Fact-sheet: MELAS mitochondrial encephalopathy with lactic acidosis and stroke-like episodes
  • Mitochondrial encephalopathy, lactic acidosis and stroke-like episodes


Updated on 03/09/2026 at 10:25 AM

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Definition

MELAS mitochondrial encephalopathy with lactic acidosis and stroke-like episodes

Syndrome associating:

  • a mitochondrial myopathy,
  • an encephalopathy,
  • lactic acidosis,
  • and acute "stroke-like" neurological episodes,

caused by a mutation of mitochondrial DNA

Manifestations begin in childhood or in young adults.

Clinical features

Varied, "stroke-like" symptoms:

  • headache and vomiting,
  • confusion,
  • hemiparesis or hemianopsia suggestive of stroke.

Chronic symptoms:

  • cardiomyopathy,
  • deafness,
  • diabetes,
  • short stature, muscle weakness,
  • dementia, mental retardation, learning, memory, or attention disorders.

Laboratory findings

  • Elevated CSF lactate concentration
  • Ragged red fibers on muscle biopsy / mitochondrial myopathy
  • Genetic diagnosis

MRI

Reference imaging modality:

  • Acute episodes with cortical, subcortical, and cerebellar Diffusion & T2 FLAIR hyperintensity, ischemic in appearance but not respecting a vascular territory,
  • Increased ADC reflecting possible vasogenic edema
  • Possible outcomes: return to normal, cortical laminar necrosis, cerebral atrophy, basal ganglia calcifications
  • MR spectroscopy: look for a lactate peak in the pathological areas but also in the normal parenchyma
  • T2 FLAIR hyperintensities of the periventricular white matter

Nuclear medicine

SPECT: possible hyperperfusion before and during the acute episode

PET: decreased oxygen consumption and increased perfusion

Management

Symptomatic treatments