Functional Head Tremor: Contrasting Features with Other Tremor Etiologies

Functional tremor (FT) is considered the most common phenomenology among patients with functional movement disorders (FMDs). Most patients have limb tremor, but they can also present with tremor involving the head and trunk.

We aimed to assess the clinical phenomenology of functional head tremor (FHT) and contrast it with features of HT observed in 125 patients with other tremor etiologies (OTE), including 71 patients with essential tremor (ET).

There were 101 consecutive patients (68.3% females) with FT from which n = 36 (35.6%) had FHT. Yes-yes tremor was the most common directionality (47.2%). Functional trunk tremor was identified in n = 20 (19.8%) patients with FT. Patients with FHT were older (P < 0.05) and had greater FMDs severity with higher Simplified Functional Movement Disorders Rating Scale (S-FMDRS) scores (P < 0.001). When patients with FT were compared with those with OTE and ET, no differences were observed in the proportion of HT, but yes-yes directionality and more severe HT was more common in those with FMDs. A change in HT directionality was more frequent in patients with functional etiology (P = 0.007). This sign had high specificity (0.91) but low sensitivity (0.47) for the diagnosis of FHT. Comorbid trunk tremor had specificity of 0.89 and sensitivity of 0.28 to diagnose FHT.

HT is present in a third of patients with FT. These patients showed a grater severity of FMDs than FT without HT. A change in tremor directionality and comorbid trunk tremor had high specificity for the diagnosis for FHT compared with OTE.