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Peripheral neuropathy in patients with the 3243A>G mutation in mitochondrial DNA
Mikko Kärppä1, Pirjo Syrjälä, Uolevi Tolonen
1Department of Neurology and Biocenter, University of Oulu, P. O. Box 5000, 90014 Oulu, Finland.
Abstract:
Peripheral neuropathy is one of the clinical manifestations of the MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes) syndrome, but its frequency and phenotypic variability have not been properly characterised. We therefore studied the clinical and electrophysiological features of peripheral neuropathy in 32 patients with the 3243A > G mutation in mitochondrial DNA by using clinical examination, assessment of Neuropathy Symptom Score, Neuropathy Disability Score, and electrophysiological examinations. Seven patients (22 %; 95 % confidence interval, 9-40 %) fulfilled the electrodiagnostic criteria for polyneuropathy. Mixed axon loss and demyelinating sensorimotor neuropathy was the most common type of polyneuropathy, while one patient presented with uniform demyelinating sensorimotor polyneuropathy. Sensory more than motor neuropathy was diagnosed in four patients. Clinically and electrophysiologically confirmed carpal tunnel syndrome (CTS) occurred in three patients (9.4 %), suggesting a higher prevalence than in the general population. Patients with neuropathy were in general more severely affected than those without neuropathy, although no correlation was found between the presence of neuropathy and the degree of mutant heteroplasmy in muscle. Higher age and male gender were associated with an increased risk of neuropathy. Our results show that peripheral neuropathy is not uncommon in patients with the 3243A > G mutation, and they also may have an increased risk of CTS.
Insights
Peripheral neuropathy affects 22% of patients with MELAS syndrome (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes), often presenting as sensorimotor polyneuropathy. This study highlights increased carpal tunnel syndrome risk in these patients.
Area of Science:
- Neurology
- Mitochondrial Diseases
- Genetics
Background:
- Peripheral neuropathy is a known manifestation of MELAS syndrome (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes).
- The exact frequency and diverse clinical presentations of peripheral neuropathy in MELAS patients with the 3243A > G mutation require further characterization.
Purpose of the Study:
- To investigate the clinical and electrophysiological characteristics of peripheral neuropathy in patients carrying the 3243A > G mitochondrial DNA mutation.
- To determine the prevalence of peripheral neuropathy and associated conditions like carpal tunnel syndrome (CTS) in this patient cohort.
Main Methods:
- Clinical examination and standardized neurological assessments (Neuropathy Symptom Score, Neuropathy Disability Score).
- Electrophysiological studies to diagnose and classify peripheral neuropathy.
- Analysis of patient data for correlations between neuropathy, mutation heteroplasmy, age, and gender.
Main Results:
- 22% of patients with the 3243A > G mutation met electrodiagnostic criteria for polyneuropathy.
- The most common type was mixed axonal loss and demyelinating sensorimotor neuropathy; sensory neuropathy predominated in some.
- Carpal tunnel syndrome (CTS) was diagnosed in 9.4% of patients, suggesting a higher prevalence.
- Neuropathy was associated with more severe overall disease impact, higher age, and male gender, but not muscle heteroplasmy levels.
Conclusions:
- Peripheral neuropathy is a significant and relatively common clinical feature in patients with the 3243A > G MELAS mutation.
- Patients with this mutation may have an elevated risk for developing carpal tunnel syndrome.
- Age and male gender are identified as risk factors for neuropathy in this population.