|
A
lumbar puncture can be performed using any of the L3-L4, L4-L5,
or L5-S1 interspaces. The spinal cord ends at L1 in adults, thus
the risk of cord damage is insignificant. At these levels, the subarchnoid
space contains the nerve roots of the cauda equine floating free
in the CSF. The nerve roots are brushed aside by the penetrating
LP needle.
|
|
To
make a landmark visible throughout the procedure:
at the proposed point of needle insertion, press
the skin with a blunt object such as the base of
a pen or a man’s wedding ring for several seconds. |
|
|
To
avoid damaging the spinal cord, do not go above
the
L2-L3 space. |
|
The
posterior iliac crests are easily palpated in most patients. A line
drawn between the superior border of the posterior iliac crests
will intersect the L4 spinous process (see image). Using this surface
landmark, the L3-L4-L5 interspaces can be localized. Identify the
L4-L5 interspinous process space midline as your needle insertion
site. If insertion at this space is unsuccessful, try the L3-L4
space.
 |
The
L4-L5 interspace is likely the largest when the spine
is flexed, and therefore this space should be attempted
first. |
|
|
 |
