本文报道了一例原发于马尾的原始神经外胚层肿瘤(ＰＮＥＴｓ)。患者男性 ,5 2岁。主诉为进行性背痛、行走困难6个月 ,尿失禁、鞍区麻木 2周。体检证实Ｌ4～Ｓ2分布的左边区域与Ｓ1～Ｓ2分布的右边区域针刺感觉减退。特征性的有肛门括约肌张力减退 ,双侧直腿抬高受限 ,左大腿背 Here we report a case of primitive neuroectodermal tumors (PNETs) that originate in the cauda equina. Patient male, 5 2 years old. The chief complaint was progressive back pain, difficulty walking 6 months, urinary incontinence, sellar numbness for 2 weeks. Physical examination confirmed that the L4 ~ S2 distribution of the left area and S1 ~ S2 distribution of the right area of ​​acupuncture sensory decline. Characteristic anal sphincter tension decreased bilateral raised straight leg restriction, left thigh back