Clinical features, pathogenesis, and management of stroke-like episodes due to MELAS

Multisystem clinicopathologic and genetic analysis of MELAS

BACKGROUND AND OBJECTIVES

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome is a maternally inherited mitochondrial disorder that mostly affects the central nervous system and skeletal muscle. This study provides a comprehensive summary of the clinical symptoms, multisystemic pathogenesis, and genetic characteristics of MELAS syndrome. The aim was to improve comprehension of clinical practice and gain a deeper understanding of the latest pathophysiological theories.

METHODS

The present investigation involved a cohort of patients diagnosed with MELAS at Nanjing Drum Tower Hospital between January 2014 and December 2022. Multisystem symptoms, magnetic resonance imaging/spectroscopy (MRI/MRS), muscle biopsy, and mitochondrial DNA (mtDNA) data were summarized and subsequently analysed.

RESULTS

This retrospective study included a cohort of 29 MELAS patients who predominantly presented symptoms such as stroke-like episodes, proximal muscle weakness, and exercise intolerance. MRI scans revealed very small infarcts beneath the deep cortex during stroke-like episodes, indicating nonvascular brain damage. Pathology analyses of the brain also showed neuronal degeneration and glial cell proliferation in the cerebral parenchyma. Proton magnetic resonance spectroscopy (1H-MRS) analysis revealed an increase in the lactate peak and a reduction in the N-acetylaspartate (NAA) level. Similarly, the phosphorus magnetic resonance spectroscopy (31P-MRS) analysis revealed an abnormal ratio of inorganic phosphate (Pi) to phosphocreatine (PCr). Muscle biopsy revealed the presence of ragged red fibres (RRFs) and cytochrome c oxidase (COX) enzyme-defective cells. These abnormalities indicate structural abnormalities in the mitochondria and deficiencies in oxidative phosphorylation, respectively. In addition to the common m.3243A > G variant, other prevalent variants, including m.5628 T > C, m.6352-13952del, and a 9-bp small deletion combined with m.3243A > G, exist.

CONCLUSIONS

MELAS is a rare mitochondrial syndrome characterized by clinical heterogeneity and genetic heteroplasmy. Abnormalities in mitochondrial metabolic function and impairments in enzyme activity are the pathogenic processes underlying MELAS. Mitochondrial vasculopathy and mitochondrial neuropathy may provide a partial explanation for the unique aetiology of stroke-like episodes.

The clinical and genetic spectrum of mitochondrial diseases in China: A multicenter retrospective cross-sectional study

Mitochondrial diseases (MtDs) present diverse clinical phenotypes, yet large-scale studies are hindered by their rarity. This retrospective, multicenter study, conducted across five Chinese hospitals' neurology departments from 2009 to 2019, aimed to address this gap. Nationwide, 1351 patients were enrolled, with a median onset age of 14.0 (18.5) years. The predominant phenotype was mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) (45.0%). Mitochondrial DNA (mtDNA) mutations were prevalent (87.4%), with m.3243A>G being the most common locus (48.7%). Meanwhile, POLG mutations in nuclear DNA (nDNA) accounted for 16.5%. Comparative analysis based on age groups (with a cut-off at 14 years) revealed the highest prevalence of MELAS, with Leigh syndrome (LS) and chronic progressive external ophthalmoplegia (CPEO) being the second most common phenotypes in junior and senior groups, respectively. Notably, the most commonly mutated nuclear genes varied across age groups. In conclusion, MELAS predominated in this Chinese MtD cohort, underscored by m.3243A>G and POLG as principal mtDNA mutations and pathogenic nuclear genes. The phenotypic and genotypic disparities observed among different age cohorts highlight the complex nature of MtDs.

Stroke-like episodes in patients with adult-onset neuronal intranuclear inclusion disease and patients with late-onset MELAS: A comparative study

OBJECTIVE

To delineate the characteristics of stroke-like episodes (SLEs) in patients with adult-onset neuronal intranuclear inclusion disease (NIID) and to compare these characteristics with those of patients with MELAS.

METHODS

Twenty-three adult-onset NIID patients who presented with acute or subacute brain disorders and 13 late-onset MELAS patients were enrolled in the study. Patients with NIID were categorized into the SLEs group and the encephalopathy-like episodes (ELEs) group according to the associated stroke-like lesions (SLLs) findings. Clinical characteristics were compared between the SLEs group and the ELEs group among NIID patients and between NIID patients with SLEs and MELAS patients.

RESULTS

Eleven (47.8%) NIID patients who manifested acute or subacute brain disorders had detectable associated SLLs and were categorized into SLEs group. SLEs patients were more likely to report fever, headache, and seizures instead of sleep disorders than ELEs patients. Four (36.4%) NIID patients with SLEs absence of diagnostic or suggestive NIID imaging features. The clinical manifestations, laboratory test results, and neuroimaging and muscle biopsy histological features of NIID patients with SLEs majorly overlapped with those of late-onset MELAS patients. Older age at the first SLE (OR [95% CI], 1.203 [1.045-1.384]), symptoms of movement disorders on admission (OR [95% CI], 9.625 [1.378-67.246]), and white matter hyperintensity in corpus callosum (OR [95% CI], 16.00 [1.542-166.46]) associated with the NIID diagnosis in patients with SLEs.

INTERPRETATION

NIID patients with SLEs exhibit evident features of mitochondrial disorders. Interventions aimed at mitochondrial dysfunction might be a promising therapeutic approach for treating this disease.

Diagnosis and Management of Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes Syndrome

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a complex mitochondrial disorder characterized by a wide range of systemic manifestations. Key clinical features include recurrent stroke-like episodes, seizures, lactic acidosis, muscle weakness, exercise intolerance, sensorineural hearing loss, diabetes, and progressive neurological decline. MELAS is most commonly associated with mutations in mitochondrial DNA, particularly the m.3243A>G mutation in the MT-TL1 gene, which encodes tRNALeu (CUR). These mutations impair mitochondrial protein synthesis, leading to defective oxidative phosphorylation and energy failure at the cellular level. The clinical presentation and severity vary widely among patients, but the syndrome often results in significant morbidity and reduced life expectancy because of progressive neurological deterioration. Current management is largely focused on conservative care, including anti-seizure medications, arginine or citrulline supplementation, high-dose taurine, and dietary therapies. However, these therapies do not address the underlying genetic mutations, leaving many patients with substantial disease burden. Emerging experimental treatments, such as gene therapy and mitochondrial replacement techniques, aim to correct the underlying genetic defects and offer potential curative strategies. Further research is essential to understand the pathophysiology of MELAS, optimize current therapies, and develop novel treatments that may significantly improve patient outcomes and extend survival.

A case of alternating hemiplegia in 2-month-old children with nystagmus as the first symptom: A case report

RATIONALE

This case report delves into the rare neurological condition known as alternating hemiplegia of childhood (AHC), focusing on its clinical manifestations, diagnostic approaches, and treatment options. AHC typically presents in infants under the age of 18 months with intermittent episodes of hemiplegia, often triggered by stressors such as environmental changes, bathing, or emotional stress. Recognizing the clinical features of AHC is crucial for early identification and intervention.

PATIENT CONCERNS

The paper presents a case of a 2-month-old child with nystagmus as the initial symptom, followed by limb movement disorder in the left upper limb and weakness in the right limbs. The child's condition did not improve with treatment at an external hospital, highlighting the complexity of the disease and the need for specialized care.

DIAGNOSES

After a comprehensive review of the patient's medical history, physical examination, and imaging studies, the child was diagnosed with AHC. The diagnosis was confirmed through video electroencephalogram and whole-exome gene detection, which revealed a de novo mutation in the ATP1A3 gene, identified as pathogenic according to the American College of Medical Genetics and Genomics guidelines.

INTERVENTIONS

The child was admitted to Peking University First Hospital and treated with levetiracetam and flunarizine oral administration. These medications were chosen for their efficacy in managing the symptoms of AHC, particularly the hemiplegic episodes.

OUTCOMES

Post-treatment, the child experienced a reduction in the frequency and intensity of hemiplegic attacks compared to the initial stage. However, the child still exhibited paroxysmal symptoms and abnormal eye movements, and developmental milestones were delayed, indicating the need for ongoing care and monitoring.

LESSONS

This case underscores the importance of early recognition and prompt intervention in managing children with AHC. The varied clinical presentations of AHC necessitate vigilance for early differential diagnosis. Although AHC is currently incurable, appropriate treatment can mitigate the impact of complications and improve the long-term quality of life for affected children, facilitating better societal integration.

Mitochondrial Dysfunctions: Genetic and Cellular Implications Revealed by Various Model Organisms

Mitochondria play a crucial role in maintaining the energy status and redox homeostasis of eukaryotic cells. They are responsible for the metabolic efficiency of cells, providing both ATP and intermediate metabolic products. They also regulate cell survival and death under stress conditions by controlling the cell response or activating the apoptosis process. This functional diversity of mitochondria indicates their great importance for cellular metabolism. Hence, dysfunctions of these structures are increasingly recognized as an element of the etiology of many human diseases and, therefore, an extremely promising therapeutic target. Mitochondrial dysfunctions can be caused by mutations in both nuclear and mitochondrial DNA, as well as by stress factors or replication errors. Progress in knowledge about the biology of mitochondria, as well as the consequences for the efficiency of the entire organism resulting from the dysfunction of these structures, is achieved through the use of model organisms. They are an invaluable tool for analyzing complex cellular processes, leading to a better understanding of diseases caused by mitochondrial dysfunction. In this work, we review the most commonly used model organisms, discussing both their advantages and limitations in modeling fundamental mitochondrial processes or mitochondrial diseases.

Altered Neurovascular Coupling in Patients With Mitochondrial Myopathy, Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes (MELAS): A Combined Resting-State fMRI and Arterial Spin Labeling Study

BACKGROUND

Coupling between neuronal activity and blood perfusion is termed neurovascular coupling (NVC), and it provides a potentially new mechanistic perspective into understanding numerous brain diseases. Although abnormal brain activity and blood supply have been separately reported in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), whether anomalous NVC would be present is unclear.

PURPOSE

To investigate NVC changes and potential neural basis in MELAS by combining resting-state functional MRI (rs-fMRI) and arterial spin labeling (ASL).

STUDY TYPE

Prospective.

SUBJECTS

Twenty-four patients with MELAS (age: 29.8 ± 7.3 years) in the acute stage and 24 healthy controls (HCs, age: 26.4 ± 8.1 years). Additionally, 12 patients in the chronic stage were followed up.

FIELD STRENGTH/SEQUENCE

3.0 T, resting-state gradient-recalled echo-planar imaging and pseudo-continuous 3D ASL sequences.

ASSESSMENT

Amplitude of low-frequency fluctuation (ALFF), fractional ALFF (fALFF), regional homogeneity (ReHo), and functional connectivity strength (FCS) were calculated from rs-fMRI, and cerebral blood flow (CBF) was computed from ASL. Global NVC was assessed by correlation coefficients of CBF-ALFF, CBF-fALFF, CBF-ReHo, and CBF-FCS. Regional NVC was also evaluated by voxel-wise and lesion-wise ratios of CBF/ALFF, CBF/fALFF, CBF/ReHo, and CBF/FCS.

STATISTICAL TESTS

Two-sample t-test, paired-sample t-test, Gaussian random fields correction. A P value <0.05 was considered statistically significant.

RESULTS

Compared with HC, MELAS patients in acute stage showed significantly reduced global CBF-ALFF, CBF-fALFF, CBF-ReHo, and CBF-FCS coupling (P < 0.001). Altered CBF/ALFF, CBF/fALFF, CBF/ReHo, and CBF/FCS ratios were found mainly distributed in the middle cerebral artery territory in MELAS patients. In addition, significantly increased NVC ratios were found in the acute stroke-like lesions in acute stage (P < 0.001), with a recovery trend in chronic stage.

DATA CONCLUSIONS

This study showed dynamic alterations in NVC in MELAS patients from acute to chronic stage, which may provide a novel insight for understanding the pathogenesis of MELAS.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 1.

Mitochondrial encephalopathies and myopathies: Our tertiary center's experience

Mitochondrial diseases have a heterogeneous phenotype and can result from mutations in the mitochondrial or nuclear genomes, constituting a diagnostically and therapeutically challenging group of disorders. We report our center's experience with mitochondrial encephalopathies and myopathies with a cohort of 50 genetically and phenotypically diverse patients followed in the Neurology clinic over the last ten years. Seventeen patients had mitochondrial DNA mutations, presented over a wide range of ages with seizures, feeding difficulties, extraocular movements abnormalities, and had high rates of stroke-like episodes and regression. Twenty-seven patients had nuclear DNA mutations, presented early in life with feeding difficulty, failure-to-thrive, and seizures, and had high proportions of developmental delay, wheelchair dependence, spine abnormalities and dystonia. In six patients, a mutation could not be identified, but they were included for having mitochondrial disease confirmed by histopathology, enzyme analysis and clinical features. These patients had similar characteristics to patients with nuclear DNA mutations, suggesting missed underlying mutations in the nuclear genome. Management was variable among patients, but outcomes were universally poor with severe disability in all cases. Therapeutic entryways through elucidation of disease pathways and remaining unknown genes are acutely needed.

Etiological analysis of 167 cases of drug-resistant epilepsy in children

BACKGROUND

To analyze the etiological distribution characteristics of drug-resistant epilepsy (DRE) in children, with the aim of providing valuable perspectives to enhance clinical practice.

METHODS

In this retrospective study, clinical data were collected on 167 children with DRE who were hospitalized between January 2020 and December 2022, including gender, age of onset, seizure types, video electroencephalogram(VEEG) recordings, neuroimaging, and genetic testing results. Based on the etiology of epilepsy, the enrolled children were categorized into different groups. The rank-sum test was conducted to compare the age of onset for different etiologies.

RESULTS

Of the 167 cases, 89 (53.3%) had a clear etiology. Among them, structural factors account for 23.4%, genetic factors for 19.2%, multiple factors for 7.2%, and immunological factors for 3.6%. The age of onset was significantly earlier in children with genetic causes than those with structural (P < 0.001) or immunological (P = 0.001) causes.

CONCLUSIONS

More than half of children with DRE have a distinct underlying cause, predominantly attributed to structural factors, followed by genetic factors. Genetic etiology primarily manifests at an early age, especially among children aged less than one year. This underscores the need for proactive enhancements in genetic testing to unveil the underlying causes and subsequently guide treatment protocols.

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.

Neuronal Intranuclear Inclusion Disease with NOTCH2NLC GGC Repeat Expansion: A Systematic Review and Challenges of Phenotypic Characterization

Neuronal intranuclear inclusion disease (NIID) is a highly clinically heterogeneous neurodegenerative disorder primarily attributed to abnormal GGC repeat expansions in the NOTCH2NLC gene. This study aims to comprehensively explore its phenotypic characteristics and genotype-phenotype correlation. A literature search was conducted in PubMed, Embase, and the Cochrane Library from September 1, 2019, to December 31, 2022, encompassing reported NIID cases confirmed by pathogenic NOTCH2NLC mutations. Linear regressions and trend analyses were performed. Analyzing 635 cases from 85 included studies revealed that familial cases exhibited significantly larger GGC repeat expansions than sporadic cases (p < 0.001), and this frequency significantly increased with expanding GGC repeats (p trend < 0.001). Age at onset (AAO) showed a negative correlation with GGC repeat expansions (p < 0.001). The predominant initial symptoms included tremor (31.70%), cognitive impairment (14.12%), and muscle weakness (10.66%). The decreased or absent tendon reflex (DTR/ATR) emerged as a notable clinical indicator of NIID due to its high prevalence. U-fiber was observed in 79.11% of patients, particularly prominent in paroxysmal disease-dominant (87.50%) and dementia-dominant cases (81.08%). Peripheral neuropathy-dominant cases exhibited larger GGC repeat expansions (median = 123.00) and an earlier AAO (median = 33.00) than other phenotypes. Moreover, a significant genetic anticipation of 3.5 years was observed (p = 0.039). This study provides a comprehensive and up-to-date compilation of genotypic and phenotypic information on NIID since the identification of the causative gene NOTCH2NLC. We contribute a novel diagnostic framework for NIID to support clinical practice.

Primary mitochondrial diseases

Primary mitochondrial diseases (PMDs) are a heterogeneous group of hereditary disorders characterized by an impairment of the mitochondrial respiratory chain. They are the most common group of genetic metabolic disorders, with a prevalence of 1 in 4,300 people. The presence of leukoencephalopathy is recognized as an important feature in many PMDs and can be a manifestation of mutations in both mitochondrial DNA (classic syndromes such as mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes; myoclonic epilepsy with ragged-red fibers [RRFs]; Leigh syndrome; and Kearns-Sayre syndrome) and nuclear DNA (mutations in maintenance genes such as POLG, MPV17, and TYMP; Leigh syndrome; and mitochondrial aminoacyl-tRNA synthetase disorders). In this chapter, PMDs associated with white matter involvement are outlined, including details of clinical presentations, brain MRI features, and elements of differential diagnoses. The current approach to the diagnosis of PMDs and management strategies are also discussed. A PMD diagnosis in a subject with leukoencephalopathy should be considered in the presence of specific brain MRI features (for example, cyst-like lesions, bilateral basal ganglia lesions, and involvement of both cerebral hemispheres and cerebellum), in addition to a complex neurologic or multisystem disorder. Establishing a genetic diagnosis is crucial to ensure appropriate genetic counseling, multidisciplinary team input, and eligibility for clinical trials.

The mitochondrial tRNA MT-TW m.5537_5538insT variant presents with significant intra-familial clinical variability

Mitochondrial disorders can present with a wide range of clinical and biochemical phenotypes. Mitochondrial DNA variants may be influenced by factors such as degree of heteroplasmy and tissue distribution. We present a four-generation family in which 10 individuals carry a pathogenic mitochondrial variant (m.5537_5538insT, MT-TW gene) with differing levels of heteroplasmy and clinical features. This genetic variant has been documented in two prior reports, both in individuals with Leigh syndrome. In the current family, three individuals have severe mitochondrial symptoms including Leigh syndrome (patient 1, 100% in blood), MELAS (patient 2, 97% heteroplasmy in muscle), and MELAS-like syndrome (patient 3, 50% heteroplasmy in blood and 100% in urine). Two individuals have mild mitochondrial symptoms (patient 4, 50% in blood and 67% in urine and patient 5, 50% heteroplasmy in blood and 30% in urine). We observe that this variant is associated with multiple mitochondrial presentations and phenotypes, including MELAS syndrome for which this variant has not previously been reported. We also demonstrate that the level of heteroplasmy of the mitochondrial DNA variant correlates with the severity of clinical presentation; however, not with the specific mitochondrial syndrome.

Late-onset MELAS syndrome in a 46-year-old man with initial symptom of chest tightness: a case report

Background

Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like episodes (MELAS) syndrome is a rare mitochondrial disorder caused by mutations in mitochondrial DNA, resulting in impaired energy production and affecting multiple organs. We present a suspected MELAS syndrome case with the initial symptom of chest tightness.

Case summary

A 46-year-old man sought medical attention due to progressively worsening chest tightness during physical activity. He had been receiving treatment for type 2 diabetes for 15 years. One year ago, he presented with symptoms of hearing impairment. Transthoracic echocardiography revealed increased thickness of the left ventricular wall. Serum protein electrophoresis showed no evidence of light-chain amyloidosis, and the 99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid scan showed no definite uptake in the heart muscle. The patient's head magnetic resonance imaging (MRI) indicated lacunar infarcts. The lactate threshold test was positive. The biopsy of the skeletal muscle showed broken red fibre infiltration on modified Gomori trichrome staining, and electron microscopy revealed signs of mitochondrial cardiomyopathy, including mild mitochondrial swelling, lipid accumulation, and myofibril damage. A whole-exome genetic test was used to detect the m.3243A>G mutation in the MT-TL1 gene. Based on these findings, MELAS syndrome was the most probable diagnosis.

Discussion

The patient presented with chest tightness in adulthood, without any accompanying psychoneurological symptoms. However, the patient presented with other symptoms, including diabetes mellitus, hearing loss, abnormal lactate levels, ischaemic lesions on head MRI, and left ventricular hypertrophy. By identifying a mutation in the MT-TL1 gene and conducting a muscle biopsy, the diagnosis of MELAS syndrome was definitively confirmed.

Refractory Hypotension in a Late-Onset Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-like Episodes (MELAS) Male with m.3243 A>G Mutation: A Case Report

(1) Introduction: Symptom spectrum can be of great diversity and heterogeneity in mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) patients in clinical practice. Here, we report a case of MELAS presenting asymptomatic refractory hypotension with m.3243 A>G mutation. (2) Case representation: A 51-year-old male patient presented with a headache, vertigo, and difficulty in expression and understanding. The magnetic resonance imaging of the brain revealed an acute stroke-like lesion involving the left temporoparietal lobe. A definitive diagnosis of MELAS was given after the genetic test identified the chrM-3243 A>G mutation. The patient suffered recurrent stroke-like episodes in the 1-year follow-up. Notably, refractory hypotension was observed during hospitalizations, and no significant improvement in blood pressure was found after continuous use of vasopressor drugs and fluid infusion therapy. (3) Conclusions: We report a case of refractory hypotension which was unresponsive to fluid infusion therapy found in a patient with MELAS. Our case suggests that comprehensive management should be paid attention to during treatment. A further study on the pathological mechanism of the multisystem symptoms in MELAS would be beneficial to the treatment of patients.

Ischemic optic neuropathy as first presentation in patient with m.3243 A > G MELAS classic mutation

BACKGROUND

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a systemic disorder in which multi-organ dysfunction may occur from mitochondrial metabolism failure. Maternally inherited mutations in the MT-TL1 gene are the most frequent causes for this disorder. Clinical manifestations may include stroke-like episodes, epilepsy, dementia, headache and myopathy. Among these, acute visual failure, usually in association with cortical blindness, can occur because of stroke-like episodes affecting the occipital cortex or the visual pathways. Vision loss due to optic neuropathy is otherwise considered a typical manifestation of other mitochondrial diseases such as Leber hereditary optic neuropathy (LHON).

CASE PRESENTATION

Here we describe a 55-year-old woman, sister of a previously described patient with MELAS harbouring the m.3243A > G (p.0, MT-TL1) mutation, with otherwise unremarkable medical history, that presented with subacute, painful visual impairment of one eye, accompanied by proximal muscular pain and headache. Over the next weeks, she developed severe and progressive vision loss limited to one eye. Ocular examination confirmed unilateral swelling of the optic nerve head; fluorescein angiography showed segmental perfusion delay in the optic disc and papillary leakage. Neuroimaging, blood and CSF examination and temporal artery biopsy ruled out neuroinflammatory disorders and giant cell arteritis (GCA). Mitochondrial sequencing analysis confirmed the m.3243A > G transition, and excluded the three most common LHON mutations, as well as the m.3376G > A LHON/MELAS overlap syndrome mutation. Based on the constellation of clinical symptoms and signs presented in our patient, including the muscular involvement, and the results of the investigations, the diagnosis of optic neuropathy as a stroke-like event affecting the optic disc was performed. L-arginine and ubidecarenone therapies were started with the aim to improve stroke-like episode symptoms and prevention. The visual defect remained stable with no further progression or outbreak of new symptoms.

CONCLUSIONS

Atypical clinical presentations must be always considered in mitochondrial disorders, even in well-described phenotypes and when mutational load in peripheral tissue is low. Mitotic segregation of mitochondrial DNA (mtDNA) does not allow to know the exact degree of heteroplasmy existent within different tissue, such as retina and optic nerve. Important therapeutic implications arise from a correct diagnosis of atypical presentation of mitochondrial disorders.

De novo frameshift variant in MT-ND1 causes a mitochondrial complex I deficiency associated with MELAS syndrome

BACKGROUND

The variant m.3571_3572insC/MT-ND1 thus far only reported in oncocytic tumors of different tissues. However, the role of m.3571_3572insC in inherited mitochondrial diseases has yet to be elucidated.

METHODS

A patient diagnosed with MELAS syndrome was recruited, and detailed medical records were collected and reviewed. The muscle was biopsied for mitochondrial respiratory chain enzyme activity. Series of fibroblast clones bearing different m.3571_3572insC variant loads were generated from patient-derived fibroblasts and subjected to functional assays.

RESULTS

Complex I deficiency was confirmed in the patient's muscle via mitochondrial respiratory chain enzyme activity assay. The m.3571_3572insC was filtered for the candidate variant of the patient according to the guidelines for mitochondrial mRNA variants interpretation. Three cell clones with different m.3571_3572insC variant loads were generated to evaluate mitochondrial function. Blue native PAGE analysis revealed that m.3571_3572insC caused a deficiency in the mitochondrial complex I. Oxygen consumption rate, ATP production, and lactate assays found an impairment of cellular bioenergetic capacity due to m.3571_3572insC. Mitochondrial membrane potential was decreased, and mitochondrial reactive oxygen species production was increased with the variant of m.3571_3572insC. According to the competitive cell growth assay, the mutant cells had impaired cell growth capacity compared to wild type.

CONCLUSIONS

A novel variant m.3571_3572insC was identified in a patient diagnosed with MELAS syndrome, and the variant impaired mitochondrial respiration by decreasing the activity of complex I. In conclusion, the genetic spectrum of mitochondrial diseases was expanded by including m.3571_3572insC/MT-ND1.

Stroke-like episodes in adult mitochondrial disease

Stroke-like episode is a paroxysmal neurological manifestation which affects a specific group of patients with mitochondrial disease. Focal-onset seizures, encephalopathy, and visual disturbances are prominent findings associated with stroke-like episodes, with a predilection for the posterior cerebral cortex. The most common cause of stroke-like episodes is the m.3243A>G variant in MT-TL1 gene followed by recessive POLG variants. This chapter aims to review the definition of stroke-like episode and delineate the clinical phenomenology, neuroimaging and EEG findings typically seen in patients. In addition, several lines of evidence supporting neuronal hyper-excitability as the key mechanism of stroke-like episodes are discussed. The management of stroke-like episodes should focus on aggressive seizure management and treatment for concomitant complications such as intestinal pseudo-obstruction. There is no robust evidence to prove the efficacy of l-arginine for both acute and prophylactic settings. Progressive brain atrophy and dementia are the sequalae of recurrent stroke-like episode, and the underlying genotype in part predicts prognosis.

Creation of Mitochondrial Disease Models Using Mitochondrial DNA Editing

Mitochondrial diseases are a large class of human hereditary diseases, accompanied by the dysfunction of mitochondria and the disruption of cellular energy synthesis, that affect various tissues and organ systems. Mitochondrial DNA mutation-caused disorders are difficult to study because of the insufficient number of clinical cases and the challenges of creating appropriate models. There are many cellular models of mitochondrial diseases, but their application has a number of limitations. The most proper and promising models of mitochondrial diseases are animal models, which, unfortunately, are quite rare and more difficult to develop. The challenges mainly arise from the structural features of mitochondria, which complicate the genetic editing of mitochondrial DNA. This review is devoted to discussing animal models of human mitochondrial diseases and recently developed approaches used to create them. Furthermore, this review discusses mitochondrial diseases and studies of metabolic disorders caused by the mitochondrial DNA mutations underlying these diseases.

Pathogenesis of acute encephalopathy in acute hepatic porphyria

Acute encephalopathy (AE) can be a manifestation of an acute porphyric attack. Clinical data were studied in 32 patients during AE with or without polyneuropathy (PNP) together with 12 subjects with PNP but no AE, and 17 with dysautonomia solely. Brain neuroimaging was done in 20 attacks during AE, and PEPT2 polymorphisms were studied in 56 subjects, 24 with AE. AE manifested as a triad of seizures, confusion and/or blurred vision. Symptoms lasting 1-5 days manifested 3-19 days from the onset of an attack. 55% of these patients had acute PNP independent of AE. Posterior reversible encephalopathy syndrome (PRES) was detected in 42% of the attacks. These patients were severely affected and hyponatremic (88%). Reversible segmental vasoconstriction was rare. There was no statistical difference in hypertension or urinary excretion of porphyrin precursors among the patients with or without AE. In 94% of the attacks with AE, liver transaminases were elevated significantly (1.5 to fivefold, P = 0.034) compared to a normal level in 87% of the attacks with dysautonomia, or in 25% of patients with PNP solely. PEPT2*2/2 haplotype was less common among patients with AE than without (8.3% vs. 25.8%, P = 0.159) and in patients with PNP than without (9.5% vs. 22.9%, P = 0.207), suggesting a minor role, if any, in acute neurotoxicity. In contrast, PEPT2*2/2 haplotype was commoner among patients with chronic kidney disease (P = 0.192). Acute endothelial dysfunction in porphyric encephalopathy could be explained by a combination of abrupt hypertension, SIADH, and acute metabolic and inflammatory factors of hepatic origin.

High-dose oral glutamine supplementation reduces elevated glutamate levels in cerebrospinal fluid in patients with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes syndrome

BACKGROUND AND PURPOSE

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) syndrome is a genetically heterogeneous disorder caused by mitochondrial DNA mutations. There are no disease-modifying therapies, and treatment remains mainly supportive. It has been shown previously that patients with MELAS syndrome have significantly increased cerebrospinal fluid (CSF) glutamate and significantly decreased CSF glutamine levels compared to controls. Glutamine has many metabolic fates in neurons and astrocytes, and the glutamate-glutamine cycle couples with many metabolic pathways depending on cellular requirements. The aim was to compare CSF glutamate and glutamine levels before and after dietary glutamine supplementation. It is postulated that high-dose oral glutamine supplementation could reduce the increase in glutamate levels.

METHOD

This open-label, single-cohort study determined the safety and changes in glutamate and glutamine levels in CSF after 12 weeks of oral glutamine supplementation.

RESULTS

Nine adult patients with MELAS syndrome (66.7% females, mean age 35.8 ± 3.2 years) were included. After glutamine supplementation, CSF glutamate levels were significantly reduced (9.77 ± 1.21 vs. 18.48 ± 1.34 μmol/l, p < 0.001) and CSF glutamine levels were significantly increased (433.66 ± 15.31 vs. 336.31 ± 12.92 μmol/l, p = 0.002). A side effect observed in four of nine patients was a mild sensation of satiety. One patient developed mild and transient elevation of transaminases, and another patient was admitted for an epileptic status without stroke-like episode.

DISCUSSION

This study demonstrates that high-dose oral glutamine supplementation significantly reduces CSF glutamate and increases CSF glutamine levels in patients with MELAS syndrome. These findings may have potential therapeutic implications in these patients.

TRIAL REGISTRATION INFORMATION

ClinicalTrials.gov Identifier: NCT04948138. Initial release 24 June 2021, first patient enrolled 1 July 2021. https://clinicaltrials.gov/ct2/show/NCT04948138.

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes with an MT-TL1 m.3243A>G point mutation: Neuroradiological features and their implications for underlying pathogenesis

Objective

Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) is one of the most common inherited mitochondrial disorders. Due to the high clinical and genetic heterogeneity of MELAS, it is still a major challenge for clinicians to accurately diagnose the disease at an early stage. Herein, we evaluated the neuroimaging findings of MELAS with an m.3243A>G mutation in MT-TL1 and analyzed the possible underlying pathogenesis of stroke-like episodes.

Materials and methods

Fifty-nine imaging studies in 24 patients who had a confirmed genetic diagnosis of m.3243A>G (MT-TL1; tRNA ^Leu) associated with MELAS were reviewed in our case series. The anatomic location, morphological features, signal/intensity characteristics and temporal evolution of lesions were analyzed on magnetic resonance imaging (MRI), and computed tomography (CT) images. The supplying vessels and metabolite content of the lesions were also evaluated by using MR angiography (MRA)/CT angiography (CTA), and MR spectroscopy (MRS), respectively.

Results

The lesions were most commonly located in the posterior brain, with 37 (37/59, 63%) in the occipital lobe, 32 (32/59, 54%) in the parietal lobe, and 30 (30/59, 51%) in the temporal lobe. The signal characteristics of the lesions varied and evolved over time. Bilateral basal ganglia calcifications were found in 6 of 9 (67%) patients who underwent CT. Cerebral and cerebellar atrophy were found in 38/59 (64%) and 40/59 (68%) patients, respectively. Lesion polymorphism was found in 37/59 (63%) studies. MRS showed elevated lactate doublet peaks in 9/10 (90%) cases. MRA or CTA revealed that the lesion-related arteries were slightly dilated compared with those of the contralateral side in 4 of 6 (67%) cases.

Conclusion

The imaging features of MELAS vary depending on the disease stage. Polymorphic lesions in a single imaging examination should be considered a diagnostic clue for MELAS. Stroke-like episodes may be involved in a complex pathogenetic process, including mitochondrial angiopathy, mitochondrial cytopathy, and neuronal excitotoxicity.

Mitochondrial encephalomyopathy

Mitochondrial dysfunction, especially perturbation of oxidative phosphorylation and adenosine triphosphate (ATP) generation, disrupts cellular homeostasis and is a surprisingly frequent cause of central and peripheral nervous system pathology. Mitochondrial disease is an umbrella term that encompasses a host of clinical syndromes and features caused by in excess of 300 different genetic defects affecting the mitochondrial and nuclear genomes. Patients with mitochondrial disease can present at any age, ranging from neonatal onset to late adult life, with variable organ involvement and neurological manifestations including neurodevelopmental delay, seizures, stroke-like episodes, movement disorders, optic neuropathy, myopathy, and neuropathy. Until relatively recently, analysis of skeletal muscle biopsy was the focus of diagnostic algorithms, but step-changes in the scope and availability of next-generation sequencing technology and multiomics analysis have revolutionized mitochondrial disease diagnosis. Currently, there is no specific therapy for most types of mitochondrial disease, although clinical trials research in the field is gathering momentum. In that context, active management of epilepsy, stroke-like episodes, dystonia, brainstem dysfunction, and Parkinsonism are all the more important in improving patient quality of life and reducing mortality.

Case report: A unusual case of delayed propionic acidemia complicated with subdural hematoma

Background

Propionic acidemia (PA) is an inherited autosomal recessive metabolic disorder that is classified as early-onset or late-onset, depending on the onset time of clinical symptoms. It clinically manifests as numerous lesions in the brain, pancreas, liver, and muscle. Muscle biopsies show myopathic changes, which help to distinguish late-onset propionic acidemia from other metabolic diseases involving muscles.

Case presentation

A 19-year-old Chinese girl was admitted to the hospital because of poor eating and fatigue. Head magnetic resonance imaging suggested metabolic diseases, and we administered symptomatic support treatment. Her symptoms gradually worsened, and she began to show convulsions and disturbances of consciousness. Muscle pathology showed myopathy-like changes. The presence of organic acids in the blood and urine suggested PA. Genetic analyses identified two compound heterozygous mutations in the patient's PCCB gene, confirming the diagnosis of delayed PA.

Conclusions

The muscle pathological examination of late-onset PA provides valuable information that is helpful for distinguishing delayed-onset PA from metabolic diseases. In the absence of a history of trauma, subdural hematoma may be a very rare complication of late-onset PA and can be regarded as a poor prognostic sign; therefore, it is suggested to perform head computed tomography as part of the routine neurological evaluation of PA patients.

Arginine for the Treatment of Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-Like Episodes: A Systematic Review

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a mitochondrial disease that lacks a definitive treatment. Lately, there has been an increased interest in the scientific community about the role of arginine in the short and long-term settings of the disease. We aim to conduct a systematic review of the clinical use of arginine in the management of MELAS and explore the role of arginine in the pathophysiology of the disease. We used PubMed advanced-strategy searches and only included full-text clinical trials on humans written in the English language. After applying the inclusion/exclusion criteria, four clinical trials were reviewed. We used the Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines and Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol for this systematic review. We used the Cochrane Collaboration risk-of-bias tool to assess the bias encountered in each study. Overall, IV arginine seems to be effective in improving symptoms during acute attacks of MELAS, while oral arginine supplementation increases endothelial function, preventing further stroke-like episodes.

Stroke-like Episodes in Inherited Neurometabolic Disorders

Stroke-like episodes (SLEs) are significant clinical manifestations of metabolic disorders affecting the central nervous system. Morphological equivalents presented in neuroimaging procedures are described as stroke-like lesions (SLLs). It is crucial to distinguish SLEs from cerebral infarction or intracerebral hemorrhage, mainly due to the variety in management. Another significant issue to underline is the meaning of the main pathogenetic hypotheses in the development of SLEs. The diagnostic process is based on the patient’s medical history, physical and neurological examination, neuroimaging techniques and laboratory and genetic testing. Implementation of treatment is generally symptomatic and includes L-arginine supplementation and adequate antiepileptic management. The main aim of the current review was to summarize the basic and actual knowledge about the occurrence of SLEs in various inherited neurometabolic disorders, discuss the possible pathomechanism of their development, underline the role of neuroimaging in the detection of SLLs and identification of the electroencephalographic patterns as well as histological abnormalities in inherited disorders of metabolism.

Microhemorrhages in MELAS Lesions: A Case Report

Introduction:

Microhemorrhages have not been described in mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes syndrome (MELAS) on magnetic resonance imaging (MRI). Main symptoms and/or important findings: A MELAS-patient had a rapid succession of 3 stroke-like episodes with dysphasia, visual field deficits and paresis of the right arm. MRI showed a lesion with corticosubcortical vasogenic edema without reduced diffusion, conforming to a stroke-like MELAS-lesion. Microhemorrhages within MELAS-lesions were detected on MRI. The main diagnoses, therapeutic interventions, and outcomes: Microhemorrhages are an atypical imaging finding in MELAS. The patient was treated with L-arginine.

Conclusion:

Microhemorrhages can present on MRI in (sub)acute MELAS lesions and may reflect mitochondrial microangiopathy.

Thalamic aphasia associated with mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes: A case report

BACKGROUND

Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with aphasia is a rare disorder, with the associated aphasia reported as either Wernicke's or Broca's. Herein, we report a patient with MELAS complicated by thalamic aphasia.

CASE

A 15-year-old right-handed girl presented with headache, nausea, right homonymous hemianopsia, and aphasia. She could repeat words said by others, but had word-finding difficulty, paraphasia, and dysgraphia. Brain MRI revealed abnormal signals from the left occipital lobe to the temporal lobe and left thalamus, but Wernicke's area and Broca's area were not involved. Additionally, she had short stature, lactic acidosis, bilateral sensorineural hearing loss, and a maternal family history of diabetes and mild deafness. Based on clinical findings and the presence of a mitochondrial A3243G mutation, she was diagnosed with MELAS. With treatment, the brain MRI lesions disappeared and her symptoms improved. Her aphasia was classified as amnesic aphasia because she could repeat words, despite having word-finding difficulty, paraphasia, and dysgraphia. Based on MRI findings of a left thalamic lesion, we diagnosed her with thalamic aphasia.

CONCLUSION

Thalamic aphasia may be caused by MELAS. Assessment of whether repetition is preserved is important for classifying aphasia.

Mitochondrial Impairment: A Common Motif in Neuropsychiatric Presentation? The Link to the Tryptophan-Kynurenine Metabolic System

Nearly half a century has passed since the discovery of cytoplasmic inheritance of human chloramphenicol resistance. The inheritance was then revealed to take place maternally by mitochondrial DNA (mtDNA). Later, a number of mutations in mtDNA were identified as a cause of severe inheritable metabolic diseases with neurological manifestation, and the impairment of mitochondrial functions has been probed in the pathogenesis of a wide range of illnesses including neurodegenerative diseases. Recently, a growing number of preclinical studies have revealed that animal behaviors are influenced by the impairment of mitochondrial functions and possibly by the loss of mitochondrial stress resilience. Indeed, as high as 54% of patients with one of the most common primary mitochondrial diseases, mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome, present psychiatric symptoms including cognitive impairment, mood disorder, anxiety, and psychosis. Mitochondria are multifunctional organelles which produce cellular energy and play a major role in other cellular functions including homeostasis, cellular signaling, and gene expression, among others. Mitochondrial functions are observed to be compromised and to become less resilient under continuous stress. Meanwhile, stress and inflammation have been linked to the activation of the tryptophan (Trp)-kynurenine (KYN) metabolic system, which observably contributes to the development of pathological conditions including neurological and psychiatric disorders. This review discusses the functions of mitochondria and the Trp-KYN system, the interaction of the Trp-KYN system with mitochondria, and the current understanding of the involvement of mitochondria and the Trp-KYN system in preclinical and clinical studies of major neurological and psychiatric diseases.

Elevated glutamate and decreased glutamine levels in the cerebrospinal fluid of patients with MELAS syndrome

Background

Mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome is a genetically heterogeneous disorder caused by mitochondrial DNA (mtDNA) mutations in the MT-TL1 gene. The pathophysiology of neurological manifestations is still unclear, but neuronal hyperexcitability and neuron–astrocyte uncoupling have been suggested. Glutamatergic neurotransmission is linked to glucose oxidation and mitochondrial metabolism in astrocytes and neurons. Given the relevance of neuron–astrocyte metabolic coupling and astrocyte function regulating energetic metabolism, we aimed to assess glutamate and glutamine CSF levels in MELAS patients.

Methods

This prospective observational case–control study determined glutamate and glutamine CSF levels in patients with MELAS syndrome and compared them with controls. The plasma and CSF levels of the remaining amino acids and lactate were also determined.

Results

Nine adult patients with MELAS syndrome (66.7% females mean age 35.8 ± 3.2 years) and 19 controls (63.2% females mean age 42.7 ± 3.8 years) were included. The CSF glutamate levels were significantly higher in patients with MELAS than in controls (18.48 ± 1.34 vs. 5.31 ± 1.09 μmol/L, p < 0.001). Significantly lower glutamine concentrations in patients with MELAS than controls were shown in CSF (336.31 ± 12.92 vs. 407.06 ± 15.74 μmol/L, p = 0.017). Moreover, the CSF levels of alanine, the branched-chain amino acids (BCAAs) and lactate were significantly higher in patients with MELAS.

Conclusions

Our results suggest the glutamate–glutamine cycle is altered probably due to metabolic imbalance, and as a result, the lactate–alanine and BCAA–glutamate cycles are upregulated. These findings might have therapeutic implications in MELAS syndrome.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10942-7.

Unlocking the Complexity of Mitochondrial DNA: A Key to Understanding Neurodegenerative Disease Caused by Injury

Neurodegenerative disorders that are triggered by injury typically have variable and unpredictable outcomes due to the complex and multifactorial cascade of events following the injury and during recovery. Hence, several factors beyond the initial injury likely contribute to the disease progression and pathology, and among these are genetic factors. Genetics is a recognized factor in determining the outcome of common neurodegenerative diseases. The role of mitochondrial genetics and function in traditional neurodegenerative diseases, such as Alzheimer’s and Parkinson’s diseases, is well-established. Much less is known about mitochondrial genetics, however, regarding neurodegenerative diseases that result from injuries such as traumatic brain injury and ischaemic stroke. We discuss the potential role of mitochondrial DNA genetics in the progression and outcome of injury-related neurodegenerative diseases. We present a guide for understanding mitochondrial genetic variation, along with the nuances of quantifying mitochondrial DNA variation. Evidence supporting a role for mitochondrial DNA as a risk factor for neurodegenerative disease is also reviewed and examined. Further research into the impact of mitochondrial DNA on neurodegenerative disease resulting from injury will likely offer key insights into the genetic factors that determine the outcome of these diseases together with potential targets for treatment.

Mitochondrial Strokes: Diagnostic Challenges and Chameleons

Mitochondrial stroke-like episodes (SLEs) are a hallmark of mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS). They should be suspected in anyone with an acute/subacute onset of focal neurological symptoms at any age and are usually driven by seizures. Suggestive features of an underlying mitochondrial pathology include evolving MRI lesions, often originating within the posterior brain regions, the presence of multisystemic involvement, including diabetes, deafness, or cardiomyopathy, and a positive family history. The diagnosis of MELAS has important implications for those affected and their relatives, given it enables early initiation of appropriate treatment and genetic counselling. However, the diagnosis is frequently challenging, particularly during the acute phase of an event. We describe four cases of mitochondrial strokes to highlight the considerable overlap that exists with other neurological disorders, including viral and autoimmune encephalitis, ischemic stroke, and central nervous system (CNS) vasculitis, and discuss the clinical, laboratory, and imaging features that can help distinguish MELAS from these differential diagnoses.

Knowledge about the characteristics of stroke-like lesions is expandable

Stroke-like episodes (SLEs) are a common phenotypic feature of various syndromic and non-syndromic mitochondrial disorders (MIDs), particularly of mitochondrial encephalopathy, lactic acidosis, and stroke-like episode syndrome (MELAS). The morphological equivalent of a SLE is the stroke-like lesion (SLE), a dynamic lesion, which initially expands to regress after weeks or months. SLLs present with typical morphological and structural abnormalities on multimodal magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), and FDG-PET. It is crucial to clearly delineate SLLs from ischemic stroke, as treatment and outcome vary significantly between the two.