Arterial entrapment is a tear within the arterial wall layer that causes blood components to enter the vessel wall through the broken intima, causing the vessel wall to delaminate, resulting in stenosis, occlusion, or formation of a pseudoaneurysm. Intercalated aneurysm is a pathological entrapment occurring within the mesenteric layer or peeling between the mesenteric and epicranial membranes, where the wall of the cerebral artery bulges and aneurysmal dilatation of the vertebral artery entrapment aneurysm occurs.
Intracranial artery entrapment is a pathological entrapment of the cerebral vessel wall involving the intima of the artery, forming a subintimal hematoma and dilating between the intima and the mesentery. An entrapment aneurysm or arterial dissection is a pathologic entrapment that occurs within the mesenteric layer or between the mesentery and the epicranium, and the wall of the cerebral artery bulges and becomes aneurysmically dilated.
Features
1.Small damage to the endothelial membrane of the endothelial valve without hematoma may manifest only as painful pain.
2, Endothelial valve combined with subendothelial and intermural hematoma thrombus formed by the subendothelium and extended to the lumen of the vessel, which may manifest as ischemic symptoms caused by the thrombus.
3, the defect of the arterial wall of the entrapped aneurysm leads to its aneurysmal expansion, the arrow shows the direction of blood flow in the aneurysm, which may manifest as bleeding symptoms.
4. Intermural hematoma intermural hemorrhage with vascular stenosis.
Epidemiology
The annual incidence of vertebrobasilar system coarctation aneurysm is 1/100,000-1.5/100,000, and there is no epidemiological data for a large sample in China. There is no significant difference in incidence between men and women, and 80% occur in people aged 30 to 50 years, with youth and middle age as the high incidence periods.
Etiology
1, history of head and neck trauma: minor trauma, such as neck massage and massage, over-extension and over-bending, head turning and other movements, even coughing, vomiting, sneezing, etc. can also cause vertebral artery entrapment.
2, underlying arterial disease: it may lead to the vulnerability of the vessel wall, and the intima is prone to tearing. Hereditary connective tissue disease is an obvious associated cause of spontaneous arterial entrapment.
3, muscle fiber dysplasia: about 15% to 20% of patients with this disease develop cranial and carotid artery entrapment, with about 50% of them developing bilateral internal carotid arteries
4, migraine: may be related to edema of the vessel wall, tearing of the vessel wall or enlargement of the entrapment and subarachnoid hemorrhage.
5.Infection: Recent infection, especially upper respiratory tract infection, can induce cerebral artery entrapment, which is characterized by the involvement of multiple arteries, probably due to oxidative stress caused by infection, autoimmune and other mechanisms that damage the vessel wall.
6, hypertensive disease.
7.Oral contraceptive pills
Pathology and pathogenesis
1.In some cases, the laceration injury occurs in the endothelium, and blood flow invades the mesentery along the injury to form an intramural hematoma, at which time an internal valve is often visible in the endothelium.
2. If the intramural hematoma extends outward to the subepithelium, it can cause arteriovenous dilatation and cause occupying effects such as compression of cranial nerves or brainstem.
If the hematoma breaks through the outer membrane and ruptures, it may cause subarachnoid hemorrhage in the intracranial space and pseudoaneurysm in the extracranial space.
Clinical manifestations
Acute ischemic manifestations: severe migraine is the main symptom of the disease, cerebral ischemia, stroke occurs a few days after the initial symptoms, recurrent symptoms within 2 weeks, Horner syndrome, vascular pulsatile murmur, basal A entrapment complication symptoms – brainstem ischemia, headache, brainstem infarction.
2, Chronic ischemia: entrapment aneurysm may produce occult thrombotic particles → intracranial artery embolism, large or occupying effect entrapment aneurysm, limited neurological deficits, cranial nerve symptoms.
3. The main manifestations of SAH: headache, with SAH mostly suggesting that the aneurysm of the entrapped vertebral artery in the extracranial segment extends intracranially, and the entrapped vertebral artery in the intracranial segment occurs at the beginning of PICA. Brainstem ischemia is now Wallenberg syndrome, ataxia, migraine and partial consciousness disorder, and thereafter neck pain, neck stiffness, sudden tinnitus, etc.
Imaging features
Imaging features of intracranial artery entrapment and entrapped aneurysm
1. MRA is highly sensitive for the diagnosis of entrapment aneurysm, and high-resolution MRI can show arterial lumen, arterial wall and intermural hematoma, and the signal intensity changes with the absorption of hematoma. In the subacute stage, T1 and T2 arterial entrapment shows crescentic intermural high signal, which can only suggest the diagnosis and cannot be used as the gold standard, but can be used as a reference for follow-up.
(1) intra-arterial wall hematoma, showing thickened arterial wall with smooth edges of the thickened wall, TW1 and proton image shows crescentic, curve-like, band, star and ring abnormal signal in the arterial wall. the corresponding part of DSA wire bead sign shows stripe-like high intensity signal in T1W.
(2) The double lumen is the true and false lumen formed after the separation of the arterial wall from the interlayer. T1W and proton images show that the true lumen is narrower, round-like and low signal, which is an incompletely occluded lumen with blood flow; the false lumen is wider, crescent-shaped and high signal, which is caused by the separation of the inner lumen from the interlayer, with hematoma formation. (Conventional MRI has a low positive rate of detecting double lumen, and its positive rate is as high as 50% one year after the onset of the disease. Double lumen is a direct sign of entrapment aneurysm and can be used as a basis for diagnosis.
(3) Endothelial flap is caused by the separation of the inner lumen of the arterial wall. T1W, T2W and proton images can be seen as flap-like structures with high signal, which are located in the lumen of the vessel, and T2W imaging is easy to see, and T2W imaging is superior to DSA in observing endothelial flap, and about half of the patients can show endothelial flap with T2W imaging.
2.MRA has diagnostic value for patients with wire bead sign, aneurysmal dilatation, pseudoaneurysm and vascular occlusion, and can be used for dynamic observation. However, MRA cannot detect small coarctation aneurysms, cannot accurately show the degree of stenosis, cannot distinguish whether it is slow flow or intermural hematoma, and cannot show the unique signs such as double lumen, so it is not ideal for the diagnosis of coarctation aneurysm.
DSA is a more reliable diagnostic method for this disease. DSA shows irregular lumen combined with proximal stenosis, spindle-shaped dilatation, proximal and/or distal stenosis (beaded or thread-like sign), double lumen, irregular fan-shaped stenosis, and contrast retention in the venous phase.
(1) Intermural hematoma may present as.
(i) complete occlusion.
(ii) string sign.
(iii) luminal narrowing with mostly tapering conical or flame-shaped ends, which may also be round or pouch-shaped.
(2) The aneurysmal dilatation caused by intermural hematoma is shuttle-shaped, sac-shaped, irregular-shaped, tubular or serpentine.
(3) The intermural hematoma enlarges the artery and manifests as a beaded sign in conjunction with its proximal or distal vascular stenosis.
(4) Retention of intraluminal contrast in intermural hematomas is also more common.
(5) If the intermural hematoma is recanalized with the lumen of the vessel, it may appear as.
(i) double lumen.
(ii) Endoluminal flaps.
(iii) In some cases, the true vascular lumen or its mixing with the pseudolumen is seen in the arterial phase of the angiogram, while in the venous phase only the pseudolumen formed by contrast retention is seen; (iv) Pseudoaneurysm is formed after the rupture of a coarctation aneurysm.
⑤ The intra-arterial lumen may be concave and uneven, showing a rose sign.
Diagnosis
1.Diagnosis of vertebral artery entrapment aneurysm is more difficult
2. The clinical manifestations of a coarctation aneurysm lack specificity, such as headache, ischemic stroke and SAH, and the diagnosis is mainly based on the specific changes of imaging.
3. MR and DSA show endothelial flap, double lumen sign, intermural hematoma, vertebral artery shuttle expansion, with distal stenosis are the characteristics of vertebral artery clogged aneurysm.
DSA is the gold standard for diagnosis.
Treatment principles
1. Treatment of ruptured aneurysms should be aggressive and require urgent surgical intervention when SAH occurs
The location of PlCA branches should be individualized.
3.The choice of intervention and surgery. Compared with open surgery, interventional treatment is more suitable and can avoid the huge trauma of open surgery. In addition, there is no real aneurysm neck in the entrapped aneurysm, and clamping surgery is often difficult to complete.
4.Endovascular treatment of vertebral artery entrapment aneurysm, endo-isolation and proximal occlusion of entrapment aneurysm, stent-assisted GDC, double stent or multi-stent, dense mesh stent, overlapping stent.