Overview Snapshot A 59-year-old man presents to the emergency department with altered mental status. The patient is accompanied by his wife who says that the patient had a fever and headache for the past few days. On physical exam the patient is oriented to person but not place or time. Photophobia and neck stiffness is present. A lumbar puncture is performed for CSF analysis and shows a lymphocytic pleocytosis with normal glucose and protein. A PCR of the CSF is positive for HSV-1, and he is started on intravenous acyclovir. (Viral meningitis caused by HSV-1) Introduction Lumbar puncture (LP) is a procedure where a spinal needle is advanced into the subarachnoid space in order to collect cerebral spinal fluid (CSF) login to view 11 more bullets Complications login to view 4 more bullets Cerebrospinal Fluid Analysis Test Normal Bacterial Viral Fungal/TB Opening pressure ≤ 20 cm H2O ↑ normal or slightly ↑ ↑ Color Clear Cloudy Clear Cloudy Cell count 0-5 cells/µL ↑ (PMN) ↑ (Lymphocytes) ↑ (Lymphocytes) Protein < 45 mg/dL ↑ Slighty ↑ ↑ CSF:Serum glucose > 0.6 ↓ Normal ↓ Technique Patient position login to view 5 more bullets Needle entry login to view 3 more bullets In cases where there are unsuccessful attempts in obtaining CSF, imaging guidance can be used such as login to view 2 more bullets