinical. As a result, there is often a significant diagnostic delay that in turn may impact institution of disease-modifying therapy and access to other optimal patient management. Biomarkers of pathological UMN involvement are also required to ensure patients with suspected ALS have timely access to appropriate therapeutic trials. The present review provides an analysis of current and recently developed assessment techniques, including novel imaging and electrophysiological approaches used to study corticomotoneuronal pathology in ALS.

Impaired corticopontocerebellar tracts underlie pseudobulbar affect in motor neuron disorders

OBJECTIVE

The objectives of the study were (1) to determine the prevalence and characteristics of pseudobulbar affect (PBA) in patients with primary lateral sclerosis (PLS) and amyotrophic lateral sclerosis (ALS) in an outpatient clinic population, and (2) to test the hypothesis that damage of inputs to the cerebellum, leading to cerebellar dysmodulation, is associated with PBA.

METHODS

Chart review of all patients with PLS and ALS seen between 2000 and 2013. The examining neurologist documented the presence or absence of PBA in 87 patients. Forty-seven patients also had diffusion tensor imaging (DTI) studies. Tract-based spatial statistics were used to compare DTI of patients with and without PBA to identify altered white matter tracts associated with PBA.

RESULTS

Thirty-one of 50 patients with PLS and 12 of 37 patients with ALS had PBA. Psychiatric/emotional assessment found congruence between mood and affect during episodes, but excessive magnitude of the response. DTI studies of 25 PLS and 22 ALS patient brains showed reduced fractional anisotropy of the corticospinal and callosal white matter tracts in all patients. Patients with PBA additionally had increased mean diffusivity of white matter tracts underlying the frontotemporal cortex, the transverse pontine fibers, and the middle cerebellar peduncle.

CONCLUSIONS

PBA is common in PLS. Imaging findings showing disruption of corticopontocerebellar pathways support the hypothesis that PBA can be viewed as a "dysmetria" of emotional expression resulting from cerebellar dysmodulation.

T₂-weighted MRI detects presymptomatic pathology in the SOD1 mouse model of ALS

Neuroinflammation has been identified as a potential therapeutic target in amyotrophic lateral sclerosis (ALS), but relevant biomarkers are needed. The superoxide dismutase (SOD1)(G93A) transgenic mouse model of ALS offers a unique opportunity to study and potentially manipulate presymptomatic pathology. While T₂-weighted magnetic resonance imaging (MRI) has been shown to be sensitive to pathologic changes at symptom onset, no earlier biomarkers were previously identified and the underlying histopathologic correlates remain uncertain. To address these issues, we used a multimodal MRI approach targeting structural (T₂, T₁, apparent diffusion coefficient (ADC), magnetization transfer ratio (MTR)), vascular (gadolinium diethylene triamine pentaacetic acid), and endothelial (vascular cell adhesion molecule-microparticles of iron oxide) changes, together with histopathologic analysis from presymptomatic to symptomatic stages of disease. Presymptomatic changes in brainstem nuclei were evident on T₂-weighted images from as early as 60 days (P<0.05). Histologic indices of vacuolation, astro- and microglial activation all correlated with T₂-weighted changes. Significant reductions in ADC (P<0.01) and MTR (P<0.05) were found at 120 days in the same brainstem nuclei. No changes in T₁ relaxation, vascular permeability, or endothelial activation were found at any stage of disease. These findings suggest that T₂-weighted MRI offers the strongest biomarker potential in this model, and that MRI has unique potential for noninvasive and longitudinal assessment of presymptomatically applied therapeutic and neuroprotective agents.

The blockade of the neurotransmitter release apparatus by botulinum neurotoxins

The high toxicity of the seven serotypes of botulinum neurotoxins (BoNT/A to G), together with their specificity and reversibility, includes them in the list A of potential bioterrorism weapons and, at the same time, among the therapeutics of choice for a variety of human syndromes. They invade nerve terminals and cleave specifically the three proteins which form the heterotrimeric SNAP REceptors (SNARE) complex that mediates neurotransmitter release. The BoNT-induced cleavage of the SNARE proteins explains by itself the paralysing activity of the BoNTs because the truncated proteins cannot form the SNARE complex. However, in the case of BoNT/A, the most widely used toxin in therapy, additional factors come into play as it only removes a few residues from the synaptosomal associate protein of 25 kDa C-terminus and this results in a long duration of action. To explain these facts and other experimental data, we present here a model for the assembly of the neuroexocytosis apparatus in which Synaptotagmin and Complexin first assist the zippering of the SNARE complex, and then stabilize and clamp an octameric radial assembly of the SNARE complexes.

A prospective pilot study measuring muscle volumetric change in amyotrophic lateral sclerosis

Our objective was to investigate the potential of muscle volume, measured with magnetic resonance (MR), as a biomarker to quantify disease progression in patients with amyotrophic lateral sclerosis (ALS). In this longitudinal pilot study, we first sought to determine the stability of volumetric muscle MR measurements in 11 control subjects at two time-points. We assessed feasibility of detecting atrophy in four patients with ALS, followed at three-month intervals for 12 months. Muscle power and MR volume were measured in thenar eminence (TEm), first dorsal interosseous (1DIO), tibialis anterior (TA) and tongue. Changes over time were assessed using linear regression models and t-tests. Results demonstrated that, in controls, no volumetric MR changes were seen (mean volume variation in all muscles < 5%, p > 0.1). In patients, between-subject heterogeneity was identified. Trends for volume loss were found in TEm (mean, - 26.84%, p = 0.056) and TA (- 8.29%, p = 0.077), but not in 1DIO (- 18.47%, p = 0.121) or tongue (< 5%, p = 0.367). In conclusion, volumetric muscle MR appears a stable measure in controls, and progressive volume loss was demonstrable in individuals with ALS in whom clinical weakness progressed. In this small study, subclinical atrophy was not demonstrable using muscle MR. Clinico-radiological discordance between muscle weakness and MR atrophy could reflect a contribution of upper motor neuron pathology.

An in vivo ultrahigh field 14.1 T (1) H-MRS study on 6-OHDA and α-synuclein-based rat models of Parkinson's disease: GABA as an early disease marker

The detection of Parkinson's disease (PD) in its preclinical stages prior to outright neurodegeneration is essential to the development of neuroprotective therapies and could reduce the number of misdiagnosed patients. However, early diagnosis is currently hampered by lack of reliable biomarkers. (1) H magnetic resonance spectroscopy (MRS) offers a noninvasive measure of brain metabolite levels that allows the identification of such potential biomarkers. This study aimed at using MRS on an ultrahigh field 14.1 T magnet to explore the striatal metabolic changes occurring in two different rat models of the disease. Rats lesioned by the injection of 6-hydroxydopamine (6-OHDA) in the medial-forebrain bundle were used to model a complete nigrostriatal lesion while a genetic model based on the nigral injection of an adeno-associated viral (AAV) vector coding for the human α-synuclein was used to model a progressive neurodegeneration and dopaminergic neuron dysfunction, thereby replicating conditions closer to early pathological stages of PD. MRS measurements in the striatum of the 6-OHDA rats revealed significant decreases in glutamate and N-acetyl-aspartate levels and a significant increase in GABA level in the ipsilateral hemisphere compared with the contralateral one, while the αSyn overexpressing rats showed a significant increase in the GABA striatal level only. Therefore, we conclude that MRS measurements of striatal GABA levels could allow for the detection of early nigrostriatal defects prior to outright neurodegeneration and, as such, offers great potential as a sensitive biomarker of presymptomatic PD.

Neuroimaging in amyotrophic lateral sclerosis

The catastrophic system failure in amyotrophic lateral sclerosis is characterized by progressive neurodegeneration within the corticospinal tracts, brainstem nuclei and spinal cord anterior horns, with an extra-motor pathology that has overlap with frontotemporal dementia. The development of computed tomography and, even more so, MRI has brought insights into neurological disease, previously only available through post-mortem study. Although largely research-based, radionuclide imaging has continued to provide mechanistic insights into neurodegenerative disorders. The evolution of MRI to use advanced sequences highly sensitive to cortical and white matter structure, parenchymal metabolites and blood flow, many of which are now applicable to the spinal cord as well as the brain, make it a uniquely valuable tool for the study of a multisystem disorder such as amyotrophic lateral sclerosis. This comprehensive review considers the full range of neuroimaging techniques applied to amyotrophic lateral sclerosis over the last 25 years, the biomarkers they have revealed and future developments.

Is magnetic resonance imaging a plausible biomarker for upper motor neuron degeneration in amyotrophic lateral sclerosis/primary lateral sclerosis or merely a useful paraclinical tool to exclude mimic syndromes? A critical review of imaging applicability in clinical routine

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease that affects motor neurons in the cerebral cortex, brainstem, and spinal cord, brain regions in which conventional magnetic resonance imaging is often uninformative. Although the mean time from symptom onset to diagnosis is estimated to be about one year, the current criteria only prescribe magnetic resonance imaging to exclude "ALS mimic syndromes". Extensive application of non-conventional magnetic resonance imaging (MRI) to the study of ALS has improved our understanding of the in vivo pathological mechanisms involved in the disease. These modern imaging techniques have recently been added to the list of potential ALS biomarkers to aid in both diagnosis and monitoring of disease progression. This article provides a comprehensive review of the clinical applicability of the neuroimaging progress that has been made over the past two decades towards establishing suitable diagnostic tools for upper motor neuron (UMN) degeneration in ALS.

Estimation of the brain stem volume by stereological method on magnetic resonance imaging

Neuron loss that occurs in some neurodegenerative diseases can lead to volume alterations by causing atrophy in the brain stem. The aim of this study was to determine the brain stem volume and the volume ratio of the brain stem to total brain volume related to gender and age using new Stereo Investigator system in normal subjects. For this purpose, MR images of 72 individuals who have no pathologic condition were evaluated. The total brain volumes of female and male were calculated as 966.81 ± 77.44 and 1,074.06 ± 111.75 cm3, respectively. Brain stem volumes of female and male were determined as 18.99 ± 2.36 and 22.05 ± 4.01 cm3, respectively. The ratios of brain stem volume to total brain volume were 1.96 ± 0.17 in female and 2.05 ± 0.29 in male. The total brain and brain stem volumes were observed smaller in female and it is statistically significant. Among the individuals whose ages are between 20 and 40, total brain and brain stem volume measurements with aging were not statistically significant. As a result, we believe that the measurement of brain stem volume with an objective and efficient calculation method will contribute to the early diagnosis of neurodegenerative diseases, as well as to determine the rate of disease progression, and the outcomes of treatment.

Spinal cord markers in ALS: diagnostic and biomarker considerations

Despite considerable involvement of the spinal cord in amyotrophic lateral sclerosis (ALS), current biomarker research is primarily centred on brain imaging and CSF proteomics. In clinical practice, spinal cord imaging in ALS is performed primarily to rule out alternative conditions in the diagnostic phase of the disease. Quantitative spinal cord imaging has traditionally been regarded as challenging, as it requires high spatial resolution while minimizing partial volume effects, physiological motion and susceptibility distortions. In recent years however, as acquisition and post-processing methods have been perfected, a number of exciting and promising quantitative spinal imaging and electrophysiology techniques have been developed. We performed a systematic review of the trends, methodologies, limitations and conclusions of recent spinal cord studies in ALS to explore the diagnostic and prognostic potential of spinal markers. Novel corrective techniques for quantitative spinal cord imaging are systematically reviewed. Recent findings demonstrate that imaging techniques previously used in brain imaging, such as diffusion tensor, functional and metabolic imaging can now be successfully applied to the human spinal cord. Optimized electrophysiological approaches make the non-invasive assessment of corticospinal pathways possible, and multimodal spinal techniques are likely to increase the specificity and sensitivity of proposed spinal markers. In conclusion, spinal cord imaging is an emerging area of ALS biomarker research. Novel quantitative spinal modalities have already been successfully used in ALS animal models and have the potential for development into sensitive ALS biomarkers in humans.

Presymptomatic spinal cord neurometabolic findings in SOD1-positive people at risk for familial ALS

OBJECTIVE

It has been speculated that amyotrophic lateral sclerosis (ALS) is characterized by a premanifest period during which neurodegeneration precedes the appearance of clinical manifestations. Magnetic resonance spectroscopy (MRS) was used to measure ratios of neurometabolites in the cervical spine of asymptomatic individuals with a mutation in the SOD1 gene (SOD1+) and compare their neurometabolic ratios to patients with ALS and healthy controls.

METHODS

A cross-sectional study of (1)H-MRS of the cervical spine was performed on 24 presymptomatic SOD1+ volunteers, 29 healthy controls, and 23 patients with ALS. All presymptomatic subjects had no symptoms of disease, normal forced vital capacity, and normal electromyographic examination. Relative concentrations of choline (Cho), creatine (Cr), myo-inositol (Myo), and N-acetylaspartate (NAA) were determined.

RESULTS

NAA/Cr and NAA/Myo ratios are reduced in both SOD1+ subjects (39.7%, p = 0.001 and 18.0%, p = 0.02) and patients with ALS (41.2%, p < 0.001 and 24.0%, p = 0.01) compared to controls. Myo/Cr is reduced (10.3%, p = 0.02) in SOD1+ subjects compared to controls, but no difference was found between patients with ALS and controls. By contrast, NAA/Cho is reduced in patients with ALS (24.0%, p = 0.002), but not in presymptomatic SOD1+ subjects compared to controls.

CONCLUSIONS

Changes in neurometabolite ratios in the cervical spinal cord are evident in presymptomatic SOD1+ individuals in advance of symptoms and clinical or electromyographic signs of disease. These changes reflect a reduction in NAA/Cr and NAA/Myo. Neurometabolic changes in this population resemble changes observed in patients with clinically apparent ALS. This suggests that neurometabolic changes occur early in the course of the disease process.

Autoimmunity in amyotrophic lateral sclerosis: past and present

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease affecting particularly motor neurons for which no cure or effective treatment is available. Although the cause of ALS remains unknown, accumulative evidence suggests an autoimmune mechanism of pathogenesis. In this paper, we will summarize the current research related to autoimmunity in the sporadic form of ALS and discuss the potential underlying pathogenic mechanisms and perspectives. Presented data supports the view that humoral immune responses against motor nerve terminals can initiate a series of physiological changes leading to alteration of calcium homeostasis. In turn, loss of calcium homeostasis may induce neuronal death through apoptotic signaling pathways. Additional approaches identifying specific molecular features of this hypothesis are required, which will hopefully allow us to develop techniques of early diagnosis and effective therapies.

Neuroimaging in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a motor neuron disease characterized by progressive degeneration of upper motor neurons (UMN) and lower motor neurons (LMN). While LMN dysfunction can be confirmed by electromyography (EMG) and muscle biopsy, UMN involvement is more difficult to detect, particularly in the early phase. Objective and sensitive measures of UMN dysfunction are needed for early diagnosis and monitoring of disease progression and therapeutic efficacy. Advanced magnetic resonance imaging (MRI) techniques, such as diffusion, perfusion, magnetization transfer imaging, functional MRI, and MR spectroscopy, provide insight into the pathophysiological processes of ALS and may have a role in the identification and monitoring of UMN pathology. This article provides an overview of these neuroimaging techniques and their potential roles in ALS.

Magnetic resonance spectroscopy of the cervical cord in amyotrophic lateral sclerosis

The objective of this study was to use magnetic resonance spectroscopy (MRS) to compare metabolite ratios in the cervical spinal cord of ALS patients to healthy controls. Fourteen ALS patients and 16 controls were scanned using a 3T scanner. A rectangular voxel (8 × 5 × 35 mm) was placed along the main axis of the cord with the lower limit at the inferior aspect of the C2 vertebral body. MRS was performed with a point-resolved spectroscopy (PRESS) sequence. Water signals were suppressed using a three-pulse chemical shift selective (CHESS) saturation sequence. Relative concentrations of choline (Cho), creatine (Cr), myo-inositol (Myo), and NAA were computed from metabolite peaks. Differences in metabolite ratios between ALS patients and controls were assessed with a Wilcoxon rank-sum test. The relationship of metabolite ratios to clinical measures (ALSFRS-R and FVC) was determined by Pearson correlation. The NAA/Cr and NAA/Myo ratios were reduced by 40% and 38%, respectively, in ALS patients. The reduction in NAA/Myo and NAA/Cho correlated significantly with FVC, with correlation coefficients of 0.66 and 0.60, respectively. In conclusion, MR spectra can reliably be obtained from the cervical spinal cord in ALS. MRS of the cervical cord may be a useful biomarker of disease progression.

Degeneration of the mid-cingulate cortex in amyotrophic lateral sclerosis detected in vivo with MR spectroscopy

BACKGROUND AND PURPOSE

Various lines of evidence implicate cerebral involvement beyond the motor cortex in ALS, including the cingulate gyrus and the thalamus. The purpose of this study was to assess neurodegeneration in these regions in vivo by using MRSI.

MATERIALS AND METHODS

Fourteen patients with ALS and 14 healthy controls underwent MRSI by using a coronal acquisition scheme. The NAA/Cho ratio was quantified in the MCC, thalamus, and motor cortex (PCG).

RESULTS

NAA/Cho was reduced in the MCC in patients with ALS compared with the controls (P = .0004). There was no difference in NAA/Cho in the thalamus (P = .59). We also found a strong correlation of NAA/Cho among the PCG, MCC, and the thalamus in controls, which was absent in patients with ALS.

CONCLUSIONS

Neurodegeneration beyond the motor cortex is present in the MCC in ALS. The significant correlation of NAA/Cho among the PCG, MCC, and the thalamus in healthy subjects likely reflects the neuronal connectivity among these regions. The loss of these relationships in patients with ALS suggests that such connectivity is not responsible for the pattern of degeneration in these regions.

MR spectroscopy findings in early stages of motor neuron disease

BACKGROUND AND PURPOSE

Upper motor neuron degeneration varies in different phenotypes of MND. We used single-voxel MR spectroscopy of the primary motor cortex to detect corticomotoneuron degeneration and glial hyperactivity in different phenotypes of MND with a relatively short disease duration, contributing to further delineation of the phenotypes.

MATERIALS AND METHODS

We prospectively included patients with ALS-B, ALS-L, and PMA and compared their data with those of patients with PLS and healthy controls. Each cohort consisted of 12 individuals. Disease duration was <1 year in ALS and PMA, but longer in PLS by definition. Follow-up examination was at 6 months. We measured ALSFRS-R, finger- and foot-tapping speed, and levels of the following: 1) NAAx, 2) mIns, and 3) Glx in the primary motor cortex.

RESULTS

At baseline, we found significantly decreased NAAx levels and increased mIns levels in PLS. Levels of NAAx and mIns in patients with ALS-L and ALS-B were not significantly different from those in controls, but NAAx levels were significantly lower compared with those in PMA. At follow-up, only in PMA was a decrease of NAAx demonstrated. Glx levels varied widely in all groups. Levels of NAAx and mIns correlated well with clinical variables.

CONCLUSIONS

Metabolite changes suggest neuronal dysfunction and active glial involvement in PLS. The corticomotoneuron is affected in early ALS-B and ALS-L, but at a later stage also in PMA. MR spectroscopy data are useful to obtain insight into the disease process at the level of the upper motor neuron in various phenotypes of MND.

Study of the features of proton MR spectroscopy ((1)H-MRS) on amyotrophic lateral sclerosis

PURPOSE

To study the features of proton magnetic resonance spectroscopy ((1)H-MRS) on amyotrophic lateral sclerosis (ALS) and its relation with clinical scale.

MATERIALS AND METHODS

Fifteen patients with definite or probable ALS and 15 age- and gender-matched normal controls were enrolled. (1)H-MRS was performed on a 3.0 Tesla GE imaging system (GE Healthcare, Milwaukee, WI). TE-averaged Point Resolved Selective Spectroscopy was used. N-acetylaspartate (NAA), creatine (Cr), Glu, and Glx (glutamate + glutamine) values of the motor cortex and posterior limb of internal capsule were acquired. The t-test was used to compare differences between groups, and the correlations between the above values and clinical scale were analyzed.

RESULTS

The motor area and posterior limb of the internal capsule of ALS patients had lower NAA/Cr (1.91 +/- 0.34, 1.53 +/- 0.17) compared with normal subjects (2.23 +/- 0.33, 1.66 +/- 0.07), and the differences between groups were statistically significant (P < 0.01, 0.01). ALS patients had higher Glu/Cr (0.34 +/- 0.05, 0.29 +/- 0.06) and Glx/Cr (0.40 +/- 0.04, 0.33 +/- 0.06) compared with normal subjects (0.30 +/- 0.03, 0.25 +/- 0.04) and (0.32 +/- 0.05, 0.26 +/- 0.03), and the differences between groups were statistically significant (P < 0.01, 0.01). The Norris scale was negatively correlated with Glx/Cr of primary motor cortex by lineal correlation analysis (r = -0.75), and this correlation had statistical significance (F = 16.60; P = 0.001).

CONCLUSION

Neuronal loss and Glu+Gln increase can be detected by using proton MRS in ALS patients. (1)H-MRS is an useful tool in reflecting the characteristic changes of metabolite in ALS.

The present and the future of neuroimaging in amyotrophic lateral sclerosis

In patients with ALS, conventional MR imaging is frequently noninformative, and its use has been restricted to excluding other conditions that can mimic ALS. Conversely, the extensive application of modern MR imaging-based techniques to the study of ALS has undoubtedly improved our understanding of disease pathophysiology and is likely to have a role in the identification of potential biomarkers of disease progression. This review summarizes how new MR imaging technology is changing dramatically our understanding of the factors associated with ALS evolution and highlights the reasons why it should be used more extensively in studies of disease progression, including clinical trials.

EFNS guidelines on the use of neuroimaging in the management of motor neuron diseases

BACKGROUND AND PURPOSE

These European Federation of Neurological Societies guidelines on neuroimaging of motor neuron diseases (MNDs) are designed to provide practical help for the neurologists to make appropriate use of neuroimaging techniques in patients with MNDs, which ranges from diagnostic and monitoring aspects to the in vivo study of the pathobiology of such conditions.

METHODS

Literature searches were performed before expert members of the Task Force wrote proposal. Then, consensus was reached by circulating drafts of the manuscript to the Task Force members and by discussion of the classification of evidence and recommendations.

RESULTS AND CONCLUSIONS

The use of conventional MRI in patients suspected of having a MND is yet restricted to exclude other causes of signs and symptoms of MN pathology [class IV, level good clinical practice point (GCPP)]. Although the detection of corticospinal tract hyperintensities on conventional MRI and a T2-hypointense rim in the pre-central gyrus can support a pre-existing suspicion of MND, the specific search of these abnormalities for the purpose of making a firm diagnosis of MND is not recommended (class IV, level GCPP). At present, advanced neuroimaging techniques, including diffusion tensor imaging and proton magnetic resonance spectroscopic imaging, do not have a role in the diagnosis or routine monitoring of MNDs yet (class IV, level GCPP). However, it is strongly advisable to incorporate measures derived from these techniques into new clinical trials as exploratory outcomes to gain additional insights into disease pathophysiology and into the value of these techniques in the (longitudinal) assessment of MNDs (class IV, level GCPP).

Multinuclear magnetic resonance spectroscopy for in vivo assessment of mitochondrial dysfunction in Parkinson's disease

Parkinson's disease (PD) is a common and often devastating neurodegenerative disease affecting up to one million individuals in the United States alone. Multiple lines of evidence support mitochondrial dysfunction as a primary or secondary event in PD pathogenesis; a better understanding, therefore, of how mitochondrial function is altered in vivo in brain tissue in PD is a critical step toward developing potential PD biomarkers. In vivo study of mitochondrial metabolism in human subjects has previously been technically challenging. However, proton and phosphorus magnetic resonance spectroscopy ((1)H and (31)P MRS) are powerful noninvasive techniques that allow evaluation in vivo of lactate, a marker of anaerobic glycolysis, and high energy phosphates, such as adenosine triphosphate and phosphocreatine, directly reflecting mitochondrial function. This article reviews previous (1)H and (31)P MRS studies in PD, which demonstrate metabolic abnormalities consistent with mitochondrial dysfunction, and then presents recent (1)H MRS data revealing abnormally elevated lactate levels in PD subjects.

MR spectroscopy in neurodegenerative disease

Unlike traditional, tracer-based methods of molecular imaging, magnetic resonance spectroscopy (MRS) is based on the behavior of specific nuclei within a magnetic field and the general principle that the resonant frequency depends on the nucleus' immediate chemical environment. Most clinical MRS research has concentrated on the metabolites visible with proton spectroscopy and measured in specified tissue volumes in the brain. This methodology has been applied in various neurodegenerative disorders, most frequently utilizing measures of N-acetylaspartate as a neuronal marker. At short echo times, additional compounds can be quantified, including myo-inositol, a putative marker for neuroglia, the excitatory neurotransmitter glutamate and its metabolic counterpart glutamine, and the inhibitory neurotransmitter gamma-aminobutyric acid. 31P-MRS can be used to study high-energy phosphate metabolites, providing an in vivo assessment of tissue bioenergetic status. This review discusses the application of these techniques to patients with neurodegenerative disorders, including Parkinson's disease, Alzheimer's disease, and amyotrophic lateral sclerosis.

[Indications for cerebral MR proton spectroscopy in 2007]

Magnetic resonance spectroscopy (MRS) is being increasingly performed alongside the more conventional MRI sequences in the exploration of neurological disorders. It is however important to clearly differentiate its clinical applications aiming at improving the differential diagnosis or the prognostic evaluation of the patient, from the research protocols, when MRS can contribute to a better understanding of the pathophysiology of the disease or to the evaluation of new treatments. The most important applications in clinical practice are intracranial space occupying lesions (especially the positive diagnosis of intracranial abscesses and gliomatosis cerebri and the differential diagnosis between edema and tumor infiltration), alcoholic, hepatic, and HIV-related encephalopathies and the exploration of metabolic diseases. Among the research applications, MRS is widely used in multiple sclerosis, ischemia and brain injury, epilepsy and neuro degenerative diseases.

The Role of Quantitative Neuroimaging Indices in the Differentiation of Ischemia From Demyelination: An Analytical Study With Case Presentation

BACKGROUND AND PURPOSE

Differentiation of acute and subacute ischemic stroke lesions from acute demyelinating lesions of multiple sclerosis (MS) may not be possible on conventional magnetic resonance imaging (MRI). Both lesion types enhance on T1 with gadolinium (Gd) contrast and both are hyperintense on diffusion-weighted imaging (DWI). This study is an analysis of two quantitative MR indices: (1) calculated apparent diffusion coefficients (ADCs) and (2) T2 relaxation times (T2R) as means toward differentiating acute ischemic lesions from acute demyelinating lesions. Chronic ischemic and demyelinating lesions were evaluated for comparison as well.

METHODS

The MRI of nine patients with both acute and chronic ischemic lesions and six patients with both acute and chronic demyelinating lesions were analyzed for ADC and T2Rs. The indices were measured by manually placing regions of interest (ROIs) at the anatomic center of the acute lesion. Acute ischemic lesions were chosen by their hyperintensity on DWI and hypointensity on ADC mapping. Acute demyelinating lesions were selected by peripheral contrast enhancement after the administration of Gd. Computation of the ADC involved the diffusion coefficient on a region by region basis as follows: D = -(b(0)/b(1000))ln(S(b1000)/S(b0)), where S(b1000) is the signal intensity on DWI and S(b0) is the signal intensity on T2 with diffusion sensitivities of b(0) and b(1000), respectively. Computation of the T2R was made as follows: T2R = (TE(T2)--TE(PD))/(ln SI(PD)--ln SI(T2)), where TE is the echo time of the different pulse sequences, SI is signal intensity on the different echo sequences, and PD represents proton density sequence.

RESULTS

Twenty-nine acute ischemia, 27 acute demyelination, 28 chronic ischemia, and 43 chronic demyelination image sets were analyzed. The differences between ADC(acute infarct) (0.760) versus ADC(acute plaque) (1.106) were significant (p < 0.02). The differences between T2R(acute infarct) (235.5) versus T2R(acute plaque) (170.5) were also significant (p < 0.02).

CONCLUSIONS

ADC in combination with T2R is a useful tool to differentiate acute ischemic from acute demyelinating lesions. The use of these neuroimaging indices along with magnetic resonance spectroscopy metabolite ratios is then demonstrated in elucidating the pathophysiological mechanism for a case of delayed posttraumatic bilateral internuclear ophthalmoplegia.

Brainstem 1H-MR spectroscopy in patients with Parkinson's disease with REM sleep behavior disorder and IPD patients without dream enactment behavior

OBJECTIVES

The objective of our study was to evaluate brainstem involvement by 1H-MR spectroscopy (1H-MRS) method in patients with idiopathic Parkinson's disease (IPD) with REM sleep behavior disorder (RBD) and IPD without dream enactment behavior.

PATIENTS AND METHODS

We prospectively studied 12 IPD (3 females, 9 males) with a clinically and electrophysiologically confirmed RBD and 12 IPD (3 females, 9 males) patients without dream enactment behavior followed in Outpatient Clinics for Movement Disorders of Department of Neurology, Haseki Hospital. Using long and short TE single voxel 1H-MRS directed at ventral and dorsal pons, long TE NAA/Cr, Ch/Cr and short TE NAA/Cr, Ch/Cr, MI/Cr values of both groups were compared.

RESULTS

Although no difference was found between groups with RBD and IPD without dream enactment behavior in demographic characteristics, duration of disease, mean levodopa dosage and duration of levodopa use, all UPDRS scores (total, motor and cognitive) were worse in RBD group (p<0.05). There was no statistically significant difference in long TE NAA/Cr, Ch/Cr and short TE NAA/Cr, Ch/Cr, MI/Cr values obtained in both groups (p>0.05).

CONCLUSION

1H-MRS does not detect marked metabolic differences in the pons in subjects with IPD with RBD and IPD without dream enactment behavior. This finding suggests either that present methodologies are not sensitive to detect subtle metabolic changes in the pons of subjects with RBD or that the primary lesion of RBD exists in other REM sleep-related brain regions beyond the pons such as the substantia nigra, the basal ganglia or the limbic system.

ALS surrogate markers. MRS

Magnetic resonance spectroscopy (MRS) allows the quantitative assessment of neuronal integrity in vivo based on the resonance intensity of N-acetylaspartate (NAA). A simple approach to quantitation that is commonly used is to quantify the resonance intensity of NAA with respect to creatine (Cr). In patients with ALS, NAA/Cr density is decreased in areas of the brain that contribute significantly to the corticospinal tract. Since MRS is non-invasive, it can be easily used to monitor the evolution of regional changes in NAA/Cr over time. The changes in NAA/Cr over a period of months are small, however, and challenge the precision of the method.

Reduced NAA in motor and non-motor brain regions in amyotrophic lateral sclerosis: a cross-sectional and longitudinal study

OBJECTIVES

After replication of previous findings we aimed to: 1) determine if previously reported (1)H MRSI differences between ALS patients and control subjects are limited to the motor cortex; and 2) determine the longitudinal metabolic changes corresponding to varying levels of diagnostic certainty.

METHODS

Twenty-one patients with possible/suspected ALS, 24 patients with probable/definite ALS and 17 control subjects underwent multislice (1)H MRSI co-registered with tissue-segmented MRI to obtain concentrations of the brain metabolites N-acetylaspartate (NAA), creatine, and choline in the left and right motor cortex and in gray matter and white matter of non-motor regions in the brain.

RESULTS

In the more affected hemisphere, reductions in the ratios, NAA/Cho and NAA/Cre+Cho were observed both within (12.6% and 9.5% respectively) and outside (9.2% and 7.3% respectively) the motor cortex in probable/definite ALS. However, these reductions were significantly greater within the motor cortex (P<0.05 for NAA/Cho and P<0.005 for NAA/Cre+Cho). Longitudinal changes in NAA were observed at three months within the motor cortex of both possible/suspected ALS patients (P<0.005) and at nine months outside the motor cortex of probable/definite patients (P<0.005). However, there was no clear pattern of progressive change over time.

CONCLUSIONS

NAA ratios are reduced in the motor cortex and outside the motor cortex in ALS, suggesting widespread neuronal injury. Longitudinal changes of NAA are not reliable, suggesting that NAA may not be a useful surrogate marker for treatment trials.

Age-related metabolic changes in the upper brainstem tegmentum by MR spectroscopy

Several neurodegenerative disorders have a profound metabolic and structural impact on the brainstem. MR spectroscopy provides metabolic information non-invasively and has the potential to characterize the changes associated with normal aging and differentiate them from neurodegenerative alterations. The present work was aimed at studying the upper brainstem tegmentum at the midbrain and pontine levels in 57 adult normal volunteers, aged 23-79 years, with long-echo time proton MR spectroscopy to evaluate possible regional differences and the effect of age. Higher ratios of N-acetyl aspartate (NAA)/total creatine (Cr) and choline-containing compounds (Cho)/Cr were observed in the pons compared to the midbrain, resulting from higher net NAA and Cho content. In the midbrain, there was a linear decline of NAA and Cho with age in subjects over 50, most probably related to neuronal tissue loss. In the pons, such an aging effect was not observed, with subjects over 50 showing higher Cr and Cho than the under-50 subjects. Our findings provided evidence of regional differences and suggest different effects of age on the two studied brainstem segments, hitherto undescribed.

Neuroimaging in amyotrophic lateral sclerosis

Several neuroimaging modalities have been used with varying success to aid the clinical process of establishing the diagnosis of amyotrophic lateral sclerosis (ALS). By demonstrating evidence of occult upper motor neuron degeneration in vivo, a speedier and more definitive diagnosis in suspected cases could lead to earlier treatment and earlier enrollment in clinical trials. Findings compatible with ALS on routine MRI are not consistently found and are non-specific. Thus, routine anatomic imaging is useful in ruling out diseases that mimic ALS, but not in classification of new cases. Functional imaging techniques, such as PET and fMRI, have provided fascinating insights into the cortical functional reorganization that accompanies muscular weakness. PET and SPECT have revealed involvement of regions of the brain beyond the motor cortex, something not well appreciated by pathological examination. Of great need is a surrogate marker of therapeutic efficacy to make drug evaluation more efficient; neuroimaging, and magnetic resonance spectroscopy in particular, holds great promise in this regard in addition to helping us better understand the of neurodegeneration.

Different types of botulinum toxin in humans

In humans, botulinum neurotoxin (BoNT) serotype A (BoNT/A) is a useful therapeutic tool, but different BoNT serotypes may be useful when a specific immune resistance related to BoNT/A is proved. BoNT serotype F (BoNT/F) was injected into human muscles but its effects are shorter compared to BoNT/A, whereas BoNT serotype B (BoNT/B) is effective in humans only if injected at very high doses. BoNT serotype C (BoNT/C) has a general profile of action similar to BoNT/A. Nevertheless, a comparison between these different BoNTs in human has not yet been reported. To establish the general profile of these different BoNTs in humans and the spread in near and untreated muscles we conducted an electrophysiological evaluation in 12 healthy volunteers by injecting BoNT/A (BOTOX 15MU), BoNT/B (NeuroBloc 1500MU), BoNT/F (15MU), BoNT/C (15MU) and a saline solution (placebo) in the abductor digiti minimi muscle (ADM) in a double-blind manner. The compound muscle action potential (CMAP) amplitude variation, before and at 2, 4, 6 and 8 weeks after the injections, was evaluated in the ADM, the fourth dorsal interosseus, the first dorsal interosseus and the abductor pollicis brevis APB. We detected an earlier recovery for BoNT/F when compared to the other BoNTs. No significant differences in the local or distant BoNT spread was observed among the different serotypes. We conclude that in humans, BoNT/B and BoNT/C have a general profile similar to BoNT/A and as such these serotypes could be alternative therapies to BoNT/A. BoNT/F might be useful when only a short duration of neuromuscular blockade is required.

Proton magnetic resonance spectroscopy: clinical applications in patients with brain lesions

CONTEXT

Proton spectroscopy has been recognized as a safe and noninvasive diagnostic method that, coupled with magnetic resonance imaging techniques, allows for the correlation of anatomical and physiological changes in the metabolic and biochemical processes occurring within previously-determined volumes in the brain. There are two methods of proton magnetic resonance spectroscopy: single voxel and chemical shift imaging.

OBJECTIVE

The present work focused on the clinical applications of proton magnetic resonance spectroscopy in patients with brain lesions.

CONCLUSIONS

In vivo proton spectroscopy allows the detection of certain metabolites in brain tissue, such as N-acetyl aspartate, creatine, choline, myoinositol, amino acids and lipids, among others. N-acetyl aspartate is a neuronal marker and, as such, its concentration will decrease in the presence of aggression to the brain. Choline increase is the main indicator of neoplastic diseases. Myoinositol is raised in patients with Alzheimer's disease. Amino acids are encountered in brain abscesses. The presence of lipids is related to necrotic processes.

Amyotrophic lateral sclerosis and primary lateral sclerosis: evidence-based diagnostic evaluation of the upper motor neuron

Magnetic resonance imaging and MR spectroscopy are important tools in the diagnostic evaluation of patients with suspected motor neuron disease. Further investigation is needed to determine and to compare the utility of various neuroimaging markers for diagnosis and disease progression [112]. Newer MR tools, such as diffusion tensor imaging, magnetization transfer imaging, and functional MR imaging, have substantial promise as scientific and clinical tools in this ongoing endeavor.

A prospective, randomized, placebo-controlled evaluation of corticoneuronal response to intrathecal BDNF therapy in ALS using magnetic resonance spectroscopy: feasibility and results

During the multicenter, phase III trial of intrathecal BDNF in ALS, we evaluated the neuronal marker N-acetylaspartate (NAA) as a surrogate marker of therapeutic efficacy using proton magnetic resonance spectroscopic imaging (MRSI) in a prospective and blinded manner. Selected subjects tolerated the study well without pump malfunction. The NAA to creatine (Cr) intensity ratio (NAA/Cr) was measured in the precentral and postcentral gyri, the superior parietal lobule, the supplementary motor area, and the premotor cortex. After 4.5+/-0.6 weeks treatment, NAA/Cr did not change significantly in any of the regions in the BDNF-treated group (n=5) compared to the placebo group (n=6). The lack of change in NAA correlated with the lack of clinical efficacy and supports the validity of NAA/Cr as a surrogate in this setting. MRSI is a feasible and safe method to evaluate intrathecal therapies in ALS.

Single-voxel long TE 1H-MR spectroscopy of the normal brainstem and cerebellum

PURPOSE

To evaluate the feasibility of single voxel 1H-MRS of the CNS structures contained in the posterior cranial fossa and to determine the distribution of the normal metabolite ratios, concentrations, and T2 relaxation times in the midbrain, pons, medulla, dentate nucleus and cerebellar vermis.

MATERIALS AND METHODS

A total of 147 single voxel 1H-MR spectra with a point-resolved proton spectroscopy sequence (PRESS) sequence and echo time (TE) of 136 or 272 msec were obtained in the midbrain, pons, medulla, dentate, and vermis of 31 healthy volunteers. In seven additional patients; the concentrations and T2 relaxation times of metabolites were obtained in the same locations (except the medulla) with an external phantom calibration method and a four TE PRESS technique.

RESULTS

Ten (27%) of 36 spectra acquired in the medulla were of poor quality. A similar ranking of the N-acetyl aspartate (NAA)/creatine (Cr) ratio and choline(Cho)/Cr ratios in the five locations for the two TEs was observed, with the highest values in the pons (mean NAA/Cr = 4.16 +/- 0.6 and Cho/Cr =2.66 +/- 0.6 at TE 272) and the lowest values in the dentate and vermis (mean NAA/Cr = 1.66 +/- 0.2 and Cho/Cr = 1.20 +/- 0.2 at TE 272). The analysis of variance showed significant regional differences of the NAA and Cr concentrations, which had the highest values in the dentate. Non-significant regional differences were observed for the concentration of Cho and for the T2 of the metabolites.

CONCLUSION

With the exception of the medulla, single voxel 1H-MRS enables an in vivo biochemical analysis of the CNS structures contained in the posterior cranial fossa. Regional differences in the metabolite ratios and concentrations must be considered when employing 1H-MRS for evaluation of diseases of the brainstem and cerebellum.