Freezing is the sudden inability in a patient with parkinsonism to move or to walk, i.e., gait failure, as though the patient were turned to ice or the feet were nailed to the floor. This is one of the unpredictable motor fluctuations in late Parkinson’s disease (associated with longer duration of disease and treatment) which may lead to falls, usually forward onto the knees, and injury. It may occur in confined spaces (e.g., doorways), when trying to turn, or when trying to do two things at once. It is not seen in the early years of levodopa therapy.
Two variants are encountered, occurring either during an off period or wearing off period, or randomly, i.e., unrelated to drug dosage or timing.
Treatment strategies include use of dopaminergic agents and, anecdotally, L-threodops, but these agents are not reliably helpful, particularly in random freezing. Use of visual targets (real or imagined) may help, e.g., stepping over a line.
Freezing may also occur in multiple system atrophy, and has also been reported as an isolated phenomenon.