Objective: To study the clinical characteristics and electrophysiological findings of laboratory -supported FT in comparison with OrgT.To study the clinical characteristics and electrophysiological findings of laboratory -supported FT in comparison with OrgT.
Background: Making a diagnosis of functional tremor (FT) is challenging due to clinical overlap between FT and organic tremor (OrgT). A number of clinical clues and certain electrophysiological features may aid the differential diagnosis of FT.
Method: 13 patients with suspected FT due to variability of tremor and additional clinical clues were recruited. Clinical characteristics and electrophysiological features of FT were reviewed and compared with OrgT.
Results: Of the 13 patients, 7 patients (53%) were confirmed as having FT according to the electrophysiological criteria. Presenting symptoms of FT were mostly unilateral (86%) and position-specific (71%) with a possible dystonic posture. Variability occurred in both FT and OrgT, while distractibility significantly occurred in FT (100% vs 1%, p=0.002). The number of clinical signs as a clue for FT were higher in FT than OrgT (4 vs 2 signs, p<0.001). (table 1) Significant electrophysiological features were distractibility/frequency shift with tapping (100% vs 0%, p<0.001), ballistic movements (57% vs 0%, p=0.03), and loading (57% vs 0%, p=0.03) respectively. The aetiologies of OrgT that mimicked FT were enhanced physiological tremor (EPT) (5 patients), dystonic tremor (DT) (1 patient) and parkinsonian tremor (1 patient). In addition, 2 patients in the FT group were categorised as DT with functional overlay due to signs of FT plus co-contraction at baseline that was interpreted as a co-activation sign.
Conclusion: Our study demonstrates that an electrophysiological investigation has an important role in the diagnosis of FT. Variability is not always FT and can be found in EPT and DT. Clinical signs and electrophysiological confirmation of distractibility appear to be the most consistent clues in supporting the diagnosis of FT.
To cite this abstract in AMA style:
S. Virameteekul, P. Panyakaew, R. Bhidayasiri. Variability of tremor is not always functional: A feasibility study on the aetiological differentiation of tremor [abstract]. Mov Disord. 2021; 36 (suppl 1). https://www.mdsabstracts.org/abstract/variability-of-tremor-is-not-always-functional-a-feasibility-study-on-the-aetiological-differentiation-of-tremor/. Accessed June 15, 2025.« Back to MDS Virtual Congress 2021
MDS Abstracts - https://www.mdsabstracts.org/abstract/variability-of-tremor-is-not-always-functional-a-feasibility-study-on-the-aetiological-differentiation-of-tremor/