Abstract
Mitochondrial chronic progressive external ophthalmoplegia (CPEO) is a major manifestation of human mitochondrial encephalomyopathies. Previous studies have shown cognitive deficits in patients with mitochondrial diseases. However, these studies often included patients with heterogeneous subtypes of mitochondrial diseases. Here, we aimed to provide a better cognitive profile of patients with CPEO by applying a comprehensive battery of neuropsychological assessments in a pure sample of patients with CPEO. We recruited 28 patients with CPEO (19 women, age 16–62 years) and 38 age- and education-matched healthy control subjects (25 women, age 16–60 years). The neuropsychological assessments covered global cognition and five cognitive domains (executive functions, language, working memory, memory, and visuospatial functions). We found that the patients were impaired in global cognition [Montreal Cognitive Assessment (MoCA)], executive functions [Trail Making Test Part B (TMT-B)], and language [Boston Naming Test (BNT)], but not in working memory, memory or visuospatial functions. Moreover, individual patients' performances in the TMT-B (completion time) were predicted by the severity of non-ophthalmoplegia mitochondrial symptoms/signs [Newcastle Mitochondrial Disease Adult Scale (NMDAS)] and duration of the mitochondrial disease (years). Namely, patients with more severe non-ophthalmoplegia mitochondrial symptoms/signs and a longer disease duration took a longer time to complete the TMT-B. No clinical measures predicted individual patients' performances in the BNT.
Highlights
Mitochondrial encephalomyopathies are a heterogeneous group of inherited multisystem disorders that predominantly affect tissues with major aerobic metabolisms, including the central nervous system, muscle, retina, and tubular epithelium (1, 2)
Neuropsychological studies showed that patients with MELAS are impaired in general intelligence (Wechsler Intelligence Scale), executive functions (Wisconsin Card Sorting Test and Trail Making Test), language [Boston Naming Test (BNT) and Verbal Fluency Test], attention/working memory (Digit Span Test), memory (Auditory Verbal Learning Test), and visuospatial functions (Rey-Osterrieth Complex Figure Test and Block Design Test) (4–6)
We evaluated the severity of the mitochondrial disease using the Newcastle Mitochondrial Disease Adult Scale (NMDAS) (16)
Summary
Mitochondrial encephalomyopathies are a heterogeneous group of inherited multisystem disorders that predominantly affect tissues with major aerobic metabolisms, including the central nervous system, muscle, retina, and tubular epithelium (1, 2). The major manifestations of mitochondrial encephalomyopathy include mitochondrial encephalopathy, lactic acidosis and stroke-like episodes (MELAS), chronic progressive external ophthalmoplegia (CPEO), Kearn-Sayre syndrome (KSS), and myoclonus epilepsy with ragged-red fibers syndrome (MERRF). Cognitive Profile of CPEO and five cognitive domains (executive functions, language, working memory, memory, and visuospatial functions). Neuropsychological studies showed that patients with MELAS are impaired in general intelligence (Wechsler Intelligence Scale), executive functions (Wisconsin Card Sorting Test and Trail Making Test), language [Boston Naming Test (BNT) and Verbal Fluency Test], attention/working memory (Digit Span Test), memory (Auditory Verbal Learning Test), and visuospatial functions (Rey-Osterrieth Complex Figure Test and Block Design Test) (4–6). Patients with MELAS often show more severe deficits in working memory, memory, and visuospatial functions than patients with CPEO and patients with KSS (7). Brain imaging studies showed that patients with MELAS have a higher water and lactate level in the parietal and occipital regions, as well as calcification of the basal ganglia (6, 8)
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