Background: Insula infarction is an early computed tomographic sign of middle cerebral artery (MCA) territory stroke and may affect cardiovascular autonomic function. Abstract:Objective: To determine insula involvement in MCA territory infarction and its relationship with infarcts in the remainder of the MCA territory, stroke severity, and clinically relevant cardiovascular conditions. Design: Case series (August 1, 1997, to June 30, 2000). Setting: Academic stroke center. Patients: A total of 150 consecutive patients with nonlacunar MCA territory stroke who underwent magnetic resonance imaging within 48 hours of stroke onset. Main Outcome Measures: Association of insula infarction with the National Institutes of Health Stroke Scale (NIHSS) score, location of vascular occlusion, and cardiovascular events. Results: Insular lesions were present in 72 patients (48%); 34 (23%) had major insular lesions and 38 (25%) had minor lesions. Insula infarction was associated with lenticulostriate territory infarction (46%vs 14%; P < .001), more than one third of MCA territory infarction (35%vs 3%; P < .001), higher NIHSS score (13.5 vs 6; P < .001), and proximal vascular occlusion detected on magnetic resonance angiography. These associations were strongest for patients with major insular lesions. Clinically significant new arrhythmia was present in 15 of 72 with insula infarction (13 atrial fibrillations) and 4 of 78 without (P=.06). Insula infarction was associated with lower diastolic blood pressure at admission but was not associated with pulse rate, QTc interval, myocardial infarction, or sudden death. Conclusions: The insular cortex is involved in almost half of patients with nonlacunar ischemic MCA territory strokes. Major insula involvement is associated with large MCA territory infarcts, proximal MCA occlusions, and greater stroke severity. Insula infarction was not a predictor of clinically significant acute cardiovascular events during hospital stay in our patients. Background: Insula infarction is an early computed tomographic sign of middle cerebral artery (MCA) territory stroke and may affect cardiovascular autonomic function. Abstract: Objective: To determine insula involvement in MCA territory infarction and its relationship with infarcts in the remainder of the MCA territory Settings: Academic stroke center. Patients: A total of 150 consecutive patients with nonlacunar MCA territory stroke who underwent magnetic resonance Imaging within 48 hours of stroke onset. Main Outcome Measures: Association of insula infarction with the National Institutes of Health Stroke Scale (NIHSS) score, location of vascular occlusion, and cardiovascular events. Results: Insular lesions were present in 72 patients (48% ); 34 (23%) had major insular lesions and 38 (25%) had minor lesions. Insula infarction was associated with lenticulostriate t (46 vs 14%; P <.001), more than one third of MCA territory infarction (35% vs 3%; P <.001), higher NIHSS score (13.5 vs 6; Clinically significant new arrhythmia was present in 15 of 72 with insula infarction (13 atrial fibrillations) and 4 of 78 without (P = .06) and proximal vascular occlusion detected on magnetic resonance angiography . Insula infarction was associated with lower diastolic blood pressure at admission but was not associated with pulse rate, QTc interval, myocardial infarction, or sudden death. Conclusions: The insular cortex is involved in almost half of patients with nonlacunar ischemic MCA territory strokes. Major insula infarction was not a predictor of clinically significant acute cardiovascular events during hospital stay in our patients.