A General Neurologist's Practical Diagnostic Algorithm for Atypical Parkinsonian Disorders: A Consensus Statement.

Purpose of Review: The most common four neurodegenerative atypical parkinsonian disorders (APDs) are progressive supranuclear palsy (PSP), multiple system atrophy (MSA), corticobasal syndrome (CBS), and dementia with Lewy bodies (DLB). Their formal diagnostic criteria often require subspecialty experience to implement as designed and all require excluding competing diagnoses without clearly specifying how to do that. Validated diagnostic criteria are not available at all for many of the other common APDs, including normal pressure hydrocephalus (NPH), vascular parkinsonism (VP), or drug-induced parkinsonism (DIP). APDs also include conditions of structural, genetic, vascular, toxic/metabolic, infectious, and autoimmune origin. Their differential diagnosis can be challenging early in the course, if the presentation is atypical, or if a rare or non-neurodegenerative condition is present. This review equips community general neurologists to make an early provisional diagnosis before, or in place of, referral to a tertiary center. Early diagnosis would allay diagnostic uncertainty, allow prompt symptomatic management, provide disease-specific information and support resources, avoid further pointless testing and treatments, and create the possibility of trial referral.
Recent Findings: We address 64 APDs using one over-arching flow diagram and a series of detailed tables. Most instances of APDs can be diagnosed with a careful history and neurological exam, along with a non-contrast brain MRI. Additional diagnostic tests are rarely needed but are delineated where applicable. Our diagnostic algorithm encourages referral to a tertiary center whenever the general neurologist feels it would be in the patient's best interest. Our algorithm emphasizes that the diagnosis of APDs is an iterative process, refined with the appearance of new diagnostic features, availability of new technology, and advances in scientific understanding of the disorders. Clinicians' proposals for all diagnostic tests for the APDs, including repeat visits, should be discussed with patients and their families to ensure that the potential information to be gained aligns with their larger clinical goals.
Summary: We designed this differential diagnostic algorithm for the APDs to enhance general neurologists' diagnostic skills and confidence and to help them address the less common or more ambiguous cases.
Competing Interests: M.K. Bruno: no relevant conflict of interest. She does have research funding from Michael J. Fox Foundation; R. Dhall: no relevant conflict of interest. He has received financial support from the following within the last year: Amneal pharmaceuticals, Sage Therapeutics, Neuroderm, Cerevel Therapeutics, Neurocrine, Neuraly, Alexion, Sun Pharma, Praxis Precision Medicines, Parkinson's Foundation, Aeon Biopharma, Abbvie, Pharma Two B, NIH Parent Grant #UL1TR003107 TRI Pilot Grant “Research Benefitting Rural Populations”. Dr. Dhall has received consulting revenues from Mitsubishi Tanabe Pharma America and Best Doctors. Dr. Dhall reports stock ownership (all at <$10,000) in medically related fields for Armata Pharmaceuticals, Compass Pathways, Biogen Idec, Atea Pharmaceuticals, Gilead Sciences, Imara, Inc, and SQZ Biotech; L.S. Honig: consulted for Biogen Eisai, Genentech/Roche, Medscape, and Prevail/Lilly. L.S. Honig has received research funding from Abbvie, Acumen, Alector, Biogen, Bristol-Myer Squibb, Cognition, Eisai, Genentech/Roche, Janssen/Johnson & Johnson, Eli Lilly, Transposon, UCB, and Vaccinex; Z. Mari: no relevant conflict of interest. He is immediate past Chair of the Movement Disorder Society's Telemedicine Study Group, Director of the Cleveland Clinic Lou Ruvo Center for Brain Health Parkinson's Foundation Center of Excellence, Chair of Parkinson Study Group's Motor Features WG, Associate Editor of Parkinsonism & Related Disorders, president-elect for the Clark County Medical Society, which he also is a Trustee; Z. Mari serves on the IAPRD's Congress Site Selection Committee and Website Committee, and the PPMI's Wearable Devices Task Force. Z. Mari has been recipient of institutional grant support from the NIH, PF, MJFF, Biogen, Eli Lilly, AbbVie, Cerevel, and Praxis Precision Medicines; is cofounder and CMO of Neuraly, Inc, and Z NeuroSciences LLC; is shareholder of D&D PharmaTech, NeuroReserve, Neunos Inc, and Sensory Cloud; and has received honoraria for consulting and advisory board service from GB Sciences, GKC, Bial, Supernus, AbbVie, ACADIA, Sunovion. N.R. McFarland: received research support from the NIH-NINDS, Michael J. Fox Foundation, and Parkinson Foundation. He receives royalties from UpToDate and serves on advisory committee for ONO Pharmaceutical. L. Montaser-Kouhsari received consultant fees from Darmyian, Trinity Life Sciences, Guidepoint, and Techspert, has received research support from the NIH (NINDS), and has received Talk honorarium from Cleveland Clinic. A.M. Wills: no relevant conflict of interest. She does have consulting agreements with Genentech, Amylyx, and Ono pharmaceuticals and have research funding from the NIH, Parkinson's Foundation, and CurePSP. L.I. Golbe: consults for AI Therapeutics, Amylyx, Apellis, Aprinoia, Ferrer, IQVIA, Mitochon, Mitsubishi Tanabe, P3Lab, Roche, Switch, UCB and Woolsey. He serves on advisory boards for Amylyx, CurePSP, Roche, Rossy Centre and Springer. He receives royalties from Rutgers University Press, licensing fees from Rutgers University and travel expenses from CurePSP. The rest of the authors report no relevant conflicts of interest. Full disclosure form information provided by the authors is available with the full text of this article at Neurology.org/cp.
(Copyright © 2024 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Neurology.)