The clinical spectrum and natural history of pure akinesia with gait freezing.

Gait freezing as a presenting and relatively restricted condition is uncommon but a distinctive disorder. This entity was initially defined as "pure akinesia with gait freezing", and later a neuropathological substrate of progressive supranuclear palsy has been recognized. Limited studies have reported the clinical evolution after presentation, which is important for patient counseling. The objective of this study was to assess the demographic and clinical features, treatment-response, neuroimaging, and evolution of pure akinesia with gait freezing. A retrospective review of patients with this phenotype as previously defined was performed. Patients included had no or minimal limb rigidity and/or bradykinesia and no resting tremor, and all underwent neuroimaging of the brain after onset. Inclusion criteria were met by 30 patients, who were followed up to 21 years after symptom onset. During their course, 28 patients had falls (93 %), 12 patients had dysarthria (40 %), and 13 had handwriting changes (43 %). All patients had progression of their gait disorder over time, but with a variable interval until falls occurred. None of the patients developed vertical gaze palsy or met diagnostic criteria for an alternative parkinsonian disorder. Pure akinesia with gait freezing is a distinctive disorder that can be recognized in the clinic. Despite the previously reported progressive supranuclear palsy-like neuropathology, the clinical course is much less aggressive and disabling than classic Richardson syndrome, although fall risk eventually develops in nearly all patients. Bradykinesia, tremor, and rigidity do not develop, distinguishing pure akinesia with gait freezing from Parkinson's disease and other parkinsonian disorders.