SERUM AMINO-ACID LEVELS AS A POSSIBLE DIAGNOSTIC DIFFERENTIATION BETWEEN ESSENTIAL TREMOR AND PARKINSONIAN TREMOR

When tremor is the presenting symptom, a differential diagnosis betwee n early stages of essential (familial) tremor and Parkinson's disease is extremely difficult. In this study, we measured the levels of 17 am ino acids in the serum of patients with tremor as an early symptom of confirmed essential tremor or Parkinson's disease. The arginine and me thionine levels were significantly lower in Parkinson's patients than in controls, whereas valine levels were elevated. In contrast, the amo unts of asparagine, serine, glutamine, arginine, tyramine, methionine, isoleucine and lysine were all lower in patients with essential tremo r than in controls. Glutamine, glycine, tyrosine, alanine, methionine and isoleucine levels were significantly different between Parkinson's and essential tremor patients. We propose that a consideration of the levels of amino acids may be a useful diagnostic criterion, aiding th e discrimination and thus early appropriate treatment of the two disor ders.