When Stroke Strikes Early: Unusual Causes of Intracerebral Hemorrhage in Young Adults

<b>Background/Objectives:</b> Intracerebral hemorrhage (ICH) is primarily a disease of older adults, commonly linked to chronic hypertension and cerebral amyloid angiopathy. In young adults, however, ICH is rare and often driven by distinct structural, hematologic, or vascular causes. <b>Methods</b>: Using the National Inpatient Sample (2016-2022), we identified hospitalizations with a primary diagnosis of ICH (ICD-10-CM: I61.x). Patients younger than 18 years were excluded. Patients were stratified into <b>18-39 vs. ≥40 years</b>. Comorbidities were defined using validated ICD-10 codes (E08-E13 for diabetes mellitus, I10-I15 for hypertension), excluding transient hyperglycemia (R73.x). Weighted analyses using NIS discharge weights compared demographics, comorbidities, rare etiologies, and outcomes, including in-hospital mortality, length of stay (LOS), and total hospital charges. Survey-weighted multivariable logistic regression identified independent predictors of mortality. <b>Results</b>: Among 76,264 ICH hospitalizations, 4012 (5.3%) occurred in patients < 40 years. Compared with older adults, younger patients had lower prevalence of hypertension (47.8% vs. 84.1%) and diabetes (10.2% vs. 60.4%) but higher rates of substance use (27.7% vs. 15.6%). Rare etiologies were more frequent, including arteriovenous malformation/aneurysm (14.0% vs. 3.6%), Moyamoya disease (1.4% vs. 0.2%), sickle cell disease (1.1% vs. 0.1%), and pregnancy-related ICH (0.05%). In-hospital mortality was lower among young adults (15.7% vs. 21.7%, <i>p</i> < 0.001), though LOS was longer (12.1 vs. 8.7 days, <i>p</i> < 0.001), and mean hospital charges were higher ($228,000 vs. $125,000, <i>p</i> < 0.001). <b>Conclusions</b>: Young-adult ICH is uncommon but etiologically distinct, often associated with vascular malformations, hemoglobinopathies, and substance use. Despite lower mortality, these patients experience longer and more resource-intensive hospitalizations, underscoring a substantial clinical and economic burden.