Relationship between freezing of gait (FOG) and other features of Parkinson’s: FOG is not correlated with bradykinesia

BACKGROUND The pathophysiology of freezing of gait (FOG) is unclear. OBJECTIVE To assess the relationships between FOG and other parkinsonian features in Parkinson's disease (PD), focusing on levodopa effects. METHODS Nineteen PD patients with significant FOG in "off" were assessed while "off" and "on". Three observers independently viewed videotapes of a 130-m walk and scored FOG frequency. The Unified Parkinson's disease Rating Scale was used to evaluate clinical state. RESULTS FOG frequency was not correlated with other parkinsonian features in "off" and only with speech and writing in "on". Levodopa significantly decreased FOG frequency (p<0.001). This reduction was strongly correlated with improvement of tremor (R=0.80, p<0.01) and speech (R=0.62, p<0.05), but not with improvement in rigidity, bradykinesia, or balance. CONCLUSION Levodopa decreases FOG in PD. FOG is apparently an independent motor symptom, caused by a paroxysmal pathology that is different from that responsible for bradykinesia, rigidity or postural instability.