We analyzed
rest tremor, one of the etiologically most elusive hallmarks of
Parkinson disease (PD), in 12 consecutive PD patients during a specific task activating the locus coeruleus (LC) to investigate a putative role of
noradrenaline (NA) in
tremor generation and suppression. Clinical diagnosis was confirmed in all subjects by reduced
dopamine reuptake transporter (DAT) binding values investigated by single photon computed tomography imaging (SPECT) with [(123)I] N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) tropane (
FP-CIT). The intensity of
tremor (i.e., the power of Electromyography [EMG] signals), but not its frequency, significantly increased during the task. In six subjects,
tremor appeared selectively during the task. In a second part of the study, we retrospectively reviewed SPECT with
FP-CIT data and confirmed the lack of correlation between dopaminergic loss and
tremor by comparing DAT binding values of 82 PD subjects with bilateral
tremor (n = 27), unilateral
tremor (n = 22), and no
tremor (n = 33). This study suggests a role of the LC in Parkinson
tremor.