Cranial Tremors in Essential Tremor: Prevalence, Anatomic Distribution and Predictors of Occurrence.

Background: There are few published data on the prevalence, pattern of anatomic distribution and predictors of various cranial tremors (eg, head, voice, jaw) in essential tremor (ET). Given the high levels of diagnostic misclassification in ET, data on observed clinical patterns would be valuable.

Objectives: To assess the prevalence, pattern of anatomic distribution and predictors of occurrence of cranial tremors in ET.

Methods: ET cases who enrolled in two studies (respective n's = 301 and 175, total n = 476) underwent a detailed clinical assessment, which included a videotaped neurological examination. A senior movement disorders neurologist reviewed the examination and coded a range of cranial tremors as present or absent.

Results: The proportion of cases with any cranial tremor was 57.1% (Study 1) and 73.7% (Study 2). The following patterns emerged: (1) Head only and head + voice were the most commonly observed anatomical distribution of tremor. (2) Jaw tremors were rare, and face and tongue tremors, exceedingly rare. (3) There was a general layering-on of tremor from head to head + voice to head + voice + jaw in more advanced cases. (4) Women were more likely to have head tremors than men, although there was no sex predilection tremor in other locations. (5) The likelihood of cranial tremor increased with greater tremor severity and age but was unrelated to tremor duration.

Conclusion: We observed and quantified several patterns in the expression of cranial tremors in ET. Data on such patterns may assist clinicians and researchers in assigning diagnoses.