Freezing of gait in Parkinson's disease: the paradoxical interplay between gait and cognition

BACKGROUND: Freezing of gait is a disabling episodic gait disturbance common in patients with Parkinson's disease. Recent evidences suggest a complex interplay between gait impairment and executive functions. Aim of our study was to evaluate whether specific motor conditions (sitting or walking) influence cognitive performance in patients with or without different types of freezing. METHODS: Eight healthy controls, eight patients without freezing, nine patients with levodopa-responsive and nine patients with levodopa-resistant freezing received a clinical and neuropsychological assessment during two randomly performed conditions: at rest and during walking. Results : At rest, patients with levodopa-resistant freezing performed worse than patients without freezing on tests of phonological fluency (p = 0.01). No differences among the four groups were detected during walking. When cognitive performances during walking were compared to the performance at rest, there was a significant decline of verbal episodic memory task (Rey Auditory Verbal Learning Test) in patients without freezing and with levodopa-responsive freezing. Interestingly, walking improved performance on the phonological fluency task in patients with levodopa-resistant freezing (p = 0.04). CONCLUSIONS: Compared to patients without freezing, patients with levodopa-resistant freezing perform worse when tested while seated in tasks of phonological verbal fluency. Surprisingly, gait was associated with a paradoxical improvement of phonological verbal fluency in the patients with levodopa-resistant freezing whilst walking determined a worsening of episodic memory in the other patient groups