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Acute Lymphoblastic Leukemia




Lumbar Puncture


Usually done at same time as diagnostic bone marrow aspirate and biopsy.

CSF is evaluated for presence or absence of blast cells at time of diagnosis as this affects both prognosis and future treatment. 

CSF is centrifuged in lab and hematopathologist reviews morphology.  Patient categorized as follows:

Category of CSF involvement



No blasts seen on cytocentrifuge (CNS negative)


Total Nucleated Cell Count <5 x 106/L but blasts seen on cytocentrifuge.


Total Nucleated Cell Count ≥ 5 x 106/L with blasts on cytocentrifuge and/or signs of CNS leukemia (e.g. cranial nerve palsy).


Usually first dose of chemotherapy (Cytarabine arabinoside) is given by the intrathecal route (directly into the CSF via the lumbar puncture into the thecal sac) at time of the first LP (lumbar puncture).



  • There is ongoing discussion about the acceptable minimum platelet count prior to LP and platelet thresholds for procedures may vary by institution. 
  • C17 (the Canadian Consortium) will most likely recommend that the platelet count be a minimum of 20 prior to LP.
  • Many institutions use a higher value with a minimum platelet count of 50 prior to LP.





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