Proton magnetic resonance spectroscopy: a metabolic approach of cerebral tumors and their follow-up after external radiation therapy

The same physical principles are the basis of magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI). Proton MRS is easily performed with clinical magnets (> or = 1.5 T) and may be added to routine MRI studies to provide metabolic information on pathological tissues. It represents an important tool to detect several metabolic compounds. The article will review the current status of proton MRS with a particular emphasis upon its clinical utility for the diagnosis of brain tumors and for the evaluation of the efficacy of radiotherapy.     

Magnetic resonance spectroscopy: use in monitoring MELAS treatment

BACKGROUND: Sodium dichloroacetate has been used to treat patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS). Magnetic resonance spectroscopy (MRS) has been used to assess cerebral metabolism in MELAS, but to our knowledge, the findings of serial MRS studies performed after therapeutic intervention of strokelike episodes have not been reported. METHODS: Proton MRS was serially used to measure brain metabolites in strokelike regions and in clinically uninvolved brain regions in a patient with MELAS. PATIENT: A patient with MELAS and a strokelike episode clinically improved after treatment with sodium dichloroacetate. An elevated lactate-creatine ratio in the "stroke" region decreased on MRS studies after treatment. After a second episode, the lactate-creatine ratio increased from baseline in a region of the brain that was normal on magnetic resonance imaging scans. CONCLUSIONS: To our knowledge, this is the first study to assess the response to treatment of a MELAS strokelike episode and the first to show an increase in the lactate-creatine ratio in a brain region that was associated with a clinical abnormality, even though it appeared normal on magnetic resonance imaging. We conclude that MRS may help to monitor therapeutic efficacy in mitochondrial encephalomyopathies.     

Daily variations in pineal melatonin concentrations in inbred and outbred mice

Magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) and magnetic resonance spectroscopy (MRS) were successively recorded in a 3-year-old girl with the acute hemiplegia syndrome. She was admitted to our hospital with complaints of fever, loss of consciousness and right side dominant clonic convulsions evolving into status epilepticus, and then recovered with sequelae of aphasia and right hemiparesis. Electroencephalography showed a generalized slow rhythm at the onset, and very low activities on the left hemisphere in the follow-up records. Brain CT and MRI revealed edema of the left hemisphere initially, followed by left side dominant brain atrophy. No cerebral vascular lesion was detected by magnetic resonance angiography. N-Isopropyl-[123I]-iodoamphetamine SPECT showed marked hypoperfusion of the left hemisphere accompanied by crossed cerebellar diaschisis. MRS at the initial stage detected decreased N-acetyl-aspartic acid and increased lactic acid signals in the bilateral hemisphere, which subsequently normalized only on the right side. These findings suggested brain damage and neural cell death in the left cerebral hemisphere, caused by acute encephalopathy. SPECT and MRS are useful new techniques to study the pathophysiology of the acute hemiplegia syndrome.     

Malignoma versus bacterial spondylodiscitis: value of spinal MRI for the differential diagnosis in an emergency situation. Description in an acute case with progressive paraplegia

BACKGROUND: For the radiation oncologist in an emergency situation with acute progressive paraplegia distinguishing between benign versus malignant vertebral compression fracture without known malignoma may cause a severe diagnostic problem, when a rapid therapeutic decision is required. PATIENT AND METHOD: A case of an elderly diabetic patient with acute onset of a progressive neurologic deficit is reported. No malignancy was known so far. The CT of the spine showed a destruction of the 7th and 8th thoracic vertebral body with compression of the spinal cord. The patient was referred to the radiotherapist for radiation of a presumed malignant spinal process. RESULT: For differential diagnosis a magnetic resonance imaging (MRI) of the spine was performed and could lead to the correct diagnosis of an infectious spondylodiscitis. CONCLUSION: The MRI of the spine has a potential role for correct differentiation between benign and malignant spinal lesions and may thereby assist the radiotherapist in the decision making in an emergency situation.     

Clinical value of proton magnetic resonance spectroscopy for differentiating recurrent or residual brain tumor from delayed cerebral necrosis

PURPOSE: Delayed cerebral necrosis (DN) is a significant risk for brain tumor patients treated with high-dose irradiation. Although differentiating DN from tumor progression is an important clinical question, the distinction cannot be made reliably by conventional imaging techniques. We undertook a pilot study to assess the ability of proton magnetic resonance spectroscopy (1H MRS) to differentiate prospectively between DN or recurrent/residual tumor in a series of children treated for primary brain tumors with high-dose irradiation. METHODS AND MATERIALS: Twelve children (ages 3-16 years), who had clinical and MR imaging (MRI) changes that suggested a diagnosis of either DN or progressive/recurrent brain tumor, underwent localized 1H MRS prior to planned biopsy, resection, or other confirmatory histological procedure. Prospective 1H MRS interpretations were based on comparison of spectral peak patterns and quantitative peak area values from normalized spectra: a marked depression of the intracellular metabolite peaks from choline, creatine, and N-acetyl compounds was hypothesized to indicate DN, and median-to-high choline with easily visible creatine metabolite peaks was labeled progressive/recurrent tumor. Subsequent histological studies identified the brain lesion as DN or recurrent/residual tumor. RESULTS: The patient series included five cases of DN and seven recurrent/residual tumor cases, based on histology. The MRS criteria prospectively identified five out of seven patients with active tumor, and four out of five patients with histologically proven DN correctly. Discriminant analysis suggested that the primary diagnostic information for differentiating DN from tumor lay in the normalized MRS peak areas for choline and creatine compounds. CONCLUSIONS: Magnetic resonance spectroscopy shows promising sensitivity and selectivity for differentiating DN from recurrent/progressive brain tumor. A novel diagnostic index based on peak areas for choline and creatine compounds may provide a simple discriminant for differentiating DN from recurrent or residual primary brain tumors.     

Brain imaging and its clinical application in psychiatry

The common structural and functional brain imaging techniques are described from a practical, clinical point of view. The clinical indications for brain imaging in psychiatry are reviewed in relation to the specific limitations and advantages of each technique. The clinical applications of computerized tomography (CT), magnetic resonance imaging (MRI) and single photon emission computerized tomography (SPECT) are discussed in relation to the differential diagnosis between organic and functional psychiatric disorders. In a 55-year-old man with late onset of behavioral changes but without neurological signs the application of structural brain imaging (CT and MRI) in case management was demonstrated. The imaging findings involved the differential diagnosis between depression and focal brain lesions. In a 38-year-old man with personality changes and depression following a traumatic brain injury, time interval repeated functional brain imaging (SPECT) was used. Brain imaging reflected improvement in clinical status following treatment and was able to differentiate between reversible and permanent traumatic brain injuries. The superior yield of time interval repeated functional imaging in diagnosis and management of postconcussion syndrome is discussed.     

Cerebral metabolic alterations in human immunodeficiency virus-related encephalopathy detected by proton magnetic resonance spectroscopy. Comparison between sequences using short and long echo times

RATIONALE AND OBJECTIVES: The aim of this study is to evaluate comparatively the metabolic information afforded by proton magnetic resonance (MR) spectroscopy with stimulated-echo acquisition mode (STEAM) (echo time [TE], 20 mseconds) and point-resolved spectroscopy sequence (PRESS) (TE, 135 mseconds) spectra in HIV-related encephalopathy. METHODS: Sixty-three human immunodeficiency virus (HIV) patients and 8 controls were examined by single-voxel proton MR spectroscopy at 1.5 tesla, using both PRESS (TE, 135 mseconds) and STEAM (TE, 20 mseconds) sequences performed during the same MR examination, in the same volume of interest. Cerebral atrophy was quantitated using bicaudate ratio (BCR) and bifrontal ratio (BFR). RESULTS: With the STEAM (TE, 20 mseconds) spectra, mean N-acetylaspartate (NAA)/choline (Cho) and NAA/creatine and phosphocreatine (Cr-PCr) ratios are reduced in acquired immunodeficiency syndrome (AIDS) dementia complex (ADC) patients but not in neuroasymptomatics. The proportion of inositol signal is increased, that of NAA decreased in ADC patients. NAA/Cho and NAA/ Cr-PCr mean values measured with PRESS (TE, 135 mseconds) spectra are significantly reduced in ADC and neuroasymptomatic patients. Bifrontal ratio only correlates with NAA/Cr-PCr and NAA/Cho measured on the PRESS spectrum. PRESS (TE, 135 mseconds) spectra allow a definition of different metabolic patterns in HIV-related encephalopathy. At last, no correlation has been found between the NAA raw signals measured on the PRESS (TE, 135 mseconds) and STEAM (TE, 20 mseconds) spectra obtained in the same MR examination. CONCLUSIONS: STEAM (TE, 20 mseconds) spectra provide more metabolic information-namely an evaluation of glial-neuronal status-than PRESS (TE, 135 mseconds) spectra, which afford a metabolic classification of the HIV-related encephalopathy. Because both sequences afford a similar diagnostic gain, MR spectroscopy examination probably requires spectrum acquisition with both sequences.     

Human fibroblasts in culture metabolize differently exogenous G(M3) ganglioside species containing C18 and C20 sphingosine

Applications of magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) in studies of body composition are discussed. MRI is an accurate method for volume quantification of lean and adipose tissue in the human body, while MRS is used to study in vivo metabolism of soft tissues. In particular, combination of MRI and phosphorus (31P) MRS, used to asses muscle energy metabolism, may be of great importance in body composition studies. Examples of use of MRI and 31P MRS in studying the effect of caloric restriction on body composition and skeletal muscle metabolism are given.     

Magnetic resonance imaging of the fetus: a study of 20 cases performed without curarization

Twenty patients underwent magnetic resonance imaging (MRI) at a mean gestational age of 32 weeks. There were 12 patients with suspected fetal brain abnormality and four with intrauterine growth retardation (IUGR), while the remaining four cases were studied for other reasons. The MRI examinations were performed on a 0.5 Tesla machine, with surface coils. One minute acquisition time T1 sequences were used. All the studies were performed without fetal curarization, and only under maternal sedation using flunitrazepam given per os 1 h before MRI examination. Three examinations were incomplete because of fetal movement artefacts. In the remaining cases, MRI allowed the examination of fetal brain anatomy. In five cases, it helped to differentiate isolated hydrocephalus and corpus callosum agenesis. Sub-ependymal nodules were depicted in a case of fetal tuberous sclerosis. One suspected arachnoid cyst was proved to be an ultrasound artefact. Decreased fetal fat on MR images was correlated with low birth weight in cases of IUGR. Due to its better spatial resolution, ultrasonography was more accurate for the diagnosis of facial and lumbar anomalies. Fetal MRI may be performed without curarization. Surface coils allow the detailed analysis of brain parenchyma, and thus MRI is especially useful in the difficult prenatal diagnosis of fetal brain abnormalities.     

Sequential observations of brain edema with proton magnetic resonance imaging and spectroscopy

The purpose of this study was to assess the relationship between morphological and metabolic changes in brain edema using proton magnetic resonance systems. The serial changes during the first 24 hours in the cold-injury trauma rat brain model were investigated by proton magnetic resonance imaging (1H MRI) and high-resolution proton MR spectroscopy (1H MRS). We also analyzed the efficacy of AVS 1,2-bis (nicotinamide)-propane which can scavenge free radicals to the edema in this experiment. The edema was developing extensively via the corpus callosum in ipsi- and contralateral hemispheres as shown by gradually increased signal intensity on 1H MRI. 1H MRS initially showed accumulation of acetate and lactate, and transient increasing of glutamine. After 24 hours, the increased glutamine decreased below the control, alanine increased, and N-acetyl asparatate decreased with the edema development. AVS-treatment significantly suppressed edema development, increases of lactate and alanine and decreases of N-acetyl asparatate. We suggest that the cold-induced lesion contains anaerobic glycolysis deterioration and results in severe brain tissue breakdown. AVS is proved valuable for the treatment of this edema lesion. Clinical 1H MRS showed prolonged lactate elevation and significant decreases of other metabolites in human ischemic stroke edema. In peritumoral edema, decreased N-acetyl asparatate gradually improved, and slightly elevated lactate disappeared after tumor removal. 1H MRS feasibly characterizes the ischemic and peritumoral edema and makes a quantitative analysis in human brain metabolism. We believe the combined 1H MRI and MRS study is a practical method to monitor the brain conditions and will make it easy and possible to find new therapeutic agents to some brain disorders.     

Magnetic resonance spectroscopy in psychiatry: basic principles and applications

In vivo magnetic resonance spectroscopy (MRS) is a safe and non-invasive tool which can be used to study aspects of brain chemistry and metabolism. Although a relatively recent technique in the field of psychiatric research, it has already been used in the study of anxiety and affective disorders, dementia, schizophrenia, and neurodevelopmental disorders. This review outlines the basic principles of MRS and summarises the research findings in psychiatric disorders. Although mostly preliminary, these findings highlight the capacity of MRS to detect subtle neurobiological abnormalities in mental disorders. They also suggest a future role for MRS in differential diagnosis and monitoring illness progression. Initial MRS studies have also focused on the metabolic effects of psychiatric treatments and could provide information about their relationship to clinical variables.     

Regional variations in cerebral proton spectroscopy in patients with chronic hepatic encephalopathy

Regional variations in proton magnetic resonance spectroscopy (MRS) were assessed in 26 patients and 14 healthy volunteers using a two dimensional chemical shift imaging technique. Patients were classified as being neuropsychiatrically unimpaired, or as having subclinical or overt chronic hepatic encephalopathy (CHE). Peak area ratios of choline (Cho), glutamine and glutamate (Glx) and N-acetylaspartate (NAA) relative to creatine (Cr) were measured. Significant reductions in mean Cho/Cr and elevations in mean Glx/Cr were observed in the patient population, which correlated with the severity of CHE. There were significant regional variations in these metabolite ratios with the mean Cho/Cr lowest in the occipital cortex and the mean Glx/Cr highest in the basal ganglia. NAA/Cr remained relatively constant in all areas of the brain analysed. The regional variation in the metabolite ratios suggests that spectral information from more than one voxel may be useful in the assessment of patients with CHE.     

Plasmapheresis and pain]

Lymphomatoid granulomatosis is an angiocentric lymphoproliferative process that involves the lungs. In a 52-year-old-man with lymphomatoid granulomatosis who presented with encephalopathy, magnetic resonance imaging (MRI) of the brain demonstrated unusual multiple areas of enhancement that were both punctate and linear. These findings may be relatively specific for inflammation of deep cerebral vessels and have implications for MRI findings in other inflammatory cerebrovascular disorders.     

1H-MRS differentiates white matter hyperintensities in subcortical arteriosclerotic encephalopathy from those in normal elderly

BACKGROUND AND PURPOSE: White matter hyperintensities in MRI of the brain are often seen in normal elderly subjects. Radiologically, these hyperintense regions are similar to those in symptomatic patients with subcortical arteriosclerotic encephalopathy (SAE). Our aim was to discriminate white matter hyperintensities (WMH) on MRI in patients with SAE from similar appearing changes in normal elderly. METHODS: Three groups of elderly patients were studied: symptomatic patients with WMH of SAE (n = 5); asymptomatic subjects with diffuse, confluent WMH (n = 4); and elderly control subjects (n = 5). Proton density images revealed WMH in the occipital lobes. Proton magnetic resonance spectroscopy (1H-MRS) was used to acquire spectra in these hyperintensities. Metabolite concentrations were calculated from peak areas of N-acetylaspartate (NAA), creatine (Cre), and choline (Cho). RESULTS: The NAA/Cre and NAA/Cho ratios were reduced in the SAE group compared with the two asymptomatic groups (P < .05). NAA was decreased and Cho elevated in SAE compared with control subjects (P < .05). The average volumes of WMH in the SAE group (65.5 cm3) and in asymptomatic control subjects (59.4 cm3) were similar, and greater than those of the normal control group (4.0 cm3). CONCLUSIONS: Proton MRS discriminates WMH in SAE patients from those in asymptomatic elderly, suggesting differing causes of the hyperintensities.     

Correlative studies of MR findings with neuropathology in Shy-Drager syndrome and striatonigral degeneration

OBJECTIVE: To determine the pathologic bases of the abnormal signal intensities detected on magnetic resonance imaging (MRI) in Shy-Drager syndrome (SDS) and striatonigral degeneration (SND). METHODS: The correlation of MRI and pathological findings was prospectively evaluated by postmortem scanning of the brain in a case of SDS and another of SND. MRI was performed by using a 1.0 T superconductive magnetic unit, with spin echo (SE) pulse sequences. The brain sections were prepared parallel to the MRI planes. The gross and microscopic pathological studies were conducted according to the corresponding abnormal signal intensities on MRI. RESULTS: In SDS, abnormal hypointense signals on T2 weighted MR images were symmetrically demonstrated in bilateral putamen, where a remarkable positive Prussian blue stain reaction was revealed on pathological examinations. In SND, MRI showed isointense signals on T1 weighted images and hyperintense signals on T2 weighted images in bilateral putamen, and the microscopic findings included necrosis, abundant reactive fibrillary astrocytes and prominence of capillary vascular networks, as well as marked lipofuscin. The number of neurons decreased in both cases. CONCLUSIONS: The demonstration of the abnormal signals in the putamen on MRI is of important value in establishing an antemortem diagnosis of SDS and SND.     

Cerebral infarction associated with vasculitis due to varicella zoster virus in patients infected with the human immunodeficiency virus

Cases of herpes zoster ophtalmicus (HZO) with delayed contralateral hemiparesis caused by hemispheric stroke secondary to granulomatous angiitis have been reported and are a well-recognized complication of herpes zoster. Similar cases have been reported more recently during infection with human immunodeficiency virus (HIV). We describe two HIV+ patients without any clinical history of zoster dermatitis who developed a sudden hemiparesis followed 2 weeks later for one by an acute retinal necrosis. Computerized tomography (CT) scan, magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), and digital subtraction angiography (DSA) were performed and showed a hemispheric stroke with evidence of a segmental arteritis of the carotid syphon. Varicella zoster virus (VZV) was found in the cerebro spinal fluid (CSF) in the two patients and after puncture of the vitreous fluid of the patient with the acute retinal necrosis. These two cases exemplify the difficulty of diagnosis of stroke in HIV+ patients, which seems to be more frequent than in similarly aged non-infected patients and demonstrates that VZV needs to be taken in consideration and identified even without any past history of zoster dermatitis.     

Magnetic resonance imaging of normal and pathologic fetal brain

A total of 78 pregnant patients who had previously been studied by ultrasound (US) underwent magnetic resonance (MRI) because of suspected fetal abnormality. The first 20 cases were performed using fetal curarization. Even in the 27 cases in which the MR examination concerned other body regions, a brain study was always performed to analyze the normal anatomy at different gestational ages. There is a brief discussion on normal MRI anatomy of the fetal brain. There were 45 studies that concerned central nervous system pathology, and the most frequent malformative and neoplastic disorders were revealed. A comparison between MRI and US is proposed for each. In conclusion, MRI can be regarded as a complementary method that can be helpful in the rare cases when the US diagnosis is doubtful.     

Nuclear magnetic resonance spectroscopy: methodology and applications to the study of asphyxia neonatorum

Cerebral metabolism has been extensively studied by magnetic resonance spectroscopy (MRS). MRS allows the study of neonates brain maturation as well as the onset and the evolution of brain injury. The use of phosphorous spectroscopy allows the quantification of phosphorylated metabolites. Thus, the measurement of the relative concentrations of creatine-phosphate and inorganic-phosphate is a prognostic factor of the outcome of a neonate after birth asphyxia. Absolute concentrations have more recently been studied and seem to be more significant. Proton MRS gives access to brain metabolites such as choline, lactate, N-acetyl aspartate and taurine. Its use is more recent than the phosphorous spectroscopy but first results already show its potential in neonatology.     

Magnetic resonance spectroscopy in Parkinson's disease and multiple system atrophy

Recent advances in magnetic resonance spectroscopy(MRS) allow to assay noninvasively key molecules of brain metabolism in living patients. There are several reports of MRS in Parkinson's disease(PD) and multiple system atrophy(MSA). 1H-MRS of the striatum revealed the reduced NAA/Cr and Cho/Cr ratio in MSA patients and the preserved NAA/Cr and Cho/Cr ratio in PD patients. The reduced NAA/Cr ratio probably reflects striatal neuronal loss. 1H-MRS of the striatum showed increased Cho/Cr ratio in the "on" state compared with that in the "off" state in the PD patients. The increased Cho/Cr ratio may reflect some membrane alteration or change of choline metabolism in PD with the "wearing-off" phenomena. Although studies are still preliminary, MRS shows great possibility for aiding in the differential diagnosis of parkinsonism and it will contribute to a better understanding of the pathogenesis of PD and MSA.