**5. Comments**

It is of utmost importance that a clinical neurophysiologist performing ENMG studies recognizes different types of spontaneous activity. Confusing end plate spikes with fibrillation potentials may cause false positive findings of axonal damage. Even the difference between rhythmic and irregular fibrillation potentials may be difficult to grasp and there are differences between individual examiners in this respect (Trillenberg & Spencer 2010). False classification of potentials is a frequent error, especially among resident-level examiners (Kendall & Werner 2006). We studied parameters by which it could be possible to distinguish between different types of fibrillation potentials: rhythmic, random, and slightly irregular fibrillations with pauses, "myokymic" fibrillations, and end plate spikes. The most effective differentiating variables in this respect proved to be the minimum interval, APCID and MCD. Interval analysis of the activity of a single motor unit also shows an entirely different discharge pattern compared to spontaneous potentials (Conrad et al. 1972). The functionality to calculate these variables for sequences of spontaneous EMG potentials should be included in future ENMG devices. The lack of tools for editing and interval analysis of EMG potential sequences can be considered to be a major shortcoming in the present ENMG machines.

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