Clinical features and nigrostriatal dysfunction in patients with combined postural and resting tremors

Background: The characteristics of clinical features and nigrostriatal dopaminergic dysfunction in patients with combined postural and resting tremors have been less clearly reported. Methods: The present study examined 43 patients with a visible persistent bilateral postural tremor and a unilateral/bilateral resting tremor involving the hands and forearms. The patients had experienced tremors for more than 3 years, with no evidence of Parkinson's disease or other parkinsonian disorders. Visual and quantitative analyses of [¹⁸F] N-(3-fluoropropyl)-2beta-carbon ethoxy-3beta-(4-iodophenyl) nortropane (FP-CIT) PET in 36 patients were performed. Seventeen age-matched normal controls were also studied. Results: On visual analysis, 28 patients (78%) showed normal [¹⁸F] FP-CIT uptake and eight (22%) showed significantly reduced uptake, suggesting nigrostriatal dopaminergic neuronal degeneration. The reduced [¹⁸F] FP-CIT uptake was significantly associated with earlier age-at-onset of tremor and asymmetric presentation of resting tremor. On quantitative analysis, there were statistically significant differences in the [¹⁸F] FP-CIT uptake ratio in the posterior putamen between patients with reduced uptake (2.37±1.83) and patients with normal uptake (6.39±1.35) (P<0.001). However, posterior putamen uptake levels in patients with normal [¹⁸F] FP-CIT uptake on visual analysis were similar to those in normal controls (7.22±1.29) (P=0.291). Conclusion: The nigrostriatal dopaminergic dysfunction in patients with combined postural and resting tremors may be associated with earlier age-at-onset of tremor and asymmetric pattern of resting tremor, which might help to correctly diagnose patients with mixed tremors.