background Movement disorders as dyskinesia and parkinsonism are regarded as core features of schizophrenia and it's genetic vulnerability (Koning et al 2008 in press). However, most individual studies on first degree-relatives failed to find this association possibly due to insufficient sensitivity of the applied clinical rating scales. Quantitative instrumental measurements can be more sensitive to detect subclinical movement disorders (Cortese 2005).
aim To compare mean scores of dyskinesia and parkinsonism in patients with schizophrenia, healthy siblings and matched controls using instrumental assessments.
methods Instrumental measurements of tongue and finger dyskinesia and resting tremor as a measure of parkinsonism were carried out in 44 medicated patients with a non-affective psychosis (70% schizophrenia), 44 healthy siblings and 32 controls. All subjects were screened for Axis-1 pathology using cash-interviews. Siblings and controls were matched according to age, sex and years of education.
results Siblings displayed significantly more dyskinesia and tremor of the finger than controls (2.35% vs.1.97%; p = 0.02 and 0.30% vs. 0.25%; p = 0.01 respectively). There was no difference in tongue dyskinesia (16.7% vs 16.9%; p = 0.88). In addition, patients not only demonstrated more finger dyskinesia and resting tremor than siblings (2.80% vs. 2.35%; p = 0.03 and 0.43% vs 0.30% p < 0.01 respectively), but also more tongue dyskinesia (21.2% vs. 16.7%; p < 0.01). Demographic information of patients, siblings and controls are given for age, years of education and percentage of males (27.2, 27.7 and 25.7 years), (12.1, 14.2 and 14.7 years) and (82%, 55% and 50%).
conclusion This is the first study that used instrumental assessments to show that siblings have more dyskinetic and parkinsonian movements of the fingers than controls suggesting it to be a (genetic) risk of developing schizophrenia. Instrumental measurement can be used for detecting subclinical movement disorders in high risk populations.