Dear editor,We read with great interest the article entitled "Carotid Artery Perivascular Adipose Tissue Density and Response to Intravenous Tissue Plasminogen Activator in Acute Ischemic Stroke" by Gencer et al. 1 We congratulate the authors and would like to discuss some points about the relationship between carotid artery perivascular adipose tissue density (CAPATd) and prognosis in acute stroke patients.Gencer et al. 1 divided their patients with acute stroke into two groups according to the modified Rankin scale (mRS) and compared outcomes. Carotid artery perivascular adipose tissue density (CAPATd)-average and CAPATd-maximum values were higher on the ipsilateral side of carotid artery stenosis >60%. They also showed that CAPATd-maximum ipsilateral emerged as an independent predictor for both mRS 0-2 (52%) [exp(β) = 0.984] and mRS 0-1 outcome (32%) [exp(β) = 0.828] in addition to admission National Institutes of Health Stroke Scale, age, and carotid plaque burden. They concluded that higher maximum CAPATd measured on emergency CTA indicates poorer functional prognosis in acute stroke patients.Zhang and colleagues 2 reported that CAPATd was significantly associated with the presence of cerebrovascular symptoms (OR, 1.13; 95% CI, 1.07-1.19; P < .001). Similarly, another study 3 reported that CAPATd before mechanical thrombectomy is an indicator of worse postprocedural arterial revascularization and worse functional outcome in acute stroke patients. Furthermore, another study demonstrated that higher CAPATd is associated with the presence of intraplaque hemorrhage (IPH) in the carotid artery, providing a novel marker to identify carotid IPH and risk stratification. 4 These findings suggested that CAPATd may be a beneficial biomarker of prognosis in patients with cerebrovascular disease.Why CAPATd is associated with prognosis has not been clearly defined. CAPATd is the adipose tissue depot that surrounds the carotid artery; it juxtaposes the vascular adventitia without an anatomic barrier, allowing direct communication with vascular cells. 5,6 CAPATd is closely related to inflammatory changes 7 and is a marker of vulnerable plaques which are closely linked to cerebrovascular ischemic events. 8,9 We infer that the mechanisms involved may be multifactorial.In summary, Gencer et al. 1 demonstrated that CAPATd is a useful biomarker to predict prognosis. Further studies on the mechanisms involved and potential therapeutic options are warranted.