Many aspects of
epilepsy in
mitochondrial disorders (MDs) need to be further clarified. To this aim, we explored retrospectively a cohort of individuals with MDs querying the "Nationwide Italian Collaborative Network of
Mitochondrial Diseases" (NICNMD) database (1467 patients included since 2010 to December 2016). We collected information on age at
epilepsy onset, seizure type and frequency, genetic findings, and
antiepileptic drugs (AEDs). At the time of our survey, 147/1467 (10%) patients in the NICNMD database had
epilepsy. Complete information was available only for 98 patients, 52 males and 46 females, aged 5-92 years (mean age 40.4 ± 18.4; 14/98 children/teenagers and 84 adults).
Epilepsy was the presenting feature of MD in 46/98 (47%) individuals, with onset at a median age of 19 years (range, 0.2-68; < 3 years in 14/97 (14%), 3-19 years in 36/97 (37%), > 19 years in 47/97 (49%)). Moreover, 91/98 patients (93%) displayed multiple
seizures, with daily or weekly frequency in 25/91 (28%). Interictal EEG was abnormal in 70/78 (90%) patients, displaying abnormal background (47/70; 67%) and/or interictal paroxysms (53/70; 76%). Eighty of 90 patients (89%) displayed a 50-100% reduction of
seizures on AEDs;
levetiracetam was the most commonly used. Forty-one patients (42%) carried the m.3243A>G mutation, 16 (16%) the m.8344A>G, and 9 (9%) nuclear
DNA (nDNA) mutations. Individuals with early-onset
seizures mainly carried nDNA mutations and had a more severe
epilepsy phenotype, higher seizure frequency, and disorganized background EEG activity. A better definition of
epilepsy in MDs may foster the diagnostic workup, management, and treatment of affected patients, and allow more homogeneous patient stratification.