Investigators from the Oncology Unit, Royal Children's Hospital, Melbourne, Australia, compared the frequency of headache and procedure time following lumbar puncture (LP) in a randomized crossover trial using a 25-gauge compared to a 22-gauge needle. LP headache occurs within 7 days after the procedure, becomes worse within 1.5 min of standing up and improves within 30 min of lying down. As part of their treatment for leukemia, 93 children, aged 4-15 years, were allocated a random sequence of 4 LPs, two with a 22-guage needle and two with a 25-gauge needle, all performed under general anesthesia (sevoflurane). A single needle insertion was used in 320 (94%) procedures; multiple attempts were required in 21 (9 with 22-gauge needle and 12 with 25-gauge (p=0.5).
Analysis of 341 LPs showed an incidence of 7.2% post-LP headache that followed the use of a 22-gauge needle was not significantly different from an incidence of 4.6% when using a 25-gauge needle (p=0.3). Also, the incidence of any headache following LP was not related to needle size (18% with 22-gauge needle and 15% with 25- gauge needle; p=0.4). Having one LP headache did not predispose to recurrence; only one child had two LP headaches. LP procedure time (time for collection of 22 drops [1 ml] CSF) was doubled when using the 25-gauge needle. Incidence of post-LP headache was not lower in younger children and was unrelated to age; it was higher in girls than in boys (11% vs 3%, respectively, p=0.014). The overall functional impact of post-LP headache in a child with leukemia was assessed as moderate or severe in 55% of families. 
COMMENTARY. Incidence of post-LP headache in children treated for leukemia is higher following use of a 22-gauge compared to a 25-gauge needle, but the difference is not significant. The authors conclude that either gauge may be appropriate for LP in a child. In contrast, adults have a significantly lower incidence of LP headache when using smaller diameter needles and needles with a blunt, pencil-type point rather than the traditional cutting point [2, 3].