title: 128-channel somatosensory evoked potentials in the differential diagnosis of parkinsonian disorders.
abstract: OBJECTIVE
  The differential diagnosis of parkinsonian disorders can be very difficult, especially at an early stage. In this study, we investigated whether SEP amplitude recorded by 128-channel EEG is useful for diagnosis of parkinsonian disorders, and in particular whether SEP asymmetry can differentiate corticobasal degeneration (CBGD) from other parkinsonian disorders.
  
  
  METHODS
  We recorded median nerve SEPs in 47 patients suspected of CBGD, supranuclear palsy or definite Parkinson's disease at an early stage. We compared SEP asymmetry and parietal peak amplitudes of the patients after grouping them based on their clinical diagnosis after 1-5 years of follow-up. In nine subjects the diagnosis remained unclear.
  
  
  RESULTS
  Three of 13 patients with a clinical diagnosis of CBGD had an abnormal SEP asymmetry. Furthermore, we found extremely high N20 amplitudes in three other patients with CBGD. However, similar asymmetry abnormalities were found in patients with other Parkinsonian disorders.
  
  
  CONCLUSIONS
  Despite the use of 128-channel SEP recordings and analysis techniques, which are more accurate than conventional techniques, sensitivity and specificity of cortical median nerve SEP asymmetry and parietal amplitude for differentiating CBGD from other parkinsonian disorders were low at an early stage of the disease. A possible reason for this may be that the hand area of the primary somatosensory cortex was not yet affected in most CBGD patients.
authors.affiliation: Department of Neurology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands. w.j.g.van.de.wassenberg@neuro.umcg.nl
authors.forename: W J G
authors.initials: WJ
authors.lastname: van de Wassenberg
authors.forename: J H
authors.initials: JH
authors.lastname: van der Hoeven
authors.forename: K L
authors.initials: KL
authors.lastname: Leenders
authors.forename: N M
authors.initials: NM
authors.lastname: Maurits
mesh_terms: D000368:Aged; D003937:Diagnosis, Differential; D004569:Electroencephalography / Q000379:methods*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000502:physiology; D008875:Middle Aged; D020734:Parkinsonian Disorders / Q000175:diagnosis* / Q000503:physiopathology*; D011446:Prospective Studies; D012189:Retrospective Studies; D013494:Supranuclear Palsy, Progressive / Q000175:diagnosis / Q000503:physiopathology