Freezing of gait and executive functions in patients with Parkinson's disease

Freezing of gait (FOG) is a frequent, disabling symptom of Parkinson's disease (PD). FOG usually lasts a few seconds. It refers to brief paroxysmal events during which a subject is unable to start or continue locomotion. Despite its frequency, FOG pathophysiology is unclear. Because a frontal lobe dysfunction or a disconnection between the frontal lobe and basal ganglia has been implicated in FOG, we explored frontal functions in PD patients using neuropsychological tests. Thirteen early-stage PD patients [Hoehn & Yahr score (H&Y) < or = 2.5] with freezing during "on " state (FOG+), and 15 age-, H&Y score-, and disease-duration-matched PD patients without freezing (FOG-) were investigated. No patient was demented or depressed. Assessment included the Unified Parkinson's Disease Rating Scale (UPDRS), FOG questionnaire, Mini Mental State Examination (MMSE), frontal assessment battery (FAB), phonemic verbal fluency, Stroop test (parts II and III), and ten-point clock test (TPCT). UPDRS and MMSE scores did not differ between the two groups. FAB, verbal fluency, and TPCT scores were significantly lower in FOG+ patients than in FOG- patients (FAB: P = 0.008; phonemic verbal fluency: P = 0.011; TPCT: P = 0.024). FOG correlated with lower scores at frontal tests in patients with early-stage PD.