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Fibrillation and sharp-waves: do we need them to diagnose ALS?
M de Carvalho1, C Bentes, T Evangelista
1Department of Neurology-EMG Laboratory, Hospital de Santa Maria, Av. Prof. Egas Moniz, 1600 Lisbon, Portugal. mamedemg@mail.telepac.pt
Summary
Absence of fibrillation/sharp-waves (fibs-sw) on initial EMG does not rule out Amyotrophic Lateral Sclerosis (ALS), particularly in bulbar-onset patients. Early upper-limb-onset ALS may also present without fibs-sw, but with fasciculations.
Area of Science:
- Neurophysiology
- Neurology
- Electromyography (EMG)
Background:
- Fibrillation/sharp-waves (fibs-sw) are critical neurophysiological markers for Amyotrophic Lateral Sclerosis (ALS).
- Initial electrophysiological evaluations in ALS patients sometimes lack these characteristic fibs-sw.
Purpose of the Study:
- To determine the frequency of absent fibs-sw in initial EMG evaluations of ALS patients.
- To assess the diagnostic implications of missing fibs-sw in different ALS onset types.
Main Methods:
- Analysis of initial EMG studies from 68 ALS patients.
- Assessment for fibs-sw presence in limb and cranial-innervated muscles.
Main Results:
- No fibs-sw were detected in cranial-innervated muscles across all patients.
- 7/15 bulbar-onset ALS patients lacked fibs-sw in limb muscles.
- 2/28 early upper-limb-onset ALS patients showed no fibs-sw, but presented with fasciculations and denervation-reinnervation.
Conclusions:
- The absence of fibs-sw on EMG should not exclude an ALS diagnosis, especially in bulbar-onset cases.
- Early-stage upper-limb-onset ALS may present without fibs-sw, but with significant fasciculations and muscle weakness indicators.