title: Movement-related beta responses in essential tremor and Parkinson's disease.
abstract: OBJECTIVE
  To investigate the pathomechanism of essential (ET) and parkinsonian tremor (PT) by studying the correlation between tremor severity and movement-related beta rhythm changes of the human electroencephalogram.
  
  
  METHODS
  We recorded the electroencephalogram of 10 patients with essential tremor, 10 with Parkinsonian tremor and 10 controls. In a preliminary session we determined the side with lower and higher tremor intensity (T+, T++ respectively), using accelerometry. Subjects pressed an on-off switch in a self-paced manner with left and right thumb. After digitalization of the EEG from Cz, C3, C4 electrodes, the movement reactive beta frequency (MRBF), its minimum/maximum peak power values and their latencies triggered to movement offset were determined.
  
  
  RESULTS
  The time course and amplitude of movement related beta desynchronization (ERD) were similar in each group regardless of tremor intensity. In ET tremor severity did not influence post-movement beta synchronization (PMBS) amplitude (PMBS(ET+) = 100.98 +/- 48.874%, PMBS(ET++) = 135.1 +/- 92.87%; p = 0.231), however it was significantly delayed after the movement of the more tremulous hand (latPMBS(ET+) = 1.26 +/- 0.566 s, latPMBS(ET++) = 1.57 +/- 0.565 s, p = 0.003). In the PT group on the side of pronounced tremor the amplitude of PMBS decreased but it was not delayed, compared to the less affected hand (PMBS(PT+) = 115.19 +/- 72.131%, PMBS(PT++) = 77.84 +/- 53.101%, p = 0.0028; latPMBS(PT+) = 1.4 +/- 0.74 s, latPMBS(PT++) = 1.25 +/- 0.797 s, p = 0.191). In controls the power and latency of PMBS was similar on both sides.
  
  
  CONCLUSIONS
  The results suggest that neuronal mechanisms underlying PMBS generation are differently affected by ET and PT. Investigation of PMBS might be used for the differential diagnosis of essential tremor and Parkinson's disease.
authors.affiliation: Semmelweis Egyetem, Altalános Orvostudományi Kar, Neurológiai Klinika, Budapest.
authors.forename: Gertrúd
authors.initials: G
authors.lastname: Tamás
authors.forename: László
authors.initials: L
authors.lastname: Pálvölgyi
authors.forename: Annamária
authors.initials: A
authors.lastname: Takáts
authors.forename: Imre
authors.initials: I
authors.lastname: Szirmai
authors.forename: Anita
authors.initials: A
authors.lastname: Kamondi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001611:Beta Rhythm; D004569:Electroencephalography; D020329:Essential Tremor / Q000503:physiopathology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009068:Movement; D010300:Parkinson Disease / Q000503:physiopathology*; D012720:Severity of Illness Index