Abstract
Objective: To characterize peripheral nerve involvement in patients with chronic progressive external ophthalmoplegia (CPEO) with single and multiple mitochondrial DNA (mtDNA) deletions, based on clinical scores and detailed nerve conduction studies.
Methods: Peripheral nerve involvement was prospectively investigated in 33 participants with CPEO (single deletions n = 18 and multiple deletions n = 15). Clinically, a modified Total Neuropathy Score (mTNS) and a modified International Cooperative Ataxia Rating Scale (mICARS) were used. Nerve conduction studies included Nn. suralis, superficialis radialis, tibialis, and peroneus mot. Early somatosensory evoked potentials were obtained by N. tibialis stimulation.
Results: Participants with multiple deletions had higher mTNS and mICARS scores than those with single deletions. Electrophysiologically in both sensory nerves (N. suralis and N. radialis superficialis), compound action potential (CAP) amplitudes and nerve conduction velocities were lower and mostly abnormal in multiple deletions than those in single deletions. Early somatosensory evoked potentials of N. tibialis revealed increased P40 latencies and decreased N35-P40 amplitudes in multiple deletions. Both sensory nerves had higher areas under the receiver operating characteristic curves for the decreased CAP amplitudes than the 2 motor nerves. The N. suralis had the best Youden index, indicating a sensitivity of 93.3% and a specificity of 72.2% to detect multiple deletions.
Conclusions: Peripheral nerve involvement in participants with multiple mtDNA deletions is an axonal type of predominant sensory neuropathy. This is clinically consistent with higher mTNS and mICARS scores. Sensory nerve involvement in participants with multiple deletions was not correlated with age at onset and duration of disease.
GLOSSARY
- AUC=
- area under the curve;
- CAP=
- compound action potential;
- CPEO=
- chronic progressive external ophthalmoplegia;
- mICARS=
- modified International Cooperative Ataxia Rating Scale;
- mtDNA=
- mitochondrial DNA;
- mTNS=
- modified Total Neuropathy Score;
- NCV=
- nerve conduction velocity;
- SANDO=
- sensory ataxic neuropathy with dysarthria and ophthalmoparesis
Footnotes
Funding information and disclosures are provided at the end of the article. Go to Neurology.org/ng for full disclosure forms. The Article Processing Charge was paid by the Newcastle University.
Supplemental data at Neurology.org/ng
- Received April 14, 2016.
- Accepted in final form September 7, 2016.
- © 2016 American Academy of Neurology
This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (CC BY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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- Mitochondrial neuropathy in chronic progressive external ophthalmoplegia (CPEO)
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