白血病细胞侵犯中枢神经系统（ＣＮＳ），早期常先累及蛛网膜的浅表部分，脑脊髓管间皮仍完整，因而脑脊液（ＣＳＦ）中尚无白血病细胞，此时一般亦无中枢神经系统白血病（ＣＮＳＬ）的临床表现。据研究，在光学显微镜下每微升ＣＳＦ中能发现１个白血病细胞，ＣＳＦ中就存... Leukemia cells invade the central nervous system (CNS) and often involve the superficial portion of the arachnoid in the early stages. The cerebrospinal fluid is still intact. Therefore, there is no leukemia cell in the cerebrospinal fluid (CSF), and there is generally no central nervous system leukemia. Clinical manifestations of CNSL). According to the study, a leukemia cell can be found in every microlitre of CSF under the light microscope.