Functional tremor

Diagnosis

Characteristics of functional tremor include: (Schwingenschuh and Deuschl, 2016)

- Unusual temporal course, including sudden onset and spontaneous remissions of tremor, and variability of body part affected by tremor

- Combination of tremor characteristics (rest, postural, and kinetic tremor)

- Improvement during distraction techniques

- Tremor entrainment (adaptation to the frequency of contralateral limb movements)

- Tremor variability (body part, frequency, amplitude)

- Coactivation sign (underlying antagonistic muscle activation with tremor)

- Suggestibility (i.e. applying a tuning fork and suggesting it may reduce symptoms)

- Excessive exhaustion during examination

- History of other functional neurologic disorders or somatization or appearance of other unrelated neurological signs

Treatment

- An open trial of 12 weekly CBT sessions with 15 patients with functional tremor led to significant improvement in tremor (exclusion criteria were admittedly significant and included resting tremor that would interfere with fMRI, not agreeing or understanding their FND diagnosis, any comorbid FND or neurological disorder, or were on benzodiazepines) (Espay et al, 2019).

References

Espay, A. J. et al. Clinical and neural responses to cognitive behavioral therapy for functional tremor. Neurology 93, e1787–e1798 (2019). https://pubmed.ncbi.nlm.nih.gov/31586023/

Schwingenschuh, P. & Deuschl, G. Functional tremor. in Handbook of Clinical Neurology vol. 139 229–233 (Elsevier, 2016). https://pubmed.ncbi.nlm.nih.gov/27719841/