Creatine monohydrate therapy in a Leigh syndrome patient with A8344G mutation

A guide to diagnosis and treatment of Leigh syndrome

Leigh syndrome is a devastating neurodegenerative disease, typically manifesting in infancy or early childhood. However, also late-onset cases have been reported. Since its first description by Denis Archibald Leigh in 1951, it has evolved from a postmortem diagnosis, strictly defined by histopathological observations, to a clinical entity with indicative laboratory and radiological findings. Hallmarks of the disease are symmetrical lesions in the basal ganglia or brain stem on MRI, and a clinical course with rapid deterioration of cognitive and motor functions. Examinations of fresh muscle tissue or cultured fibroblasts are important tools to establish a biochemical and genetic diagnosis. Numerous causative mutations in mitochondrial and nuclear genes, encoding components of the oxidative phosphorylation system have been described in the past years. Moreover, dysfunctions in pyruvate dehydrogenase complex or coenzyme Q10 metabolism may be associated with Leigh syndrome. To date, there is no cure for affected patients, and treatment options are mostly unsatisfactory. Here, we review the most important clinical aspects of Leigh syndrome, and discuss diagnostic steps as well as treatment options.

Treatment of mitochondrial disorders

Treatment of mitochondrial disorders (MIDs) is a challenge since there is only symptomatic therapy available and since only few randomized and controlled studies have been carried out, which demonstrate an effect of some of the symptomatic or supportive measures available. Symptomatic treatment of MIDs is based on mainstay drugs, blood transfusions, hemodialysis, invasive measures, surgery, dietary measures, and physiotherapy. Drug treatment may be classified as specific (treatment of epilepsy, headache, dementia, dystonia, extrapyramidal symptoms, Parkinson syndrome, stroke-like episodes, or non-neurological manifestations), non-specific (antioxidants, electron donors/acceptors, alternative energy sources, cofactors), or restrictive (avoidance of drugs known to be toxic for mitochondrial functions). Drugs which more frequently than in the general population cause side effects in MID patients include steroids, propofol, statins, fibrates, neuroleptics, and anti-retroviral agents. Invasive measures include implantation of a pacemaker, biventricular pacemaker, or implantable cardioverter defibrillator, or stent therapy. Dietary measures can be offered for diabetes, hyperlipidemia, or epilepsy (ketogenic diet, anaplerotic diet). Treatment should be individualized because of the peculiarities of mitochondrial genetics. Despite limited possibilities, symptomatic treatment should be offered to MID patients, since it can have a significant impact on the course and outcome.

Metabolic myopathies: update 2009

Metabolic myopathies are inborn errors of metabolism that result in impaired energy production due to defects in glycogen, lipid, mitochondrial, and possibly adenine nucleotide metabolism. Fatty acid oxidation defects (FAOD), glycogen storage disease, and mitochondrial myopathies represent the 3 main groups of disorders, and some consider myoadenylate deaminase (AMPD1 deficiency) to be a metabolic myopathy. Clinically, a variety of neuromuscular presentations are seen at different ages of life. Newborns and infants commonly present with hypotonia and multisystem involvement (liver and brain), whereas onset later in life usually presents with exercise intolerance with or without progressive muscle weakness and myoglobinuria. In general, the glycogen storage diseases result in high-intensity exercise intolerance, whereas the FAODs and the mitochondrial myopathies manifest predominately during endurance-type activity or under fasted or other metabolically stressful conditions. The clinical examination is often normal, and testing requires various combinations of exercise stress testing, serum creatine kinase activity and lactate concentration determination, urine organic acids, muscle biopsy, neuroimaging, and specific genetic testing for the diagnosis of a specific metabolic myopathy. Prenatal screening is available in many countries for several of the FAODs through liquid chromatography-tandem mass spectrometry. Early identification of these conditions with lifestyle measures, nutritional intervention, and cofactor treatment is important to prevent or delay the onset of muscle weakness and to avoid potential life-threatening complications such as rhabdomyolysis with resultant renal failure or hepatic failure. This article will review the key clinical features, diagnostic tests, and treatment recommendations for the more common metabolic myopathies, with an emphasis on mitochondrial myopathies.

The neuroprotective role of creatine

Significant progress has been made in identifying neuroprotective agents and their translation to patients with neurological disorders. While the direct causative pathways of neurodegeneration remain unclear, they are under great clinical and experimental investigation. There are a number of interrelated pathogenic mechanisms triggering molecular events that lead to neuronal death. One putative mechanism reported to play a prominent role in the pathogenesis of neurological diseases is impaired energy metabolism. If reduced energy stores play a role in neuronal loss, then therapeutic strategies that buffer intracellular energy levels may prevent or impede the neurodegenerative process. Recent studies suggest that impaired energy production promotes neurological disease onset and progression. Sustained ATP levels are critical to cellular homeostasis and may have both direct and indirect influence on pathogenic mechanisms associated with neurological disorders. Creatine is a critical component in maintaining cellular energy homeostasis, and its administration has been reported to be neuroprotective in a wide number of both acute and chronic experimental models of neurological disease. In the context of this chapter, we will review the experimental evidence for creatine supplementation as a neurotherapeutic strategy in patients with neurological disorders, including Huntington's disease, Parkinson's disease, amyotrophic lateral sclerosis, and Alzheimer's disease, as well as in ischemic stroke, brain and spinal cord trauma, and epilepsy.