Updated: 7/13/2017

Lumbar Puncture

Review Topic
  • 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)
  • Lumbar puncture (LP) is a procedure where a spinal needle is advanced into the subarachnoid space in order to collect cerebral spinal fluid (CSF)
    • the LP can allow the physician to determine
      • the etiology of meningitis
      • if the patient has a subarachnoid hemorrhage in the setting of a normal non-contrast head CT
      • the presence of a malignancy affecting the central nervous system (e.g., leptomeningeal carcinomatosis)
      • the presence of a demyelinating disease (e.g., multiple sclerosis)
      • if the patient has symptoms concerning for Guillain-Barre syndrome
    • caution should be taken in performing the LP in patients with
      • increased intracranial pressure
        • the patient runs the risk of brain herniation
      • thrombocytopenia or other bleeeding diathesis
      • signs and symptoms concerning for a spinal epidural abscess
  • Complications
    • post-LP headache
    • infection
    • bleeding
    • cerebral herniation
Cerebrospinal Fluid Analysis
Test Normal Bacterial Viral Fungal/TB
Opening pressure
  • ≤ 20 cm H
  • normal or slightly ↑
  • Clear
  • Cloudy
  • Clear
  • Cloudy
Cell count
  • 0-5 cells/µL
  • ↑ (PMN)
  • ↑ (Lymphocytes)
  • ↑ (Lymphocytes)
  • < 45 mg/dL
  • Slighty ↑
CSF:Serum glucose
  • > 0.6
  • Normal
  • Patient position
    • lateral recumbent position
      • preferred for accurate opening pressure measurement
    • prone position
      • better for fluoroscopy guided LP
    • sitting upright
  • Needle entry
    • into the subarachnoid space at L3-4 or L4-5 interspace
      • remember that the spinal cord ends in L1-2
        • thus there should not be any trauma to the spinal cord if properly performed
  • In cases where there are unsuccessful attempts in obtaining CSF, imaging guidance can be used such as
    • fluoroscopy
    • ultrasound

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