Although many organ systems are affected by mitochondrial (mt) DNA point mutations, the nervous system is particularly vulnerable. Maternally inherited mtDNA point mutations may cause chronic progressive encephalopathies and mental retardation. Patients with MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) syndrome have the A3243G point mutation and elevated brain lactate levels. Research has shown that lactic acidosis is associated with progressive impairment in patients with MELAS. This study will evaluate the effectiveness of DCA in lowering lactate levels and slowing the progression of MELAS.

Patients with the A3243G mitochondrial mutation and who have had either a stroke or a seizure will be enrolled in this study. Patients will be randomized to receive either DCA or a placebo. At a predetermined time point, patients receiving DCA will be switched to placebo and patients receiving placebo will be switched to DCA. Patients will have study visits every 3 months for 3 years. Study visits will include neurological exams, cognitive testing, nerve conduction tests, and MRIs. Study medicine, testing, hospitalization for research purposes, and travel expenses will be fully covered by the study.

Inclusion Criteria

• A3243G mtDNA point mutation or maternally related to someone who has the mutation
• Symptomatic with MELAS, including previous seizure or stroke
• Certain laboratory values
• Ability to comply with the study protocol