Aaron Artiles1,2, Dietrich Haubenberger MD1, Silvina Horovitz PHD1, Bernard Voller MD1, Emily Lines BA1, Gayle McCrossin RN1, Vijay Ramchandani PHD3, Vatsalya Vatsalya MD3, Sherry Vorbach1, Sule Tinaz MD1, Rainer Paine MD1, Codrin Lungu MD1, Mark Hallett MD1
1Human Motor Control Section, Medical Neurology Branch, NINDS/NIH, Bethesda, MD;
2Boston College, Chestnut Hill, MA;
3Laboratory of Clinical and Translational Studies, NIAAA/NIH, Bethesda, MD
Essential Tremor (ET) is a common movement disorder characterized by action tremor mainly involving arms and hands in 95% of ET patients. Tremor is less common in other parts of the body including head, face, legs, and voice. According to historical information, alcohol (ethanol) is known to suppress these movements in approximately two thirds of ET patients. Tremor can be measured objectively using neurophysiological techniques such as digital spiral analysis. The aim of this study was to investigate whether alcohol levels differ between ET patients defined as ethanol responders and non-responders. We looked at whether subjective response to ethanol predicts objective response. Furthermore, we investigated subjectively rated non-tremor effects of ethanol in patients with ET and again compared responders versus non-responders.
Under a protocol investigating the neurophysiological correlates of the ethanol-response in ET (CNS IRB #10-N-0199), 66 patients diagnosed with ET were asked to consume a standardized drink of 95% ethanol (dose calculated using total body water estimate, diluted 1:3 with a vehicle) with the goal of reaching a peak breath alcohol content (BrAC) of 0.05 g/dl. Frequency and amplitude of the tremor was measured objectively using digital spirography as described before (Haubenberger et al, 2011). Patients drew spirals on a tablet PC using custom software (Neuroglyphics). Patients were asked to draw spirals on the tablet before, and every 20 minutes following alcohol administration. Response to ethanol was defined as a 35% or more decrease in tremor amplitude of the dominant hand at the 60-minute time point compared to the baseline amplitude. In addition, before the study patients indicated their subjective tremor response to alcohol (yes, no, or uncertain). Patients were asked to complete standardized questionnaires on biphasic effects of ethanol (BAES), as well as general drug effects (with alcohol being the drug, “Drug Effects Questionnaire”) and urge to drink alcohol (Alcohol Urge Questionnaire), every 20 minutes during the study after administration. Patients with hazardous alcohol consumption or possible alcoholism (defined per AUDIT score of ≥8) were excluded from the study. The aim of this study was to describe the relationship between breath alcohol levels and tremor measures and screen for potential group differences between responders and non-responders using descriptive statistics, as this is an ongoing study.
There was a significant correlation found between tremor amplitude and BrAC (Pearson r=-0.247, p<0.001). Also, a difference was seen in BrAC between the responder and non-responder groups at the 20, 40, and 60 minute time points. This BrAC difference was reflected by a difference in drug feel and feeling of intoxication between the two response groups at the 0, 20, and 40 minute time points. Finally, no difference was seen between the three subjective response groups in BrAC or tremor amplitude.
Our results show that there is a statistically significant correlation between tremor amplitude and BrAC. Also, non-responders seem to have lower alcohol levels than non-responders. These findings suggest that tremor response is dependent on the alcohol level. Therefore, whether somebody would be considered a responder or non-responder depends on the level of alcohol. Finally, we found no difference in BrAC or tremor response to alcohol between subjective responder groups. This indicates that subjective response to ethanol does not predict if a patient will actually respond.
Last updated November 26, 2013