Lumbar puncture.

Lumbar puncture has been in widespread clinical use for nearly a century. It is used in emergency medicine primarily as a tool for the diagnosis of meningoencephalitis and subarachnoid hemorrhage. The development of computed tomography has changed the position that lumbar puncture has held in the diagnostic sequence of a number of clinical entities. The procedure is contraindicated if there is soft-tissue infection adjacent to the puncture site and if there are findings of increased intracranial pressure due to a mass lesion. Performance in the setting of a coagulopathy may also be hazardous. The most serious potential complication is cerebral herniation. The commonest complication is postlumbar puncture headache, which is due to CSF hypotension resulting from persistent spinal fluid leakage through the meningeal puncture site. Spinal hematoma, diplopia, and intraspinal dermoid tumor formation are less common complications. Meningitis has been found to follow lumbar puncture in children with bacteremia. The lumbar puncture is a useful test for providing information regarding the cellular, chemical, and microbiologic composition of the CSF. Fluid obtained should be evaluated for cell count, Gram's stain, bacterial culture, glucose and protein levels, and other tests as clinically indicated.