Page 44 - Radiology Book

lumbar Puncture continued
2. Lumbar Puncture Landmarks
· Locate the vertebral interspace between the posterior iliac crests (L3–L4).
· Mark the site. Go up one (L2–L3) or down one (L4–L5) interspace if needed.
· Insert the spinal needle bevel side up and angle it toward the umbilius in the cephalad angle.
If the patient has any of the following criteria, get a head CT prior to the LP to minimize the risk of brainstem herniation:
· Age >60 years
· Immunocompromised state
· History of CNS lesion
(mass lesion, stroke, and/or focal CNS infection)
· Seizure in the week prior to presentation
· Neurological ndings (altered mental status, inability to
correctly answer 2 questions or follow 2 commands, and/or any focal neurologic ndings such as gaze palsy or arm drift)
This test has a 97% negative predictive value if the answer to all questions was “no.”
(Hasbun R, et al. N Engl J Med. 2001;345:1727-1733.)
Xanthochromia appears 2–4 hours after subarachnoid hemorrhage and persists for 2–4 weeks.
tests to order on lumbar Puncture
Tube
Description
Amount
1
· Gram stain (STAT) · Culture
· Sensitivities
2–4 mL
2
· Glucose · Protein
· LDH
2mL
3
Cell count and differential (STAT)
2mL
4
Specialized test:
· Cryptococcal antigen · Oligoclonal bands
· VDRL cytology
· Fungal cultures
· HSV/VZV PCR
· Varicella, West Nile, TB, enterovirus
5–10 mL
Southfield16
Procedures