[Essential tremor: a follow-up study].

41 patients who had been diagnosed as having essential tremor at least two years previously have been controlled. In 39 cases this diagnosis was confirmed. One patient was completely symptom-free after bilateral thalamotomy and another patient was now considered to have Parkinson's disease which had been discussed already four years before. 61% of the patients gave a positive family history for essential tremor, only two had non-first degree relatives suffering from Parkinson's disease. The present study does not provide any evidence for a correlation between essential tremor and Parkinson's disease. However, it should be noted that discrete other "extrapyramidal" signs may occasionally be found in patients having essential tremor.