Magnetic resonance spectroscopy: use in monitoring MELAS treatment

Magnetic resonance spectroscopy in MELAS syndrome: correlation with CSF and plasma metabolite levels and change after glutamine supplementation

PURPOSE

MELAS syndrome is a genetic disorder caused by mitochondrial DNA mutations. We previously described that MELAS patients had increased CSF glutamate and decreased CSF glutamine levels and that oral glutamine supplementation restores these values. Proton magnetic resonance spectroscopy (1H-MRS) allows the in vivo evaluation of brain metabolism. We aimed to compare 1H-MRS of MELAS patients with controls, the 1H-MRS after glutamine supplementation in the MELAS group, and investigate the association between 1H-MRS and CSF lactate, glutamate, and glutamine levels.

METHODS

We conducted an observational case-control study and an open-label, single-cohort study with single-voxel MRS (TE 144/35 ms). We assessed the brain metabolism changes in the prefrontal (PFC) and parieto-occipital) cortex (POC) after oral glutamine supplementation in MELAS patients. MR spectra were analyzed with jMRUI software.

RESULTS

Nine patients with MELAS syndrome (35.8 ± 3.2 years) and nine sex- and age-matched controls were recruited. Lactate/creatine levels were increased in MELAS patients in both PFC and POC (0.40 ± 0.05 vs. 0, p < 0.001; 0.32 ± 0.03 vs. 0, p < 0.001, respectively). No differences were observed between groups in glutamate and glutamine (Glx/creatine), either in PFC (p = 0.930) or POC (p = 0.310). No differences were observed after glutamine supplementation. A positive correlation was found between CSF lactate and lactate/creatine only in POC (0.85, p = 0.003).

CONCLUSION

No significant metabolite changes were observed in the brains of MELAS patients after glutamine supplementation. While we found a positive correlation between lactate levels in CSF and 1H-MRS in MELAS patients, we could not monitor treatment response over short periods with this tool.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04948138; initial release 24/06/2021; first patient enrolled on 1/07/2021. https://clinicaltrials.gov/ct2/show/NCT04948138.

In-vivo magnetic resonance spectroscopy of lactate as a non-invasive biomarker of dichloroacetate activity in cancer and non-cancer central nervous system disorders

The adverse effects of lactic acidosis in the cancer microenvironment have been increasingly recognized. Dichloroacetate (DCA) is an orally bioavailable, blood brain barrier penetrable drug that has been extensively studied in the treatment of mitochondrial neurologic conditions to reduce lactate production. Due to its effect reversing aerobic glycolysis (i.e., Warburg-effect) and thus lactic acidosis, DCA became a drug of interest in cancer as well. Magnetic resonance spectroscopy (MRS) is a well-established, non-invasive technique that allows detection of prominent metabolic changes, such as shifts in lactate or glutamate levels. Thus, MRS is a potential radiographic biomarker to allow spatial and temporal mapping of DCA treatment. In this systematic literature review, we gathered the available evidence on the use of various MRS techniques to track metabolic changes after DCA administration in neurologic and oncologic disorders. We included in vitro, animal, and human studies. Evidence confirms that DCA has substantial effects on lactate and glutamate levels in neurologic and oncologic disease, which are detectable by both experimental and routine clinical MRS approaches. Data from mitochondrial diseases show slower lactate changes in the central nervous system (CNS) that correlate better with clinical function compared to blood. This difference is most striking in focal impairments of lactate metabolism suggesting that MRS might provide data not captured by solely monitoring blood. In summary, our findings corroborate the feasibility of MRS as a pharmacokinetic/pharmacodynamic biomarker of DCA delivery in the CNS, that is ready to be integrated into currently ongoing and future human clinical trials using DCA.

Vessel flow void sign and hyperintense vessel sign on FLAIR images distinguish between MELAS and AIS

OBJECTIVE

This study aimed to evaluate the sensitivity and specificity of the vessel signs, including the Vessel Flow Void Sign (VFVS) and the Hyperintense Vessel Sign (HVS) in Fluid Attenuated Inversion Recovery (FLAIR) images during the differentiation of Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS) in Acute Ischemic Stroke (AIS).

METHODS

Magnetic Resonance Imaging (MRI) scans of 13 MELAS and 20 AIS patients were obtained during the acute stage of the diseases (median time to scan <1 day from symptom onset). To evaluate VFVS and HVS on the FLAIR images, Logistic Regression was used to analyze their correlation with MELAS. Then, a new scale of scoring, involving two aspects (VFVS and HVS) on FLAIR images was established. Receiver operating characteristic (ROC) curves were used to evaluate the efficacy of the developed criterion.

RESULTS

FLAIR images from 12 of the 13 MELAS patients exhibited VFVS while none exhibited HVS. Moreover, FLAIR images from 3 of the 20 AIS patients exhibited VFVS while 17 exhibited HVS. Logistic Regression showed that VFVS and the absence of HVS (NoHVS) were independent MELAS predictors. If there were VFVS, the patient scored 2 points, while there were NoHVS, the patient scored 1 point. Patients with >1.5 scores were prone to be MELAS, while patients with <1.5 scores were prone to be AIS. Sensitivity was found to be 92.3%, specificity was 85%, with an AUC of 0.94.

CONCLUSION

We have established a new scoring criterion, with a high sensitivity and specificity, for differentiating between MELAS and AIS in patients during the acute stage.

Mitochondrial metabolic stroke: Phenotype and genetics of stroke-like episodes

Stroke-like episodes (SLEs) are the hallmark of mitochondrial encephalopathy with lactic acidosis and stroke-like episode (MELAS) syndrome but rarely occur also in other specific or nonspecific mitochondrial disorders. Pathophysiologically, SLLs are most likely due to a regional disruption of the blood-brain barrier triggered by the underlying metabolic defect, epileptic activity, drugs, or other factors. SLEs manifest clinically with a plethora of cerebral manifestations, which not only include features typically seen in ischemic stroke, but also headache, epilepsy, ataxia, visual impairment, vomiting, and psychiatric abnormalities. The morphological correlate of a SLE is the stroke-like lesion (SLL), best visualised on multimodal MRI. In the acute stages, a SLL presents as vasogenic edema but may be mixed up with cytotoxic components. Additionally, SLLs are characterized by hyperperfusion on perfusion studies. In the chronic stage, SLLs present with a colorful picture before they completely disappear, or end up as white matter lesion, cyst, laminar cortical necrosis, focal atrophy, or as toenail sign. Treatment of SLLs is symptomatic and relies on recommendations by experts. Beneficial effects have been reported with nitric-oxide precursors, antiepileptic drugs, antioxidants, the ketogenic diet, and steroids. Lot of research is still needed to uncover the enigma SLE/SLL.

MELAS: Monitoring treatment with magnetic resonance spectroscopy

BACKGROUND

To assess the utility of Magnetic Resonance Spectroscopy (MRS) as a biomarker of response to L-arginine in mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS).

AIMS

To describe a case of MELAS treated with L-arginine that showed improvement clinically and on serial MRS METHODS: MRS was performed on a 1.5-Tesla scanner to evaluate a MELAS patient before, during, and after intravenous (IV) L-arginine therapy for the treatment of stroke-like episodes. L-arginine was infused at a dose of 500 mg/kg daily for 7 days followed by oral arginine therapy.

RESULTS

The patient had clinical improvement after treatment with IV L-arginine. MRS performed before, during, and after treatment with IV L-arginine showed significant improvement in brain lactate and increase in the N-acetylaspartate/Choline (NAA/Cho) ratio compared to pre-treatment baseline.

CONCLUSION

Serial MRS imaging showed significant improvement in lactate peaks and NAA/Cho ratios that corresponded with clinical improvement after L-arginine therapy. Given this correlation between radiologic and clinical improvement, MRS may be a useful biomarker assessing response to treatment in MELAS.

Comparison of magnetic resonance spectroscopy (MRS) with arterial spin labeling (ASL) in the differentiation between mitochondrial encephalomyopathy, lactic Acidosis, plus stroke-like episodes (MELAS) and acute ischemic stroke (AIS)

To compare the utility and limitation of magnetic resonance spectroscopy (MRS) and arterial spin labeling (ASL) in the differentiation between mitochondrial encephalomyopathy, lactic acidosis, plus stroke-like episodes (MELAS) and acute ischemic stroke (AIS), a retrospective review of 17 MELAS and 26 AIS patients were performed. In all patients both MRS and ASL scans were performed within 1 week after admission. Demographic, clinical, laboratory and MR imaging data were reviewed and compared between the two groups. Compared with AIS, MELAS patients had a younger age of onset, a longer disease duration, a higher occurrence of epilepsy attack, occipital and parietal lesions, and dilated cerebral arteries (P < 0.05). In all MELAS patients lactate peak and hyperperfusion of the lesion was revealed. However in AIS lactate peak was observed in only 69.2% and hyperperfusion was observed in only 34.6% ischemic lesions (P < 0.05). Choline/Creatine ratios and Lactate/Creatine ratios were higher in AIS, while in MELAS cerebral blood flow and lesion-normal perfusion ratio was much higher (P < 0.05). No correlations was found between metabolite ratios and perfusion parameters in either group (P > 0.05). Area under curve (AUC) of perfusion for the differentiation between MELAS and AIS was 0.958 (P < 0.001). The cut-off value was 2.075, with a sensitivity of 88.2% and a specificity of 96.2%. AUC of Lactate/Creatine ratio was 0.469 (P = 0.737). Utility of MRS is limited in the differentiation between MELAS and AIS, while MR perfusion profiles are much more sensitive and specific.

Migratory stroke-like lesions in a case of adult-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome and a review of imaging findings

Imaging findings of adult-onset mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is poorly documented. The authors present a 48-year-old woman with subacute onset of word-finding difficulties and right arm stiffness. Magnetic resonance imaging performed 2 weeks prior revealed left temporal lobe diffusion and fluid-attenuated inversion recovery hyperintensity predominantly involving the cortex. The apparent diffusion coefficient map showed preserved signal in the temporal cortex. Subsequent magnetic resonance imagings demonstrated a new diffusion signal abnormality extending to the left parietal cortex and occipital cortex with resolving diffusion hyperintensity in the temporal lobe. MR spectroscopy showed scattered areas of lactate deposition. Diagnosis of MELAS syndrome was confirmed by genetic analysis. Fluctuating, migratory stroke-like lesions with a predilection for the parietal, temporal, and occipital cortex that do not conform to a vascular territory and a lactate spike at 1.3 ppm on MR spectroscopy are characteristic of MELAS syndrome. Preserved signal intensity on apparent diffusion coefficient is useful to distinguish MELAS syndrome from ischemic infarction where the signal is typically reduced.

Diagnostic value of MRS-quantified brain tissue lactate level in identifying children with mitochondrial disorders

Objectives

Magnetic resonance spectroscopy (MRS) of children with or without neurometabolic disease is used for the first time for quantitative assessment of brain tissue lactate signals, to elaborate on previous suggestions of MRS-detected lactate as a marker of mitochondrial disease.

Methods

Multivoxel MRS of a transverse plane of brain tissue cranial to the ventricles was performed in 88 children suspected of having neurometabolic disease, divided into ‘definite’ (n = 17, ≥1 major criteria), ‘probable’ (n = 10, ≥2 minor criteria), ‘possible’ (n = 17, 1 minor criterion) and ‘unlikely’ mitochondrial disease (n = 44, none of the criteria). Lactate levels, expressed in standardized arbitrary units or relative to creatine, were derived from summed signals from all voxels. Ten ‘unlikely’ children with a normal neurological exam served as the MRS reference subgroup. For 61 of 88 children, CSF lactate values were obtained.

Results

MRS lactate level (>12 arbitrary units) and the lactate-to-creatine ratio (L/Cr >0.22) differed significantly between the definite and the unlikely group (p = 0.015 and p = 0.001, respectively). MRS L/Cr also differentiated between the probable and the MRS reference subgroup (p = 0.03). No significant group differences were found for CSF lactate.

Conclusion

MRS-quantified brain tissue lactate levels can serve as diagnostic marker for identifying mitochondrial disease in children.

Key points

• MRS-detected brain tissue lactate levels can be quantified.

• MRS lactate and lactate/Cr are increased in children with mitochondrial disease.

• CSF lactate is less suitable as marker of mitochondrial disease.

Stroke and Stroke-like Episodes in Muscle Disease

Background:

Though not obvious at a first glance, myopathies may be associated with ischemic stroke. Stroke-like episodes resemble ischemic stroke only to some extent but are a unique feature of certain mitochondrial disorders with a pathogenesis at variance from that of ischemic stroke. Only limited data are available about ischemic stroke in pri-mary myopathies and the management of stroke-like episodes in mitochondrial disorders. This review aims to summarize and discuss current knowledge about stroke in myopathies and to delineate stroke-like episodes from ischemic stroke.

Methods:

Literature review via PubMED using the search terms “stroke”, “cerebrovascular”, “ischemic event”, “stroke-like episode”, “stroke-mimic”, “mitochondrial disorder”.

Results:

Stroke in myopathies is most frequently cardioembolic due to atrial fibrillation or atrial flutter, dilated cardio-myopathy, or left-ventricular hypertrabeculation (noncompaction). The second most frequent cause of stroke in myopathies is angiopathy from atherosclerosis or vasculitis, which may be a feature of inflammatory myopathies. Athero-sclerosis may either result from classical risk factors, such as diabetes, arterial hypertension, hyperlpidemia, or smoking, associated with muscle disease, or may be an inherent feature of a mitochondrial disorder. In case of severe heart failure from cardiomyopathy as a manifestation of muscle disease low flow infarcts may occur. Thrombophilic stroke has been described in polymyositis and dermatomyositis in association with anti-phospholipid syndrome. Stroke-like episodes occur particularly in mitochondrial encephalopathy, lactacidosis and stroke-likeepisode syndrome but rarely also in Leigh-syndrome and other mitochondrial disorders. Stroke-like episodes are at variance from ischemic stroke, pathogenically, clinically and on imaging. They may be the manifestation of a vascular, metabolic or epileptic process and present with predominantly vasogenic but also cytotoxic edema on MRI. Differentiation between ischemic stroke and stroke-like episodes is essential in terms of management and prognosis. Management of ischemic stroke in patients with myopathy is not at variance from the treatment of ischemic stroke in non-myopathic patients. There is no standardized treatment of stroke-like episodes but there is increasing evidence that these patients profit from the administration of L-arginine and conse-quent antiepileptic treatment if associated with seizure activity.

Conclusions:

Ischemic stroke may be a complication of myopathy and needs to be delineated from stroke-like episodes, which are unique to mitochondrial disorders, particularly mitochondrial encephalopathy, lactacidosis and stroke-likeepisode syndrome. Ischemic stroke in myopathies is most frequently cardioembolic and treatment is not at variance from non-myopathic ischemic stroke. Treatment of stroke-like episodes is not standardized but seems to respond to L-arginine and adequate antiepileptic treatment.

Neuroimaging of stroke-like episodes in MELAS

Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) shows sudden neurological deficits that are called 'stroke-like episodes'. With regard to the pathophysiology of stroke-like episodes, so-called mitochondrial angiopathy and cytopathy theories have been proposed, but the subject is still controversial. To clarify this matter and to contribute to the development of a treatment for MELAS, we review here current neuroimaging research and consider the pathophysiology of stroke-like lesions. With regard to diffusion-weighted imaging findings, early reports often showed an elevated apparent diffusion coefficient (ADC) in stroke-like lesions; this was considered to be mainly vasogenic edema in the acute phase and is a different pattern than that in stroke. However, there has recently been an increase in the number of reports of a decrease in ADC; these cases are considered to be cytotoxic edema in the acute phase, which is compatible with stroke. With regard to (1)H-magnetic resonance spectroscopy findings in stroke-like lesions, a decrease in N-acetylaspartate and an increase in lactate have been reported. With regard to single photon emission computed tomography findings for stroke-like lesions in MELAS, an overall trend is hyperperfusion in the acute stage (within 1 month) of stroke-like episodes and hypoperfusion in the chronic stage (several months later). With regard to positron emission tomography, nearly all of these reports are consistent with the mitochondrial cytopathy theory. With regard to neuropathology in MELAS, the most common findings during the chronic stage of stroke-like episodes include foci of necrosis and peculiar vascular changes (abnormalities of mitochondria in small arteries). Concerning the pathology of the acute stage of stroke-like episodes, extensive petechial hemorrhage along the gyri of the cortex corresponding to acute stroke-like lesions has been reported. To clarify the true pathophysiology of stroke-like episodes, we offer three suggestions. First, we must define the precise onset of stroke-like episodes. Second, current studies are limited by the difficulty of imaging just before and just after (within a few minutes) the onset of stroke-like episodes. Third, we hope to establish an experimental animal model. We should conduct a simultaneous multimodal imaging and histological study just before and just after (within a few minutes) the onset of stroke-like episodes in an experimental animal model.

Initial experiences with proton MR spectroscopy in treatment monitoring of mitochondrial encephalopathy

PURPOSE

Mitochondrial encephalopathy (ME) is a rare disorder of energy metabolism. The disease course can roughly be evaluated by clinical findings. The purpose of this study was to evaluate metabolic spectral changes using proton MR spectroscopy (MRS), and to establish a way to monitor ME by neuroimaging.

MATERIALS AND METHODS

Proton MRS data were retrospectively reviewed in 12 patients with muscle biopsy-confirmed ME (M : F = 7 : 5, Mean age = 4.8 years). All received 1H-MRS initially and also after a ketogenic diet and mitochondrial disease treatment cocktail (follow up average was 10.2 months). Changes of N-acetylaspartate/ creatine (NAA/Cr) ratio, choline/creatine (Cho/Cr) ratio, and lactate peak in basal ganglia at 1.2 ppm were evaluated before and after treatment. Findings on conventional T2 weighted MR images were also evaluated.

RESULTS

On conventional MRI, increased basal ganglia T2 signal intensity was the most common finding with ME (n = 9, 75%), followed by diffuse cerebral atrophy (n = 8, 67%), T2 hyperintense lesions at pons and midbrain (n = 4, 33%), and brain atrophy (n = 2, 17%). Lactate peak was found in 4 patients; 2 had disappearance of the peak on follow up MRS. Quantitative analysis showed relative decrease of Cho/Cr ratio on follow up MRS (p = 0.0058, paired t-test, two-tailed). There was no significant change in NAA/Cr ratio.

CONCLUSION

MRS is a useful tool for monitoring disease progression or improvement in ME, and decrease or disappearance of lactate peak and reduction of Cho/Cr fraction were correlated well with improvement of clinical symptoms.

The appearance of ADCs in the non-affected areas of the patients with MELAS

INTRODUCTION

The exact mechanism of the mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) remain unclear. Diffusion-weighted imaging (DWI) is a magnetic resonance (MR) imaging technique for studying the pathophysiologic change of the MELAS. The purpose of the study is to see whether the apparent diffusion coefficient (ADC) of MELAS in the non-affected areas is different from the ADC of the normal subjects and to speculate the pathophysiological mechanisms of the MELAS.

METHODS

Sixteen cases of MELAS were retrospectively analyzed. Thirty healthy subjects were chosen to constitute the control group. All of them were performed on the 3.0T whole-body MR scanner with axial view T2 fluid attenuated inversion recovery (flair), T2-weighted imaging, T1flair, and DWI. An ADC map was reconstructed in the workstation. Two to five regions of interest were put in the non-affected frontal lobe and basal ganglia. All data took statistical analysis.

RESULTS

There were significant differences between the ADC of the patients with MELAS and the controls in the non-affected areas, including the superior frontal gyrus, precentral gyrus, corpus striatum, thalamus, and white matter of the semi-oval centrum.

CONCLUSION

ADCs in the non-affected areas of the patients with MELAS are higher than those of the normal subjects. Pathological changes take place in the non-affected areas of the patients with MELAS.

Pediatric neurodegenerative white matter processes: leukodystrophies and beyond

Pediatric neurodegenerative white matter processes are complex, numerous and result from a vast array of causes ranging from white matter injury or inflammation to congenital metabolic disorders. When faced with a neurodegenerative white matter process on neuroimaging, the first step for the radiologist is to determine whether the findings represent a congenital metabolic leukodystrophy or one of various other white matter processes. In this review we first describe a general approach to neurodegenerative white matter disorders. We will briefly describe a few white matter diseases that mimic metabolic leukodystrophies. In the second half of the review we discuss an approach to distinguishing and classifying white matter leukodystrophies.

The in-depth evaluation of suspected mitochondrial disease

Mitochondrial disease confirmation and establishment of a specific molecular diagnosis requires extensive clinical and laboratory evaluation. Dual genome origins of mitochondrial disease, multi-organ system manifestations, and an ever increasing spectrum of recognized phenotypes represent the main diagnostic challenges. To overcome these obstacles, compiling information from a variety of diagnostic laboratory modalities can often provide sufficient evidence to establish an etiology. These include blood and tissue histochemical and analyte measurements, neuroimaging, provocative testing, enzymatic assays of tissue samples and cultured cells, as well as DNA analysis. As interpretation of results from these multifaceted investigations can become quite complex, the Diagnostic Committee of the Mitochondrial Medicine Society developed this review to provide an overview of currently available and emerging methodologies for the diagnosis of primary mitochondrial disease, with a focus on disorders characterized by impairment of oxidative phosphorylation. The aim of this work is to facilitate the diagnosis of mitochondrial disease by geneticists, neurologists, and other metabolic specialists who face the challenge of evaluating patients of all ages with suspected mitochondrial disease.

Chronic progressive external ophthalmoplegia: MR spectroscopy and MR diffusion studies in the brain

OBJECTIVE

The purpose of our study was to show how, despite pathognomonic signs of cerebral involvement in chronic progressive external ophthalmoplegia (CPEO), mitochondrial respiratory chain insufficiency is associated with increased lactate and reduced N-acetylaspartate. CPEO and mitochondrial myopathy are caused by mitochondrial DNA mutations leading to impaired oxidative phosphorylation. Cortical and subcortical metabolites, cerebral diffusivity, and structural MRI were assessed to characterize possible subclinical cerebral pathology in CPEO.

SUBJECTS AND METHODS

Ten patients with CPEO (n = 8), mitochondrial myopathy (n = 1), and Kearns-Sayre syndrome (n = 1) and 13 control group volunteers were studied by MRI, both long TE (144) proton MR spectroscopic imaging (1H MRSI), and diffusion-weighted imaging. Relative concentrations of N-acetylaspartate, choline, creatine, and lactate were estimated by Linear Combination of Model Spectra (LCModel) in healthy-appearing white matter, gray matter, and white matter hyperintensities.

RESULTS

Of five patients with cortical atrophy, it was moderate in three and severe in two. One patient had severe and four had moderate cerebellar atrophy. Six of 10 patients showed unspecific white matter lesions, whereas the remainder had hyperintensities in the pyramidal tract (n =2) and middle cerebellar peduncle (n = 1) despite clinical signs. No basal ganglia lesions were found. Physiologic metabolite ratios were normal and lactate was absent in supratentorial healthy-appearing cortex and subcortical white matter. Global diffusion histogram metrics revealed no abnormalities.

CONCLUSION

Normal spectroscopic imaging in radiologic unaffected brain and healthy global brain parenchymal diffusion findings do not support the hypothesis of a generalized cerebral energy loss in CPEO. Bilateral structural alteration of central motor pathways in two patients without clinical pyramidal signs may, however, reflect subclinical axonal injury in predilection sites in some patients.

The mitochondrial myopathy encephalopathy, lactic acidosis with stroke-like episodes (MELAS) syndrome: a review of treatment options

Mitochondrial encephalomyopathies are a multisystemic group of disorders that are characterised by a wide range of biochemical and genetic mitochondrial defects and variable modes of inheritance. Among this group of disorders, the mitochondrial myopathy, encephalopathy, lactic acidosis with stroke-like episodes (MELAS) syndrome is one of the most frequently occurring, maternally inherited mitochondrial disorders. As the name implies, stroke-like episodes are the defining feature of the MELAS syndrome, often occurring before the age of 15 years. The clinical course of this disorder is highly variable, ranging from asymptomatic, with normal early development, to progressive muscle weakness, lactic acidosis, cognitive dysfunction, seizures, stroke-like episodes, encephalopathy and premature death. This syndrome is associated with a number of point mutations in the mitochondrial DNA, with over 80% of the mutations occurring in the dihydrouridine loop of the mitochondrial transfer RNA(Leu(UUR)) [tRNA(Leu)((UUR))] gene. The pathophysiology of the disease is not completely understood; however, several different mechanisms are proposed to contribute to this disease. These include decreased aminoacylation of mitochondrial tRNA, resulting in decreased mitochondrial protein synthesis; changes in calcium homeostasis; and alterations in nitric oxide metabolism. Currently, no consensus criteria exist for treating the MELAS syndrome or mitochondrial dysfunction in other diseases. Many of the therapeutic strategies used have been adopted as the result of isolated case reports or limited clinical studies that have included a heterogeneous population of patients with the MELAS syndrome, other defects in oxidative phosphorylation or lactic acidosis due to disorders of pyruvate metabolism. Current approaches to the treatment of the MELAS syndrome are based on the use of antioxidants, respiratory chain substrates and cofactors in the form of vitamins; however, no consistent benefits have been observed with these treatments.

MR Spectroscopy of Metabolic Disorders

The application of MR spectroscopy (MRS) in pediatric brain disorders yields valued information on pathologic processes, such as ischemia, demyelination, gliosis, and neurodegeneration. Because these processes manifest in inborn errors of metabolism, the purposes of this article are to (1) describe the spectral changes that are associated with the relatively common metabolic disorders, with summaries of known spectroscopic features of these disorders; (2) offer suggestions for recognition and distinction of disorders; and (3) provide general guidelines for MRS implementation. Although many conditions have a similar presentation, MRS offers valuable information for the individual patient in diagnosis and therapy when integrated fully into the clinical setting.

Platelet mitochondrial evaluation during cytochrome c and dichloroacetate treatments of MELAS

We hypothesized that serial changes in platelet (PLT) mitochondrial enzyme (ME) activities might correspond to the effects of medications for mitochondrial encephalomyopathy and stroke-like episodes (MELAS). Cytochrome c and sodium dichloroacetate (DCA) were given to a 7-year-old girl with MELAS who had an A3243G mitochondrial DNA mutation. The effects were evaluated with whole PLT-ME assays, developed by our group, using a microplate-reader. During cytochrome c treatment, complex II+III (II+III), complex IV (IV) and citrate synthase (CS) activities showed gradual but statistically significant decrease. II+III activity dropped below normal. II+III/CS activity was initially below normal, followed by a transient improvement, then decreased again before the appearance of central nervous system symptoms. II+III, IV, II+III/CS and IV/CS activities reached their lowest levels in association with a stroke-like episode, then increased with DCA treatment. Our results suggest that progressive mitochondrial dysfunction may occur before the stroke-like episodes in MELAS and that DCA treatment may increase mitochondrial activities. Our whole PLT-ME assay system may be useful for serially evaluating mitochondrial functions in relation to clinical symptoms.

Non-invasive quantification of lactate by proton MR spectroscopy and its clinical applications

Lactate is an important metabolite in clinical cases indicating the status of metabolic impairment. We applied a clinically relevant simple method for lactate quantification using magnetic resonance spectroscopy (MRS). We used two long in-phase echo time (TE=272,544 ms) to calculate T2 relaxation time and the absolute concentration of lactate. This method was optimized using phantom study and applied to clinical cases. This technique does not require complicated processing and could be applied in daily clinical practice. Moreover, this technique enables lactate quantification in cases (e.g. tumor) where lipid peak is overlapped with the lactate peak at short echo times.

Magnetic resonance spectroscopy in patients with MELAS

Localized magnetic resonance spectroscopy (MRS) yields sensitive metabolic markers to provide insight into the pathophysiology of mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) in vivo. Findings in full MELAS syndrome at 1H MRS of the brain typically include severely elevated lactate and reduced N-acetylaspartate, glutamate, myo-inositol, and total creatine concentrations in stroke-like lesions. Similar but less extreme alterations are also common in gray matter (GM) regions that appear normal at magnetic resonance imaging. Phosphorus spectroscopy of peripheral muscle permits investigation of the bioenergetic status. A decline of the phosphorylation potential indicates a low energy reserve at rest. Phosphocreatine resynthesis during post-exercise recovery is delayed pointing to reduced mitochondrial capacity. As MRS is inherently non-invasive, follow-up studies can be performed to assess treatment response quantitatively.

Beneficial effect of L-arginine for stroke-like episode in MELAS

We here reported the clinical course and therapeutic details of a 16-year-old girl with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) who had had five stroke-like episodes (two episodes were clinically mild, while the three subsequent episodes were severe). Among the three episodes, the symptoms improved earliest and magnetic resonance spectroscopy abnormality was minimal when given L-arginine in addition to prednisolone, glycerol and edalavone. L-arginine administration during the acute phase of MELAS might be a potential therapy to reduce brain damage due to mitochondrial dysfunction.

Chronic treatment of mitochondrial disease patients with dichloroacetate

Clinical features are reported for 37 patients with various mitochondrial disorders, treated with sodium dichloroacetate (DCA) for 3 weeks to 7 years (mean 3.25 years) at 11-50 mg/kg/day (34.6+/-13.1) in an open-label format. DCA pharmacokinetics showed half-times approximately 86 min for the first intravenous dose of 50 mg/kg, 3.2 h for a subsequent intravenous dose 4-6 h later, and 11 h after continued oral dosing of 12.5-25 mg/kg twice daily. Basal blood and CSF lactate (mean values at entry 29.6 and 46.8 mg/dL, respectively) decreased at 3 months (to 18.1 and 34.2, respectively) and 12 months (to 17.7 and 33.1, respectively). There was some attenuation of the blood lactate response to oral fructose but not glucose, although the baseline lactate was lower with DCA. A standardized neurologic inventory showed stabilization or improvement over one year. The subjective impression of overall disease course was worsening in 21.6%, improvement in 48.6%, and no discernable effect in 29.7%. Among 8 patients who had 17 stroke-like events in 0.25-5 years prior to study entry, there were a total of 2 events over 3-6 years of treatment. In two cases institution of DCA resulted in dramatic relief of severe headaches which had been refractory to narcotics. Given variability of symptoms and limited understanding of natural history of mitochondrial disease, it is difficult to determine the efficacy of DCA in this open-label study, but there did appear to be some cases in which there were at least temporary benefits.

A practical approach to the diagnosis and management of MELAS: case report and review

BACKGROUND

Mitochondrial encephalomyopathy, lactic acidosis with stroke-like episodes (MELAS) is a mitochondrial disorder and an important diagnostic consideration in the young patient with nonhemorrhagic stroke. Its presentation is varied and diagnosis is based on early recognition of the clinical features and correct interpretation of laboratory and radiologic studies.

SUMMARY

In this article, we report a patient with MELAS and review the clinical, laboratory, and neuroradiologic features of the condition. In the young patient with multiple stroke-like episodes in different vascular territories and neuroradiologic features of transient abnormalities in varying regions, laboratory testing for MELAS must be performed. The presence of ragged red fibers in skeletal muscle and biochemical demonstration of defects in mitochondrial respiratory enzymes strongly support the diagnosis. Molecular genetic testing for abnormalities in mitochondrial DNA will confirm the diagnosis. The importance of a thorough assessment of family history is also emphasized. The basic principles of mitochondrial genetics and the common point mutations and rearrangements of mitochondrial DNA associated with MELAS are reviewed. Although treatment options are limited, several therapeutic agents have been studied.

CONCLUSIONS

The diagnosis of MELAS should be considered in the young patient with stroke, especially when accompanied by other clinical features such as seizures, encephalopathy, and muscle weakness. Laboratory evaluation can provide an accurate diagnosis, especially when the appropriate mitochondrial DNA studies are performed. Genetic counseling should be provided to patients with MELAS associated with mitochondrial DNA point mutations. Better understanding of the molecular basis of the condition may result in the development of effective treatment strategies.

Application of NMR spectroscopy to monitoring MELAS treatment: a case report

1H magnetic resonance spectroscopy (MRS) of the brain and (31)P MRS and saturation transfer of resting skeletal muscle were used to investigate intracellular metabolites and fluxes through the creatine kinase (CK) reaction in a patient with the syndrome of mitochondrial myopathy, encephalopathy, lactic acidosis, and strokelike episodes (MELAS). Acute cortical lesions were characterized by severely elevated lactate levels and reduced concentrations of N-acetylaspartyl compounds, glutamate, and myo-inositol. Similar but less extreme alterations were also observed in gray matter regions that appeared normal on magnetic resonance images. Investigation of the gastrocnemius muscle at rest demonstrated a reduced phosphocreatine level, elevated concentrations of inorganic phosphate and free adenosine 5'-diphosphate, and an abnormally low phosphorylation potential. Besides a moderately increased muscular phosphocreatine concentration, none of the metabolic disturbances detected on MRS improved with oral creatine supplementation. Forward and reverse fluxes through the CK reaction did not significantly change upon creatine treatment. Follow-up MRS investigations may thus provide objective markers of treatment response in vivo without the hazards or inconvenience of biopsy.

Evaluation of accumulated mucopolysaccharides in the brain of patients with mucopolysaccharidoses by (1)H-magnetic resonance spectroscopy before and after bone marrow transplantation

In seven patients with mucopolysaccharidoses (1 Hurler, 1 Hurler-Scheie, 4 Hunter, 1 Sly), cranial (1)H-magnetic resonance spectroscopy was performed to evaluate the accumulation of mucopolysaccharides and biochemical changes in the CNS in vivo before and after bone marrow transplantation (BMT). In two of seven patients, (1)H-magnetic resonance spectroscopy was performed before and after BMT. Nuclear magnetic resonance spectra of dermatan sulfate and chondroitin sulfate-C and magnetic resonance spectroscopy of chondroitin sulfate-C and urine from patients with mucopolysaccharidoses showed resonance higher than the chemical shift of myoinositol in the brain (3.7 ppm). The resonance was considered to contain signals from mucopolysaccharide molecules. The resonance was measured as presumptive mucopolysaccharides (pMPS). In white matter lesions detected by magnetic resonance imaging, pMPS/creatine ratios and choline/creatine ratios were consistently higher than control ratios. In white matter without lesions, choline/creatine ratios were higher than control ratios. Patients with higher developmental quotient or intelligence quotient tended to show higher N:-acetylaspartate/creatine ratios and lower pMPS/creatine ratios in basal ganglia. After BMT, the pMPS/creatine ratio in white matter lesions of patient 3, with Hunter syndrome, was slightly decreased, but in none of the patients was the ratio ever below the control ratios, even 7 y after BMT. In white matter without lesions, the pMPS/creatine ratio in patient 3 was decreased to the control ratios after BMT, but although the choline/creatine ratios were gradually decreased, they remained higher than the control ratio, 2 y after BMT. These results suggest that evaluation of pMPS, choline, and N:-acetylaspartate by (1)H-magnetic resonance spectroscopy is an important technique that may provide useful biochemical information in vivo on the neurologic process and the efficacy of BMT in patients with mucopolysaccharidoses.

Increased anaerobic glycolysis in mitochondrial trifunctional protein-deficient brain

Deficiency of mitochondrial trifunctional protein (TP), beta-oxidation enzyme, is characterized by recurrent rhabdomyolysis in adult patients. Positron emission tomography was used to measure brain oxygen (CMRO(2)) and glucose (CMRGlc) metabolisms in an adult patient with TP deficiency who had a homozygous G1331A transition of the beta-subunit gene. The molar ratio of oxygen to glucose consumption showed diffuse reduction; CMRO(2) was markedly decreased, whereas CMRGlc increased. Oxidative metabolism may be impaired and anaerobic glycolysis stimulated in the brain of this patient with TP deficiency.

Non-invasive methods for studying brain energy metabolism: what they show and what it means

This review summarises the ways in which magnetic resonance spectroscopy (MRS) and related methods can be used as windows on brain energy metabolism in vivo. (31)P-MRS can measure acute changes in non-oxidative ATP synthesis in transient states, and at steady state reflects the balance of ATP demand and mitochondrial function. (13)C-MRS labelling methods can measure a variety of carbon fluxes. The few (31)P- and (13)C-MRS studies of the response to functional activation suggest quite large increases in oxidative metabolism. Functional magnetic resonance imaging measures the hyperoxygenation that results from increase in cerebral blood flow in excess of glucose oxidation, attenuated somewhat by a smaller increase in oxygen consumption. Previous positron emission tomography studies disagree on the size of activation response. These are powerful but demanding techniques, valuable in understanding both normal physiology and pathophysiology. However, discrepancies remain to be reconciled, and this will require increasing sophistication of both techniques and analytical models.

Stroke in children: genetic and metabolic issues

The study of genetic and metabolic etiologies of pediatric stroke, both vascular and metabolic, allows an understanding of the causes of acute focal neurologic deficits in childhood. Here, the mendelian and mitochondrial genetic causes of pediatric stroke syndromes are reviewed. This approach elucidates the etiology of childhood stroke and illustrates many of the genetic risk factors that are found in adult-onset cerebrovascular disease. Therefore, the study of childhood stroke serves as a model to elucidate the potential risk factors for all stroke. Ultimately this will serve to develop a more rational preventive and therapeutic approach for all cerebrovascular disease.

Magnetic resonance spectroscopy in toxic encephalopathy and neurodegeneration

Magnetic resonance spectroscopy allows neurochemistry to be probed noninvasively in vivo. Recent advances in our understanding of the biochemical significance of the various neurochemicals that are observable allow a variety of pathologic states of relevance to encephalopathies and neurodegenerative disorders to be observed. Measurements of brain glutamate and glutamine allow observation of neuronal/glial substrate cycling and ammonia detoxification. Myo-inositol allows changes in cerebral osmolarity and gliosis to be observed. N-acetylaspartate is a marker of neuronal health and number. Lactate allows nonoxidative glycolysis to be observed. These molecules are now being used to ask etiologic questions that are of relevance to encephalopathies and neurodegeneration, as well to probe longitudinally both natural history and therapeutic interventions in these conditions. Combined with recent advances in anatomic magnetic resonance imaging as well as perfusion magnetic resonance imaging, magnetic resonance spectroscopy has the potential to aid greatly in our understanding of neuronal dysfunction in a wide variety of neurologic pathologies, even in single patients.