My brother has carotid artery dissection. is that something important?

Yes: Need to follow treatment recommendations of his doctor closely so dissection can heal without causing a stroke.

Yes: This is typically a self limited event that is triggered by hypertension or an injury to the neck. He should be followed by a vascular surgeon that will be able to guide him through the treatment options. He will likely only need ultrasound follow up for this along with blood pressure control.