The brainstem includes (inferior mesencephalon, midbrain, pontocerebellum, and medulla oblongata), and biopsy is risky and has a heavy postoperative response. The medulla oblongata lesions are generally not advocated for biopsy. The best sites for brainstem lesions and tumors are the pontocerebellum and pontocerebellar arms, so they are also the most common. Ninety percent of brainstem tumors are gliomas, while more than half are astrocytomas, most of which are located in the pontine brain, followed by the medulla oblongata, and rarely in the midbrain. Astrocytomas in the brainstem can be seen on CT as thickening of the brainstem, asymmetry between the left and right and the appearance of hypodense or mixed density tumor lesions. However, CT is not as ideal as MRI to show brainstem glioma. The biopsy trajectory should be parallel to the brainstem in the sagittal position, and the puncture path should follow the longitudinal axis of the brainstem and the medial border of the cerebellar curtain in the coronal plane, and the biopsy needle should avoid passing through the interpeduncular and circumferential pools. For lesions in the pontocerebellum and pontine arm below the level of the midfoot of the cerebellum, the patient may be placed in a prone or lateral position, and a transcranial approach through the posterior cranial fossa via the side of the cerebellum is used. Illustration ③ Brainstem lesions are small in size, and the biopsy specimen cannot be collected in large numbers, so the specimen can be taken by fine needle aspiration. Amadani summarized the data from 13 biopsy centers, the positive rate of stereotactic biopsy of brainstem lesions was 96%, and the biopsy diagnosis was glioma, metastatic carcinoma in half of the cases, and hematoma, vascular malformation, lymphoma, demyelinating lesion, cyst, radionecrosis, abscess, vasculitis, infarction, leukemia, cryptococcal infection or granuloma in the other half. goncalves- Ferreira et al. reported 30 stereotactic biopsies of suspected brainstem gliomas, and only half of them were also confirmed as astrocytomas, and most (8/14) were small nodular non-invasive tumors.