Deep Brain Stimulation, alleviating tremour, and impulse control?
Deep Brain Stimulation (DBS) is a new treatment for Parkinson’s Disease (PD). It alleviates or altogether eliminates the parkinsonism symptoms of tremour. This wonderful video from youtube demonstrates this beautifully. Although there is no Google translate for speech yet (lol), I do catch the essence of what the person is saying, and his reference to Michael J. Fox.
But it also makes me wonder if such treatment does affect other problems associated with PD. Studies, also cited in our recent work, demonstrates that PD patients, in relation to their low dopamine levels, display less sensitivity to rewards. This is known to affect gambling and risk taking, in which untreated PD patients are typically more risk averse and less reward sensitive than healthy controls.
Dopamine agonist treatment, increasing the dopamine levels, can induce dramatic changes in such behaviours. Specifically, this treatment increases reward sensitivity and reduces risk aversion to normal levels, but one side effect can be an overshoot. Here, PD patients can develop problem behaviours such as pathological gambling.
So, any studies showing similar effects of DBS on gambling behaviour? According to one study, impulse control disorder and dopamine dysregulation seems to persist, or even worsen, after DBS surgery. Another study suggested that compulsive behaviours were not different between DBS patients and medically treated patients. However, this study found a significantly worse impulse control in DBS patients and a higher ratio of impulse control disorders in this group, compared to the medically treated group. However, as this study made these measures post-surgery, there might be a selection bias between the groups. Saying this, an earlier report describes two patients that benefit from DBS in the treatment of pathological gambling and dopamine treatment addiction.
So, it still seems to be uncertain whether DBS leads to other behavioural changes than reducing/eliminating tremour. It may be, as suggested by one of the studies, that DBS treatment leads to unwanted behavioural side effects in a subgroup of patients. This may be related to the overall symptomalogy of the individual PD patient, but it may also be related to individual differences in premorbid neurotransmission, IOW genetic differences. This, again, demonstrates that individualized treatment should be sought before applying DBS, although at this stage, much more work needs to be done before such firm decisions can be made.