Methods and System for Characterising Tremors

A method of characterising tremor stability in a subject is described for a subject having an involuntary tremor symptomatic of a neurological disorder. The method comprising: identifying a series of tremor cycles from measured tremor data of the subject,said tremor cycles measuring periodic variation in movement of the subject due to the tremor; determining an instantaneous frequency for each tremor cycle and collating the instantaneous frequencies; determining an instantaneous variation between the instantaneous frequencies of each pair of adjacent tremor cycles within the series; comparing the instantaneous variation to the collation of determined instantaneous frequencies to determine a distribution of instantaneous variations; and determining an index value of the distribution of the instantaneous variations, said index value defining the stability of the tremor.