后颅窝肿瘤所致扁桃体下疝继发脊髓空洞症较少报道。本文对164例后颅窝肿瘤患者的MRI进行再研究,重点注意有否扁桃体下疝和脊髓空洞。结果发现24例有扁桃体疝形成,其中听神经瘤8例,小脑星形细胞瘤6例,成血管细胞瘤4例,脑膜瘤4例,成神经管细胞瘤1例,转移瘤1例。在脊髓矢状位像上,未见扁桃体疝的140例病人颈脊髓无异常,24例伴扁桃体疝者有5例出现脊髓空洞症(脑膜瘤 Posterior fossa tumor secondary to tonsillar herniation less reported syringomyelia. In this paper, 164 cases of posterior fossa tumors in patients with MRI re-focus, with or without attention to whether there is tonsil hernia and syringomyelia. Twenty-four patients had tonsil hernias. Among them, 8 had acoustic neuroma, 6 had cerebellar astrocytoma, 4 had hemangioblastoma, 4 had meningioma, 1 had medulloblastoma, and 1 had metastatic tumor. In the spinal sagittal images, no cases of tonsil hernia in 140 cases of cervical spinal cord abnormalities, 24 patients with tonsil herniation in 5 cases of syringomyelia (meningioma