 Freezing of gait FOG is among the most disabling motor features of Parkinson disease PD and is present in other forms of parkinsonism as well. FOG is a brief usually lasting 30 seconds episode of absence or a greatly reduced forward movement of the feet despite intention to walk. It typically occurs when patients initiate gait so-called start hesitation and when attempting to turn. It is a leading cause of falls and often results in a wheelchair-dependent state. FOG greatly interferes with activities of daily living, causes social isolation and poor quality of life. 