Cerebrovascular malformations: 1. Cerebral arteriogram Cerebral arteriovenous malformations have the following typical manifestations: 1) showing malformed vessels. This is a characteristic manifestation of a mass of tortuous and dilated vessels with similar diameters entangled 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 cerebral hemisphere cortex. (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 a large amount with the short circuit of the malformed blood vessel, therefore, the malformed part of the blood 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, there is no occupying sign in cerebral vessels and cerebral vessels are not displaced. 2.CT performance: There is a more typical CT performance before the cerebral arteriovenous malformation ruptures and bleeds. In plain scan, focal high-low or low-mixed density shadow is seen, which is in the form of speckles, clumps 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-like enhancement, and even tortuous vascular shadows, blood supply arteries and draining veins are visible after hemorrhage, and intracerebral hematoma, subarachnoid and ventricular system hemorrhage are seen. Depending on the duration of hemorrhage, high-density shadow, mixed dense shadow and low-density shadow are seen, and there is a low-density edema area around the hematoma. There are also occupational effects such as ventricular compression and deformation and midline shift. After contrast injection, some of the hematoma edges may show tortuous reinforcement of malformed vessels, while the mixed dense shadow hematoma often has ring reinforcement. MRI is superior in the diagnosis of cerebral arteriovenous malformation, especially for posterior cranial fossa lesions, and its diagnostic value is greater than that of CT. Therefore, MRI is the first choice of imaging examination when a patient is suspected of having cerebrovascular malformation. The vascular component of cerebral arteriovenous malformation 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, and with time, the hematoma gradually changes to iso- or low-signal on T1-weighted images and remains high signal on T2-weighted images.