Abstract
Atypical parkinsonian disorders (APD), such as progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal syndrome (CBS), and Lewy body dementia (LBD) are frequently misdiagnosed, commonly as Parkinson’s disease (PD). The study aims to assess the utility of the interpeduncular angle (IPA) in distinguishing APD from PD across age ranges. This retrospective study was conducted with 225 patients (75 with APD, 75 with PD, and 75 healthy controls). Patients were categorized into three age groups: (51–60, 61–70, and 71–80 years). Two independent raters measured the IPA from T1-weighted axial brain magnetic resonance images (MRIs) at a level below the mammillary bodies using standardized measurement techniques. The APD group included 51 (68%) with PSP, 16 (21.33%) with MSA, 5 (6.67%) with LBD, and 3 (4%) with CBS. Bland-Altman analysis for angle measurement suggested good to excellent agreement between raters (P < 0.001). IPA measurements among the different diagnostic groups showed that PSP was higher than controls (P < 0.001) and PD (P < 0.001), and MSA was higher than controls (P < 0.001) and PD (P = 0.003). There was no significant association between IPA and age in the APD phenotypes. With increasing age, the significance between APD and IPD groups decreased (P < 0.001 in 51–60 years to P = 0.686 in 71–80 years). Receiver Operating Characteristic (ROC) analysis revealed increasing IPA thresholds for PSP versus PD (67.66° in 51–60 years to 75.71° in 71–80 years). IPA is not reliable in differentiating APD, particularly PSP and MSA, from PD and controls.
Keywords: Atypical Parkinsonism, interpeduncular angle, Parkinson’s disease, progressive supranuclear palsy, MRI
Introduction
Atypical parkinsonian disorders (APD), such as progressive supranuclear palsy (PSP), multiple system atrophy (MSA), Lewy body dementia (LBD), and corticobasal syndrome (CBS), often present with features such as early dementia, frequent falls, or ataxia.[1] Rapid functional decline is frequently observed in APD compared to Parkinson’s disease (PD), making early diagnosis essential. However, misdiagnoses are common in the early stages, with high error rates in clinical diagnosis even at specialized centers.[2] Variation in management strategies underscores the need for an objective method to distinguish these diseases. For example, PSP shows midbrain and superior cerebellar peduncular atrophy on brain magnetic resonance imaging (MRI), often described as a “hummingbird” or “mickey mouse” sign.[1] These signs are subjective and not easily standardized.
A possible objective radiological marker is the interpeduncular angle (IPA), defined as the angle subtended by the medial aspects of the cerebral peduncles, with the posterior-most point of the interpeduncular cistern representing the vertex.[3] Previous studies have shown an association between IPA widening and certain atypical neurodegenerative disorders such as PSP.[4,5,6] Additionally, no available literature describes IPA as a diagnostic marker in an Indian population, highlighting an unmet need for this study. This study therefore aims to assess the diagnostic effectiveness of IPA as an objective criterion in differentiating APD from PD.
Methods
Study population
This retrospective study was initiated after obtaining institutional ethical approval. Patients clinically diagnosed with APD (PSP, MSA, CBS, and LBD as per the latest diagnostic criteria) and PD were identified, and their electronic medical records were used to retrospectively verify their diagnosis. The chosen patients were categorized into three age groups (51-60, 61-70, and 71-80 years) and compared with a control population. The criteria for the control group required that patients be free of structural brain disease (space-occupying lesions and large infarcts) and have available brain MRI scans. These included patients evaluated for headache who were found to have no neurological abnormalities and patients with minute lacunar infarcts that did not interfere with integral anatomical landmarks significant in determining IPA.
Image selection
MRI scans were available for all patients. The MRI was performed at 1.5 T (1.5 Tesla GE HDxt MRI Scanner) or 3.0 T (3 Tesla GE Discovery MR750 3T MRI Machine) with a slice thickness of 4 mm and a 1 mm gap. MRI scans showing irregular interpeduncular cistern contours were excluded. We used 2-Dimensional (2D) axial spin-echo T1-weighted slices (owing to comparatively higher anatomical detail) taken parallel to the Anterior Commissure-Posterior Commissure line using sagittal slices. These axial slices at the level of the mammillary bodies or immediately below, as proposed previously, were pre-selected prior to angle measurement and read on Picture Archiving and Communication System software.[7]
Angle measurement
We considered the IPA to be the angle measured by the medial aspects of the cerebral peduncles, with the posteriormost midline point of the interpeduncular cistern representing the vertex of the angle, and adopted the method of a previous study that classified images based on inflection points (the point at which the curvature shows a sudden visible change) on the medial border of the peduncles.[3,6] Type 1 IPA was observed in midbrain sections without bilateral inflections [Figure 1a and b], while Type 2 IPA showed one or two inflection points [Figure 1d and e]. Midbrain sections without bilateral inflection points (those with a unilateral or no inflection point) were classified as Type 1 [Figure 1a and b], while those with bilateral inflection points were classified as Type 2 [Figure 1dande]. Due to the curvilinearity of Type 2 images, two angle measurements were taken. Type 1 and Type 2 ϴ1 angles were measured by drawing two lines parallel to the medial borders of the midbrain peduncle on either side and estimating the angle subtended by the two lines [Figure 1c]. The Type 2 ϴ2 angle was measured as the angle subtended by the inflection points on either side of the peduncles, using the same vertex as the Type 2 ϴ1 angle [Figure 1f]. Measurements were made at 200% magnification, independently by two investigators who were blinded to the patient’s diagnosis, and verified by a trained neuroradiologist.
Figure 1.
(a) T1-weighted MRI at the level below the mammillary bodies with a V-shape between the cerebral peduncles, classified as Type 1. (b) Image A with vertex (marked in yellow) and medial aspects of the cerebral peduncles (green arrows). (c) Image A showing Type 1 IPA measurement. (d) T1-weighted MRI at the level below the mammillary bodies with a U-shape between the cerebral peduncles, classified as Type 2. (e) Image D with vertex (marked in yellow), medial aspects of the cerebral peduncles (green arrows), and bilateral inflection points (blue arrows). (f) Image B showing Type 2 IPA measurement (θ1 in yellow, θ2 in green). IPA: interpeduncular angle, MRI: Magnetic Resonance Imaging
Statistical analysis
Observations were expressed as mean and standard deviation. The intra-class correlation coefficient (ICC) was performed to assess inter-rater agreement of IPA measurements. One-way Analysis of Variance (ANOVA) and posthoc testing was used to assess statistical significance, with Bonferroni multiple comparison as the posttest. Receiver Operating Characteristic (ROC) curve analysis was employed to determine the threshold value of IPA that would best differentiate the three groups. All statistical analyses were performed using International Business Machines Statistical Package for Social Sciences (SPSS) Statistics (Version 21).
Results
Out of 239 patients, 14 were excluded due to irregular MRI interpeduncular cistern contours. The 225 patients included in the study were categorized based on their primary diagnosis [atypical parkinsonism (n = 75), PD (n = 75), or healthy controls (HC) (n = 75)]. A total of 75 patients (atypical parkinsonism (n = 25), PD (n = 25), HC (n = 25) were collected in each age group. Male preponderance was observed overall (75.11%). Further demographic details are mentioned in Table 1.
Table 1.
Demographic data
| Variables | N=225 |
|---|---|
| Sex | |
| Male | 169 (75.11%) |
| Female | 56 (24.89%) |
| Age | |
| 51–60 years | 75 (33.3%) |
| 61–70 years | 75 (33.3%) |
| 71–80 years | 75 (33.3%) |
| Diagnosis | |
| Atypical Parkinsonism | 75 (33.3%) |
| Parkinson’s Disease | 75 (33.3%) |
| Healthy Controls | 75 (33.3%) |
| IPA Angle Type | |
| Type 1 | 157 (69.78%) |
| Type 2 | 68 (30.22%) |
| Atypical Parkinsonism Phenotype (n=75) | |
| PSP | 51 (68.00%) |
| MSA-P | 9 (12.00%) |
| MSA-C | 7 (9.33%) |
| CBS | 3 (4.00%) |
| LBD | 5 (6.67%) |
All values are presented as number (%). CBS: corticobasal syndrome, IPA: interpeduncular angle, LBD: Lewy body dementia, MSA-C: multiple system atrophy-cerebellar type, MSA-P: multiple system atrophy-parkinsonian type, PSP: progressive supranuclear palsy
Midbrain sections for 157 participants were measured using the Type 1 approach, and 68 participants were measured using the Type 2 approach [Figure 1]. The ICC with a 95% confidence interval for agreement of angle measurements between both readers were 0.907 for Type 1 angles, 0.906 for Type 2ϴ1 angles, and 0.773 for Type 2ϴ2 angles (P < 0.001). All further analyses used the mean of Type 1 and Type 2ϴ1 angles from both raters, henceforth referred to as IPA. Type 2ϴ2 angles were excluded due to lower significance compared to the other measurement techniques. The Kolmogorov–Smirnov test confirmed normal data distribution.
The phenotypes of atypical parkinsonism were as follows: PSP (n = 51), MSA (n = 16, MSA-C = 9, MSA-P = 7), CBS (n = 3), and LBD (n = 5). For ease of understanding, further analysis regarding atypical parkinsonism patients—henceforth referred to as APD (n = 67)—excludes the CBS and LBD patients.
The IPA was 72.02° ± 8.87° for the PSP group, 74.26° ± 5.59° for the MSA group, 65.24 ± 10.44° for the PD group, and 63.86 ± 9.01° for the HC group [Supplementary Figure 1 (590.8KB, tif) ]. We observed that the IPA of PSP was larger than PD (P < 0.001) and HC (P < 0.001). The IPA of MSA was larger than PD (P = 0.003) and HC (P < 0.001).
There was no significance observed between IPA and age in the APD phenotypes. However, a significant association was observed with increasing age and IPA in PD (P < 0.001) and HC (P < 0.001). When comparing the primary diagnosis and IPA within age groups, it was observed that with increasing age, the significance between the APD and PD groups decreased (51–60 years [P < 0.001), 61–70 years (P < 0.001), and 71–80 years (P = 0.686). IPA in APD was consistently greater than that of HC (51–60 years (P < 0.001), 61–70 years (P = 0.027), and 71–80 years (P = 0.004)] [Table 2].
Table 2.
Comparison of interpeduncular angle (IPA) among diagnostic categories [atypical parkinsonism, idiopathic Parkinson’s Disease (IPD), and healthy controls (HC)] within each age group (51–60, 61–70, and 71–80 years)
| Age group (years) | Mean IPA |
Subgroup difference | ||
|---|---|---|---|---|
| Atypical Parkinsonism (a) | PD (b) | HC (c) | ||
| 51–60 | 71.78±9.75 | 58.23±8.00 | 57.60±8.43 | a>b; P<0.001* a>c; P<0.001* b>c; P=0.789 |
| 61–70 | 72.33±7.17 | 64.99±7.30 | 67.65±7.05 | a>b; P=0.001* a>c; P=0.027* b<c; P=0.196 |
| 71–80 | 73.63±7.58 | 72.50±10.60 | 66.34±8.21 | a>b; P=0.686 a>c; P=0.004* b>c; P=0.026* |
| Total | 72.56±8.26 | 65.24±10.44 | 63.86±9.01 | a>b; P<0.001* a>c; P<0.001* b>c; P=0.096 |
All values are presented as mean±SD. HC: healthy controls, IPA: interpeduncular angle, PD: Parkinson’s disease
ROC curves were used to determine the threshold IPA between PSP and PD for each age group [Supplementary Figure 2 (1MB, tif) ]. The 51–60 years group yielded a value of 67.66° as the threshold with a sensitivity of 68.4% and a specificity of 88.0%. The 61–70 years group yielded a value of 68.78° as the threshold with a sensitivity of 63.6% and a specificity of 68.0%. The 71–80 years group yielded a value of 75.71° as the threshold with a sensitivity of 50.0% and a specificity of 56.0%.
Another set of ROC curves were used to determine the threshold IPA between different age groups of PSP and HC [Supplementary Figure 3 (1MB, tif) ]. The 51–60 years group yielded a value of 66.39° as the threshold with a sensitivity of 70.6% and a specificity of 88.0%. The 61–70 years group yielded a value of 68.86° as the threshold with a sensitivity of 59.1% and a specificity of 56%. The 71–80 years group yielded a value of 70.58° as the threshold with a sensitivity of 58.3% and a specificity of 72.0%.
ROC curves were further employed to determine the IPA thresholds to differentiate APD from PD for each age group [Supplementary Figure 4 (1,000.5KB, tif) ]. The threshold for the 51–60 years group was 66.13°, offering 77.3% sensitivity and 80.0% specificity. For the 61–70 years group, the threshold was 68.78°, with 66.7% sensitivity and 68.0% specificity. In the 71–80 years group, the threshold increased to 68.84°, with sensitivity and specificity of 71.4% and 48.0%, respectively.
Discussion
Diagnosing neurodegenerative parkinsonism is often challenging due to variable clinical presentations, with reliance on features like vertical gaze restriction often unreliable.[1] These issues highlight the need for a reliable diagnostic marker. Advantages of IPA as a marker include its application in low-resource settings and a better learning curve.
Several criteria have been proposed to potentially identify APD, particularly PSP. These include the midbrain-to-pons ratio and the magnetic resonance parkinsonism index (MRPI), known to be highly accurate in distinguishing PSP from PD and other parkinsonian disorders.[8,9] A previous study comparing PSP and HC between different indices showed significant differences in both MRPI and IPA measurements; however, no equivalence was noted in all MRPI cases (P = 1.00), while IPA was equivalent (P < 0.01).[4]
PSP patients characteristically exhibit atrophy of superior cerebellar peduncles, midbrain tegmentum, and the periaqueductal gray matter with preserved cerebral peduncles, leading to prominent imaging signs such as the hummingbird sign and Mickey Mouse sign.[1] These pathological changes result in altered morphology of the interpeduncular cistern, thereby widening the IPA.[10]
The number of subjects in this study was larger than in previous studies.[3,5] Analysis of the PSP subgroup with age revealed no increase in IPA, which may be attributed to a pre-existing widened angle due to the disease pathology described previously, contrary to PD patients, where age was found to be strongly correlated with angle widening.[10]
Our results corroborate the findings of similar previously conducted studies.[4,5,11] A retrospective study of 99 patients demonstrated excellent interobserver reliability in concordance with our study but, contrary to our findings, concluded that there was no significant difference in IPA between the PSP and PD groups.[4] Eraslan et al. concluded that MRPI and IPA were strong predictors of PSP with high sensitivity and specificity in their study.[5] Oktay et al. concluded that the IPA was significantly higher in PSP than in PD, with a sensitivity and specificity of 71% and 79%, respectively.[11] The IPA also demonstrated excellent inter- and intraobserver reliability, correlating well with our findings.
Current literature predominantly focuses on the utility of IPA in PSP and PD patients, with limited evaluation of other APDs.[3,5,6] Our MSA cohort includes patients with the MSA-C subtype, which is linked to significant brainstem atrophy and a wider IPA.[12] To the best of our knowledge, our study involves the largest cohort of MSA assessing the utility of IPA. Our ROC analysis between nonPSP APD (predominantly MSA, with a few CBS and LBD cases) and PD showed good sensitivity [see Supplementary Figure 5 (504.1KB, tif) ], suggesting its potential in the diagnosis of MSA as well. Further studies with larger cohorts are needed to validate these findings.
A major strength of our study is the age-wise grouping of patients, which allowed us to study angle variation across age groups and to understand the role of aging in the mechanism of widening IPA, which was not performed previously. Our findings show that IPA may be an age-dependent variable, reliable in diagnosing the disease in middle-aged patients. Other strengths include the large sample size, standardized angle measurements, and image selection criteria. A limitation of this study is that the diagnoses of all cases were made clinically, which may lead to heterogeneity in the disease groups analyzed. The control group included patients with lacunar infarcts on brain MRI that did not interfere with the structural morphology of the brainstem and other anatomical landmarks, which would be significant in determining accurate IPA measurements. While this criteria may not be ideal, identifying sufficiently large samples of neurologically normal patients who have available MRI scans would be impractical. Our study included few patients diagnosed with CBS and LBD, leading to their exclusion from nearly all analysis. Additionally, this study was conducted retrospectively, so accurate classification of PSP subtypes, such as PSP-Richardson’s syndrome, and documentation of disease duration could not be done.
Conclusions
We believe that IPA may be a possible age-dependent variable to differentiate APD from PD and control populations in middle-aged populations but may not be appropriate at older age brackets. Further studies to assess these trends would help reliably validate these findings. This highlights the importance of early diagnosis in view of clinical suspicion of APD.
Author contributions
TS: methodology; investigation; data curation; writing - original draft; writing - review & editing. MS: methodology; investigation; data curation; writing - original draft; writing - review & editing. US: methodology; validation; investigation; resources; writing - review & editing; supervision. RK: validation; investigation; resources; writing - review & editing. SK: conceptualization; validation; investigation; resources; writing - review & editing. AS: formal analysis. Vn: resources; writing - review & editing. SG: resources; writing - review & editing. GU: resources; writing - review & editing. AA: resources; writing - review & editing.
Conflicts of interest
There are no conflicts of interest.
Data availability statement
The data supporting the findings of the study are available from the corresponding author upon reasonable request.
Scatter plot superimposed with an error bar comparing the mean angle (y-axis) across the disease groups (x-axis). The mean IPA was 74.26 ± 5.59° for the MSA group, 72.02 ± 8.87° for the PSP group, 63.86 ± 9.01° for the Control group and 65.24 ± 10.44° for the IPD group. IPA: Interpeduncular Angle, MSA: multiple system atrophy, PSP: progressive supranuclear palsy, IPD: idiopathic Parkinson’s disease, CI: confidence interval
ROC curves between PSP and IPD groups for 51-60, 61-70 and 71-80 age groups respectively; ROC Curve (a) identified an IPA threshold of 67.66° (Sensitivity 68.4%, Specificity 88%), ROC Curve (b) identified an IPA threshold of 68.78° (Sensitivity 63.6%, Specificity 68%). ROC Curve (c) identified an IPA threshold of 75.71° (Sensitivity 50%, Specificity 56%). PSP: progressive supranuclear palsy, IPD: idiopathic Parkinson’s disease, IPA: interpeduncular angle, ROC: receiver operating characteristic
ROC curves between PSP and control for 51-60, 61-70 and 71-80 age groups respectively; ROC curve (a) identified an IPA threshold of 66.39° (Sensitivity 70.6%, Specificity 88.0%), ROC Curve (b) identified an IPA threshold of 68.86° (Sensitivity 59.1%, Specificity 56%). ROC Curve (c) identified an IPA threshold of 70.58° (Sensitivity 58.3%, Specificity 72.0%). PSP: progressive supranuclear palsy, IPA: interpeduncular angle, ROC: receiver operating characteristic
ROC curves between Atypical Parkinsonism and IPD for 51-60, 61-70 and 71-80 age groups respectively; ROC curve (a) identified an IPA threshold of 66.13° (Sensitivity 77.3%, Specificity 80%), ROC Curve (b) identified an IPA threshold of 68.78° (Sensitivity 66.7%, Specificity 68%). ROC Curve (c) identified an IPA threshold of 68.84° (Sensitivity 71.4%, Specificity 48.0%). ROC: receiver operating characteristic, IPD: idiopathic Parkinson’s disease, IPA: interpeduncular angle
ROC curve between non-PSP Atypical Parkinsonism and IPD groups identified an IPA threshold of 68.05° (Sensitivity 83.3%, Specificity 65.3%). ROC: receiver operating characteristic, PSP: progressive supranuclear palsy, IPD: idiopathic Parkinson’s disease, IPA: interpeduncular angle
Acknowledgments
The authors declare that there are no acknowledgements for this paper.
Funding Statement
Nil.
References
- 1.McFarland NR. Diagnostic approach to atypical Parkinsonian syndromes. Continuum (Minneap Minn) 2016;22:1117–42. doi: 10.1212/CON.0000000000000348. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Armstrong MJ, McFarland N. Handbook of Clinical Neurology. Vol. 167. Elsevier B.V.; 2019. Recognizing and treating atypical Parkinson disorders; pp. 301–20. [DOI] [PubMed] [Google Scholar]
- 3.Fatterpekar GM, Dietrich A, Pantano P, Saba L, Knopp EA, Piattella MC, et al. Cerebral peduncle angle: An objective criterion for assessing progressive supranuclear palsy richardson syndrome. Am J Roentgenol. 2015;205:386–91. doi: 10.2214/AJR.14.12724. [DOI] [PubMed] [Google Scholar]
- 4.Ugga L, Cuocolo R, Cocozza S, Pontillo G, Elefante A, Quarantelli M, et al. Magnetic resonance Parkinsonism indices and interpeduncular angle in idiopathic normal pressure hydrocephalus and progressive supranuclear palsy. Neuroradiology. 2020;62:1657–65. doi: 10.1007/s00234-020-02500-1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Eraslan C, Acarer A, Guneyli S, Akyuz E, Aydin E, Colakoglu Z, et al. MRI evaluation of progressive supranuclear palsy: Differentiation from Parkinson’s disease and multiple system atrophy. Neurol Res. 2019;41:110–7. doi: 10.1080/01616412.2018.1541115. [DOI] [PubMed] [Google Scholar]
- 6.Tipton PW, Konno T, Broderick DF, Dickson DW, Wszolek ZK. Cerebral peduncle angle: Unreliable in differentiating progressive supranuclear palsy from other neurodegenerative diseases. Parkinsonism Relat Disord. 2016;32:31–5. doi: 10.1016/j.parkreldis.2016.08.009. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Wang DJ, Pandey SK, Lee DH, Sharma M. The interpeduncular angle: A practical and objective marker for the detection and diagnosis of intracranial hypotension on brain MRI. Am J Neuroradiol. 2019;40:1299–303. doi: 10.3174/ajnr.A6120. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 8.Mangesius S, Hussl A, Krismer F, Mahlknecht P, Reiter E, Tagwercher S, et al. MR planimetry in neurodegenerative parkinsonism yields high diagnostic accuracy for PSP. Parkinsonism and Related Disorders. 2018;46:47–55. doi: 10.1016/j.parkreldis.2017.10.020. [DOI] [PubMed] [Google Scholar]
- 9.Heim B, Mangesius S, Krismer F, Wenning GK, Hussl A, Scherfler C, et al. Diagnostic accuracy of MR planimetry in clinically unclassifiable parkinsonism. Parkinsonism Relat Disord. 2021;82:87–91. doi: 10.1016/j.parkreldis.2020.11.019. [DOI] [PubMed] [Google Scholar]
- 10.Tsuboi Y, Slowinski J, Josephs KA, Honer WG, Wszolek ZK, Dickson DW. Atrophy of superior cerebellar peduncle in progressive supranuclear palsy. Neurology. 2006;60:1766–9. doi: 10.1212/01.wnl.0000068011.21396.f4. [DOI] [PubMed] [Google Scholar]
- 11.Oktay C, Özkaynak SS, Eseroğlu E, Karaali K. Contribution of the mesencephalon indices to differential diagnosis of Parkinsonian disorders. Can Assoc Radiol J. 2020;71:100–9. doi: 10.1177/0846537119888411. [DOI] [PubMed] [Google Scholar]
- 12.Ortiz JF, Betté S, Tambo W, Tao F, Cozar JC, Isaacson S. Multiple system atrophy – cerebellar type: Clinical picture and treatment of an often-overlooked disorder. Cureus. 2020;12:e10741. doi: 10.7759/cureus.10741. [DOI] [PMC free article] [PubMed] [Google Scholar]
Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Scatter plot superimposed with an error bar comparing the mean angle (y-axis) across the disease groups (x-axis). The mean IPA was 74.26 ± 5.59° for the MSA group, 72.02 ± 8.87° for the PSP group, 63.86 ± 9.01° for the Control group and 65.24 ± 10.44° for the IPD group. IPA: Interpeduncular Angle, MSA: multiple system atrophy, PSP: progressive supranuclear palsy, IPD: idiopathic Parkinson’s disease, CI: confidence interval
ROC curves between PSP and IPD groups for 51-60, 61-70 and 71-80 age groups respectively; ROC Curve (a) identified an IPA threshold of 67.66° (Sensitivity 68.4%, Specificity 88%), ROC Curve (b) identified an IPA threshold of 68.78° (Sensitivity 63.6%, Specificity 68%). ROC Curve (c) identified an IPA threshold of 75.71° (Sensitivity 50%, Specificity 56%). PSP: progressive supranuclear palsy, IPD: idiopathic Parkinson’s disease, IPA: interpeduncular angle, ROC: receiver operating characteristic
ROC curves between PSP and control for 51-60, 61-70 and 71-80 age groups respectively; ROC curve (a) identified an IPA threshold of 66.39° (Sensitivity 70.6%, Specificity 88.0%), ROC Curve (b) identified an IPA threshold of 68.86° (Sensitivity 59.1%, Specificity 56%). ROC Curve (c) identified an IPA threshold of 70.58° (Sensitivity 58.3%, Specificity 72.0%). PSP: progressive supranuclear palsy, IPA: interpeduncular angle, ROC: receiver operating characteristic
ROC curves between Atypical Parkinsonism and IPD for 51-60, 61-70 and 71-80 age groups respectively; ROC curve (a) identified an IPA threshold of 66.13° (Sensitivity 77.3%, Specificity 80%), ROC Curve (b) identified an IPA threshold of 68.78° (Sensitivity 66.7%, Specificity 68%). ROC Curve (c) identified an IPA threshold of 68.84° (Sensitivity 71.4%, Specificity 48.0%). ROC: receiver operating characteristic, IPD: idiopathic Parkinson’s disease, IPA: interpeduncular angle
ROC curve between non-PSP Atypical Parkinsonism and IPD groups identified an IPA threshold of 68.05° (Sensitivity 83.3%, Specificity 65.3%). ROC: receiver operating characteristic, PSP: progressive supranuclear palsy, IPD: idiopathic Parkinson’s disease, IPA: interpeduncular angle
Data Availability Statement
The data supporting the findings of the study are available from the corresponding author upon reasonable request.