The potential association of neurologic, infectious, or hemorrhagic complications with lumbar puncture (LP) during remission induction or consolidation treatment of acute lymphoblastic leukemia (ALL) with thrombocytopenia was determined at St Jude Children’s Research Hospital, Memphis, TN. The records of 958 consecutive patients, ages 1 month to 18 years (median, 5.5 years), with newly diagnosed ALL treated between Feb 1984 and July 1998, were reviewed retrospectively, with special attention to the platelet count at the time of LP. Of 895 LPs performed at diagnosis, serious complications were rarely encountered despite platelet counts of 10 x 109/L or less in 11 cases, 20 x 109/L or less in 67, and 50 x 109/L or less in 306. Among a total of 5223 LPs performed either at diagnosis or during a median of 4 LPs for intrathecal chemotherapy (methotrexate, hydrocortisone, cytarabine), the estimated probabilities of serious complications (95% confidence intervals) in relation to platelet count (pc x 109/L) were 0-40.19% with 1-5 pc, 0-13.21% with 6-10pc, 0-2.05% with ll-20pc, and 0-0.10% with >100pc. Traumatic LP recorded in 548 procedures (10.5%) was not associated with adverse sequelae. LPs preceded by prophylactic platelet transfusion (n=167) and without post-transfusion platelet counts were excluded. LPs were performed by pediatric oncologists, pediatric oncology fellows, pediatric residents, and nurse practitioners. Only 29 LPs were performed in patients with platelet counts of 10 x 109/L or less, and the potential risks associated with LP without platelet transfusion in this group of patients is not determined. 
COMMENT. In the management of children with acute lymphoblastic leukemia, diagnostic and therapeutic lumbar puncture (LP) procedures may be performed without risk of serious hemorrhagic complication despite thrombocytopenia. Prophylactic platelet transfusion is not advised prior to LP when platelet counts are higher than 10 x 109/L Below this number of platelets, the safety of LP is unproven. An article entitled “the perils of platelet transfusions”  is cited as a contraindication to platelet transfusion as a routine practice.
Consultation with my colleagues in the Division of Hematology/Oncology at Children’s Memorial Hospital, Chicago, corroborates these findings and practice. Platelet transfusion is not routinely administered prior to LP. Furthermore, no serious hemorrhagic complication has been encountered even with platelet counts of 3-4 x 109/L. The majority of patients undergoing LP on this service receive a short-acting sedative and a topical application of lidocaine cream (Emla®), since the risks of potential hemorrhage may be increased in patients requiring excessive restraint. (personal communication)