Sexual dimorphism in clinical neurology - Predictors of successful lumbar puncture in an "expanding" population

Objective To determine the proportion of patients who would have an unsuccessful lumbar puncture (LP) due to commonly used LP needles being too short. Methods Three hundred consecutive adults (age 16-99, mean age 56) who underwent abdominal CT over a 6-month period were identified. The distance from the skin to the midpoint of the spinal canal was measured in the axial plane, at the level of the iliac crest. This was compared to the length of commonly used spinal needles (88 mm) to assess the number of patients who would have an unsuccessful LP due to this distance being greater than 88 mm from the skin. Results In 72/300 (24%) patients, the midpoint of the spinal canal was greater than 88 mm from the skin. A total of 54/72 (75%) of those patients were female. Of the female participants, 54/159 (34%) had the midpoint of their spinal canal at a distance of greater than 88 mm from the skin. In the male patients, only 18/141 (13%) had a similar finding. Conclusion This is the first high-quality study to demonstrate that 24% of the population will have an unsuccessful LP procedure if commonly available spinal needles. We demonstrated that 34% of female patients would have an unsuccessful procedure while, in contrast, a successful LP should be possible in 87% of male patients.