Clinical and electrophysiological features for differentiating MMN from hand-onset ALS

Area of Science:

• Neurology
• Clinical Electrophysiology

Background:

• Differentiating multifocal motor neuropathy (MMN) from amyotrophic lateral sclerosis (ALS) presents diagnostic challenges, especially in early stages with hand-onset weakness and absent upper motor neuron (UMN) signs.
• Accurate early diagnosis is critical for appropriate patient management and treatment.

Purpose of the Study:

• To identify distinct clinical and electrophysiological features that facilitate the early differentiation between MMN and ALS.
• To improve diagnostic accuracy in cases with overlapping early symptoms.

Main Methods:

• Retrospective analysis of clinical, laboratory, and electrophysiological data from patients diagnosed with MMN and ALS.
• Utilized a standardized nerve conduction study protocol with extended motor stimulation.

Main Results:

• MMN patients were significantly younger at symptom onset compared to ALS patients (43.1 vs. 58.7 years).
• MMN patients exhibited lower serum creatine kinase (CK) and higher serum IgM levels than ALS patients.
• Conduction block (CB) on nerve conduction studies was significantly more prevalent in MMN (87.5%) than in ALS (19.7%) or hand-onset ALS (31.0%).

Conclusions:

• A combination of clinical presentation, serum CK and IgM levels, and electrophysiological findings of CB aids in distinguishing MMN from ALS.
• These markers are valuable for improving early diagnostic accuracy between MMN and ALS.