The term 'abnormal narrowing' can be summarized as 'STENOSIS', which is a medical condition in which the diameter of a blood vessel or other hollow organ is reduced. This can lead to decreased blood flow, increased pressure, and other symptoms depending on the affected area. STENOSIS can be caused by a variety of factors, including inflammation, trauma, and congenital defects. Treatment for STENOSIS may include medications, lifestyle changes, or surgery.