Abstract Details

Title Increasing National Burden of Encephalitis, Myelitis, and Encephalomyelitis: Insights from the ICD-10 Era and Implications for Diagnostic Coding

Topic Autoimmune Neurology

Presentation(s) P1 - Poster Session 1 (12:00 PM-1:00 PM)

Poster/Presentation
Number 1-038

Objective To evaluate national trends in hospitalizations for encephalitis, myelitis, and encephalomyelitis in the United States using the National Inpatient Sample (NIS) from 2016 to 2023.

Background Encephalitis, myelitis, and encephalomyelitis represent a heterogeneous group of inflammatory disorders of the central nervous system with diverse etiologies and clinical presentations. In the ICD-10 era, the extent to which broad diagnostic codes capture the national burden of these distinct conditions remains limited.

Design/Methods We conducted a retrospective cross-sectional study using the Healthcare Cost and Utilization Project NIS from 2016 through 2023. Adult hospitalizations with a principal diagnosis of ICD-10 code “G04*” were identified. Survey-weighted analyses were performed to generate national estimates, accounting for the complex sampling design. Temporal trends in hospitalization volume were assessed.

Results

A total of 147,970 weighted hospitalizations were identified during the study period. Annual hospitalizations increased from 14,795 (95% CI, 13,444–16,146) in 2016 to 21,585 (95% CI, 20,286–22,884) in 2023, representing an approximate 46% increase. A modest plateau was observed in 2019–2020, which may reflect disruptions in healthcare utilization during the COVID-19 pandemic, followed by continued increases through 2023.

Conclusions Hospitalizations for encephalitis, myelitis, and encephalomyelitis have increased substantially in the United States from 2016 to 2023. However, this trend must be interpreted in the context of the clinical and etiologic heterogeneity encompassed within the G04* diagnostic category. The absence of more granular ICD-10 codes for distinct conditions such as autoimmune encephalitis, a well-recognized clinical entity, may contribute to the aggregation of diverse disease processes under a single code. These findings highlight limitations in diagnostic specificity and underscore the need for more refined coding frameworks to better characterize disease subtypes and inform clinical and epidemiologic research.

Authors/Disclosures
Ka-Ho Wong (U of U Neurology Clinic) PRESENTER	Mr. Wong has received personal compensation in the range of $0-$499 for serving as a Consultant for CRISPR Therapeutics. The institution of Mr. Wong has received research support from The Sumaira Foundation . The institution of Mr. Wong has received research support from The Siegel Rare Neuroimmune Association. The institution of Mr. Wong has received research support from TG Therapeutics. The institution of Mr. Wong has received research support from Sanofi.
Ava M. Easton, PhD (Encephalitis International)	Dr. Easton has received publishing royalties from a publication relating to health care. Dr. Easton has received personal compensation in the range of $500,000-$999,999 for serving as a Chief Executive with Encephalitis International.
Melissa A. Wright, MD (University of Utah)	Dr. Wright has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Novartis .
Yoji Hoshina, MD (University of Utah Health)	Dr. Hoshina has nothing to disclose.
Sydney Lee, MD (University of Utah)	Dr. Lee has nothing to disclose.
Tammy L. Smith, MD, PhD (Imaging and Neurosciences Center)	Dr. Smith has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for EMD Serono. The institution of Dr. Smith has received research support from Alexion/AstraZeneca.
Adam De Havenon, MD, FAAN (Yale University)	Dr. De Havenon has received personal compensation in the range of $10,000-$49,999 for serving as a Consultant for Novo Nordisk. Dr. De Havenon has or had stock in Certus.Dr. De Havenon has or had stock in TitinKM. The institution of Dr. De Havenon has received research support from NIH/NINDS. Dr. De Havenon has received publishing royalties from a publication relating to health care.
Stacey Clardy, MD, PhD, FAAN (University of Utah)	Dr. Clardy has received personal compensation for serving as an employee of Veterans Health Administration (VHA). Dr. Clardy has received personal compensation for serving as an employee of University of Utah Health. Dr. Clardy has received personal compensation in the range of $5,000-$9,999 for serving on a Scientific Advisory or Data Safety Monitoring board for AstraZeneca/Alexion. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Amgen/Horizon. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Arialys. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Kyverna. Dr. Clardy has received personal compensation in the range of $10,000-$49,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Neurology/AAN Publications. The institution of Dr. Clardy has received research support from NIH/NINDS. The institution of Dr. Clardy has received research support from SRNA. The institution of Dr. Clardy has received research support from Alexion/AstraZeneca. The institution of Dr. Clardy has received research support from Kyverna. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving as a AAN Summer Meeting CoDirector Travel and Lodging with AAN. Dr. Clardy has received personal compensation in the range of $500-$4,999 for serving as a Grand Rounds Travel/Lodging/Honoraria with U of Iowa, Miami, Stanford, Barrow, Advent Health Florida, Beaumont Health, CCF, Emory, Penn State Health, Mayo Clinic, Walter Reed.

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