The Usefulness of Muscle Biopsy in Initial Diagnostic Evaluation of Mitochondrial Encephalomyopathy, Lactic Acidosis, and Stroke-Like Episodes

PURPOSE: The disease entity mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) is characterized by an early onset of stroke-like episodes. MELAS is the most dominant subtype of mitochondrial disease. Molecular genetic testing is important in the diagnosis of MELAS. The mitochondrial DNA (mtDNA) 3243A>G mutation is found in 80% of MELAS patients. Nevertheless, molecular analysis alone may be insufficient to diagnose MELAS because of mtDNA heteroplasmy. This study aimed to evaluate whether muscle biopsy is useful in MELAS patients as an initial diagnostic evaluation method. MATERIALS AND METHODS: The medical records of patients who were diagnosed with MELAS at the Department of Pediatrics of Gangnam Severance Hospital between January 2006 and January 2017 were reviewed. The study population included 12 patients. They were divided into two subgroups according to whether the results of muscle pathology were in accordance with mitochondrial diseases. Clinical variables, diagnostic evaluations, and clinical outcomes were compared between the two groups. RESULTS: Of the 12 patients, seven were muscle pathology-positive for mitochondrial disease. No statistically significant difference in clinical data was observed between the groups that were muscle pathology-positive and muscle pathology-negative for mtDNA 3243A>G mutation. Additionally, the patients with weakness as the initial symptom were all muscle pathology-positive. CONCLUSION: The usefulness of muscle biopsy appears to be limited to an initial confirmative diagnostic evaluation of MELAS. Muscle biopsy can provide some information in MELAS patients with weakness not confirmed by genetic testing.

Lennox-Gastaut Syndrome in Mitochondrial Disease

PURPOSE: Previous studies have shown that neurologic symptoms are dominant in patients with mitochondrial diseases, and most of these patients have seizure-related disorders. The epileptic classification of these patients as Lennox-Gastaut syndrome (LGS) is as high as 25%. This study aimed to investigate the clinical manifestations, diagnoses, treatments, and epilepsy in LGS, which is associated with mitochondrial disease. MATERIALS AND METHODS: A retrospective study was conducted on 372 patients who were diagnosed with mitochondrial disease between 2006 and 2016. Of these 372 patients, 40 patients diagnosed with LGS were selected, and they were classified into two groups based on the history of West syndrome. Patient characteristics were reviewed, and associations between clinical factors and outcomes after the treatment were analyzed. RESULTS: The proportion of individuals with mitochondrial disease with LGS with a history of West syndrome was 32.5%. Among the patients with mitochondrial disease with LGS, neonatal seizure (p=0.029), seizure as the first symptom (p=0.018), and generalized paroxysmal fast activity frequency on electroencephalogram (p=0.018) in the group with a history of West syndrome were statistically significantly high. The first symptom onset (0.6±0.4 yrs vs. 1.6±0.9 yrs, p=0.003) and first seizure onset (0.9±0.7 yrs vs. 3.9±3.1 yrs, p < 0.001) were significantly faster in patients with a history of West syndrome. CONCLUSION: Close monitoring of the medical condition and early intervention might improve the prognosis of individuals with mitochondrial disease with LGS and a history of West syndrome.

Age-Based Characteristics of West Syndrome in Patients with Mitochondrial Disease / 대한소아신경학회지

PURPOSE: West syndrome is a severe form of age-specific epilepsy that typically affects infants younger than 2 years of age with mitochondrial disease. We aimed to examine age-specific characteristics of the syndrome in these patients. METHODS: We retrospectively analyzed 54 patients with West syndrome diagnosed with mitochondrial disease between March 2006 and March 2016. We compared treatment strategies and diagnostic and clinical variables between patients with early-onset ( < 6 months of age) and late-onset (≥6 months of age) seizures. RESULTS: Seizure was the first symptom in 30 (90.9%) and 13 (65%) patients of the early-onset and late-onset groups, respectively (P=0.046). Delayed development was observed in 3 (9.1%) and 7 (35%) patients of the early-onset and late-onset groups, respectively (P=0.023). Lactate levels were normal in 17 patients (55%) of the early-onset group and 5 (25%) of the late-onset group (P=0.036), while initial brain magnetic resonance imaging (MRI) findings were normal in 23 (67.6%) and 8 (40%) patients of the early-onset and late-onset groups, respectively. Final MRI findings were abnormal in 32 patients (94.1%) of the early-onset group and 18 (90%) of the late-onset group (P=0.036). Although ketogenic diets reduced seizure frequency in both groups, the difference was not significant. CONCLUSION: There is no significant difference in epilepsy-related variables when patients are divided based on a cut-off age of 6 months. However, differences in the first symptom at onset and MRI findings were observed. Although lactate levels were not of significant diagnostic value in the early-onset group, they may be in the late-onset group.