Interpeduncular Angle: A Marker To Differentiate Atypical Parkinsonism from Idiopathic Parkinson's Disease
Tejas Shivarthi1, Mahima Sriram1, Sudheeran Kannoth1, Udit Saraf1, Rajesh Kannan2, Vivek Nambiar1, Siby Gopinath1, Gopikrishnan Unnikrishnan1, Anandakumar Anandakuttan1, Abish Sudhakar3
1Department of Neurology, 2Department of Radiology, 3Department of Pediatric Cardiology, Amrita School of Medicine, Amrita Institute of Medical Sciences, Amrita Vishwa Vidyapeetham University, Kochi, Kerala India
Objective:

To assess the utility of the Interpeduncular Angle in distinguishing Atypical Parkinsonian Syndromes from Idiopathic Parkinson's Disease across age ranges.


Background:

Atypical parkinsonian syndromes such as Progressive Supranuclear Palsy (PSP), Multiple System Atrophy (MSA), Corticobasal Degeneration (CBD) and Lewy Body Dementia (LBD) are frequently inaccurately diagnosed, with a common misdiagnosis being Idiopathic Parkinson’s Disease (IPD). This study seeks to evaluate the Interpeduncular Angle (IPA) as a diagnostic criterion.


Design/Methods:
This retrospective study was conducted with 225 patients (75 with Atypical Parkinsonism, 75 with IPD 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 MRIs at a level below the mammillary bodies using a standardized measurement approach.
Results:

The Atypical Parkinsonism group included 51 patients (68.0%) with PSP, 16 (21.33%) with MSA, 5 (6.67%) with LBD, and 3 (4.0%) with CBD. Bland-Altman analysis for angle measurement suggested good to excellent agreement between both readers (p<0.001). IPA was significantly higher in patients with PSP, as compared to patients with IPD. Mean IPA measurements between the diagnosis groups showed statistical significance (p<0.001), isolated to PSP versus controls (p<0.001), PSP versus IPD (p<0.001), MSA versus controls (p<0.001) and MSA versus IPD (p=0.003). Pearson Correlation Coefficient between mean IPA and age showed positive correlation in IPD (0.577) and control group (0.433) (p<0.001). ROC analysis identified an IPA threshold of 68.39° for Atypical Parkinsonism versus IPD (sensitivity 69.3%, specificity 68%) and 68.06° for non-PSP Atypical Parkinsonism versus IPD (sensitivity 83.3%, specificity 65.3%).

Conclusions:

The Interpeduncular Angle is a reliable marker to differentiate Atypical Parkinsonian syndromes, particularly PSP and MSA, from Parkinson’s Disease and Controls.


10.1212/WNL.0000000000210616
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