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Multifocal motor neuropathy and visual pathway impairment: A case report
Keisuke Kido1,2, Shinichi Wada3, Yuwa Oka4,5
1Center for Sleep-related Disorders, Kansai Electric Power Hospital, Osaka, Japan.
Clinical Neurophysiology Practice
|July 26, 2021
Summary
Multifocal motor neuropathy (MMN) can impact the visual pathway, as seen in a case with improved vision and visual evoked potential (VEP) after treatment. This suggests MMN may involve autoimmune mechanisms affecting vision.
Area of Science:
- Neuroimmunology
- Neurology
- Ophthalmology
Background:
- Multifocal motor neuropathy (MMN) is a rare autoimmune disorder primarily affecting peripheral nerves.
- Cranial nerve involvement is an uncommon MMN presentation.
- Visual pathway impairment in MMN has not been previously documented.
Observation:
- A 36-year-old male presented with progressive muscle weakness and atrophy in the distal upper limbs.
- Diagnosis of MMN was confirmed by positive anti-GM1 ganglioside antibodies and nerve conduction studies showing conduction block.
- The patient experienced blurred vision, which improved with intravenous immunoglobulin (IVIg) therapy.
Findings:
- Visual evoked potentials (VEP) demonstrated prolonged P100 latency, indicating visual pathway dysfunction.
- Post-IVIg treatment, VEP showed shortened P100 latency, correlating with clinical visual improvement.
- These positive treatment effects persisted for 3.5 years.
Implications:
- This case suggests that the visual pathway can be affected in MMN.
- Autoimmune mechanisms may underlie visual pathway involvement in MMN.
- VEP can serve as a valuable tool for detecting and monitoring visual pathway dysfunction in MMN.
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