Presentation of adult mitochondrial epilepsy

Purpose: Mitochondrial disorders (MIDs) frequently manifest phenotypically as epilepsy (mitochondrial epilepsy). Mitochondrial epilepsy occurs in early-onset as well as late-onset syndromic and non-syndromic MIDs. We were interested in the types of epilepsy, the prevalence of mitochondrial epilepsy, the type and effectiveness of treatment, and in the outcome of adult MID patients with epilepsy. Methods: We retrospectively evaluated adult patients with syndromic or non-syndromic MIDs and epilepsy. MIDs were classified according to the modified Walker criteria as definite, probable, and possible. Results: Epilepsy in adult patients with a MID was classified as "structural/metabolic" in two-thirds of the cases and as "genetic" in one-third of the cases. Although all types of seizures may occur in mitochondrial epilepsy, adult patients most frequently presented with generalised tonic-clonic seizures, partial seizures, convulsive status epilepticus, or non-convulsive status epilepticus. Cerebral imaging was normal in one-third of the patients. Two-thirds of the adult patients with mitochondrial epilepsy who took antiepileptic drugs received monotherapy, one-third combination treatment. The antiepileptic drugs most frequently administered included levetiracetam, lamotrigine, valproic acid, and gabapentin. Antiepileptic drugs were usually well tolerated and the outcome favourable. Conclusions: Adult mitochondrial epilepsy appears to be less frequent than previously believed but the prevalence strongly depends on patient selection. Mitochondrial epilepsy is most frequently "structural/metabolic". AEDs recommended for mitochondrial epilepsy include levetiracetam, lamotrigine, gabapentin and lacosamide. The outcome of mitochondrial epilepsy may be more favourable if mitochondrion-toxic AEDs are avoided. Only if non-mitochondrion- toxic AEDs are ineffective, mitochondrion-toxic AEDs may be used. © 2012 British Epilepsy Association.