The external capsule is a band of longitudinal fibers (white matter) limited by two deep gray matter structures, the putamen medially and the claustrum laterally (Figure 1).
This structure is mainly composed of axons that connect different areas of the cerebral cortex with the tegmentum (corticotegmental fibers).
Ischemic strokes confined to the external capsule are extremely rare, representing 0.3% of patients enrolled in a large hospital-based ischemic stroke registry.
External capsule infarcts may be related to different pathogenic mechanisms, including large artery disease, cardiogenic brain embolism, sporadic cerebral small vessel disease, or to a combination of them.
In addition, external capsule infarcts have been typically reported in a hereditary form of cerebral small vessel disease known as CADASIL (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy).
