Intracranial metastases are metastases of malignant tumors from other parts of the body to the skull, and carcinomas, sarcomas and melanomas can all metastasize to the skull. Most of the intracranial metastases seen clinically are metastases from cancer tumors, accounting for more than 90%. There are three ways for malignant tumors to metastasize into the skull: blood flow; lymphatic; and direct invasion. The most common route is via blood flow. The metastatic route and metastatic site are related to the site of the primary tumor. For example, lung cancer, breast cancer and skin cancer mainly metastasize through blood stream, and are prone to form multiple metastatic cancers in the brain, which can lead to rapid death without treatment. Gastrointestinal tract carcinoma is more likely to metastasize through lymphatic system and spread in meninges. 1.Cranial X-ray is often used for patients with cranial metastasis, and it is more helpful to diagnose patients with signs of increased intracranial pressure, especially those with pineal gland displacement. CT examination is the first choice for diagnosing intracranial metastases, which can not only detect brain metastases in most cases, but also show the shape, size, location, number, accompanying cerebral edema and secondary hydrocephalus and the degree of midline structural displacement of metastases, which are mostly located in the cortex or subcortex, round or round-like, showing hypodensity, isodensity, high density or mixed density. They may also be cystic masses with nodules in the cystic cavity, and may show high density areas or fluid planes when accompanied by hemorrhage. If the tumor grows fast, it may show necrosis and cystic changes in the central part of the tumor. 3.MRI examination MRI examination can not only provide further imaging inherent characteristics of metastases, but also can discover multiple lesions and make diagnosis easily. Because MRI can detect smaller tumors than CT, and multiple lesions are the characteristics of metastases. For lesions in the posterior cranial fossa and near the skull base, they are easily detected because of the removal of bony artifacts. The typical metastases show long T1 and T2 signals with longer surrounding edema bands. Since the edema often shows obvious long T2 signals on T2-weighted images, it is easier to detect lesions than T1-weighted images, especially for smaller lesions. It is often used to determine whether intracranial metastases have occurred in acute leukemia, non-Hodgkin’s lymphoma, etc. The cerebrospinal fluid can be used to guide clinical treatment when tumor cells are detected.