Deep brain stimulation / cognitive and behavioural functions

Deep brain stimulation, mainly of the subthalamic nucleus, has become a widely performed surgical procedure for the treatment of advanced Parkinson`s disease when pharmacologic treatment is no longer effective in reducing disability. The deep brain stimulation is a reversible and adaptable treatment which produces marked improvement in the cardinal motor symptoms of Parkinson`s disease, through a functional inhibition of the subthalamic nucleus. The theoretical basis is the basal ganglia-thalamo-cortical model. Although the beneficial effects of chronic bilateral subthalamic deep brain stimulation on motor symptoms are well documented, there are only few data about the effects on neurobehavioural functions. Most of the studies found a worsening in verbal fluency after the procedure. In addition, a decline in tasks sensitive to frontal lobe dysfunction and in verbal/visuospatial memory tasks has been reported in some studies but not in others. A few studies reported improvements in working memory and psychomotor speed. High frequency stimulation of the subthalamic nucleus may not produce a global frontal decline, but it can have a negative effect on specific executive functions, verbal and visuospatial memory. A higher risk for cognitive decline after surgery has been reported for patients over 69 years and for patients with a preoperative existing cognitive impairment. Moreover behavioural changes like worsening of depression, suicide attempts, apathy and mania have been described in patients after deep brain stimulation. Most of these results base on unsystematically investigations, often with a very small sample size, short test-retest intervals and without comparison of the results with a control group. The importance of a controll group is given by the chronical course of the illness and possible practice effects by repeated testing. There are no data concerning the possible effects of the anatomical electrode position and stimulation parameters on neurobehavioural function. Further, none of the studies investigated the influence of this treatment on the caregivers burden and their quality of life. In the present study, we have four main objectives: 1. to investigate systematically the effects of bilateral subthalamic deep brain stimulation on cognitive and behavioural functions in 30 patients with Parkinson`s disease and to compare the results with a matched unoperated group of 30 patients with Parkinson`s disease, 2. to examine the possible influence of the anatomical electrode position and effects of the stimulation parameters on neurobehavioural functions, 3. to evaluate the effects of the treatment on the quality of life of the patients and their activities of daily living, 4. to examine the influence of the deep brain stimulation on the caregivers burden and their quality of life. After a baseline assessment before surgical treatment, patients and their caregivers will be followed up for a period of one year with repeated examinations. Neuropsychological functions will be assessed using sophisticated neuropsychological tests. Mood, behavior, quality of life and caregivers burden will be evaluated with self-rating scales. The control group will have their testing parallel to the study group.

Deep brain stimulation, mainly of the subthalamic nucleus, has become a widely performed surgical procedure for the treatment of advanced Parkinson`s disease when pharmacologic treatment is no longer effective in reducing disability. The deep brain stimulation is a reversible and adaptable treatment which produces marked improvement in the cardinal motor symptoms of Parkinson`s disease, through a functional inhibition of the subthalamic nucleus. The theoretical basis is the basal ganglia-thalamo-cortical model. Although the beneficial effects of chronic bilateral subthalamic deep brain stimulation on motor symptoms are well documented, there are only few data about the effects on neurobehavioural functions. Most of the studies found a worsening in verbal fluency after the procedure. In addition, a decline in tasks sensitive to frontal lobe dysfunction and in verbal/visuospatial memory tasks has been reported in some studies but not in others. A few studies reported improvements in working memory and psychomotor speed. High frequency stimulation of the subthalamic nucleus may not produce a global frontal decline, but it can have a negative effect on specific executive functions, verbal and visuospatial memory. A higher risk for cognitive decline after surgery has been reported for patients over 69 years and for patients with a preoperative existing cognitive impairment. Moreover behavioural changes like worsening of depression, suicide attempts, apathy and mania have been described in patients after deep brain stimulation. Most of these results base on unsystematically investigations, often with a very small sample size, short test-retest intervals and without comparison of the results with a control group. The importance of a controll group is given by the chronical course of the illness and possible practice effects by repeated testing. There are no data concerning the possible effects of the anatomical electrode position and stimulation parameters on neurobehavioural function. Further, none of the studies investigated the influence of this treatment on the caregivers burden and their quality of life. In the present study, we have four main objectives: 1. to investigate systematically the effects of bilateral subthalamic deep brain stimulation on cognitive and behavioural functions in 30 patients with Parkinson`s disease and to compare the results with a matched unoperated group of 30 patients with Parkinson`s disease, 2. to examine the possible influence of the anatomical electrode position and effects of the stimulation parameters on neurobehavioural functions, 3. to evaluate the effects of the treatment on the quality of life of the patients and their activities of daily living, 4. to examine the influence of the deep brain stimulation on the caregivers burden and their quality of life. After a baseline assessment before surgical treatment, patients and their caregivers will be followed up for a period of one year with repeated examinations. Neuropsychological functions will be assessed using sophisticated neuropsychological tests. Mood, behavior, quality of life and caregivers burden will be evaluated with self-rating scales. The control group will have their testing parallel to the study group.