Association between stroke-like episodes and neuronal hyperexcitability in MELAS with m.3243A>G: A case report

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.

L-arginine in Mitochondrial Encephalopathy, Lactic Acidosis, and Stroke-like Episodes: A Systematic Review

Background and Objectives

Stroke management in the context of primary mitochondrial disease is clinically challenging, and the best treatment options for patients with stroke-like episodes remain uncertain. We sought to perform a systematic review of the safety and efficacy of l-arginine use in the acute and prophylactic management of stroke-like episodes in patients with mitochondrial disease.

Methods

The systematic review was registered in PROSPERO (CRD42020181230). We searched 6 databases from inception to January 15, 2021: MEDLINE, Embase, Scopus, Web of Science, CINAHL, and ClinicalTrials.gov. Original articles and registered trials available, in English, reporting l-arginine use in the acute or prophylactic management of stroke-like episodes in patients with genetically confirmed mitochondrial disease were eligible for inclusion. Data on safety and treatment response were extracted and summarized by multiple observers. Risk of bias was assessed by the methodologic quality of case reports, case series, and a risk-of-bias checklist for nonrandomized studies. Quality of evidence was synthesized with the Oxford Centre for Evidence-Based Medicine Levels of Evidence and Grade of Recommendations. The predetermined main outcome measures were clinical response to l-arginine treatment, adverse events, withdrawals, and deaths (on treatment and/or during follow-up), as defined by the author.

Results

Thirty-seven articles met inclusion criteria (0 randomized controlled trials; 3 open-label; 1 retrospective cohort; 33 case reports/case series) (N = 91 patients; 86% m.3243A>G). In the case reports, 54% of patients reported a positive clinical response to acute l-arginine, of which 40% were concomitantly treated with antiepileptic drugs. Improved headache at 24 hours was the greatest reported benefit in response to IV l-arginine in the open-label trials (31 of 39, 79%). In 15 of 48 patients (31%) who positively responded to prophylactic l-arginine, antiepileptic drugs were either used (7 of 15) or unreported (8 of 15). Moderate adverse events were reported in the follow-up of both IV and oral l-arginine treatment, and 11 patients (12%) died during follow-up or while on prophylactic treatment.

Discussion

The available evidence is of poor methodologic quality and classified as Level 5. IV and oral l-arginine confers no demonstrable clinical benefit in either the acute or prophylactic treatment of mitochondrial encephalopathy, lactic acidosis, and stroke-like episodes, with more robust controlled trials required to assess its efficacy and safety profile.

Novel homozygous TSFM pathogenic variant associated with encephalocardiomyopathy with sensorineural hearing loss and peculiar neuroradiologic findings

TSFM is a nuclear gene encoding the elongation factor Ts (EFTs), an essential component of mitochondrial translational machinery. Impaired mitochondrial translation is responsible for neurodegenerative disorders characterized by multiple respiratory chain complex defects, multisystemic involvement, and neuroradiological features of Leigh-like syndrome. With the use of a next-generation sequencing (NGS)-based multigene panel for mitochondrial disorders, we identified the novel TSFM homozygous variant c.547G>A (p.Gly183Ser) in a 5-year-old boy with infantile early onset encephalocardiomyopathy, sensorineural hearing loss, and peculiar partially reversible neuroimaging features. Our findings expand the phenotypic spectrum of TSFM-related encephalopathy, offering new insights into the natural history of brain involvement and suggesting that TSFM should be investigated in pediatric mitochondrial disorders with distinctive neurologic and cardiac involvement.

Antiepileptics and NO-precursors may be beneficial for stroke-like episodes

Pathogenesis and management of stroke-like episodes in mitochondrial disorders is under debate and no consensus has been reached thus far how this phenomenon should be managed. Frequently applied are nitric oxide (NO) precursors but a well-designed study confirming the effectiveness of such an approach is lacking. Administration of antiepileptic drugs can be meaningful if there is paroxysmal activity on EEG or if a patient presents with seizures. The case reported by Sakai et al. suggests that administration of antiepileptic drugs for a stroke-like episode may be beneficial even in the absence of seizures or paroxysmal EEG activity.