Freezing of Gait (FOG) occurs when patients are unable to move their feet when trying to walk. It affects half of all people who have Parkinson’s disease, is not responsive to treatment, and is a common factor leading to nursing home placement. The mechanisms underlying Freezing of Gait (FOG) are not well understood and current treatments are often ineffective in controlling this symptom.
FOG may also occur while patients are walking. There is an abrupt decrease of step length and increase of step frequency and step-to-step variability that precedes a complete blockade of gait and falls. Another important characteristic is the occurrence of an irregular rapid trembling in both knees. FOG is often triggered by characteristic circumstances such as a half or 360°-turn, obstacle (doorway) clearance, spaces with a narrow passage or unexpected visual or auditory stimuli. Fatigue, stressful situations, cognitive load anxiety and depression may also elicit FOG. Usually, FOG is improved by visual (eg, marks on the ground) or auditory cueing (rhythmic sounds). Paradoxically, running, cycling or climbing stairs are performed more easily than usual gait.
Many patients with freezing may notice that different tricks while walking help alleviate a freezing episode:
- Shifting the weight of the body from one leg to another
- Listening to rhythmical music and stepping with the rhythm
- Stepping over an imaginary line in front of them
- Using a mobile laser device that creates a line in front of the patient to step over.
In this video by the ABC Catalyst program Simon Lewis Associate Professor at the Brain & Mind Research Institute takes a look inside the brain to understand why freezing of gait (FOG) occurs.