摘要篇首： A 10-year-old boy appeared with a headache, mainly in the forehead, and with lethargy at noon on November 10, 2004. He reported discontinuous gas pains, no nausea, no vomiting and no blurred vision. He thought that he had a "common cold", but treatment for 3days produced no result. He was diagnosed as having viral encephalitis after an examination including an electroencephalogram (EEG),blood biochemistry and lumbar puncture, etc. in a local hospital on November 15. After further treatment for 3 days his symptoms became aggravated showing instability of gait and involuntary movement of his head and extremities. Cranial CT showed: a 4.0 cmx 4.0cm x 5.0 cm lump in the cerebellar vermis which intruded into the fourth ventricle inducing evident distention of the third and lateral ventricle. He was diagnosed with blastoma of the cerebellum.