When do you NOT do an LP?

[engineeredout]

We seem to keep getting different information on when and when not to do an LP because of increased ICP.

On one hand, you don't want to do it if you suspect increased ICP because you'll herniate everything out. On the other hand, in "Idiopathic Intracranial Hypertension/Pseudotumor cerebri" we are told to diagnose it by checking LP pressure.

Anyone know when you're actually supposed to do it (aside from meningitis)?

---

Members don't see this ad.

 

[It'sElectric]

Briefly:
In addition to meningitis, you also frequently do LPs when you suspect intracranial hemorrhage, despite a negative head CT - the CT is not 100% sensitive (I think it's like 95% or so). Negative tap and head CT should effectively R/O head bleed, at least in the ED setting.

If you strongly suspect elevated ICP, you should do a CT. If you don't suspect it (no physical/historical signs/symptoms), then tap away. Others can feel free to correct me.

 

[TexasTriathlete]

If you suspect increased ICP, you would do a CT to check for it. You'd look for dilated ventricles,, etc that would not be present with pseudotumor cerebri.

You also would not do an LP with a localized infection at the site of the tap.

In the event that LP is contraindicated, there are other less-desireable ways to get a csf sample.