Are high lumbar punctures safe? A magnetic resonance imaging morphometric study of the conus medullaris.

Authors:
Vivek Yedavalli
Vivek Yedavalli
Stanford University
Neuroradiology Fellow
Neuroradiology
Palo Alto, California | United States

Clin Anat 2019 Jul 12;32(5):618-629. Epub 2019 Mar 12.

Division of Neuroimaging and Neurointervention, Department of Radiology, Stanford University School of Medicine, Stanford, California.

A high lumbar puncture (LP) at L2-L3 or above is often necessary to consider on technical grounds, but complications of conus medullaris (CM) damage during high LP are potentially concerning. We hypothesized that a high LP might be safer than previously thought by accounting for movements of the CM upon patient positional changes. We retrospectively reviewed standard normal supine lumbar spine magnetic resonance imaging of 58 patients and used electronic calipers on axial images at the T12-L1, L1-L2, and L2-L3 disc levels to measure the transverse diameter of the CM relative to the size of the dorsal thecal sac space (DTSS) through which a spinal needle could be inserted. On 142 axial images, the means for CM diameters were 8.2, 6.0, and 2.9 mm at the three levels, respectively. We then used known literature mean CM displacement values in the legs flexed and unflexed lateral decubitus position (LDP) to factor in CM shifts to the dependent side. We found that at all three levels, the likely positional shift of the CM would be too small and insufficient to displace the entire CM out of the DTSS. However, if needle placement could be confined to the midsagittal plane, an LP in the unflexed LDP would theoretically be entirely safe at both L1-L2 and L2-L3, and almost so at L2-L3 in the legs flexed LDP. Thus, high LPs at L1-L2 and L2-L3 are in theory likely safer than considered previously, more so in the legs unflexed than in the flexed LDP. Clin. Anat. 32:618-629, 2019. © 2019 Wiley Periodicals, Inc.

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http://dx.doi.org/10.1002/ca.23359DOI Listing
July 2019
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Arai Y et al.
Bull Hosp Jt Dis 2001
The vertebral level of termination of the spinal cord during normal and abnormal development
Barson AJ et al.
J Anat 1969

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