Slavin et al described five angiographic appearence of SAM,
with a radiological sign associated.
All the radiological signs are shown in the images in this section.
- Arterial dilatation: muscular lysis with fibrin deposit in the outer layer.
- Single aneurysm:destruction of the internal elastic lamina,
progresses towards the intima in a segmental way.
- Multiple aneurysm: multiple segmental aneurysms with areas of normal vascular wall.
Morphology in "string of beads".
- Dissecting hematomas:separation between the external elastic lamina and the adventitia.
- Arterial stenosis and occlusion: repair phenomena and fibrosis.
Diagnosis
SAM does not have diagnostic markers and a definitive diagnosis requires biopsy of the affected artery.
Even though is highly recommended,
biopsies are rarely performed due to the location of the arteries.
Instead,
clinical and imaging features of SAM are used for diagnosis.
Diagnostic criteria:
- Exclude connective tissue diseases (Ehlers-Danlos,
Marfan),
atherosclerosis,
fibromuscular dysplasia,
and other types of vasculitides
- Evidence of dissection and / or an aneurysm with or without organ infarction in one or more of the mesenteric or renal arteries.
- Absence of inflammatory markers such as erytrocyte sedimentation rate (ESR),
ancinuclear antibodies (ANA) and C-reactive protein.
All three criteria must be met to establish the diagnosis of SAM.
They are based of reports of the literature,
and further studies are required to validate the diagnostic criteria.
Fibromuscular dysplasia (FMD) is the most difficult diagnosis to differentiate from SAM.
However, they differ in demographics,
distribution of the affected arteries and clinical symptoms.
FMD presents in young to middle-aged women,
is rarely painful,
and is usually asymptomatic or associated with symptoms of occlusive disease or premature hypertension.
On the other hand,
as we have already said,
SAM presents at any age,
has no gender predilection,
and more associated with hemorrhage and arterial dissections.
In FMD patients involment of renal and carotid arteries is more common than the visceral arteries (only 9%),
direct opposite of SAM where visceral arteries are the predominantly affected.
Despite these differences,
some authors suggest that SAM is fundamentally a precursor of a variant of FMD,
based on the observation that healed SAM lesions resemble FMD.
Treatment and Prognosis
SAM can evolve to:
- Spontaneous resolution,
such as stable vascular injury
- Progress
It requires an imaging control within the first 24-48 hrs or earlier according to evolution.
There is no evidence for treatment. The use of anticoagulants and antiplatelets is controversial because of the high risk of aneurysmal rupture.
Mortality rate from SAM after the recent introduction of endovascular management has reportedly improved to 25% and prognosis is good,
but far from being the treatment of choice,
because during the procedure patient need anticoagulation that can lead to complications afterwards.
Even though there are successful publications of endovascular management of SAM,
there is no evidence to propose interventional radiology as the election management,
as it may predispose to new dissections and thrombosis.
Also there is no evidence to use corticosteroids in the management of SAM.