Fibrillation and sharp-waves: do we need them to diagnose ALS?

BACKGROUND

Fibrillation/sharp-waves (fibs-sw) are considered an essential neurophysiological marker in Amyotrophic Lateral Sclerosis (ALS). We investigated how frequently an initial electrophysiological (EMG) evaluation, performed in ALS patients, revealed no fibs-sw.

METHODS

The initial EMG studies from 68 ALS patients were analysed. The presence of fibs-sw in at least two muscles of each limb and two cranial-innervated muscles was assessed.

RESULTS

We observed no fibs-sw in cranial-innervated muscles, and 7/15 bulbar-onset patients had no fibs-sw in limb muscles. Two of 28 upper-limb-onset patients, who had a short history before EMG, showed no fibs-sw. All lower-limb-onset patients had fibs-sw. Generally patients with no fibs-sw had diffuse abundant fasciculations.

CONCLUSIONS

The absence of fibs-sw should not necessarily preclude the neurophysiological diagnosis of ALS in bulbar-onset patients. Early affected upper-limb-onset patients might show no fibs-sw, but profuse fasciculations associated with mild to moderate denervation-reinnervation in weak muscles are found.