A Proposed Model for Understanding the Phenomenon of Freezing of Gait in Parkinson’s Disease and the Potential Role of Functional Neuroimaging
Parkinson’s disease (PD) is a common neurodegenerative condition affecting around 100,000 patients in Australia. Although symptomatic treatments are effective in controlling symptoms during the earlier stages of the disease patients experience increasing difficulties as their condition progresses. Over half of those with advanced disease will suffer from the phenomenon of freezing of gait (FOG) in which they experience sudden unwanted arrests in their movement leading to an increased risk of falls. This symptom is not easily treated and has a significant impact upon quality of life maybe even necessitating nursing home care.
The specific abnormalities within the brain underlying FOG in PD are not known but it is felt likely that they will relate to the severe depletion of dopamine resulting in a loss of functional integration within the neural circuitry connecting the basal ganglia, cerebral cortex and spinal cord, which is critical in normal locomotion. Previous neuroimaging studies have demonstrated that the modulation of dopamine levels can disrupt these circuits resulting in both movement and some of the memory disturbances observed in PD patients.
The work reported in this pilot study aims for the first time to model the phenomenon of FOG and allows the proposal of an underlying mechanism for this behaviour that would be amenable to testing with both functional MRI and PET studies. It is hoped that identifying the abnormal circuitry responsible for FOG and the role of dopamine in this phenomenon will promote the development of new targeted therapeutic strategies to improve quality of life.