title: Specificity of transcranial sonography in parkinson spectrum disorders in comparison to degenerative cognitive syndromes.
abstract: BACKGROUND
  Hyperechogenicity of the substantia nigra (SN+), detected by transcranial sonography (TCS), was reported as a characteristic finding in Parkinson's disease (PD), with high diagnostic accuracy values, when compared mainly to healthy controls or essential tremor (ET) group. However, some data is accumulating that the SN + could be detected in other neurodegenerative and even in non-neurodegenerative disorders too. Our aim was to estimate the diagnostic accuracy of TCS, mainly focusing on the specificity point, when applied to a range of the parkinsonian disorders, and comparing to the degenerative cognitive syndromes.
  
  
  METHODS
  A prospective study was carried out at the Hospital of Lithuanian University of Health Sciences from January until September 2011. Initially, a TCS and clinical examination were performed on 258 patients and 76 controls. The General Electric Voluson 730 Expert ultrasound system was used. There were 12.8% of cases excluded with insufficient temporal bones, and 4.3% excluded with an unclear diagnosis. The studied sample consisted of the groups: PD (n = 71, 33.2%), ET (n = 58, 27.1%), PD and ET (n = 10, 4.7%), atypical parkinsonian syndromes (APS) (n = 3, 1.4%), hereditary neurodegenerative parkinsonism (HDP) (n = 3, 1.4%), secondary parkinsonism (SP) (n = 23, 10.8%), mild cognitive impairment (MCI) (n = 33, 15.4%), dementia (n = 13, 6.1%), and control (n = 71).
  
  
  RESULTS
  There were 80.3% of PD patients at stages 1 & 2 according to Hoehn and Yahr. At the cut-off value of 0.20 cm² of the SN+, the sensitivity for PD was 94.3% and the specificity - 63.3% (ROC analysis, AUC 0.891), in comparison to the rest of the cohort. At the cut-off value of 0.26 cm², the sensitivity was 90% and the specificity 82.4%.The estimations for the lowest specificity for PD, in comparison to the latter subgroups (at the cut-off values of 0.20 cm² and 0.26 cm², respectively) were: 0% and 33.3% to APS, 33.3% and 66.7% to HDP, 34.8% and 69.6% to SP, 55.2% and 82.8% to ET, 75% and 91.7% to dementia.
  
  
  CONCLUSIONS
  The high sensitivity of the test could be employed as a valuable screening tool. But TCS is more useful as a supplementary diagnostic method, due to the specificity values not being comprehensive.
authors.affiliation: Department of Neurology, Lithuanian University of Health Sciences, Academy of Medicine, Mickevičiaus street 9, Kaunas, Lithuania. kristina.lauckaite@lsmuni.lt
authors.forename: Kristina
authors.initials: K
authors.lastname: Laučkaitė
authors.forename: Daiva
authors.initials: D
authors.lastname: Rastenytė
authors.forename: Danguolė
authors.initials: D
authors.lastname: Šurkienė
authors.forename: Antanas
authors.initials: A
authors.lastname: Vaitkus
authors.forename: Andrius
authors.initials: A
authors.lastname: Sakalauskas
authors.forename: Arūnas
authors.initials: A
authors.lastname: Lukoševičius
authors.forename: Rymantė
authors.initials: R
authors.lastname: Gleiznienė
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging*; D003704:Dementia / Q000000981:diagnostic imaging; D020329:Essential Tremor / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010300:Parkinson Disease / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D010302:Parkinson Disease, Secondary / Q000000981:diagnostic imaging*; D020734:Parkinsonian Disorders / Q000175:diagnosis* / Q000000981:diagnostic imaging*; D011237:Predictive Value of Tests; D011446:Prospective Studies; D012680:Sensitivity and Specificity; D013378:Substantia Nigra / Q000000981:diagnostic imaging*; D014463:Ultrasonography