The clinical spectrum of freezing of gait in atypical parkinsonism.

Freezing of gait (FOG), commonly seen in advanced Parkinson's disease (PD), has been classified as its fifth cardinal feature. However, its presence frequently leads to a misdiagnosis of PD. FOG is actually more common in atypical parkinsonism (AP): including vascular Parkinsonism (VP), progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal degeneration (CBD), dementia with Lewy bodies (DLB), and higher level gait disorders (HLGDs). VP is the result of multiple small vessel infarcts (lacunar state or Binswanger's disease), particularly involving the frontal, parietal, and basal ganglia regions. Approximately 50% have FOG (often referred to as lower body parkinsonism). FOG is also common in neurodegenerative forms of AP, present in 45-57%. Of these, FOG is present in 53% of PSP, 54% MSA, 54% DLB, 25% CBD, and 40% HLGD. It is generally seen in the late stages. There are two syndromes closely associated with AP that are dominated by FOG; pure akinesia (PA) and primary progressive freezing gait (PPFG). PA is characterized by akinesia of gait (including FOG), writing, and speech. Tremor, rigidity, dementia, and response to levodopa are notably absent. PPFG is defined by early FOG (often the initial feature) that progresses to include postural instability. It is accompanied by bradykinesia, rigidity, postural tremor, dementia, and levodopa unresponsiveness. Both syndromes are heterogeneous but PSP seems to be the most common cause. CBD and DLB can also present as PPFG. FOG is a common feature of AP and although typically occurring late in disease may also be an early symptom. (c) 2008 Movement Disorder Society.