Lumbar puncture indications
Diagnostically it is used to collect cerebrospinal fluid (CSF) to confirm or exclude conditions such as meningitis and subarachnoid hemorrhage and it may be used in diagnosis of other conditions.
If non-contrast head CT is not definitive (time to study, patient elements [i.e., severe anemia], interpretation limitations [i.e., trainee radiologist, motion artifact], etc) the next recommended diagnostic tool is the lumbar puncture LP. In these instances the LP is looking for two elements that raise the concern for SAH: 1) RBCs; and 2) xanthochromia (bilirubin in cerebrospinal fluid [CSF])
Therapeutically it may be used to reduce increased intracranial pressure.