Definition of Stroke in Young Adults
Stroke in young individuals is typically defined as occurring in patients under 45-50 years of age, with the clinical definition remaining the same as in older adults: an acute or sudden onset of focal neurological deficits attributed to vascular injury (infarction or hemorrhage) of the central nervous system. 1, 2
Age Cutoffs Used in Clinical Practice and Research
The age threshold for defining "young stroke" varies across guidelines and studies, but the most commonly used cutoffs are:
- Under 45 years of age is the most frequently cited definition in American Heart Association guidelines and major stroke studies 1, 3
- Under 50 years of age is also commonly used as an alternative threshold in research and clinical practice 1, 2, 4
- Under 55 years of age represents the upper limit used in some meta-analyses examining prothrombotic mutations and stroke risk 1
Clinical Definition Remains Unchanged
The fundamental clinical definition of stroke does not differ based on age. A stroke is defined as an acute or sudden onset of focal neurological deficits, with the most common signs including focal weakness and/or numbness, aphasia (impaired language production or comprehension), visual field disturbance (homonymous hemianopia or quadrantanopia), diplopia, hemispatial neglect, dysarthria, vertigo, or ataxia. 1
Pediatric and Neonatal Stroke Definitions
For completeness, distinct age-based definitions exist for the youngest patients:
- Neonatal stroke encompasses both ischemic and hemorrhagic events from early gestation through the first month of life 1
- Perinatal stroke describes cerebrovascular lesions occurring from 28 weeks' gestation through the first 7 days of life, though some broaden this to 20 weeks' gestation to 28 days after birth 1
- Childhood stroke typically refers to patients from 1 month through 18 years of age 1
Key Distinguishing Features in Young Stroke Patients
While the clinical definition remains consistent, young stroke patients differ substantially in etiology and evaluation requirements:
- Etiologic differences: Young patients have a different spectrum of causes, with arterial dissection, structural vasculopathy (arteriovenous malformations, cavernomas), cardiac causes, and other determined diseases being more prevalent than large artery atherosclerosis 2, 4
- Distribution of stroke types: In the youngest patients (16-30 years), structural vasculopathy is the most common cause of intracerebral hemorrhage, whereas hypertensive hemorrhage predominates in those aged 31-45 years 4
- Ischemic versus hemorrhagic proportions: Young adults show a higher proportion of hemorrhagic strokes (approximately 45%) compared to the general adult population where 85% are ischemic 2, 4
Important Clinical Caveat
The 45-year age cutoff is not absolute but rather represents a practical threshold where the differential diagnosis and evaluation strategy must shift to include causes rarely seen in older adults, such as arterial dissection, inherited thrombophilias, cardiac structural abnormalities (patent foramen ovale), and vasculopathies. 1, 5, 6