MEDIAL DEGENERATION

· Medial degeneration is a degenerative disorder in which elastic tissue and muscle fibres degenerate and various amounts of ground substance are deposited

· “With advancing age the aorta becomes dilated, elongated and less elastic as a result of degeneration of the elastic and smooth muscle fibres of the media. Collagen fibres increase in number, and the amount of mucoid ground substance (acid mucopolysaccharide) increases. Clinical problems do not result, but tortuosity and ectasia of the aorta are commonly observed in chest X-rays of elderly subjects.”

· note that the now defunct term “cystic medial necrosis” is not used for medial degeneration as necrosis is not observed and the cysts are probably areas in which smooth muscle cells or elastic fibres once existed but have disappeared due to degeneration

· Medionecrosis: accumulation of mucoid material between elastic elements in the outer third of aortic wall, eventually involving the entire media [most common cause of aneurysms of the ascending aortic aneurysms]

Pathological conditions with which mediodegeneration is associated

· May be important in the pathogenesis of aortic dissection

· Marked degeneration of the aortic media is the characteristic cardiovascular abnormality in patients with Marfan’s syndrome

· Exceptionally, medial degeneration severe enough to result in aneurysm, rupture, or dissection is found in the main pulmonary arteries or in the descending aorta

· This condition is observed in two clinical forms:

1) Congenital—Marfan’s syndrome

2) Acquired form

Natural history of such pathological conditions

· This condition is observed in two clinical forms:

1) Congenital—Marfan’s syndrome

o associated with an inherited connective tissue disorder

o appears early in life [teens, twenties & thirties]

o may be associated with skeletal & ocular defects

2) Acquired form

o most common form

o occurs later in life [middle age and elderly]

· The best known clinical manifestation of medial degeneration is that which involves the ascending and transverse aortic arch causing anulo-aortic ectasia and aortic insufficiency.

· In addition to the aortic dilatation which occurs as a result of the medial weakness, mural lacerations, mural tears and acute aortic dissection may occur and lead to an early death from rupture and pericardial tamponade