Presentation
Right facial weakness and expressive aphasia.
Patient Data
Loss of corticomedullary differentiation is noted at the left insular cortex ("loss of insular ribbon sign") and operculum. There is no associated hyperdense MCA sign.
The positive finding was missed on the initial CT.
Rescanning one day later due to persistent symptoms shows a well-formed MCA territory infarct.
Case Discussion
Loss of corticomedullar differentiation along the insular cortex is caused by mild brain edema that accompanies early MCA infarcts.
The insula is arterially supplied by the insular segment of the middle cerebral artery (MCA) and its claustral branches. In early MCA ischemia, this area becomes a watershed zone, leading to the early cessation of blood supply and subsequent acute edema.
The "stroke window" (i.e. couch = 40 HU, width = 40 HU) increases sensitivity for picking up on subtle brain edema.