The Massachusetts General Hospital Handbook of Neurology

Authors: Flaherty, Alice W.; Rost, Natalia S.

Title: Massachusetts General Hospital Handbook of Neurology, The, 2nd Edition

Copyright 2007 Lippincott Williams & Wilkins

> Table of Contents > Procedures > Lumbar Puncture

Lumbar Puncture

• Indications: To rule out meningitis, hemorrhage; help diagnose carcinomatosis, demyelinating dz.

• Contraindications:

  • Increased ICP from mass lesion: Check for papilledema and retinal hemorrhages; CT for signs of mass effect (if there is high suspicion of meningitis, start Abx before CT or LP). Posterior fossa mass/edema.

  • Coagulopathy: 2 units FFP usually brings INR to <1.5.

  • Obstruction to CSF flow: Avoid LP if suspicion of mass lesion that might block spinal canal, especially in cervical/thoracic area.

  • Infection over area to be punctured: Never do an LP in a pt. with fever and back pain until you have ruled out empyema with MRI.

P.225

• Consent: Headache (in 10%; see LP headache, p. 53.), bleeding, infection, nerve damage.

• Need: Kit, gloves 2, chuck, povidone, alcohol, extra black-topped tubes, extra lidocaine. Best to have a working IV before LP, in case you need to give mannitol.

• Position:

  • Lying: Fetal position; make sure hips are even.

  • Sitting: Easier, but cannot read opening pressure. Have pt. lean over a chair.

• Locate L3-L4 interspace (parallel with superior iliac crest): Sterilize skin with iodine, don sterile gloves, drape, anesthetize skin, set up tubes and manometer.

• Advance needle slowly with bevel up and stylet in, parallel to bed and towards the navel. Withdraw stylet frequently to check for CSF flow.

  • Paresthesias: If pt. feels tingling in a leg, angle needle away from that leg.

  • Difficult punctures: Especially when the interspace is tight, or when landmarks are hard to palpate, it often helps to anesthetize a larger area and then make repeated parallel penetrations, marching up or down the spine, rather than angling the needle around within one penetration. If unsuccessful at L3-4, try L4-5 and L2-3. Try it with the pt. seated. If all fails, you can order a fluoroscopically guided LP.

• When you get flow, rotate needle so bevel points towards head, attach adaptor tube and then stopcock with manometer. Measure CSF pressure.

• Opening pressure (OP): Normal is <200 mm water.

  • If OP measurement is important: Get pt. to straighten legs before you read it.

  • If OP >400-500, give mannitol: Put stylet back, leave needle in to prevent CSF leak. Take out only amount of CSF in manometer. Infuse 20% mannitol IV 0.25-0.5 g/kg over 20-30 min (usually aim for 500 cc + urine output). Recheck pressure at end of infusion; need to get it below 400 before withdrawing needle.

• Collect CSF specimens: After measuring OP, screw first white-topped tube onto bottom of manometer. Remove manometer. Change tubes when they are full. Having pt. Valsalva may speed flow.

• Finish LP: Reinsert stylet, withdraw needle, clean off iodine.

• Send specimens: The following are possible tests do not run all of them on everyone. Save extra CSF. See Cerebrospinal Fluid, p. 19.

  • Hematology: Tubes 1 and 4 for cell count (0.5 cc each).

  • Chemistry: Glucose, protein, xanthochromia (0.5 cc), HSV PCR.

    • Xanthochromia: To spin it yourself, put 1 cc in centrifuge 2 min; look at supernatant. (Do not bother if fluid is clear.)

  • Immunology: Oligoclonal bands (>2.5 cc), IgG, IgM titers.

  • Microbiology: (>3 cc). Culture (bacterial fungal), VDRL (only if serum positive or if high suspicion), antigens (H. influenzae; streptococcus, meningococcus, and cryptococcus), AFB stain (2.5 cc), Lyme titer. Cultures are useful if drawn less than 2 h after starting empiric Abx.

  • Cytology: 2-3 cc.

  • Others: Lactate + pyruvate to rule out mitochondrial dzs (covered, on ice), paraneoplastic antibodies, protein 14-3-3.