Editors' note: The nature of postural tremor in Parkinson disease

Abstract

Using EMG of forearm muscles to study tremor, “The nature of postural tremor in Parkinson disease” suggested 2 distinct postural tremor phenotypes in Parkinson disease (PD), with different pathophysiology and treatment response. Reemergent tremor is a continuation of resting tremor during stable posturing, and it has a dopaminergic basis. Pure postural tremor is a less common type of tremor that is inherent to PD, but has a largely nondopaminergic basis. Commenting on the study, Dr. Jankovic points out that the latency between movement and the onset of the postural tremor is helpful to differentiate tremor in PD from other tremors. He also notes that sometimes tremor related to essential tremor and PD can coexist. He finally suggests that the lack of responsiveness of rest and reemergent tremor to dopaminergic drugs may be explained by involvement of nondopaminergic systems. In response, authors Dirkx et al. explain that, based on their study, reemergent tremor is fundamentally the same as resting tremor and that the latency between movement and tremor reemergence varies considerably. They add that pure postural tremor differs from reemergent tremor and agree that serotonergic (or noradrenergic, cholinergic) mechanisms may indeed play a role in pure postural tremor. Using EMG of forearm muscles to study tremor, “The nature of postural tremor in Parkinson disease” suggested 2 distinct postural tremor phenotypes in Parkinson disease (PD), with different pathophysiology and treatment response. Reemergent tremor is a continuation of resting tremor during stable posturing, and it has a dopaminergic basis.