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  • Cross table laterals are very helpful for determining needle depth. On this image, the needle is just short of the spinal canal, and advancing the needle a few mm should do it.
  • This is an MRI done while the patient valsalvas. The increased size of the epidural veins and associated mass effect on the spinal canal is remarkable. It is easy to appreciate why valsalva raises CSF pressure. (Case courtesy Andrew Plumb)
  • There is severe spinal canal narrowing at L4-L5 (arrow). It is easy to see that a lumbar puncture would not be successful at this level or below.
  • This was a young obese patient who had an unsuccessful LP attempt at multiple levels. MRI reveals abundant epidural fat effacing CSF at multiple levels (black arrows) and a thecal sac that terminates just about L5-S1 (white arrow).