Capsular warning syndrome (CWS) is an uncommon but distinctive clinical manifestation of acute ischemic cerebrovascular disease, currently recognized as a specific subtype of transient ischemic attack (TIA) (1). First characterized by Donnan in 1993, CWS is clinically defined by at least three stereotyped, transient, and completely reversible episodes of unilateral motor or sensory impairment occurring within a 24-h period. These episodes must involve at least two regions among the face, arm, or leg, without associated cortical dysfunctions such as aphasia, apraxia, agnosia, or cognitive impairment (2). CWS is most commonly associated with lacunar infarctions, which result from the occlusion of small penetrating arteries. Furthermore, TIA have been observed in approximately 10% of patients prior to the onset of lacunar infarction, suggesting a prodromal phase in some cases (3, 4). Recent advancements in neuroimaging have clarified that lesions underlying CWS are not restricted solely to the internal capsule, as initially postulated, but may extend to other deep cerebral structures, including the pons, thalamus, centrum semiovale, and corpus callosum (5, 6). Additionally, the temporal definition of CWS has evolved, with recent studies proposing expanded diagnostic windows of 48 h, 72 h, or even up to 7 days, leading to broader and more inclusive diagnostic criteria (7–9).

Despite clinical parallels with conventional TIA, CWS is associated with a significantly increased risk of progression to ischemic stroke. The 90-day stroke risk among general TIA patients is approximately 1.4% (10), whereas the reported rate of infarction among CWS patients ranges from 71.2 to 80.55% (11, 12). However, comprehensive investigations into independent risk factors specifically predicting infarction in CWS remain limited. Current literature predominantly addresses conventional vascular risk factors such as hypertension, atherosclerosis, and hyperhomocysteinemia (13). Currently, clinical management of CWS often mirrors that of TIA or acute ischemic stroke, involving antiplatelet therapy and intravenous thrombolysis (14). Among antiplatelet options, tirofiban is a fast-acting, reversible glycoprotein IIb/IIIa antagonist that inhibits the final step of platelet aggregation. Its safety and potential benefits in acute ischemic stroke have been supported by several studies (15, 16). Considering the potential contribution of platelet hyperreactivity and small-vessel pathology in CWS, tirofiban represents a biologically rational candidate for mitigating infarct development. Nevertheless, the efficacy and safety of these strategies in CWS remain uncertain due to the lack of high-quality, CWS-specific evidence. Heterogeneous designs and limited sample sizes further contribute to inconsistent conclusions and the absence of standardized treatment guidelines.

This study aims to review the clinical and imaging characteristics of CWS, identify predictors of infarction and poor prognosis, and evaluate the impact of different therapeutic strategies on clinical outcomes. By elucidating risk profiles and treatment effects in this unique population, we hope to inform earlier recognition and tailored interventions for patients at high risk of progression.

Our study set out to clarify two unresolved questions in CWS: (i) which bedside or laboratory variables truly forecast progression to infarction, and (ii) whether intensive, mechanism-directed antiplatelet therapy can improve functional recovery once infarction occurs. By analyzing 89 consecutive patients we show, first, that a composite profile of platelet hyperreactivity (elevated platelet count), early clinical severity (higher NIHSS and ABCD² scores), intracranial atherosclerosis, and male sex independently signals imminent infarction, and second, that early, weight-adjusted tirofiban infusion is associated with a three- to four-fold increase in 90-day independence relative to best-medical therapy alone.

Even modest increases within the high-normal platelet range intensified the probability of permanent infarction (17). Platelets with greater surface density not only raise the encounter rate between GP IIb/IIIa receptors and fibrinogen but also shed pro-coagulant macrovesicles that accelerate thrombin generation (18, 19). Male sex retained significance after multivariable adjustment; testosterone is known to up-regulate platelet thromboxane A₂ receptor density and augment aggregation (20) Intracranial atherosclerosis predicted infarction despite minimal large-artery stenosis in most patients, underscoring the “branch-occlusive” model in which ostial plaques obstruct perforating arteries or create platelet-rich micro emboli (21). Chronic hypertension, smoking, dyslipidemia and hyperhomocysteinemia—present in >70% of our cohort—promote lipohyalinosis, endothelial nitric-oxide depletion and basement-membrane thickening, further narrowing the perforator lumen and predisposing to flow arrest (22, 23).

Tirofiban is a short-acting, reversible glycoprotein IIb/IIIa antagonist that blocks the final common pathway of platelet aggregation without the immunogenicity of abciximab. Experimental models confirm that perforator-type infarcts are exquisitely platelet-dependent and respond poorly to P2Y12 inhibition alone (24). The SaTIS trial established safety in moderate ischemic stroke (25), and successive randomized data have documented functional benefits in selected populations—large-artery atherosclerosis (26), non-occlusive strokes, and, most recently, in combination with intravenous thrombolysis (27). Our cohort complements these trials by focusing on small-vessel-dominant pathology, a context in which platelet-rich thrombi and endothelial plugging are central. The magnitude of benefit we observed is concordant with the pooled effect of four randomized controlled trials in non-repercussed stroke (28). Nevertheless, it contrasts with a neutral signal in a prior open-label CWS series (29), possibly because our protocol mandated (i) early initiation after first sustained deficit and (ii) overlap with dual oral antiplatelets to prevent rebound aggregation. These findings are consistent with recent evidence from a multicenter cohort study, which demonstrated that tirofiban administration improved outcomes in patients with large artery atherosclerosis who achieved complete reperfusion and were presented with high NIHSS scores (30). This further supports the potential utility of tirofiban in patients with CWS, especially those with underlying atherosclerotic pathology and severe initial neurological deficits.

Our conclusions must be interpreted in light of several constraints. First, the retrospective design invites selection bias, particularly in treatment allocation—patients receiving tirofiban had more severe intrahospital fluctuations, which could lead to confounding by indication despite multivariate adjustment. Second, sample size is modest, limiting power for subgroup analyses (e.g., sex-specific efficacy) and inflating confidence intervals around some estimates. Third, lack of randomization and blinding leaves room for unmeasured confounders, including clinician preference and temporal improvements in ancillary care. Fourth, precise symptom onset-to-admission intervals were not consistently documented. However, all included patients were admitted within 24 h from symptom onset. Finally, generalizability is restricted: our hospital is a tertiary referral center in north-west China with a high background prevalence of intracranial atherosclerosis; centers with different risk profiles or practice patterns may not reproduce identical effect sizes.

Taken together, our data support a two-step management algorithm: bedside triage using the platelet-NIHSS-ABCD² composite to identify high-risk patients, followed by early tirofiban infusion in those who convert to infarction despite standard therapy. Prospective, multicenter randomized trials with stratification by platelet function and imaging-defined perforator disease are urgently required. Incorporation of blood biomarkers of endothelial dysfunction and high-resolution vessel-wall MRI could further unravel the microvascular mechanisms precipitating CWS and refine candidate selection for intensive antiplatelet therapy.

In this single-center cohort, elevated platelet count, high initial clinical scores, intracranial atherosclerosis, and male sex independently predicted infarction in CWS, while low-dose tirofiban was the only modifiable factor associated with superior 90-day functional outcomes. These findings strengthen the biological rationale for early, mechanism-specific platelet inhibition in high-risk CWS and lay the groundwork for definitive randomized evaluation.