Incidence rates of cranial tremors in essential tremor: A prospective, longitudinal study

Background: Cranial (head, jaw) tremors develop in a sizable number of essential tremor (ET) patients. They are particularly important because they are a significant source of embarrassment and are especially resistant to treatment. There are no data on the rate at which ET patients develop these cranial tremors. Our aim was to estimate the incidence rate of head and jaw tremors in ET. Methods: Cases, enrolled in a prospective, longitudinal study, were evaluated at baseline and one follow-up visit. The in-person evaluation included questionnaires and a videotaped neurological examination, which was reviewed by a senior movement disorder neurologist for the presence/absence of head and jaw tremors. The mean time between baseline and follow-up assessments was 6.3 ± 2.4 (median = 6.0; range = 1.5-12.4 years). Results: Five (6.3%) of 79 cases developed head tremor by follow-up (incidence rate = 1,012 per 100,000 person years; 95% confidence interval [CI] = 0-3,219). Twelve (10.6%) of 113 cases developed jaw tremor by follow-up (incidence rate = 1,692 per 100,000 person years; 95% CI = 0-1,692). Conclusion: These epidemiological data were designed to assist physicians in counseling ET patients when they ask about their risks of developing cranial tremors.