Mucoid degeneration of the brachial artery: case report and a review of literature
M.A. WALI1, M. DEWAN 2,
W.M. RENNO 3, M. EZZEDDIN 1
Departments of Surgery1, Pathology2 and Anatomy3,
Asir Central Hospital and College of Medicine, King Saud University, Abha, Saudi Arabia
Cystic adventitial disease (CAD) is a rare cause of intermittent claudication, occurring in approximately 1:1200 claudicants 1 or 1:1000 of those undergoing arteriography.2 It is most often described in the popliteal artery and is characterised by a mucinous cyst located in the adventitia of the artery, the contents of which resemble those of a ganglion. The origins of adventitial cysts are unknown, but connections to adjacent synovial spaces have been identified, suggesting that the cyst is a variant of a ganglion.3 In this report, we discuss a rare case of severe mucoid degeneration of the intima and media in a 67-year-old Saudi male patient. The patient presented with a saccular aneurysm of his right "mid-arm" brachial artery and critical ischemia of his right hand from distal embolisation.
Keywords: mucoid degeneration, cystic adventitial disease, brachial artery, aneurysm, distal embolisation
J.R.Coll.Surg.Edinb., 44, April 1999, 126-129
A 67-year-old male patient presented with a one month duration of rest pain in the right forearm and right hand which was associated with numbness of the tips of the fingers and weakness of his hand grip. His past history was unremarkable. On examination, his heart, lung, blood count and chemistry were all within normal limits. His right hand was pale with delayed capillary filling, but no discolouration, gangrene or tissue loss. There was aneurysmal dilatation of the right midbrachial artery measuring about 2 x 1cm, with a normal brachial artery pulse at the elbow. Both radial and ulnar arterial pulses were absent at the wrist. Examination by continuous wave Doppler (CWD) probe revealed weak flow signals in the ulnar artery and no signals in the radial artery. At operation, there was a small saccular aneurysm of the brachial artery with bossy areas that contained small clots. The aneurysm was resected. An intra-operative angiogram through the open distal end of the brachial artery revealed occlusion of the radial artery in the proximal forearm and short occlusion of the ulnar artery near its origin with good distal run-off down to the wrist (see Figure 1). Using an elbow-sited, S-shaped skin incision, selective embolectomy of both the radial and the ulnar arteries was successfully performed through a longitudinal bifurcation arteriotomy that was repaired with a long saphenous vein patch. The continuity of the brachial artery was later restored using an interposition reversed long saphenous vein graft, with restoration of both the radial and the ulnar arterial pulses at the wrist.
Figure 1: Intra-operative angiogram through the distal end of the brachial artery after excision of the aneurysmal part, showing occlusion of the ulnar artery near its origin and of the radial artery in the proximal forearm
The resected sac-like segment of the right brachial artery weighed 0.7gm and measured 1.7 x 0.6cm. Microscopic examination of sections from the aneurysm, using haematoxylin and eosin stains, showed mucoid degeneration of the intima and the media circumferentially, dissecting and destroying the muscle bundles (see Figure 2a). The muscle bundles were replaced by Alcian blue-positive mucoid material, which distended the wall and produced bulges in the lumen (see Figure 2b). A few patchy areas of the adventitia also revealed some mucoid tissue. In occasional foci, granulation tissue with sparse mononuclear cell infiltrate was observed in the intact adventitial coat. Elastic Von Gieson stain revealed sparse to absent elastic fibres in the affected segment. Intima and media were totally devoid of elastic fibers and external elastic lamina was seen only in patchy areas. Red thrombus with early organisation was observed in the tissue labelled clinically as embolus.
Figure 2a: Microscopic specimen of the brachial artery aneurysm (magnification 20x) using haematoxylin and eosin stains, showing intimal and medial thickening with the wall bulging into the lumen
 |
 |
| Figure 2b: Microscopic specimen of the aneurysm wall (magnifi-cation 200X) using haematoxylin and eosin stains,showing mucoid degeneration of the intima and the media with pools of mucin | Figure 2c: High-power microscopic specimen (magnification 400X) of the media of the brachial artery aneurysm using haematoxylin and eosin stains, demonstrating mucin pools dissecting and replacing the smooth muscle bundles |
Cystic adventitial disease (CAD) was first described in 1947 by Atkins and Key.4 They recorded the case of a 40-year-old man with intermittent claudication associated with a palpable swelling above the inguinal ligament. At operation, a cyst was dissected from the external iliac artery and was described as a typical ganglion. The first report of involvement of the popliteal artery was made by Ejrup in 1954.5 The world literature has been reviewed by Flanigan on three occasions, most recently in 1979.6 Of the 115 cases he studied, the popliteal artery was affected in 85 per cent. Currently, more than 200 case reports are available in the world literature, with only 6 patients younger than 15 years of age.7 Approximately 85 per cent of the patients are male and the average age at presentation is 42 years3 (range 11 - 70 years).8,9 Apart from the popliteal artery, CAD has also been described in the external iliac artery, femoral artery10, radial and ulnar arteries11 and in branches of the popliteal artery.12 We did not come across a single report of involvement of the brachial artery, although involvement of the veins, like the common femoral vein13, have been described on a few occasions.
Our patient presented with an abrupt onset of rest pain in his right hand together with coldness, numbness, paraesthesia and a weak grip. On examination, the saccular aneurysmal dilatation of the brachial artery was palpable in the mid-arm region, away from the elbow joint. Distally, the brachial artery pulse was normal at the elbow while both the radial and the ulnar pulses were absent at the wrist. In almost all the cases described in the literature, intermittent claudication is the presenting feature. The onset is characteristically abrupt, possibly due to sudden rupture of the cyst14 or to hemorrhage within it5 and this may suggest the correct diagnosis in older patients.15 On examination, there are usually no stigmata of generalised arterial disease16, as is the case with our patient. Rarely, the adventitial cyst itself is palpable. When the vessel is only partially occluded, peripheral pulses may be present with the limb extended, but disappear during joint flexion17, and a bruit may be audible.18 Typically, as the cyst enlarges, it produces distal ischemia by vascular compression with stenosis or occlusion. In our patient there was no adventitial cyst, but circumferential myxoid degeneration of the arterial wall leading to saccular aneurysm formation, intramural clots and embolic occlusion of the distal arteries.
The cause of the deposition of gelatinous material between the adventitia and the media in an arterial wall is not known, but several theories have been suggested. Simple degeneration may be unlikely since the condition has been described in childhood9,12 and there is no association with any generalised connective tissue disorder.19 The affected vessel is commonly closely related to a joint which lead to the hypothesis that repeated flexing of the arterial wall might induce activity in dormant mucin-secreting cells.20 However, this too is unlikely because biochemically, the mucin is of the nature of ground substance rather than epithelial secretion.21 This was also vividly demonstrated in our case, where the mucoid material stained positively with Alcian blue, which proves that it is a connective tissue material and not an epithelial secretion i.e. a product of connective tissue degeneration. If microtraumata were the cause, then CAD would be expected to occur both more often22, and on occasions bilaterally.16 The most prevalent postulate is that the cyst is a true ganglion arising from an adjacent joint capsule or a tendon sheath23 and, as with ganglia elsewhere, a direct communication with the joint need not persist.24 Recently, in their report on an adventitial cyst of the common femoral artery, Milleux et al25 demonstrated the articular origin of this disorder using computerised tomographic (CT) scanning. However, this belief does not explain the clinico-pathological features in our patient. The affected segment of the brachial artery was well away from the elbow joint and the main brunt of the mucoid degenerative process was in the intima and the media , with only minimal involvement of the adventitia. Interestingly, as early as 1954, Ejrup5 suggested that the aetiology of CAD was mucoid degeneration of the media. While this concept was not well received initially, it was recently supported by Inoue et al in 199226 in their case report of CAD of the popliteal artery. They noted that while some cysts were found in the adventitia, they were mainly located in the media. The media showed a remarkable decrease of the smooth muscle cells and a prominent mucinous degeneration that had occurred circumferentially. They concluded that the medial degeneration occurred prior to the adventitial cyst formation.
Based on our findings in this case, we presume that the site of the affected vessel alters the course of the disease. Since the affected vessel is commonly closely related to a joint, repeated flexing of the arterial wall might help disintegrate the external elastic lamina early in the disease process, and allow the myxoid (mucoid) material to extrude from the inner coat and produce the adventitial cysts. In our patient, the affected arterial segment was well away from joints which probably helped to keep the external elastic lamina fairly intact till late. This allowed the degenerative process to progress intramurally in the inner coat until the wall lost its turgor, weakened and became sacculated.
The newly described entity of intimomedial mucoid degeneration (IMMD) of arteries needs special consideration. The largest series published in the English language surgical literature on aneurysms due IMMD was published recently by Abdool-Carrim et al27 from South Africa. They presented 22 cases of aneurysms of the aorta and the extra-aortic arteries, mainly the subclavian and the common carotid arteries. In their practice, the condition was confined to the black African population, predominantly in females. Earlier reports by Decker et al28 describe the disease as being confined to the abdominal aorta. In 1993, Cooper29 first described the pathology in the extra-aoric arteries in six patients. Recently, what would appear to be the identical arteriopathy, has been reported in an autopsy study conducted in India by Sandhyamani.30 He noted that the changes were in the aorta and its major branches.
Different treatment procedures have been described in the literature, depending on the different presentations of cases of CAD. These procedures include needle aspiration31, simple cyst excision, patch angioplasty, resection with direct end-toend anastomosis32, resection and interposition vein graft or even bypass grafting without cyst excision. CT-guided percutaneous cyst aspiration was tried with partial success33,34, because the consistency of the cyst contents makes this difficult and recurrence is likely because the cyst is still intact. Percutaneous transluminal angioplasty (PTA) however, has been shown to be unsuccessful35, because, unlike the situation in atherosclerosis, the intima in CAD is usually normal and the cyst wall is compliant. While the condition was incidentally diagnosed in our patient , we strongly recommend excision and interposition reversed vein grafting or bypass grafting if the condition is suspected.
In conclusion, mucoid degeneration of arteries can occur at any site and is not confined to the black African population. The main brunt of the degeneration in our patient was in the inner coats of the affected arterial segment (ie intima and media) which indicates that the degenerative process was initiated there and not in the adventitia. This resulted in weakness of the arterial wall and aneurysmal dilatation rather than the usual stenosis or occlusion of the vessel lumen due to compression from outside by the cyst in the adventitia, which suggests that our case is one of IMMD rather than CAD. The entity of IMMD as a cause of aneurysmal dilatation of extra-aortic arteries needs further investigation. We are conducting an electron microscopic study to examine the morphological changes in the smooth muscle cells of the media in this case.
ACKNOWLEDGEMENT
We would like to thank Mr Eric Avilk for his technical assistance during the preparation of the specimen.
Copyright date: 18th September 1998
Correspondence: Dr. M.A. Wali, Department of Surgery, College of Medicine, King Saud University, P O Box 641, Abha, Saudi Arabia.
©1999 The Royal College of Surgeons of Edinburgh, J.R.Coll.Surg.Edinb., 44; 2: 126-129