The aim of this interventional study is to compare the response to alcohol in patients with essential tremor (ET), essential tremor plus (ETplus), dystonic tremor (DT), tremor associated with dystonia (TaD) and tremor in Parkinson´s disease (PD). The main question to be answered is:

• Is there a difference in the objective alcohol responsiveness of patients with ET, DT, TaD and PD?

Participants will receive either vodka with rum-flavoured orange juice with a target blood alcohol of 0.4 ‰ or a non-alcoholic rum-flavoured orange juice (vice versa on the second study day). Before and 30, 60 an 120 minutes after the study drink the participants will undergo a clinical examination of the tremor and accelerometry will be performed.

Researchers will compare alcohol and placebo in a randomized cross over way to see if the effect of alcohol on tremor exceeds the placebo effect.

The researchers will include 45 patients (9 each) with essential tremor (ET), essential tremor plus (ETplus), dystonic tremor (DT), tremor associated with dystonia (DaT) or tremor in Parkinson´s disease (PD) from the Movement Disorders Outpatients Clinic of the Medical University of Graz.

Participants will be asked to stop any tremor influencing medication and alcohol intake 24 hours before testing. 4 hours before testing the participants should not eat or drink anything. The participants will be asked to bring an accompanying person and are not allowed to drive at the day of the study visit.

Each participant will be examined at two different days (intervention and placebo day) with at least one day in between. During the study participation the tremor influencing medication should not be changed. The study design is a randomized cross sectional design where each participant receives either alcohol or placebo and vice versa on the second study day. The participants will be asked to finish the study drink within 15 minutes.

Interventional day:

Participants will receive vodka with rum flavored orange juice with a target blood alcohol of 0.4 ‰ 30 minutes after alcohol consumption. The required amount of vodka will be calculated with the Widmark formula.

Placebo day:

Participants will receive non-alcoholic rum flavored orange juice.

Baseline examinations:

• Questionnaire (only on the first study visit): demographics, disease duration, onset of disease, alcohol drinking habits and noticed effects of alcohol on tremor
• Movement Disorders Society Unified Parkinson's Disease Rating Scale (MDS-UPDRS)
• The Essential Tremor Ranking Scale (TETRAS)
• The Burke-Fahn-Marsden (BFM) Dystonia Rating Scale
• Placement of an indwelling venous cannula in a cubital fossa vein (for repeated blood alcohol measurements)
• Accelerometry: The participants will sit in a chair with a triaxial accelerometer transducer attached to the dorsal surface of the middle phalanx of the index finger. Each position will be recorded 30 seconds.

Recorded positions:

1. rest position: arms relaxed and hands hanging freely from the arm rest
2. posture position: arms / wrists outstretched at shoulder level

Examinations 30 minutes after the intervention (study drink):

• TETRAS Performance Subscale
• MDS-UPDRS motor examination (part III)
• BFM scale
• Accelerometry
• Evaluation of possible side effects

Inclusion Criteria:

• diagnosis of PD, DT, TaD, ET or ETplus based on clinical diagnostic criteria
• tremor in upper extremities
• accompanying person for both study visits

Exclusion Criteria:

• persons that are not willing to abstain from driving at both study days
• patients with diseases prohibiting alcohol ingestion
• patients with a history of alcohol abuse
• pregnancy