<qa>  What is the most disabling motor feature of Parkinson disease?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. 