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.

Shaky drawing: what is the rate of decline during prospective follow-up of essential tremor?

OBJECTIVE: Few studies have attempted to estimate the rate of decline over time in essential tremor (ET). The study objectives were to: (1) measure change, deriving a single summary measure for the entire group, and relate it to a commonly used clinical rating scale (ie, yearly change in points on that scale); (2) to assess change as a function of baseline clinical characteristics and (3) to answer the basic clinical question-is change perceptible/obvious during the follow-up of ET cases? SETTING: Prospective collection of longitudinal data on ET cases enrolled in a study of the environmental epidemiology of ET at Columbia University Medical Center (2000-2008). PARTICIPANTS: 116 unselected ET cases. INTERVENTIONS: Each case underwent the same evaluation at baseline and during one follow-up visit (mean follow-up interval (range)=5.8 (1.4-12.4) years). PRIMARY AND SECONDARY OUTCOME MEASURES: We assessed tremor during a commonly affected daily activity-drawing (ie, spirography), quantifying tremor using a simple, standardised 10-point rating scale developed by Bain and Findley. RESULTS: The Bain and Findley spiral score increased at an average rate of 0.12±0.23 points per year (maximum=1 point/year). In cases who had been followed for ≥5 years, the change was obvious-a blinded neurologist was able to correctly order their spirals (baseline vs follow-up) in three-fourth of cases. The rate of change was higher in cases with versus without familial ET (p=0.01). CONCLUSIONS: Tremor in ET is slowly progressive; yet in the majority of cases, a clear difference in handwritten spirals was visible with a follow-up interval of five or more years. There may be differences between familial and non-familial ET in the rate of progression. These clinical data are intended to aid in the prognostic discussions that treating physicians have with their patients with ET.