Lumbar punctures can be mercurial procedures.  There are certainly patients in whom it can be predicted that a lumbar puncture will be challenging.  Obesity, patients with known degenerative changes, and agitated patients all present unique challenges when it comes to successfully completing a lumbar puncture.  There are patients, however, who throw you a bit of a curveball.  Sometimes cooperative patients with good landmarks, in whom you had every expectation that you would find success, become seemingly impossible to successfully complete a lumbar puncture.  

For the provider, knowing how to troubleshoot the unexpectedly difficult lumbar puncture can be the difference between success and failure.