Objective:

Background:

Mitochondrial disorders are often overlooked as a cause of IESS. Shah et al. emphasized that metabolic imbalances, particularly mitochondrial dysfunction, frequently contribute to or result from ES. Lee et al. observed that patients with mitochondrial disorders continue to experience refractory epilepsy despite treatment. This study focuses on IESS in patients with genetically confirmed PMD, aiming to clarify their clinical spectrum and inform future therapeutic approaches.

Design/Methods:

We identified 14 patients with IESS treated at the Mitochondrial Medicine Clinic at our tertiary care children’s hospital. We gathered data on demographics, age of presentation, EEG, medications, and clinical response.

Results:

In a cohort of 14 patients, 7 (50%) were male. Genetic causes included MT-ATP6 (m.8993T>G) in 5 and PDHA1 in 2 patients, with single cases of MT-ATP6 (m.8993T>C), FBXL4, NDUFS8, MT-ND5(m.13513G>A), NDUFAF8, ATP5O, and POLG mutations. Onset age ranged from 2 months to 2 years, with a median of 7 months. EEG findings showed hypsarrhythmia in 7 patients (50%) and modified hypsarrhythmia in 2 (14%). Treatment strategies included ACTH, Vigabatrin, prednisone, Topamax, Clobazam, Epidiolex, Keppra and Ketogenic diet, leading to resolution of spasms in 8 patients (57%) within 1 to 24 months. Monotherapy with ACTH or Vigabatrin resolved spasms in 4 cases, though 3 later developed focal seizures. Ten patients (71%) had refractory spasms. 

Conclusions:

IESS can be the presenting seizure type in patients with PMD, highlighting the need for comprehensive metabolic and genetic evaluation in cryptogenic cases of IESS. While most patients with PMD have medically refractory spasms, some may achieve seizure freedom with monotherapy. Thus, ACTH or Vigabatrin are recommended as effective first-line treatments. Importantly, ACTH did not lead to any metabolic worsening in this cohort, as steroids can be a theoretic physiological stressor, and are not contraindicated.