Mitochondrial Disorders

What is a mitochondrial disorder?

Mitochondrial are small compartments that exist in each cell in the body. The main function of mitochondria is to provide enough energy to support the function of cells in the body.

Mitochondrial disorders are a group of conditions that impair mitochondrial function and lead to impaired ability to generate energy, resulting in dysfunction of multiple cells with a range of symptoms that include fatigue, weakness, seizures, strokes, heart, kidney and gut problems, intellectual disability, diabetes, problems with hearing and vision, and poor growth. 

How common are they?

Mitochondrial disorders are rare and occur in approximately 1 in 5,000 persons. Approximately 35-60% of cases will have seizures. 

What types of epilepsy are associated with mitochondrial disorders? 

Mitochondrial disorders can lead to various types of epilepsies which may include: 

Although epilepsy can begin at any age, most cases start in infancy or early childhood, and seizures are often drug-resistant.

What non-seizure symptoms are associated with mitochondrial disorders? 

As mitochondrial dysfunction affects many cells in the body, most persons with mitochondrial disorders have other symptoms in addition to seizures. These include intellectual disability or regression of skills, movement disorders, weakness and fatigue, strokes, problems with hearing and vision, poor growth, as well as dysfunction in other organs including the liver, heart, kidneys and gut. 

How are mitochondrial disorders diagnosed? 

  • Recognition of mitochrondrial disorders can be challenging.This diagnosis should be considered if there are drug-resistant seizures with other non-seizure symptoms (see above) and no other cause has been found.   
  • The EEG is nonspecific, and often shows slowing of the background with abnormal discharges.
  • The MRI is usually abnormal, and often shows changes in the thalami and basal ganglia.
  • Elevation of lactate levels in blood or spinal fluid is often a clue, but these may be normal. Genetic analysis can be helpful in confirming a specific diagnosis. In some cases, muscle biopsy may be needed. 

How is epilepsy associated with mitochrondrial disorders treated?

Most cases of epilepsy associated with mitochondrial disorders are drug-resistant, meaning that complete seizure control is not achieved. There is no single best medication and the choice of agent is typically based on the epilepsy type. Valproic acid should generally be avoided, as it can worsen mitochondrial disease symptoms. Valproic acid is absolutely contraindicated in those with POLG1 mutations, as it can lead to liver failure. 

In many cases, high doses of vitamins including carnitine, Co-enzyme Q, riboflavin, B-complex vitamins, arginine and/or folinic acid are tried. 

What is the outlook for epilepsy associated with mitochondrial disorders?

Many children with mitochondrial disease will have seizures that are drug-resistant. Additionally, most children have other neurological disorders such as intellectual disability and movement disorders, and other medical problems which can include breathing and heart problems, gut and digestive concerns and liver and kidney problems. 

Children with mitochondrial disease benefit from a multidisciplinary clinic and families often will require additional help in the home. 

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Authored By: 
Elaine Wirrell MD
Authored Date: