Striatal dopamine synthesis capacity in twins discordant for schizophrenia.

BACKGROUND: Elevated striatal dopamine synthesis capacity is thought to be fundamental to the pathophysiology of schizophrenia and has also been reported in people at risk of psychosis. It is therefore unclear if striatal hyperdopaminergia is a vulnerability marker for schizophrenia, or a state feature related to the psychosis itself. Relatives of patients with schizophrenia are themselves at increased risk of developing the condition. In this study we examined striatal dopamine synthesis capacity in both members of twin pairs discordant for schizophrenia. METHOD: In vivo striatal dopamine synthesis capacity was examined using fluorine-18-l-dihydroxyphenylalanine (18F-DOPA) positron emission tomography (PET) scans in seven twin pairs discordant for schizophrenia and in a control sample of 10 healthy control twin pairs. RESULTS: Striatal 18F-DOPA uptake was not elevated in the unaffected co-twins of patients with schizophrenia (p=0.65) or indeed in the twins with schizophrenia (p=0.89) compared to the control group. Levels of psychotic symptoms were low in the patients with schizophrenia who were in general stable [mean (s.d.) Positive and Negative Syndrome Scale (PANSS) total=56.8 (25.5)] whereas the unaffected co-twins were largely asymptomatic. CONCLUSIONS: Striatal dopamine synthesis capacity is not elevated in symptom-free individuals at genetic risk of schizophrenia, or in well-treated stable patients with chronic schizophrenia. These findings suggest that striatal hyperdopaminergia is not a vulnerability marker for schizophrenia.

Relationships between deep brain stimulation and impulse control disorders in Parkinson's disease, with a literature review.

Impulse control disorders (ICDs) are behavioural/neuropsychiatric complications of the pharmacological treatment of Parkinson's disease. Long term motor complications of PD can be effectively treated using deep brain stimulation (DBS) of subcortical nuclei. The relationships between ICDs and DBS treatment of the motor complications of Parkinson's disease remain unclear. We describe 50 consecutive patients in whom detailed neuropsychiatric assessments were performed as part of our routine pre-operative assessment. Eight had current or past ICDs during pre-operative assessment. These patients were more likely to be male and were younger than those without ICDs. Other psychosocial variables did not predict the presence of ICDs. Detailed neuropsychological examination failed to show any between-group differences. Our prevalence rate of 16% helps raise awareness of ICDs in this specialised clinic population and may reflect common denominators between significant motor fluctuations and dopaminergic drug - related behavioural disturbances. Four patients were deemed suitable for surgery after multi-disciplinary assessment. One had re-emergence of his ICD 18 months post-operatively, the ICD having resolved in the first 18 months. We also review published literature and the evidence regarding post-operative outcomes. We recommend the routine pre-operative examination of patients for psychopathology and emphasize the importance of post-operative psychiatric surveillance.