Personality in essential tremor: further evidence of non-motor manifestations of the disease.

OBJECTIVE: To ascertain whether patients with essential tremor have distinct definable personality traits. METHODS: A case-control study of patients with essential tremor was carried out to look for differences in personality characteristics. The controls were derived from the same source population. Using the tridimensional personality questionnaire (TPQ), personality traits were assessed in three dimensions: harm avoidance (HA), novelty seeking (NS), and reward dependence (RD). Additional analyses were conducted to address the possibility of selection bias among the patients with essential tremor. RESULTS: There were 55 patients and 61 controls. There was a difference between patients and controls in HA subscale scores (p = 0.005) but not in NS or RD scores. The difference remained significant in analyses that adjusted for age, sex, race, and education (p = 0.005). HA subscale scores did not correlate with subjective or objective measures of disability or with indices of severity of tremor. CONCLUSIONS: Patients with essential tremor scored higher on the harm avoidance subscale scores than control subjects. HA subscale scores did not correlate with the severity of tremor or with subjective and objective scales of disability, suggesting that the personality profile observed was not entirely related to functional disability caused by the tremor. Longitudinal studies of personality in essential tremor are needed to characterise the stability and evolution of these personality traits within the natural history of the disease process.

Elevation of blood beta-carboline alkaloids in essential tremor.

BACKGROUND: beta-Carboline alkaloids are normal body constituents but are also potent tremor-producing chemicals that are naturally present in the food chain. OBJECTIVE: To explore the hypothesis that high concentrations of beta-carboline alkaloids are associated with essential tremor (ET). METHODS: One hundred cases and 100 controls were frequency matched on age, sex, and ethnicity. Blood concentrations of harmane and harmine were quantified by high-performance liquid chromatography, blinded to clinical information. RESULTS: The mean log blood concentration of harmane was higher in cases than controls (0.72 +/- 0.53 vs 0.51 +/- 0.64 g(-10)/mL; p = 0.01). A nonparametric test on nontransformed data (median harmane = 5.21 g(-10)/mL in cases and 2.28 g(-10)/mL in controls) confirmed this difference (p = 0.005). The mean log blood concentration of harmine was 0.20 +/- 0.48 g(-10)/mL in cases and 0.10 +/- 0.65 g (-10)/mL in controls (p = 0.20). Log harmane concentrations were stratified based on the median value; 62% of cases vs 39% of controls had a high log harmane concentration (p = 0.001). Mean log harmane concentration was similar in the cases with (0.74 +/- 0.58 g(-10)/mL) and without (0.71 +/- 0.50 g(-10)/mL) an affected relative (p = 0.83). CONCLUSIONS: Blood concentrations of harmane were measured in ET cases compared with controls. Concentrations were elevated in cases with and without a family history of ET.