Background: Primary progressive freezing gait disorder is considered to be a distinct clinical entity that manifests predominantly as a progressive freezing gait disorder without accompanying abnormalities. However, confusion remains about its clinical presentation, natural history, and classification.
Objective: To examine the natural history, clinical and brain imaging characteristics, and response to dopaminergic medications of primary progressive freezing gait (PPFG) disorder.
Design/methods: Review of medical records, videotape examinations, and computed tomographic and magnetic resonance imaging of the brain and results of neurological evaluations, including the Unified Parkinson's Disease Rating Scale, in patients with PPFG.
Results: Thirty patients (16 male) were diagnosed as having PPFG (mean age at onset, 72.2 years; mean duration of disease, 5 years). Gait disorder was the initial complaint in 27 patients. Freezing gait was the initial manifestation in 18 and was present within the first year in 27. Natural history included 25 patients falling within 3 years of onset, 20 experiencing retropulsion within 4 years, and 16 requiring wheelchairs by 5 years. On neurological examination, bradykinesia was present in 29 patients, muscle rigidity in 15, and postural tremor in 11. Other features included speech abnormalities in 10, hyperreflexia without clonus in 17, and dementia in 8. Extraocular movement abnormalities and dysphagia were rare. All 30 patients were treated with levodopa with minimal effect. Eighteen were treated with a dopamine agonist with no notable effect. Of the 23 patients with magnetic resonance imaging scans, results were normal in 9 and included minor nonspecific changes in 14. The computed tomographic scans obtained in 12 patients showed similar results. One patient underwent fluorine F ((18)F) labeled deoxyglucose positron emission tomography, which showed mild reduction in medial frontal glucose metabolism.
Conclusions: Primary progressive freezing gait appears to be a clinically distinct progressive neurological disorder that primarily affects gait, initially resulting in freezing and later in postural instability. A wheelchair-bound state often develops within 5 years. It is accompanied by other parkinsonian features, particularly bradykinesia, but is unresponsive to dopaminergic medications. It progresses in a fairly stereotyped manner. Primary progressive freezing gait disorder should be a unifying term for this disorder that has gone by many names in the literature and should be classified as a Parkinson-plus disorder.