The following changes may be seen with mental concentration:

(1) No change in tremor amplitude (as in ET)

(2) Decrease of amplitude or cessation of tremor during the manoeuvre (as is the case of functional tremor)

(3) Increase of amplitude of tremor (a characteristic finding of parkinsonian tremor). Although this can be appreciated clinically, neurophysiological recordings permits clearer confirmation of this phenomenon, especially in doubtful cases.