Long duration asymmetrical postural tremor is likely to predict development of Parkinson's disease and not essential tremor: clinical follow up study of 13 cases.

BACKGROUND: Patients presenting with asymmetrical postural tremor with or without mild rest tremor may be diagnosed as having essential tremor (ET), although there is considerable diagnostic uncertainty as to the long term outcome of these patients.
OBJECTIVE: In this study, retrospective observations were made on 13 patients presenting originally with asymmetrical postural tremor, initially thought to have ET based on tremor characteristics, alcohol responsiveness, and family history but who subsequently met the criteria of Parkinson's disease (PD).
METHODS: The patients were observed and followed up clinically with ancillary imaging using dopamine transporter SPECT scan or levodopa challenge tests in some cases. The diagnosis at original presentation with postural tremor was made with retrospective case note review.
RESULTS: After a variable and long latent period all patients developed additional signs suggesting a clinical diagnosis of PD although picking up an initial label of ET.
CONCLUSIONS: We suggest exercising caution regarding a diagnosis of ET in patients presenting with late onset asymmetrical postural tremor even if there is no rest tremor. Alcohol sensitivity of tremor, family history of tremor, or responsiveness to beta blockers may not be helpful in diagnosing ET in these cases and some may develop PD in the long term.