2026 American Academy of Neurology Autoimmune Abstract Website

Yoji Hoshina¹, Ka-Ho Wong², Sadie McGreer¹, Justin Abbatemarco³, Bettina Balint⁴, Kyle Blackburn⁵, Stefan Blum⁶, Adrian Budhram⁷, Marinos Dalakas⁸, Josep Dalmau⁹, Livia Dutra¹⁰, Francesc Graus⁹, Jerome Honnorat¹¹, Takahiro Iizuka¹², Sarosh Irani¹³, Saiju Jacob¹⁴, Eric Lancaster¹⁵, Jenny Linnoila¹⁶, Alfonso Lopez¹³, Sara Mariotto¹⁷, Naoko Matsui¹⁸, Andrew McKeon¹³, Joao Moura¹⁹, Scott Newsome²⁰, Orna O'Toole²¹, Amanda Piquet²², Amy Quek²³, Albert Saiz²⁴, Mateus Simabukuro²⁵, Claudia Sommer²⁶, Maarten Titulaer²⁷, Alberto Vogrig²⁸, Yujie Wang²⁹, Tara Zier³⁰, Jacqueline Kraska³⁰, Giovanna Manzano³¹, Anastasia Zekeridou³², Stacey Clardy³³
¹University of Utah Health, ²U of U Neurology Clinic, ³Cleveland Clinic, ⁴University Hospital of Zurich, ⁵University of Texas Southwestern Medical Center, ⁶Princess Alexandra Hospital, ⁷London Health Sciences Centre, ⁸Thomas Jefferson University, ⁹IDIBAPS, ¹⁰Hospital Israelita Albert Einstein, ¹¹Hospices Civils de Lyon, ¹²Department of Neurology, Kitasato University School of Medicine, ¹³Mayo Clinic, ¹⁴University Hospitals Birmingham NHS Foundation Trust, ¹⁵The University of Pennsylvania, Dept. of Neurology, ¹⁶University Neurology Associates, UPMC, ¹⁷Neurology Unit, University of Verona, ¹⁸Tokushima University, ¹⁹Centro Hospitalar Universitário do Porto, ²⁰Johns Hopkins Hospital, ²¹Mercy University Hospital, ²²University of Colorado, ²³National University Hospital, ²⁴Hospital Clinico De Barcelona, ²⁵Hospital Das Clinicas, Sao Paulo U Scho of Med, ²⁶Neurologische Klinik der Universitat, ²⁷Erasmus Medical Center, ²⁸University of Udine, ²⁹UW Northwest, ³⁰The Stiff Person Syndrome Research Foundation, ³¹University of California Irvine, ³²Neuroimmunology Laboratory, Mayo Clinic, ³³University of Utah

Objective:

To establish expert consensus and identify practice variation in terminology and diagnostic approaches for stiff person syndrome (SPS) and related disorders.

Background:

SPS is a rare and clinically heterogeneous condition. Although expert-proposed diagnostic criteria exist, international consensus guidance is lacking, and approaches to terminology and diagnosis vary across centers, countries, and resource settings.

Design/Methods:

Forty international experts in SPS were identified based on peer-reviewed authorship. A modified Delphi survey was designed to evaluate agreement on terminology and diagnosis. Consensus was predefined as greater than 80% agreement.

Results:

Of 40 invited expert clinicians, 33 (83%) from 15 countries participated. Consensus was achieved for the terminology of classic SPS; partial SPS; SPS-plus; progressive encephalomyelitis with rigidity and myoclonus (PERM); and glutamic acid decarboxylase 65 (GAD65)-associated cerebellar ataxia. Consensus was also reached for key diagnostic elements, including core clinical symptoms and signs of classic/partial SPS; supportive features (exaggerated startle responses and coexisting autoimmune comorbidities in GAD65-positive cases); the importance of serologic testing; clinically relevant high-titer GAD65 antibody thresholds according to assay methodology; the diagnostic utility of glycine receptor alpha1 antibody in suspected PERM and GAD65 antibody negative SPS cases; the role of electrophysiology, especially in seronegative cases; definite diagnostic criteria for classic/partial SPS and SPS-plus; diagnostic frameworks for PERM and GAD65-associated cerebellar ataxia; and major exclusion criteria and diagnostic pitfalls. Consensus was not reached after Round 1 for the use of stiff person spectrum disorder as an umbrella term including PERM, epilepsy and cerebellar ataxia phenotypes; probable and possible SPS diagnostic criteria; and the terminology and diagnostic approach for GAD65-associated epilepsy.

Conclusions:

This international Delphi survey helps identify areas of expert agreement and variation in the diagnosis of SPS and related disorders across diverse clinical settings. These findings, supplemented by the round 2 data, may help inform future consensus recommendations.