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.

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.

Headache in cerebrovascular diseases.

Headache is a common accompanying symptom of cerebrovascular diseases. The most common patterns of headache for different cerebrovascular disorders, aetiology and pathogenesis and diagnostic workup are reviewed with emphasis on distinguishing characteristics. It will be a clinical guide for physicians who treat patients with headache or cerebral vascular disease.

Altered spontaneous brain activity at attack and remission stages in patients with mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS): Beyond stroke-like lesions.

Mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) may cause whole-brain functional changes due to mitochondrial dysfunction. Our purpose is to comprehensively evaluate the alterations of spontaneous brain activity in MELAS patients at stroke-like episodes (SLE) attack and remission stages using resting-state functional magnetic resonance imaging. Forty MELAS patients at attack stage (n = 20) and remission stage (n = 20) and 22 healthy controls were enrolled in this study. We suggested that MELAS patients presented decreased spontaneous brain activities beyond the areas of stroke-like lesions (SLLs), with a downward trend from SLE attack stage to remission stage. In addition, the regional spontaneous activity of SLL, an inherent change in MELAS, was less than that in unaffected areas. Furthermore, the fractional amplitude of low frequency fluctuations value in left precuneus may be used as a promising neuroimaging biomarker for monitoring the disease status of MELAS.

A MELAS Patient Developing Fatal Acute Renal Failure with Lactic Acidosis and Rhabdomyolysis.

We herein present a patient with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS), who developed serious acute renal failure with lactic acidosis, followed by rhabdomyolysis. Despite receiving intensive care, he suffered multiple cardiopulmonary arrests and died 10 days after presentation due to a sudden deterioration of his symptoms. Renal pathology revealed diffuse tubular necrosis with interstitial edema and tubular dilatation on light microscopy, and a severe degeneration of intracellular organelles on electron microscopy. These pathological findings could have resulted from multiple cardiopulmonary arrests; however, we must be aware of the extremely rare but sudden occurrence of these fatal conditions in MELAS patients.

Neuroimaging pattern and pathophysiology of cerebellar stroke-like lesions in MELAS with m.3243A>G mutation: a case report.

BACKGROUND: Stroke-like episodes (SLEs) in mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) with m.3243A > G mutation usually develop in the cerebral cortex. Few reports have documented SLEs in the cerebellum. The clinical neuroimaging features of cerebellar SLEs have not been fully investigated. We report distinctive features of cerebellar stroke-like lesions (SLLs) in a case of MELAS with m.3243A > G mutation. CASE PRESENTATION: A 47-year-old Japanese man with type-2 diabetes presented to our hospital with acute onset of aphasia. A brain MRI obtained on admission (day 1) showed increased diffusion-weighted imaging (DWI)/fluid-attenuated inversion recovery (FLAIR) signal in the left anterolateral temporal lobe, which subsequently spread along the cortex posteriorly accompanied by a new lesion in the right anterior temporal lobe. The patient was initially treated with acyclovir and subsequently with immunotherapy. However, on day 45, cerebellar ataxia developed. The brain MRI showed extensive increased DWI/FLAIR signals in the cerebellum along the folia without involvement of deep cerebellar nucleus or cerebellar peduncle; SLLs were incongruent with a vascular territory, similarly to classic cerebral SLLs. Apparent diffusion coefficient (ADC) map did not show reduction in ADC values in the affected folia. Genomic analysis revealed m.3243A > G mutation (heteroplasmy in leukocytes, 17%), confirming the diagnosis of MELAS. After the treatment with taurine (12,000 mg/day), L-arginine (12,000 mg/day), vitamin B1 (100 mg/day), and carnitine (3000 mg/day), the patient became able to follow simple commands, and he was transferred to a rehabilitation center on day 146. The follow-up MRI showed diffuse brain atrophy, including the cerebellum. CONCLUSIONS: SLLs develop in the cerebellum in MELAS with m.3243A > G mutation. The neuroimaging similarities to cerebral SLLs suggest the presence of the common pathophysiological mechanisms underlying both SLEs, which include microangiopathy and increased susceptibility of the cortex to metabolic derangements.

An analysis of the clinical and imaging features of mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS).

Objective: To investigate the clinical features and imaging characteristics of mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS).Methods: Seventeen patients with MELAS diagnosed in the Affiliated Hospital of Xuzhou Medical University from July 2014 to August 2018 were enrolled in this study and their clinical manifestations, imaging and histopathological features were retrospectively analysed. We also discussed and summarised the related literature.Results: All of the 12 patients had seizures; stroke-like episodes in 12 cases; audio-visual impairment in 12 cases; headache in six cases; dysplasia in four cases; mental retardation in three cases; ataxia in two cases. On cranial magnetic resonance (MR) scans, the most common manifestations were in temporal-occipital-parietal lobe, cortical or subcortical areas as well as frontal lobe, thalamus, and basal ganglia showing long or equal T1 signals, long T2 signals, and hyperintense or iso-intense diffusion-weighted imaging (DWI) signals accompanied by ventricular enlargement and brain atrophy. MR spectroscopy showed that lactic acid peaks could be found in lesion sites, normal brain tissues, and cerebrospinal fluid. Muscle biopsy and genetic testing are the gold standard for diagnosing MELAS, muscle biopsy revealed COX-negative muscle fibres and SDH-stained red ragged fibres (RRF) under the sarcolemma. Mutations of mtDNA A3243G locus were common on gene testing. Improvement of mitochondrial function was observed after symptomatic and supportive treatment.Conclusion: MELAS should be considered for patients with epileptic seizures, headache, stroke-like episodes, extraocular palsy, cognitive decline and other clinical manifestations with the lesion located in the temporal-occipital-parietal lobe regardless of the distribution of blood vessels, and further examinations including muscle biopsy and gene testing should be performed to confirm the diagnosis.

Audiological and Vestibular Findings in Subjects with MELAS Syndrome.

OBJECTIVES: The mitochondrial DNA (mtDNA) point mutation m.3243A>G is known to express the following two syndromes among others: maternally inherited diabetes and deafness (MIDD) and mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes (MELAS). Sensorineural hearing loss (SNHL) is the most frequent symptom in individuals harboring the m.3243A>G mutation. However, dysfunction of the vestibular organs has been scarcely examined. Therefore, the present study aimed to study the impact of the m.3243A>G mutation on the inner ear. MATERIALS AND METHODS: A total of 8 subjects harboring the blood-verified m.3243A>G mutation underwent thorough audiological and vestibular examinations, including tone and speech audiometry, video head impulse test (vHIT), ocular and cervical vestibular-evoked myogenic potential (oVEMP and cVEMP), and full otoneurological examination. The subjects also answered a Dizziness Handicap Inventory (DHI) questionnaire. RESULTS: SNHL was identified in all the 8 subjects, with a mean pure-tone average-4 (PTA-4) of 59 dB. Speech discrimination score (n=7) ranged from 24% to 100% (mean 74%), and vHIT (n=42) detected pathology in nine lateral semicircular canals (SCCs), five posterior SCCs, and one anterior SCC, whereas three measurements were inconclusive. All oVEMPs (n=14 ears) were absent, nine cVEMPs were absent, and two were inconclusive. Based on the DHI scores, 6 subjects reported none to mild dizziness, 1 reported moderate, and 1 reported severe dizziness. CONCLUSION: Our study population had pathological findings from every audiological and vestibular end organs. The results indicated that the pathological findings originated from within the end organs themselves and not within the superior and inferior vestibular or cochlear nerve.

Transition from Leigh syndrome to MELAS syndrome in a patient with heteroplasmic MT-ND3 m.10158T>C.

An m.10158T>C mutation in MT-ND3, encoding a subunit of respiratory complex I, causes early-onset Leigh syndrome (LS), mitochondrial encephalomyopathy with lactic acid and stroke-like episodes (MELAS) syndrome, and LS and MELAS overlapping syndrome, presumably dependent on the ratio of heteroplasmy. Herein, we report a 4-year-old girl with heteroplasmic m.10158T>C mutation, showing an evolving age-dependent phenotype from LS to MELAS syndromes. She showed mild developmental delay during infancy, which was associated with magnetic resonance imaging lesions in the brain stem and basal ganglia. At the age of 4 years, she developed rapid neurological deterioration and intractable seizures, which was associated with recurrent multiple cerebral lesions as well as basal ganglia lesions. Her cerebral lesions were located predominantly in white matter and appeared at multiple areas simultaneously, unique characteristics that are distinct from typical MELAS. Two patients with LS-MELAS overlapping syndrome with m.10158T>C have been previously reported, however, this is the first patient with m.10158T>C showing significant age-dependent changes in clinical features and neuro-images, implying an age-dependent role of complex I in the developing brain.

A cluster of disseminated small cortical lesions in MELAS: its distinctive clinical and neuroimaging features.

OBJECTIVES: To investigate a diversity of stroke-like episodes (SLEs) in mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS), and report a disseminated form of SLEs (D-SLEs) attributed to a cluster of disseminated small cortical lesions. METHODS: We retrospectively reviewed the clinical information of 27 MELAS patients seen at Kitasato University Hospital between January 1990 and April 2018. Among those, we selected 13 patients with m.3243A>G mutation [median age at onset, 35 years (11-68 years), two pediatric onset < 17 years] who had at least one SLE. SLEs were classified into classic or non-classic based on characteristic features of stroke-like lesions. RESULTS: 44 SLEs were identified during a median observational period of 119 months (3-240 months). Among those, 29 (65.9%) were classic SLEs (C-SLEs) mainly attributed to a single continuous lobular lesion incongruent to vascular territory and occasionally accompanied by a gradual spread associated with hyperperfusion and persistent seizure activity. The remaining 15 were non-classic attributed to sparsely distributed (n = 10), disseminated (n = 4) or cerebellar lesions (n = 1). C-SLEs developed in all patients but non-classic SLEs in 5; D-SLEs developed in 4 patients accounting for 4 of 44 SLEs (9.1%). Non-classic SLEs developed more frequently in pediatric-onset than in adult-onset patients (12/15 vs. 3/29, p < 0.0001). SLEs began with acute onset of symptoms in 42 SLEs (95.5%), but D-SLEs of 2 adult-onset patients began with ill-defined subacute-onset fluctuating encephalopathy. CONCLUSIONS: This study showed a diversity of SLEs in patients with m.3243A>G mutation. Further studies are required to elucidate the pathophysiological mechanisms of non-classic SLEs including D-SLEs.

Chorea-ballism as a dominant clinical manifestation in heteroplasmic mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes syndrome with A3251G mutation in mitochondrial genome: a case report.

BACKGROUND: Mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes, the most common maternally inherited mitochondrial disease, can present with a wide range of neurological manifestations including both central and peripheral nervous system involvement. The most frequent genetic mutation reported in mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes syndrome is A3243G in MT-TL1 gene. Stroke-like episodes, dementia, epilepsy, lactic acidemia, myopathy, recurrent headaches, hearing impairment, diabetes, and short stature constitute the known presentations in this syndrome. Among the abnormal involuntary movements in mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes syndrome, myoclonus is the commonest. Other movement disorders, including chorea, are rarely reported in this disorder. CASE PRESENTATION: A 14-year-old South Asian boy from rural Bengal (India), born of a second degree consanguineous marriage, with normal birth and development history, presented with abnormal brief jerky movements involving his trunk and limbs, with recurrent falls for 10 months. We present here a case of heteroplasmic mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes syndrome with A3251G mutation, in which the clinical picture was dominated by a host of involuntary abnormal movements including chorea-ballism, myoclonus, and oromandibular dystonia in a backdrop of cognitive decline, seizure, and stroke-like episode. A final diagnosis was established by muscle biopsy and genetic study. Haloperidol was administered to control the involuntary movements along with introduction of co-enzyme Q, besides symptomatic management for his focal seizures. Six months into follow-up his seizures and abnormal movements were controlled significantly with slight improvement of cognitive abilities. CONCLUSION: The dominance of hyperkinetic movements in the clinical scenario and the finding of a point mutation A3251G in MT-TL1 gene make this a rare presentation.

MELAS syndrome with m.4450 G > A mutation in mitochondrial tRNAMet gene.

Mutations in the mitochondrial tRNAMet gene have been reported in only five patients to date, all of whom presented with muscle weakness and exercise intolerance as signs of myopathy. We herein report the case of a 12-year-old girl with focal epilepsy since the age of eight years. At age 11, the patient developed sudden visual disturbances and headaches accompanied by recurrent, stroke-like episodes with lactic acidosis (pH 7.279, lactic acid 11.6 mmol/L). The patient frequently developed a delirious state, exhibited regression of intellectual ability. Brain magnetic resonance imaging revealed high-intensity signals on T2-weighted images of the left occipital lobe. Mitochondrial gene analysis revealed a heteroplasmic m.4450G > A mutation in the mitochondrial tRNAMet. The heteroplasmic rate of the m.4450G > A mutation in blood, skin, urinary sediment, hair, saliva, and nail samples were 20, 38, 59, 41, 27, and 35%, respectively. The patient's fibroblast showed an approximately 53% reduction in the oxygen consumption rate, compared to a control, and decreased complex I and IV activities. Stroke-like episodes, lactic acidosis, encephalopathy with brain magnetic resonance imaging findings, and declined mitochondrial function were consistent with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) syndrome. To our knowledge, the findings associated with this first patient with MELAS syndrome harboring the m.4450G > A mutation in mitochondrial tRNAMet expand the phenotypic spectrum of tRNAMet gene.

Reversible Dilation of Cerebral Macrovascular Changes in MELAS Episodes.

PURPOSE: To investigate the cerebral macrovascular changes as well as the relationship of large vessels and cerebral blood flow (CBF) in mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes (MELAS) using magnetic resonance angiography (MRA) and arterial spin labeling (ASL) perfusion MR imaging (MRI). METHODS: A total of 20 patients diagnosed with MELAS (12 males, 8 females; mean age, 23.3 years) underwent conventional MRI, time-of-flight (TOF) MRA and three dimensional ASL. Follow-up scans were performed in 10 patients. The changes of cerebral arteries and branches on MRA images from both acute and recovery patients were independently evaluated by two radiologists. Lesion distribution and CBF were observed on the integrated maps of MRA and ASL. RESULTS: In 14 patients with clinical onsets, increased CBF was observed in all stroke-like lesions. Dilations of a single artery (four middle cerebral arteries, two posterior cerebral arteries) were found in six patients. Dilations of multiple arteries (two anterior cerebral arteries, seven middle cerebral arteries, six posterior cerebral arteries) were found in seven patients. Normal angiography was shown in one acute patient. Cortical terminal branches feeding the lesion areas were more obviously dilated than the main trunks. The dilated vessels returned to normal on follow-up scans concurrently with decreased CBF in nine patients who were resuscitated from episode attacks. Vasodilation was even seen in one preclinical patient who suffered a recurrent episode 50 days later. CONCLUSION: Reversible dilation of cerebral macrovascular changes could be a new feature of MELAS and a presumed reason for fluctuant CBF. It would shed new light on the mitochondrial angiopathy.

Cognitive impairment, clinical severity and MRI changes in MELAS syndrome.

OBJECTIVE: To examine clinical severity, cognitive impairment, and MRI changes in patients with MELAS syndrome. METHODS: Cognitive-mnestic functions, brain MRI (lesion load, cella media index) and clinical severity of ten patients with MELAS syndrome were examined. All patients carried the m.3243A>G mutation. RESULTS: The detailed neuropsychological assessment revealed cognitive deficits in attention, executive function, visuoperception, and -construction. There were significant correlations between these cognitive changes, lesion load in MRI, disturbances in everyday life (clinical scale), and high scores in NMDAS. CONCLUSION: Patients with MELAS syndrome showed no global neuropsychological deficit, but rather distinct cognitive deficits.

Clinical profile and outcome of cardiac involvement in MELAS syndrome.

BACKGROUND: Mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like (MELAS) syndrome is a rare condition with heterogeneous clinical presentation. Cardiac involvement commonly develops during adulthood, comprising both structural and conduction/arrhythmic abnormalities; early paediatric onset has rarely been reported. We describe the clinical profile, outcome and clinical implication of MELAS-associated cardiomyopathy at a tertiary referral centre. METHODS: From 2000 to 2016 we enrolled 21 patients affected by genetically-proven MELAS. Patients were followed-up at least annually over a mean of 8.5 years. RESULTS: All patients carried the MT-TL1 3243A>G mutation. Cardiac involvement was documented in 8 (38%) patients (three <18 years; five ≥18 years), including 6 (75%) with hypertrophic cardiomyopathy, 1 (12.5%) with dilated cardiomyopathy, and 1 (12.5%) with persistent pulmonary hypertension. During follow-up, 3 patients died, all with cardiac onset <18 years. The cause of death, however, was non-cardiac (infections, respiratory failure, stroke). Neither events nor cardiac progression were recorded among patients with onset ≥18 years. Adult cardiologists were responsible for 5/8 of referrals, even in patients with long-standing extra-cardiac involvement. CONCLUSIONS: Cardiac involvement was found in over 1/3 of patients with MELAS syndrome, and exhibited a bimodal age-related distribution with distinct final outcomes. Paediatric-onset cardiomyopathy represented a hallmark of systemic disease severity, without being the main determinant of outcome. Conversely, adult-onset cardiomyopathy appeared to represent a mild and non-progressive mid-term manifestation. Adult cardiologists played an important role in the diagnostic process, triggering suspicion of MELAS in most of patients diagnosis >18 years.