Lumbar puncture: contraindications and CSF interpretation

What it is

A lumbar puncture gives CSF, and CSF analysis answers one question well and another not at all. It will tell you whether a meningitis is bacterial or viral, and it does that on 4 parameters. It will not tell you the type of bacteria or virus; that comes from the history and from the CSF culture.

The contraindications of lumbar puncture are: 1) cardiorespiratory instability; 2) focal neurological signs; 3) signs of raised intracranial pressure, given as vomiting and papilledema, where it is a must to do the CT first.

When meningitis is the question the antibiotic does not wait for the tap: IV antibiotic is to be started immediately, and a third-generation cephalosporin, for example cefotaxime or ceftriaxone, is the preferred choice to cover the most common bacterial causes.