***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Neuroimaging is known to complement clinical findings in the diagnostic work up of parkinsonian syndromes . Recently , transcranial ultrasound was reported to have a high diagnostic yield in differentiating idiopathic Parkinson ’s disease ( IPD ) from atypical parkinsonian syndromes . This report summarises the sonographic findings of 102 patients with IPD , 34 patients with multiple system atrophy , and 21 patients with progressive supranuclear palsy .  Increased echogenicity of the substantia nigra is predictive for IPD whereas a low echogenic substantia nigra , particularly when combined with a hyperechogenic lentiform nucleus , strongly suggests an atypical Parkinsonian syndrome . The underlying causes for the differential echo pattern of the substantia nigra remain unknown 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 prospect i ve 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 Background Essential tremor ( ET ) and Parkinson ’s disease ( PD ) are considered distinct disorders . The aim of the study was to look for a link or any distinguishing features by transcranial sonography ( TCS ) , together with the clinical examination findings in a group of patients with overlapping phenotype of ET and PD ( ET-PD ) . Methods A prospect i ve observational case-control study was carried out from the 3rd January 2011 until 30th January 2013 at the Hospital of Lithuanian University of Health Sciences . The final study group consisted of 15 patients with ET-PD , 116 patients with ET-only and 141 patients with PD-only . The control group included 101 subjects . Clinical diagnosis was of a diagnostic st and ard . Results The main ultrasonographic findings in the ET-PD group were similar to those of the PD-only : hyperechogenicity of the substantia nigra ( 66.7 % , p < 0.001 ) and nuclei raphe interruptions/absence ( 38.5 % , p < 0.001 ) . The single distinguishing TCS finding in ET-PD group was a lentiform nucleus hyperechogenicity ( 26.7 % ) , however this was only significant when compared to controls ( p = 0.006 ) . An asymmetrical onset of symptoms ( 73.3 % ) in ET-PD group was characteristic to PD-only . The ET-PD patients had the longest disease duration ( median 6 years , p < 0.001 ) , the most frequent rate of positive family history ( 53.3 % , p = 0.005 ) , rather low prevalence of cogwheel rigidity ( 26.7 % , p < 0.001 ) , and higher mean Hoehn & Yahr scores compared to PD-only ( 2.6 ± 0.8 vs. 1.8 ± 0.8 , p = 0.012 ) . Conclusions The main TCS findings of the present study in patients with overlapping ET-PD phenotype were similar to the PD-only group . The highest positive family history rate among ET-PD patients indicates a strong hereditary predisposition and needs genetic underpinnings . Some ET patients , who look like they may be developing co-morbid PD clinical ly , may have an alternative diagnosis for Parkinsonism , which could be delineated by TCS examination Background This study examines the clinical accuracy of movement disorder specialists in distinguishing tremor dominant Parkinson 's disease ( TDPD ) from other tremulous movement disorders by the use of st and ardised patient videos . Patients and methods Two movement disorder specialists were asked to distinguish TDPD from patients with atypical tremor and dystonic tremor , who had no evidence of presynaptic dopaminergic deficit ( subjects without evidence of dopaminergic deficit ( SWEDDs ) ) according to 123I-N-ω-fluoro-propyl- 2β-carbomethoxy-3β-(4-iodophenyl ) nortropane ( [ 123I ] FP-CIT ) single photon emission computed tomography ( SPECT ) , by ‘ blinded ’ video analysis in 38 patients . A diagnosis of parkinsonism was made if the step 1 criteria of the Queen Square Brain Bank criteria for Parkinson 's disease were fulfilled . The review er diagnosis was compared with the working clinical diagnosis drawn from the medical history , SPECT scan result , long term follow-up and in some cases the known response to dopaminergic medications . This comparison allowed a calculation for false positive and false negative rate of diagnosis of PD . Results High false positive ( 17.4 - 26.1 % ) and negative ( 6.7 - 20 % ) rates were found for the diagnosis of PD . The diagnostic distinction of TDPD from dystonic tremor was reduced by the presence of dystonic features in treated and untreated PD patients . Conclusion Clinical distinction of TDPD from atypical tremor , monosymptomatic rest tremor and dystonic tremor can be difficult due to the presence of parkinsonian features in tremulous SWEDD patients . The diagnosis of bradykinesia was particularly challenging . This study highlights the difficulty of differentiation of some cases of SWEDD from PD BACKGROUND In several pilot studies , transcranial brain sonography findings of substantia nigra and lenticular nucleus discriminated between idiopathic Parkinson disease ( PD ) and atypical parkinsonian disorders . OBJECTIVE To study the use of transcranial brain sonography in excluding the diagnosis of idiopathic PD in patients with sporadic parkinsonism . DESIGN AND SETTING All patients with parkinsonism admitted to our movement disorder clinic from January 1 , 2003 , through December 31 , 2005 , who fulfilled clinical diagnostic criteria for definite PD , probable parkinsonian variant of multiple-system atrophy ( MSA-P ) , or probable progressive supranuclear palsy ( PSP ) were prospect ively studied with transcranial brain sonography by an investigator blinded to clinical diagnoses . Patients Eligible patients included 138 with sporadic idiopathic PD ( 82 men and 56 women ; mean + /- SD age , 67.1 + /- 9.8 years ; mean + /- SD disease duration , 7.5 + /- 6.3 years ; mean + /- SD motor score on the Unified Parkinson Disease Rating Scale , 32.6 + /- 18.1 ) , 21 with MSA-P ( 10 men and 11 women ; mean + /- SD age , 65.4 + /- 9.5 years ; mean + /- SD duration of disease , 3.1 + /- 2.0 years ; mean + /- SD motor score , 33.5 + /- 16.1 ) , and 22 with PSP ( 13 men and 9 women ; mean + /- SD age , 71.2 + /- 5.5 years ; mean + /- SD duration of disease , 3.4 + /- 2.4 years ; mean + /- SD motor score , 46.2 + /- 18.9 ) . In 7 patients , transcranial brain sonography was not possible owing to insufficient temporal acoustic bone windows . MAIN OUTCOME MEASURES Sensitivity , specificity , and predictive value of transcranial brain sonography  in indicating an atypical parkinsonian syndrome rather than idiopathic PD in patients with sporadic parkinsonism . RESULTS Normal echogenic substantia nigra indicated MSA-P rather than PD ( sensitivity , 90 % ; specificity , 98 % ; positive predictive value , 86 % ) , whereas third-ventricle dilatation of more than 10 mm in combination with lenticular nucleus hyperechogenicity indicated PSP rather than PD ( sensitivity , 84 % ; specificity , 98 % ; positive predictive value , 89 % ) . Normal echogenic substantia nigra combined with lenticular nucleus hyperechogenicity indicated MSA-P or PSP ( sensitivity , 59 % ; specificity , 100 % ; positive predictive value , 100 % ) . In parkinsonism with age at onset younger than 60 years , normal echogenic substantia nigra alone indicated MSA-P or PSP ( sensitivity , 75 % ; specificity , 100 % ; positive predictive value , 100 % ) . CONCLUSIONS Distinct transcranial brain sonography findings can exclude the diagnosis of PD in patients with sporadic parkinsonism . Sonographic discrimination of atypical parkinsonian syndromes from PD is clearer in patients with onset of parkinsonism at younger than 60 years BACKGROUND AND OBJECTIVE Publication bias and other sample size effects are issues for meta-analyses of test accuracy , as for r and omized trials . We investigate limitations of st and ard funnel plots and tests when applied to meta-analyses of test accuracy and look for improved methods . METHODS Type I and type II error rates for existing and alternative tests of sample size effects were estimated and compared in simulated meta-analyses of test accuracy . RESULTS Type I error rates for the Begg , Egger , and Macaskill tests are inflated for typical diagnostic odds ratios ( DOR ) , when disease prevalence differs from 50 % and when thresholds favor sensitivity over specificity or vice versa . Regression and correlation tests based on functions of effective sample size are valid , if occasionally conservative , tests for sample size effects . Empirical evidence suggests that they have adequate power to be useful tests . When DORs are heterogeneous , however , all tests of funnel plot asymmetry have low power . CONCLUSION Existing tests that use st and ard errors of odds ratios are likely to be seriously misleading if applied to meta-analyses of test accuracy . The effective sample size funnel plot and associated regression test of asymmetry should be used to detect publication bias and other sample size related effects Transcanial sonography ( TCS ) is increasingly applied in the diagnosis of Parkinson 's disease ( PD ) , but investigator bias may influence the results of examination . Blinding the sonographer to the clinical diagnosis of 42 PD patients and 35 controls , we obtained a positive predictive value of 85.7 % and a negative predictive value of 82.9 % in the diagnosis of PD solely by interpreting the results of TCS , indicating that TCS is a valuable additional tool in the diagnosis of PD Article abstract -To detect morphologic abnormalities in Parkinson 's disease ( PD ) , we examined 30 patients with PD and 30 age- and sex-matched nonparkisonian controls by transcranial color-coded real-time sonography ( TCCS ) . In 12 severely affected PD patients , the echogenicity of the substantia nigra was distinctly increased . In the remaining 18 PD patients and in all controls , the substantia nigra was poorly visualized or nondetectable by TCCS . The 
    Output:
    
Our systematic review of the literature and meta- analysis suggest that  TCS has high diagnostic accuracy in the diagnosis of PD when compared to healthy control