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Corneal Confocal Microscopy: A Novel Non-invasive Technique to Quantify Small Fibre Pathology in Peripheral Neuropathies
Published on: January 3, 2011
Small fibre neuropathy in mitochondrial diseases explored with sudoscan
Marco Luigetti1, Guido Primiano1, Cristina Cuccagna1
1UOC Neurologia, Fondazione Policlinico Universitario A. Gemelli, Institute of Neurology, Catholic University of the Sacred Heart, Rome, Italy.
Objective:
Polyneuropathy in mitochondrial diseases (MDs) is relatively common and widely investigated, but few data are instead reported about small fibres involvement.
Methods:
In order to investigate the involvement of small fibres in MDs we performed extensive neurophysiological test (nerve conduction studies; sympathetic skin response; sudoscan) in 27 patients with genetic diagnosis of MD (7 m.3243A > G; 4 m.8344A > G; 9 single mtDNA deletion; 7 multiple mtDNA deletions).
Results:
NCS showed a polyneuropathy in 11/27 cases (41%). The incidence was very high in POLG1 (100%), m.8344A > G (75%) and m.3243A > G (43%), while only 11% of patients with single deletion had evidence of large fibres involvement. Sympathetic skin response was abnormal only in three patients (one progressive external ophthalmoplegia with single mtDNA deletion; one patient with m.3243A > G mutation; one patient with POLG1 mutation). Sudoscan revealed the presence of an autonomic small fibres dysfunction in 9/27 cases (33%), most of them (7/9) carrying a single mtDNA deletion. Sudoscan data were also confirmed in a sub-group of patients by laser evoked potentials study. Considering only patients with single mtDNA deletion 7/9 (78%) showed abnormal results at sudoscan.
Conclusions:
Small fibre neuropathy is another feature to investigate in mitochondrial diseases and seems specifically associated with the presence of single mtDNA deletion.
Significance:
The correct identification through specific neurophysiological tests of small fibres involvement in MDs represents another tile in this challenging diagnosis.
Insights
Mitochondrial diseases (MDs) can cause small fiber neuropathy, particularly in patients with single mitochondrial DNA deletions. Neurophysiological tests like Sudoscan are crucial for identifying this condition, aiding in MD diagnosis.
Area of Science:
- Neurology
- Genetics
- Mitochondrial Biology
Background:
- Polyneuropathy is a common complication of mitochondrial diseases (MDs).
- Small fiber involvement in MDs is under-investigated despite its potential clinical significance.
Purpose of the Study:
- To investigate the prevalence and characteristics of small fiber neuropathy in patients with genetically confirmed MDs.
- To evaluate the utility of specific neurophysiological tests in detecting small fiber dysfunction in MDs.
Main Methods:
- Neurophysiological assessments including nerve conduction studies (NCS), sympathetic skin response (SSR), and Sudoscan were performed on 27 MD patients.
- Patients had various genetic diagnoses: m.3243A>G, m.8344A>G, single mtDNA deletions, or multiple mtDNA deletions.
Main Results:
- NCS revealed polyneuropathy in 41% of patients, with higher incidence in POLG1 and m.8344A>G mutations.
- Sudoscan identified autonomic small fiber dysfunction in 33% of patients, notably in 78% of those with single mtDNA deletions.
- SSR abnormalities were infrequent, observed in only three patients.
Conclusions:
- Small fiber neuropathy is a significant, yet often overlooked, feature in mitochondrial diseases.
- The presence of single mitochondrial DNA deletions is specifically associated with small fiber neuropathy.
- Utilizing targeted neurophysiological tests is essential for accurate diagnosis and management of MDs.
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