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Front Neurol. 2018 Jul 13;9:570. doi: 10.3389/fneur.2018.00570. eCollection 2018.

Transient, Isolated Head Tremor in "Unaffected" Individuals: Is Essential Tremor an Even More Prevalent Disease Than We Suppose?

Author information

1
Department of Neurology, Yale School of Medicine, Yale University, New Haven, CT, United States.
2
Department of Chronic Disease Epidemiology, Yale School of Public Health, Yale University, New Haven, CT, United States.
3
Center for Neuroepidemiology and Clinical Neurological Research, Yale School of Medicine, Yale University, New Haven, CT, United States.
4
Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY, United States.
5
Taub Institute for Research on Alzheimer's Disease and the Aging Brain, College of Physicians and Surgeons, Columbia University, New York, NY, United States.
6
Department of Pathology and Cell Biology, Columbia University Medical Center, New York, NY, United States.
7
G.H. Sergievsky Center, College of Physicians and Surgeons, Columbia University, New York, NY, United States.
8
Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY, United States.
9
Division of Epidemiology, New York State Psychiatric Institute, New York, NY, United States.

Abstract

Background: Mild and transient head tremor may sometimes be observed in otherwise tremor-free relatives of essential tremor (ET) cases, although its prevalence is unclear. A diagnostic question is whether this transient, isolated head tremor, often observed as no more than a wobble, is an early manifestation of ET or whether it is a normal finding. A direct comparison with controls is needed. Methods: Two hundred and forty-one first-degree relatives of ET cases (FD-ET) and 77 spousal controls (Co) were enrolled in a study of ET. Each underwent a detailed evaluation that included a tremor history and videotaped neurological examination. None of the enrollees reported tremor, had a prior diagnosis of ET, or had significant tremor on screening spirals. All videotaped examinations were initially reviewed by a movement disorder neurologist blinded to subject type, and among those with head tremor on examination, co-reviewed by two additional movement disorders neurologists. Results: Twenty-six (10.8, 95% Confidence interval [CI] = 7.5-15.3%) of 241 FD-ET vs. 2 (2.6, 95% CI = 0.7-9.0%) of 77 Co had isolated, transient head tremor (odds ratio = 4.54, 95% CI = 1.05-19.57, p = 0.04). No enrollee had significant upper extremity tremor and none met inclusion criteria for ET based on the presence of upper extremity tremor. With one exception, head tremor occurred during or after phonation. It was always transient (generally a single back and forth wobble) and rare (observed briefly on one or two occasions during the videotaped examination) and had a faster frequency, lower amplitude and a different quality than voluntary head shaking. Conclusion: The basis for the observed isolated head tremor is unknown, but it could be an early feature of ET in ET families.Indeed, one-in-ten otherwise unaffected first-degree relatives of ET cases exhibited such tremor. To a far lesser extent it was also observed in "unaffected" controls. In both, it is likely a sign of early, emerging, undiagnosed ET, although follow-up studies are needed to confirm this. If it were ET, it would indicate that the prevalence of ET may be considerably higher than previously suspected.

KEYWORDS:

clinical; diagnosis; diagnostic misclassification; epidemiology; essential tremor; genetics; head tremor; prevalence

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