Mitochondrial Epilepsy

Mitochondrial epilepsy describes epilepsy occurring as part of a primary mitochondrial disease. It is not one syndrome and it does not refer to every seizure associated with a raised lactate. Primary mitochondrial diseases are a large group of genetic disorders that impair cellular energy production, and epilepsy is an important neurological feature in some — but not all — of them.

Because the brain has exceptionally high energy requirements, defects in mitochondrial function can affect neuronal development, electrical stability and recovery from physiological stress. The same disease may also affect muscle, liver, heart, vision, hearing, endocrine function or other organs.

What mitochondria do

Mitochondria are cellular structures that generate much of the ATP used to power normal cell function. They contain their own small genome — mitochondrial DNA, or mtDNA — while most proteins required for mitochondrial function are encoded by genes in the cell nucleus.

Primary mitochondrial disease can therefore result from pathogenic variants in mitochondrial DNA or in hundreds of different nuclear genes. This genetic diversity is one reason mitochondrial epilepsy cannot be treated as a single disease.

Why seizures can occur

Neurons need large amounts of energy to maintain membrane ion gradients, release and recycle neurotransmitters and recover after electrical activity. When mitochondrial ATP production is impaired, those processes can become unstable.

Mitochondrial disease can also cause structural brain injury, stroke-like episodes, cortical degeneration or metabolic crises. Seizures may therefore arise through several mechanisms at once rather than from one universal “mitochondrial seizure pathway”.

Which mitochondrial diseases can involve epilepsy?

Epilepsy occurs in many different mitochondrial disorders. Examples include some POLG-related diseases, MELAS-spectrum disorders, MERRF, Leigh syndrome and numerous nuclear-gene disorders affecting mitochondrial energy metabolism.

These names describe different genetic and clinical entities. A person should not be diagnosed with a specific mitochondrial syndrome simply because they have epilepsy, developmental difficulties and an elevated lactate.

The seizure types are diverse

Focal seizures, bilateral convulsive seizures, myoclonic seizures, epileptic spasms and status epilepticus can all occur in mitochondrial disease. Some disorders have characteristic tendencies — for example, occipital seizures and epilepsia partialis continua can be prominent in some POLG-related epilepsies — but no one seizure type proves a mitochondrial cause.

Epilepsy may be the presenting feature or may emerge after other neurological or systemic symptoms.

Clues that can suggest mitochondrial disease

The diagnostic picture depends on the exact disorder, but clues can include epilepsy occurring alongside:

developmental delay or regression
ataxia, dystonia, neuropathy or other movement abnormalities
muscle weakness, exercise intolerance or ptosis
hearing or vision loss
migraine-like episodes or stroke-like neurological events
cardiomyopathy or cardiac conduction abnormalities
liver disease
endocrine problems such as diabetes in some syndromes
unexplained lactic acidosis or recurrent metabolic decompensation
a maternal inheritance pattern in some mtDNA disorders, or another suggestive family history

None of these findings is specific on its own. Many mitochondrial diseases are also sporadic because the pathogenic variant is new in that person or because family members carry different levels of a mitochondrial DNA variant.

Why lactate can mislead

Blood or CSF lactate can be elevated in mitochondrial disease, but lactate is not a mitochondrial-disease test. It can rise after a generalised convulsive seizure, during infection, with poor tissue perfusion, after exercise and because of sampling difficulties.

Conversely, some people with genetically confirmed mitochondrial disease have normal lactate between episodes. Diagnosis therefore requires the whole clinical and genetic picture rather than one laboratory result.

MRI and EEG

EEG is used to classify seizures and monitor epilepsy, but mitochondrial epilepsies do not share one diagnostic EEG pattern.

MRI findings also vary. Depending on the disorder they may include cerebral or cerebellar atrophy, basal-ganglia or brainstem abnormalities, cortical lesions associated with stroke-like episodes, developmental abnormalities or sometimes a relatively non-specific scan.

Imaging patterns can provide important clues but should be interpreted alongside metabolic, genetic and clinical information.

Genetic diagnosis has become central

Modern investigation frequently uses genomic testing because primary mitochondrial disease can be caused by both mitochondrial-DNA and nuclear-DNA variants. Depending on the presentation, testing may include mtDNA analysis, a multigene panel, exome sequencing, genome sequencing or a combination.

The most informative tissue can differ between disorders. Some mtDNA variants may be difficult to detect in blood at older ages and may require analysis of another tissue. Testing strategies therefore need specialist genetics or mitochondrial-disease input.

Epilepsy treatment is not one-size-fits-all

A long-standing concern has been that antiseizure medicines might worsen mitochondrial dysfunction. Current international consensus is more nuanced. The 2024 InterERNs Mitochondrial Working Group reviewed common antiseizure medicines and concluded that many can be used according to standard epilepsy principles, while highlighting specific exceptions and disease-related cautions.

Choice of medicine should therefore consider seizure type, the underlying mitochondrial diagnosis, liver and kidney function, metabolic complications, drug interactions and the person’s wider clinical condition.

The critical POLG–valproate warning

Valproic acid and related valproate medicines are a major exception. In POLG-related disorders, valproate can precipitate or accelerate severe liver failure and is considered contraindicated.

This matters particularly in children or young people with unexplained refractory epilepsy, developmental regression, occipital seizures or other features that raise concern for a POLG-related disorder. Medication decisions should be made by an experienced clinician, and local prescribing guidance may recommend genetic assessment before valproate in selected high-risk presentations.

Other medication cautions depend on the disorder

The 2024 consensus also identifies other disease-specific cautions, such as avoiding vigabatrin in GABA-transaminase deficiency and using particular care with topiramate in people at risk of renal tubular acidosis.

These are targeted exceptions, not evidence that all people with mitochondrial disease should avoid the same medicines.

Status epilepticus and metabolic stress

Prolonged seizures create a substantial metabolic demand and can be particularly hazardous in a person whose energy metabolism is already impaired. Status epilepticus should therefore be treated promptly according to an individual emergency plan and appropriate acute-care guidance.

Infection, fever, dehydration, prolonged fasting and poor nutritional intake can also trigger deterioration in some mitochondrial disorders. Specialist services may provide illness-management plans tailored to the diagnosis.

Ketogenic dietary therapy

Ketogenic dietary therapy may help seizures in selected mitochondrial disorders, but it is not a universal treatment for all mitochondrial disease. The balance of potential benefit and metabolic risk depends on the underlying biochemical defect.

This is different from GLUT1 deficiency and primary pyruvate dehydrogenase complex deficiency, where ketogenic therapy directly bypasses a defined fuel-pathway problem and has a particularly strong mechanistic role.

Stroke-like episodes are not ordinary strokes

Some mitochondrial disorders, particularly MELAS-spectrum disease, can cause stroke-like episodes involving cortical dysfunction, seizures, headache, altered awareness and neurological deficits. The brain lesions do not necessarily follow the vascular territories expected in a conventional thrombotic stroke.

These episodes require specialist assessment because seizure activity and metabolic brain injury can interact, and management differs from routine stroke pathways.

POLG-related epilepsy deserves special attention

POLG-related disorders span a wide clinical spectrum from severe childhood encephalopathy to adult-onset neurological disease. Epilepsy can become highly drug resistant and may include focal occipital seizures, myoclonus and epilepsia partialis continua.

Liver involvement may be clinically silent early in the course. This is why recognition of a possible POLG disorder has implications not just for diagnosis but for antiseizure-medication safety.

Multisystem care

Epilepsy may be only one part of primary mitochondrial disease. Consensus care standards recommend multidisciplinary surveillance based on the individual phenotype, which may include neurological, cardiac, ophthalmological, hearing, endocrine, renal, liver, nutritional and respiratory assessment.

Treating seizures without monitoring the rest of the disease can therefore miss important complications.

Worldwide access

Mitochondrial diagnosis often requires specialist neurology, metabolic medicine, genomic testing, MRI, EEG and sometimes tissue-specific molecular or biochemical investigations. Access to those services varies sharply between and within countries.

Even after diagnosis, access to specialist emergency plans, mitochondrial clinics, genetic counselling and multidisciplinary surveillance can be limited. A person may therefore receive epilepsy treatment for years before the underlying multisystem disorder is recognised.

The central point

Mitochondrial epilepsy is not one epilepsy syndrome and not every treatment warning applies to every mitochondrial disorder. The genetic diagnosis matters because it can change medication safety, emergency planning, surveillance and counselling — most notably the strong warning against valproate in POLG-related disease.

Sources

Medical note: medication risks in mitochondrial disease are diagnosis-specific. Antiseizure medicines should not be stopped suddenly because of information on this page; treatment changes require specialist medical advice.

Evidence checked: September 2026.