Proton magnetic resonance spectroscopy in a pathologically confirmed acute demyelinating lesion

Role of Neuroimaging Modality in the Assessment of Oxidative Stress in Brain: A Comprehensive Review

Background & Objective:

Oxidative stress (OS) is the secondary source of an injury in consequence to the earlier caused primary injury; it is the condition of an imbalance between oxidants and antioxidants within the physiological system. OS causes alterations in proteins and DNA structure, leading to inflammation, apoptotic cell death, and tissue damage. Neurodegenerative diseases (NDDs) such as Alzheimer's disease, Parkinson's disease, Glioma-induced neurodegeneration and the normal aging-related neuro-degeneration are primarily associated with the increased OS. The present review article is committed to delivering a comprehensive overview of the current neuroimaging modalities which estimates an indirect correlate of OS in the brain. OS-induced changes in white matter tracts and the gray matter volumes are reviewed assessing the role of diffusion tensor imaging (DTI) and voxel-based morphometry (VBM) respectively. Further, the role of magnetic resonance spectroscopy (MRS) to assess the OS-induced alterations of chemical moieties, and thus the resultant structural implications in the neurological disorders are also briefly as well as precisely reviewed.

Conclusions:

In the present review article we present an overview of the role of neuroimaging modalities in the diagnosis, and longitudinal assessment during treatment of the OS induced changes.

Benign course of tumour-like multiple sclerosis. Report of five cases and literature review

BACKGROUND

Multiple sclerosis (MS) with initial neuroradiological features suggestive of brain tumour (tumour-like MS) may represent a challenging diagnosis.

METHODS

Among the patients seen at the MS centre of our Institution between 2000 and 2010, we identified cases presenting with a large (diameter>2 cm), well-defined lesion, suggestive of brain tumour on initial brain magnetic resonance imaging (MRI). Only patients with at least 10 years follow-up were included.

RESULTS

Five young women with MS who presented with a tumour-like lesion on initial brain MRI are described. All cases presented with sudden-onset neurological deficits due to a single large brain lesion compatible with neoplasm at MRI. Two cases underwent brain stereotactic biopsy, both misdiagnosed as astrocytoma. However, the subsequent clinical and MRI follow-up was consistent with MS in all cases. Unnecessary surgery and radiotherapy were responsible for disability in two cases. In three cases, the course of the disease remains benign after more than 13 years from symptoms onset.

CONCLUSIONS

Our report of clinical, radiological and pathological features of five tumour-like MS cases confirms that it is mandatory to consider a demyelinating process in the differential diagnosis of tumour-like brain lesions. Many tumour-like MS cases may have a favourable long term prognosis.

1H-MRS for the diagnosis of acute disseminated encephalomyelitis: insight into the acute-disease stage

BACKGROUND

Acute disseminated encephalomyelitis (ADEM) is a demyelinating disorder of the central nervous system (CNS). Differentiating ADEM from other inflammatory disorders, such as multiple sclerosis, is not always conclusive using conventional MRI.

OBJECTIVE

To evaluate longitudinal magnetic resonance spectroscopy (MRS) changes that distinguish ADEM from other inflammatory disorders.

MATERIALS AND METHODS

MRI/MRS scans were performed in seven patients with ADEM during the acute and chronic phases of the disease.

RESULTS

Partial recovery was detected between the acute and chronic phases in choline/creatine ratio. Major elevation of lipids and reduction in myo-inositol/creatine ratio was detected in all patients during the acute phase, followed by a reduction in lipids peak and elevation above normal in myo-inositol/creatine ratio during the chronic phase.

CONCLUSION

Consistent and unique MRS changes in metabolite ratios between the acute and chronic presentations of the disease were found. To the best of our knowledge, these patterns have not been described in other inflammatory disorders and might assist in the early diagnosis of ADEM.

Magnetic resonance spectroscopy features of normal-appearing white matter in patients with acute brucellosis

We aimed to evaluate whether the subtle metabolic cerebral changes are present in normal-appearing white matter on conventional MRI, in patients with acute brucellosis, by using MR spectroscopy (MRS). Sixteen patients with acute brucellosis and 13 healthy control subjects were investigated with conventional MRI and single-voxel MRS. Voxels were placed in normal-appearing parietal white matter (NAPWM). N-Acetyl aspartate (NAA)/creatine (Cr) and choline (Cho)/Cr ratios were calculated. There was no significant difference between the study subjects and the control group in NAA/Cr ratios obtained from NAPWM. However, the Cho/Cr ratios were significantly higher in patients with acute brucellosis compared to controls (p=0.01). MRS revealed metabolic changes in normal-appearing white matter of patients with brucellosis. Brucellosis may cause subtle cerebral alterations, which may only be discernible with MRS. Increased Cho/Cr ratio possibly represents an initial phase of inflammation and/or demyelination process of brucellosis.

[Pseudotumoral presentation of multiple sclerosis]

INTRODUCTION

Multiple sclerosis is one of the most common diseases of the central nervous system with a variety of clinical and radiological presentations. Several cases have been reported of demyelinating processes mimicking a tumour of the central nervous system.

OBSERVATION

A 45-year-old man was admitted with acute right hemiparesis associated with intracranial hypertension syndrome. Initial CT scan and magnetic resonance imaging of the brain revealed a mass lesion in the left hemisphere. Combined, careful history taking, assessment of the clinical course and magnetic resonance imaging findings led to the final diagnosis of multiple sclerosis.

COMMENTARY AND CONCLUSION

This case report illustrates the wide variety of multiple sclerosis presentation. Recognition of the demyelinating tumor like lesions is essential; the diagnosis of multiple sclerosis should be considered in young adults with similar presentations.

Prolonged intracortical delay of long-latency reflexes: electrophysiological evidence for a cortical dysfunction in multiple sclerosis

Convincing evidence suggests that long-latency reflexes (LLRs) are capable of testing the transcortical sensorimotor reflex arch. By subtracting the sum of the latencies of N20 (afferent branch) and transcranially elicited motor evoked potentials (MEP; efferent branch) from the LLR II latency, the cortical relay time (CRT) can also be obtained, which is alleged to represent the time required for the cortical sensorimotor integration. The aim of the present study was to investigate if a cortical dysfunction occurs in multiple sclerosis (MS). Median nerve somatosensory evoked potentials (SEPs), MEPs and LLRs were recorded from the upper limbs of 23, not severely disabled MS patients in acute phases of the disease. Eighteen age and sex matched healthy volunteers served as controls. N20, MEP, LLR II latencies were measured, and the CRT was calculated for each limb. The statistical comparison between patients and controls was only weakly significant by taking into account conduction times along either the afferent (N20) or the efferent (MEP) pathways. On the contrary, it turned out to be considerably significant if both branches of the transcortical sensorimotor reflex arch, together with the intracortical pathway, were simultaneously tested by means of the LLRs. Moreover, the patients showed a significantly higher CRT compared with that found in the control subjects. These findings are consistent with a prolonged intracortical delay of LLRs in the MS group and suggest the occurrence of conduction velocity slowing and/or synaptic transmission impairment along the sensorimotor intracortical pathway in MS.

Recurrent tumefactive demyelination in a child

A 13-year-old female presented with two episodes of hemiplegia and hemianopia involving opposite sides, each time associated with seizures. On both occasions, the magnetic resonance (MR) scan showed a giant demyelinating, peripherally enhancing lesion with mass effect. MR spectroscopy (MRS) was indistinguishable from a tumor. At the first episode, she had undergone tumor decompression but the histopathology revealed an acute demyelinating lesion with no evidence of tumor. Each time there was partial clinical recovery and resolution of the radiological lesion, the patient having received corticosteroids during both of the episodes. She also developed hemiballismus postoperatively which resolved on withdrawing phenytoin. It is suggested that a trial of corticosteroids be given in suspected tumefactive demyelinating lesions, although they may be indistinguishable from a tumor.

The nonspecific nature of proton spectroscopy in brain masses in children: a series of demyelinating lesions

MRI imaging has significantly improved the detection of brain lesions over the past few decades. It has high sensitivity to intracranial pathology but confident preoperative tissue diagnosis is relatively unusual. MR spectroscopy provides in-vivo biochemical information and has been used to improve the low specificity of tumour diagnosis. During the last decade there have been a number of reports making the case that proton spectroscopy can distinguish different grades of glial tumours and in some situations provide information on histological type. We report four children who presented with neurological symptoms and focal masses on MRI. MRS in each of them gave results consistent with textbook descriptions of malignancy, but in all four cases the abnormalities were subsequently shown to be due to demyelination. We reiterate that spectroscopic appearances are nonspecific and spectroscopic data should be evaluated in the light of concurrent imaging features and the clinical presentation.

Axonal damage in multiple sclerosis plaques: a combined magnetic resonance imaging and 1H-magnetic resonance spectroscopy study

The purpose of this study was to compare magnetic resonance imaging (MRI) features and proton MR spectroscopy (1H-MRS) patterns of multiple sclerosis (MS) plaques in order to define the metabolic substrate in different lesion subtypes. Combined MRI and single-voxel 1H-MRS investigation was performed in 54 MS patients (47 relapsing remitting (RR) and seven secondary progressive (SP)). Sixty-seven MS lesions were selected. Thirty-seven lesions were Gadolinium (Gd) enhancing (nine isointense and 28 hypointense on pre-contrast T(1)-weighted scans) and 30 Gd unenhancing (six isointense and 24 hypointense on pre- and post-contrast T(1)-weighted scans). Choline (Cho), creatine (Cr), N-acetyl aspartate (NAA) and lactate were evaluated in 1H spectra acquired from MS plaques and from normal white matter (NWM) of 22 neurological controls. MS lesions of RR patients were characterized by a significant increase of Cho/Cr and decrease of NAA/Cr and NAA/Cho ratios. No significant metabolite changes were found in lesions of SP patients. Gd enhancing plaques showed lactate signal with higher frequency (37.8%) than Gd unenhancing plaques (16.7%) (p=0.04). A significant increase of Cho/Cr was found in Gd enhancing lesions when compared to controls (p<0.01), and to Gd unenhancing lesions (p<0.05). In particular, there was evidence of a significant increase of Cho/Cr in pre-contrast T(1) hypointense Gd enhancing lesions (p<0.01 vs. controls). The Gd unenhancing lesions (p<0.01), in particular the T(1) hypointense group (p<0.05), showed a significant decrease of NAA/Cr only when compared to controls. These data confirm that in vivo MRS indicates key pathological features of MS plaques. The increased Cho/Cr ratio found in Gd-enhancing plaques, in particular in the T(1) hypointense lesions, may reflect increased membrane cell turnover. The T(1) hypointense Gd unenhancing plaques better reflect axonal damage, as suggested by the decrease of NAA/Cr. Nevertheless, the lack of statistical differences in NAA/Cr between plaque subgroups suggests that axonal impairment might occur even in the early stages.

Frontal lobe proton magnetic-resonance spectroscopy in Graves' disease: a pilot study

Patients with hyperthyroidism may show impaired performance on several neuropsychological tests that require complex visual discrimination, conceptualization, mental flexibility or organization. These neurocognitive impairments appear to be consistent with prefrontal lobe dysfunction. This pilot study was undertaken to characterize the metabolite profile in the right prefrontal cortex in six patients with untreated Graves' disease by using in vivo proton magnetic-resonance spectroscopy (1H-MRS). For comparison, 1H-MRS was also carried out in seven healthy controls. The choline/creatine (Cho/Cr) and N-acetyl aspartate/creatine (Naa/Cr) ratios were determined. Cho/Cr ratios of the hyperthyroid patients were significantly lower than that of controls (means +/- SD = 0.61 +/- 0.09 vs. 0.90 +/- 0.18, p = .05). The two groups did not differ in their Naa/Cr ratios. Follow-up data after antithyroid treatment were available in three patients: Cho/Cr ratios were higher after treatment (euthyroidism) than before treatment (1.06 vs. 0.55; 0.82 vs. 0.54; 1.15 vs. 0.76). Tentatively, these preliminary data are most consistent with reversible reductions in the concentrations of choline-containing compounds (especially glycerophosphocholine and phosphocholine) in the prefrontal area during hyperthyroidism. However, these findings await confirmation by a definitive study with a larger sample size. A possible explanation of the findings is an altered brain cholinergic-adrenergic balance in hyperthyroidism.

Magnetic resonance imaging in multiple sclerosis

Conventional magnetic resonance imaging (MRI) techniques acquire signal mainly from differences in relaxation properties and density of free water protons. Thus, the sensitivity in depicting lesions is high but pathological specificity is poor. Efforts are being made to increase the diagnostic power of MRI; better correlation with the clinical presentation and the use of better MRI criteria have increased the specificity of the conventional T2 sequences. New sequences, such as fast spin echo, turbo spin echo (TSE) or those derived from inversion recovery (fluid attenuated inversion recovery), have improved the detection of lesions. Acute phase monitoring focuses on changes in disease activity (new, recurring, enlarging, gadolinium-enhancing lesions) and chronic phase monitoring allows appreciation of the burden of the disease. However, MRI is considered as a secondary outcome measure in phase III trials because of insufficient correlation with the clinical disability. There is a continuing search for techniques that correlate better with clinical measures of the disease, such as the quantification of 'black holes' on T1-weighted images or the cerebral and spinal atrophy. The basic aspects of the pathological lesions in multiple sclerosis such as oedema, membrane disruption, demyelination, gliosis, cellular infiltration and axonal loss, can be studied more precisely by the new magnetic resonance techniques, which should better describe the actual clinical impact of the destructive process. In the past year the importance of axonal loss has simultaneously been confirmed by magnetic resonance spectroscopy and pathological findings. However, magnetization transfer imaging, magnetic resonance diffusion imaging and functional MRI are under intensive investigation for a better analysis of these different factors that impact on the reversibility of the patients disability.