Movement disorders O-MD001. The role of neurophysiological testing for differential diagnosis of functional tremor in busy clinic

Introduction. The presenting phenomenology of functional tremor (FT) is complex making clinical diagnosis challenging. However, certain features from neurophysiological testing may aid the differential diagnosis of FT. Aim of investigation: To study the clinical characteristics and neurophysiological findings of FT and compare with organic tremor (OrgT). Methods. 12 patients with suspected FT were recruited. Clinical characteristics and neurophysiological features were reviewed and compared with OrgT. Results. Of the 12 patients, 50% were neurophysiologically confirmed as having FT. There were no differences in age of onset, disease duration or psychiatric comorbidity between FT and OrgT, but FT is more common in female than OrgT (M:F: 5:1 vs 2:4, p = 0.24). Stressful events were commonly reported as a precipitating factor in FT. Presenting symptoms of FT were mostly unilateral (83%) and task-specific (67%) with a possible dystonic posture. The aetiologies of OrgT mimicking FT were enhanced physiological tremor (4 patients), PD (1 patient) and orthostatic tremor (1 patient). Clinical signs and neurophysiological features that can significantly differentiate between FT and OrgT were distractibility (83% vs 7%, p = 0.02), entrainment (67% vs 0%, p = 0.01), distractibility/frequency shift with tapping (100% vs 0%, p  Conclusion. Our study demonstrates the role of neurophysiological testing in those with suspected FT. In particular, distractibility appears to be an important clinical sign for diagnosis of FT.