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Chapter Supplement 3 The Many Causes of Rib Notching Lawrence R. Goodman, MD

Felson: “We offer this chapter as a bonus. While it doesn't quite mesh with the subject matter of the rest of the book, it is important and does embody certain principles of chest roentgenology. Besides, it was available."

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How many causes of rib notching do you know? Write them down:

You probably wrote coarctation of the aorta and then were stuck. That is by far the commonest, but there are many others.

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* This chapter is based on an exhibit by M. L. Boone, B. E. Swenson, B. Felson, H. B. Spitz, and A. S. Weinstein, shown in 1963 at the American Roentgen Ray Society meeting in Montreal and at the Radiological Society of North America meeting in Chicago. Most of the illustrations were taken, with permission, from an article of the same title by M. L. Boone, B. E. Swenson,and B. Felson, published in Am J Roentgenol 91:1075, 1964 (Charles C Thomas, Springfield, Illinois).

Notching of the inferior margin of a rib is generally caused by enlargement of one of 3 important structures in the intercostal space: the artery , the vein, or the nerve.

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Figure S3-1A

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Note the rib notching in Figure S3-1A. Incidentally, the terms scalloping (shallow wave-like indentations) and notching (narrow deep indentations) are used interchangeably since these deformities have the same significance. In close-up, Figure S3-1B, note notching under the posterior 3rd – 6th ribs (arrows).

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Figure S3-1B

First, let's discuss the intercostal arteries. Certainly, the best known and most common cause of rib notching is coarctation of the aorta . In this condition, notching is caused by the dilated and tortuous intercostal arteries.

A. B.

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Figure S3-1C

A. artery C. artery

B. artery

Figure S3-1C is an angiogram of a coarctation beyond the left subclavian (arrow). Identify:

Not surprisingly, they are very large.

brachiocephalic

left carotid

left subclavian

A.

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In coarctation, blood must bypass the aortic constriction to get to the abdomen and lower extremities. The collateral pathways arise almost exclusively from the 2 subclavian arteries. The blood then passes via the thyrocervical, costocervical, and internal branches of the subclavian, and the subdivisions of these arteries, to reach the posterior intercostals. The blood in these intercostals then flows [toward/away from] the descending aorta.

mammary

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Figure S3-2

Trace the collateral flow from the subclavian to the posterior intercostal arteries in Figure S3-2, etc. Let's review this again by means of an arterial flow chart:

subclavians

thyrocervical costocervical

intercostals

A.

Ascending aorta

right and left

branches

descendingthoracis aorta

posterior

internal mammary

(1)

(2)

(3)

(4)

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“The flow of fluids is always from the higher pressure to the lower pressure area.” *

In coarctation, the notching usually involves several posterior ribs bilaterally, from the 3rd through the 9th. The first 2 intercostal arteries do not connect directly to the and the last 3 have no connection to the subclavian system (see Figure S3-2 again).

aorta

The anterior intercostals, arising from the internal mammaries, are paired in each intercostal space. They do not lie close to the anterior ribs and therefore do not notch them.

* Tu Hunghai: Chinese Med J 14.281, 1372 BC.Figure S3-2

A.

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If the coarctation lies distal to the left subclavian artery, as it almost always does, the notching will be bilateral. If the coarctation lies proximal to the left subclavian artery, the rib notching will be [unilateral/bilateral].

The high pressure in the subclavian arteries in coarctation favors the filling of collateral pathways. When the left subclavian arises distal to the coarctation (Figure S3-3A), the pressure in this artery is low and notching will only be present on the right .The notching in this patient is confined to the right 4th to 6th ribs (Figure S3-3B).*

Patient: “Doctor, I have big troubles. Some days I feel like a curtain.”Doctor: “Pull yourself together, man.”

Figure S3-3A

* Courtesy Dr. John A. Campbell, Indianapolis.

Figure S3-3B

A. B.

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Figure S3-4B is an example of this. The left 6th and 7th ribs are notched (arrows).*

Figure S3-4A

left

* Courtesy Dr. John A. Campbell, Indianapolis.

Figure S3-4B

A. B.

If there is an anomalous right subclavian artery that arises distal to the coarctation, the notching will be unilateral (Figure S3-4A).Since little blood is reaching the right subclavian artery, the pressure in this artery is too low to permit collateral flow, and the notching will be confined to the side.

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Thus, unilateral rib notching can occur in coarctation, and one can then usually predict the pathologic anatomy of the aortic arch. The notching is always on the [same/opposite] side as the subclavian artery, which comes off proximal to the coarctation.

* Courtesy Dr. John A. Campbell, Indianapolis.

Figure S3-4A Figure S3-4B

A. B.

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* Courtesy Dr. John A. Campbell, Indianapolis.

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OK, let's summarize coarctation. The collateral flow is:

Figure S3-4A Figure S3-4B

A. B.

subclavians

thyrocervical costocervical

intercostals

Aorta

right and left

branches

descendingthoracis aorta

posterior

internal mammary

(1)

(2)

(3) (4)

(5)

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3rd 9th

Now let's really get down to work.

leftright

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Rib notching involves the through the ribs. Are all these ribs notched in an individual patient? [usually/seldom]

More summarizing and then we are through with this. Notching confined to the right ribs usually indicates that thesubclavian artery arises distal to the coarctation. Notching confined to the left side usually indicates that the subclavian artery comes off distal to the coarctation.

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In thrombosis of the abdominal aorta, the lower intercostal arteries serve as collaterals to the lower part of the body. They become large and tortuous and may cause notching of the lower ribs. Obviously, here the intercostal artery flow is [toward/away from] the aorta.

In Figure S3-5 the thoracic aortogram shows abdominal aortic occlusion with dilatation of the 8th to 10th intercostal arteries, which carry blood to the lower part of the body. Note the tortuous intercostals indenting the ribs.

Figure S3-5

A.

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You have now learned 2 mechanisms and 2 causes of rib notching.

Mechanism(a) High aortic obstruction. (Intercostal flow is the aorta.)(b) Low aortic obstruction. (Intercostal flow is the aorta.)

Cause(1) Coarctation of aorta(2) Thrombosis of abdominal aorta

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toward from

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Figure S3-6 shows a patient with unilateral notching of the 3rd to 7th left (arrows), which appeared after a left Blalock-Taussig operation.

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Figure S3-6

Deficient blood flow to the arm occurs following the Blalock-Taussig (subclavian-pulmonary artery) anastomosis for tetralogy of Fallot. A good part of the arterial collateral flow to the arm is:

Aorta

posterior intercostals

long and short thoracics

axillaryThis may eventually result in [ unilateral / bilateral ] rib notching.

A.

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Figure S3-7 is an example of pulseless disease of all the great vessels arising from the aorta and shows definite notching (arrow).

Figure S3-7

armBlalock-Taussig

A.

"Pulseless disease" is caused by either arteritis (Takayasu's disease) or arteriosclerosis obliterans. It is associated with occlusion of 2 or more of the brachiocephalic arteries at their origin. This results in diminished flow to the , similar to that following the operation, and the collateral flow is much the same. So here is another arterial cause of rib notching.

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Following the Blalock-Taussig procedure and in pulseless disease, the blood flow in the intercostal arteries is [toward/away from] the aorta. In these 2 conditions the rib notching will be on the [side of/side opposite] the occluded subclavian artery.

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coarctation aortic thrombosis

Blalock-Taussig operation

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You should now know 4 arterial causes of rib notching. Do you?High aortic obstruction: (1) Low aortic obstruction: (2) Subclavian obstruction: (3)

(4) pulseless disease

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Next, we have several conditions that occasionally cause arterial rib notching by another mechanism. In congenital cardiovascular lesions with decreased pulmonaryblood flow, the pulmonary circulation may be augmented by blood from the intercostal arteries via the bronchial arteries, branches perforating through the chest wall, etc. Example: tetralogy of Fallot.Can you think of some other congenital lesions with decreased pulmonary flow?

Figure S3-8

Figure S3-8: tetralogy of Fallot with absent right pulmonary artery. The notching of the left 6th rib (arrow) appeared a year after the Blalock-Taussig operation. The notching on the right (arrows) antedated the operation. Therefore, there are two mechanisms for rib notching in this patient.

1) pulmonary valvular stenosis

3) pseudotruncus (atresia of the main pulmonary artery) 2) absent pulmonary artery

A.

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Severe emphysema, with extreme local oligemia, can also cause unilateral rib notching. In Figure S3-9A, the pulmonary vessels are markedly diminished in the RUL (arrow points to one of several notched ribs). In Figure S3-9B, note tortuous intercostal arteries below multiple ribs. From: The Internet Journal of Pulmonary Medicine (ISSN: 1531-2984). Plaza P, HerrejonA: Pulmonary emphysema as a cause of rib-notching. Volume 2, Number 1, 2001. With permission of Internet Scientific Publications; www.ispub.com.

absent tetralogy Fallot

A.

Figure S3-9A

B.

Figure S3-9B

pulmonary

Four congenital cardiovascular lesions with decreased pulmonary flow in which rib notching has been reported are:(1) pseudotruncus(2) pulmonary artery(3) of (4) valvular stenosisThese usually cause unilateral rib notching.

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high aortic obstructioncoarctation of aorta

aortic thrombosis

Blalock-Taussig procedurepulseless disease

tetralogy of Fallotabsent pulmonary artery

pulmonary valvular stenosispseudotruncus

emphysema

absent pulmonary artery

OK, here are 4 mechanisms and 9 causes of arterial rib notching:(a)

(1)

(b) low aortic obstruction:(2)

(c) subclavian obstruction:(3)(4)

(d) pulmonary oligemia:(5) (6)(7) (8) (9)

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Now what about the intercostal veins? Can they cause notching? Sure ─ or else we wouldn't have brought it up.Fibrosing mediastinitis may cause chronic obstruction of the vena cava. The azygos system becomes a major collateral pathway, and the intercostal veins often carry a considerable amount of blood to the system.

superiorazygos

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Figure S3-10 is a right brachial venogram showing superior vena cava obstruction and numerous collateral veins in the neck and mediastinum. A large tortuous intercostal vein is notching the right 5th rib (arrow). The left 8th rib is also notched.

Figure S3-10

superior vena cava fibrosing mediastinitis

A.

The intercostal veins may become so dilated and tortuous that they notch the ribs. So far, the only reported cause of venous notching has been obstruction of the secondary to .

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Notching caused by arteriovenous fistula is the one most people forget. Will you?Figure S-3-10 shows innumerable tiny pulmonary arteriovenous fistulas in a patient with congenital familial telangiectases. The right 5th and 7th ribs show notching (the 6th has been resected).

Arteriovenous fistulas are characterized by large feeding and draining vessels. The intercostal vessels may be involved and notch the ribs. Can you name 2 sites of an arteriovenous fistula in which this might occur?(1) (2)

chest wall pulmonary

Figure S-3-10

A.

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arteriovenous

a) high aortic obstructionb) low aortic obstruction

d) pulmonary oligemia

(1) coarctation of aorta (2) aortic thrombosis (3) Blalock-Taussig procedure (4) pulseless disease(5) tetralogy of Fallot

(7) pulmonary valvular stenosis(8) pseudotruncus

(11) AV fistula of chest wall (12) pulmonary AV fistula

You have now learned an even dozen causes of rib notching ─ 9 arterial, 1 venous, and 2

Fill in the appropriate responses:

I. Arterial

II. Venous

III. Arteriovenous

c) subclavian obstruction

(10) superior vena cava obstruction

(9) emphysema

(6) absent pulmonary artery

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The third important component of the intercostal space is the .

If there is a tumor of the nerve, rib notching may occur. In neurofibromatosis, these notches may be multiple. The neurofibromamay or may not be visible. Figure S3-11 shows broad notching of the right 4th to 7th and left 6th to 8th ribs in a patient with neurofibromatosis. The mass in each pulmonary apex represents an intercostal neuroma. In a different patient, Figure S3-12A, there is a visible neurofibroma (arrowheads) and focal rib notching (arrows). Figure S3-12B shows the notched rib and the adjacent neurofibroma.

nerve

Figure S3-11 Figure S3-12A Figure S3-12B

A. B. C.

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Thus, rib notching may be caused by artery, vein, or lesions.

Along the undersurface of every rib are the two ridges in which the vessels and nerves run. If the ridges are of different heights, the undersurface of the rib is often indistinct (Figure S3-13). This is usually most noticeable on the posterior-lateral 4th-7th rib. InFigure S3-14, these normal areas may be mistaken for rib nothing.

Figure S3-13 Figure S3-14

nerve

A. B.

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29Occasionally, minimal rib notching is seen without apparent cause. When normal people can’t figure something out they say, “I don’t know.” In medicine, if we don’t know something, we call it . This “idiopathic” notching is probably dueto these uneven ridges.

“Idiopathic”*

Dr. Felson reviewed 1000 normal survey chest roentgenograms for rib notching and encountered it in mild degree (never severe) in one or two ribs with surprising frequency. (He probably had a notched retina.) These are idiopathic.*

* Idio - I don't know; pathic - I wish I did.

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So here are 2 more causes of rib notching:IV. nerve (13)V. normal (14) ridges under ribs

neurofibromatosis

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You have learned 15 causes of rib notching. We admit there may be others, but if so, they are about as common as priapism in the old men's home. Classify the ones you know in the space below:

Arterial

Arteriovenous

Nerve

Normal

high aortic obstruction low aortic obstruction

subclavian obstruction

pulmonary oligemia

coarctation of aorta

aortic thrombosis Blalock-Taussig procedure

pulseless disease tetralogy of Fallot

absent pulmonary artery

pulmonary valvular stenosispseudotruncus

emphysemasuperior vena cava obstruction

AV fistula of chest wall pulmonary VV fistula neurofibromatosis

normal ridges (idiopathic)

Now compare your answer to the one you gave in Frame 1.

Mechanism

Review

I. (a) (1) (b) (2) (c) (3)

(4)(d) (5)

(6) (7)(8)(9)

II. Venous (10) III. (11)

(12) IV. (13) V. (14)