The role of mental function in the pathogenesis of freezing of gait in Parkinson's disease.

Freezing of gait (FOG) is a disabling episodic gait disturbance that is common among patients with Parkinsonism. FOG typically lasts a few seconds and is associated with a unique sensation: the patient feels that his feet are glued to the ground, causing him to remain in place despite making a concerted effort to overcome the motor block and move forward. Traditionally, FOG has been viewed as a motor symptom of advanced Parkinson's disease. Here we describe evidence which demonstrates that mental conditions also likely play an important role in the pathogenesis of FOG. Stress, anxiety, depression and cognitively challenging situations are associated with FOG, and may set the stage for and increase the likelihood that FOG occurs. A conceptual model that explains how mental conditions may modulate FOG is developed.