123I-ALTROPANE® Reference Image Acquisition in Subjects With Diagnostically Uncertain Tremor

Inclusion Criteria: 1. Subjects must provide written informed consent prior to the initiation of any study related procedures; 2. Subjects ≥ 40 years of age; 3. Subjects with upper extremity tremor for \< 2 years duration. Exclusion Criteria: 1. Any clinically significant acute or unstable physical or psychological illness based on medical history or physical examination at Visit 1, as determined by the Principal Investigator; 2. Any unexpected clinically significant abnormal laboratory or ECG results obtained at Visit 1 and as determined by the Principal Investigator; 3. Any history of drug, narcotic, or alcohol abuse within 2 years prior to the date of informed consent, as defined by the Diagnostic and Statistical Manual of the American Psychiatric Association, 4th Edition (DSM-IVR {American Psychiatric Association, 1994 #2}); 4. Positive urine drug screen at Visit 1; 5. Participation in an investigational drug or device clinical trial within 30 days prior to the date of informed consent; 6. Previous participation in any 123I-ALTROPANE® trial; 7. Any exposure to radiopharmaceuticals within 30 days prior to the date of informed consent; 8. Positive (+) pregnancy test at Visit 1 and/or Visit 2; 9. Breast-feeding; 10. Inability to lie supine for 1 hour; 11. Any significant active thyroid disease; 12. Known sensitivity or allergy to Iodine or Iodine containing products; 13. A history of repeated head injury or sustained severe head injury in year prior to onset of tremor; 14. A definitive diagnosis of encephalitis; 15. Any uncontrolled hypertension or diabetes; 16. Any history of cerebrovascular disease; 17. Previous evaluation by a Movement Disorder Specialist (MDS); 18. Treatment within the previous six (6) months prior to informed consent with bupropion, metoclopramide, cinnarizine, flunarizine, methylphenidate, reserpine, modafinil, alpha methyldopa, amphetamine, or any anti-psychotic medication; 19. Any treatment with anti-Parkinson's drugs or anti-tremor medications within three (3) months prior to the date of the subject signing the informed consent; 20. Any new prescription or change in dose of medications for chronic conditions within four (4) weeks of Visit 2.