Etiology and pathology
Intracranial vascular malformation is a developmental malformation of the intracranial vascular bed; it manifests as an abnormal increase in blood vessels in a region of the skull. Currently, they are generally classified into 4 types.
① arteriovenous malformation ;
② capillary dilation;
③Venous hemangioma and varicose vein Z
(iv) cavernous hemangioma. Among them, arteriovenous malformations are the most common, accounting for more than half of them. This section describes the arteriovenous malformations. Arteriovenous malformations of the brain are most common in young people, with the highest incidence in young adults between the ages of 20 and 40, and more common in males than females. If some factors affect the normal development of the primitive cerebrovascular network during the embryonic period, the capillaries are incomplete and the arterioles and veins are directly connected to form a short circuit, which develops into cerebral arteriovenous malformation.
Clinical manifestations
Cerebral arteriovenous malformations are associated with no discomfort or occasional seizures. The most common symptom of cerebral arteriovenous malformation is the rupture and bleeding of the malformed blood vessel, forming an intracerebral hematoma or subarachnoid hemorrhage. Sudden onset of severe headache and stiff neck, accompanied by nausea, vomiting and some degree of impaired consciousness, lesions and hemorrhage at different sites, localization signs such as hemiparesis, hemianopia, aphasia and hemianopic sensory impairment and oculomotor disorders, ataxia and other manifestations of posterior cranial fossa arteriovenous hemorrhage. This is followed by epilepsy and headache.
Imaging manifestations
1.Brain arteriogram
Cerebral arteriovenous malformation has the following typical manifestations.
① Showing malformed vessels. This is a characteristic manifestation, showing a mass of tortuous dilated vessels with similar diameter and tangled with each other. The extent of the malformed vascular mass can be as small as a fingernail or as large as the palm of a hand, mostly in the cortex of the cerebral hemispheres.
(2) Abnormally large feeding arteries and draining veins with accelerated local circulation. This is a manifestation of local blood flow short circuit.
③The phenomenon of blood flow shunt: the contrast agent flows into the vein in large quantities with the short-circuiting of blood flow through the malformed vessels, so that the malformed part of the vessel is very clearly visualized due to the increased blood flow.
The main manifestation of hematoma is the local occupying sign. When there is no hematoma in one brain arteriovenous malformation, the occupying sign does not appear in the cerebral vessels and the cerebral vessels are not displaced.
2.CT performance.
There are more typical CT manifestations before the cerebral arteriovenous malformation is ruptured and bleeding. In plain scan, focal high-low or low-mixed density shadow is seen in the form of speckles, clusters or cords with unclear edges. The high-density shadow is due to focal gliosis, thrombus, calcification, new hemorrhage or slow blood flow within the malformation and iron-containing hemosiderin deposition, while the low-density shadow is due to small infarcts or old hemorrhage with limited cerebral atrophy around the lesion, no obvious occupying effect and no peripheral cerebral edema. In some patients, arteriovenous malformations cannot be detected on plain scan, but contrast is injected to reveal the lesion. After contrast injection, the arteriovenous malformations in the brain show mass enhancement, and even tortuous vascular shadow, blood supply arteries and draining veins are visible.
In post-hemorrhagic cerebral arteriovenous malformations, intracerebral hematomas, subarachnoid and ventricular system hemorrhages are seen. Depending on the duration of hemorrhage, high-density, mixed-density, and low-density shadows are seen, and the hematoma is surrounded by a low-density edema area. There are also occupational effects such as ventricular compression and deformation and midline shift. After contrast injection, some of the hematoma edges may have tortuous reinforcement of malformed vessels, while the mixed dense shadow hematoma often has ring reinforcement.
3.MRI performance
MRI is the first choice for the diagnosis of cerebral arteriovenous malformations, especially for posterior cranial fossa lesions, which has a greater diagnostic value than CT. The vascular component of cerebral arteriovenous malformations is shown as a signal-free flow-void vascular shadow distributed in clusters and networks. Among them, the blood supplying arteries appear as low or no signal shadow on T1 and T2-weighted images due to the flow-void phenomenon. The draining veins show low signal on T1-weighted images and high signal on T2-weighted images due to slow flow. Calcification of the vessel appears as a low or no signal dark area. The thrombus in arteriovenous malformation shows low signal interspersed with iso-signal or high signal interspersed with high signal within high signal and low signal in both T1 and T2-weighted images. ② Hematoma formed by bleeding from arteriovenous malformation shows T1 and T2-weighted image changes similar to other causes of hematoma. In the subacute stage, the hematoma is high signal on both T1 and T2-weighted images. With time, the hematoma gradually changes to iso- or low-signal on T1-weighted images and remains high signal on T2-weighted images.
[Surgical treatment]
Indications
1. The patient has one of the following conditions, and the angiography determines that the malformed vessel can be removed.
(1) History of spontaneous subarachnoid hemorrhage.
(2) Those with frequent epilepsy and poor results of drug therapy.
(3) Those with symptoms of progressive localized neurological damage or mental retardation (blood-stealing syndrome).
(4) Those with combined intracranial hematoma or intracranial hypertension.
2. Those who can be treated by the following surgical methods.
(1) Hematoma removal, for patients with hematoma after bleeding. If the patient is in good condition, cerebral angiography can be performed before surgery, and malformation vascular resection can be done at the same time during surgery. If the patient is in critical condition, hematoma removal can be performed first, cerebral angiography can be performed after recovery, and then secondary surgery for lesion removal can be performed.
(2) Malformation vascular resection is suitable for those who have had bleeding, especially repeated bleeding; progressive brain dysfunction such as progressive light hemiparesis and intractable seizures that are difficult to control by medication due to cerebral blood theft phenomenon.
(3) Ligation of supply arteries is indicated for deep lesions involving important structures such as the brainstem and deep major veins. However, there are multiple supply arteries, and ligation of only one or two of them may not be therapeutic.
(4) Manual embolization is indicated for extensive or multiple lesions that cannot be resected, or for use as a preparatory procedure before resection of extensive vascular malformations.
In this article, arteriovenous malformation resection is used as an example.
[Contraindications]
All are relative contraindications, with the improvement of technology, some of these cases can still be treated surgically.
1, Arteriovenous malformations in the deep brain, internal capsule, basal ganglia, brainstem, etc.
2, Extensive or multiple arteriovenous malformations.
3.Asymptomatic person.
4.Older people over 60 years old with serious diseases of heart, kidney and respiratory system.