Lumbar puncture

Correction for bloody tap

  1. Nl Ratio: 700 RBCs to 1 WBC
  2. Protein subtract 1mg/dL per 1000 RBCs

General Contraindications

  1. Infection at LP site
  2. Severe thrombocytopenia (platelets <50) or bleeding diathesis or INR >1.5
  3. Mass lesion suspected (do CT or MRI first)

CT findings that prohibit LP

  1. Midline shift
    1. Look for unequal pressures between the 3 cerebral compartments (left/right supretentorial compartments, posterior fossa)
    2. Look for intracerebral masses not causing midline shift
  2. Obsutrictive hydrocephalus
    1. Look for enlargement of ventricles prox to lesions and normal ventricles distal (especially 4th ventricle)
  3. Basilar cisterns compressed
    1. Look for lateral/3rd ventricles may be small due to diffuse cerebral edema or enlarged due to obstr. hydroceph. +/- shift
  4. Posterior fossa mass
    1. Look for displacement/compression of 4th ventricle

Consider contrast CT/MRI

(source: Emergency Radiology: Case Studies Schwartz)

CT Head before LP

In with meningitis suspected:

  1. AMS
  2. Focal Neurologic deficit
  3. Papilledema
  4. Head Trauma or h/o CNS disease (recent or remote)
  5. New Onset Sz (<1 wk prior to ED visit)
  6. HIV + / AIDS or any immunocompromised (transplant pt, steroids, cancer) patient
  7. Age > 60.

-Hasbun, R. et al, (Yale), NEJM, Dec 13, 2001. (prospective, 301 pts)


  1. VP shunt
  2. Febrile sx ?counts


Preterm: <25

Term: <22

Child: <7

  • May also order: cytology, VDRL, AFB stain/culture (often requires lab medicine approval), fungal stain (fungal cultures often require lab medicine approval), Cryptococcal antigen (CrAg), India Ink, oligoclonal bands, MBP, Lyme titers, HSV PCR.

Laboratory Results


Appearance Clear

Glucose (mg/dl) 50-75% serum

Protein (mg/dl) 15-45

Cell Count WBC 0-5

Differential 100% lymph, no PMN

Pressure (cm H2O) 5-20

Traumatic LP

1000 RBC for 1mg/dL protein

700 -1000 RBC gives 1 WBC

Xanthrochromia tube 4; results from RBC lysis and hemoglobin breakdown.


Appearance Bloody or xantho

Glucose (mg/dl) N or D

Protein (mg/dl) Inc but <1000

Cell Count RBC (<~50 okay)

(50-600 = gray zone)

(>600 c/w SAH)

Differential Same as blood

Pressure (cm H2O) Usually Inc


Appearance Cloudy or purulent

Glucose (mg/dl) <40 or <40% serum

Protein (mg/dl) >100-500

Cell Count 100-100,000 (>5)

Differential >80% PMN

Pressure (cm H2O) Usually Inc


Appearance Clear or cloudy

Glucose (mg/dl) 20-40

Protein (mg/dl) 25-500

Cell Count 25-1000

Differential mono& lymph

Pressure (cm H2O) N or I

India ink 50% sensitivity

LA assay for crypto antigen 80%.


Appearance Clear

Glucose (mg/dl) N or D

Protein (mg/dl) 50-200

Cell Count WBC 10-100

Differential Inc mono & PMN early, then lymph.

Pressure (cm H2O) N or I


Appearance Cloudy

Glucose (mg/dl) <40

Protein (mg/dl) 100-2000

Cell Count 50-500

Differential Most lymph, some PMN

Pressure (cm H2O) Usually I


Appearance Bloody or xantho

Glucose (mg/dl) N or D

Protein (mg/dl) 50-100

Cell Count 20-500

Differential Mostly lymph

Pressure (cm H2O) N or I


Appearance Clear or xantho

Glucose (mg/dl) 40-80

Protein (mg/dl) 50-1000

Cell Count <100

Differential Mostly lymph

Pressure (cm H2O) Usually I


Appearance Clear or cloudy

Glucose (mg/dl) Normal

Protein (mg/dl) slight Inc

Cell Count <100

Differential Mostly lymph

Pressure (cm H2O) Normal


Appearance Clear & cloudy

Glucose (mg/dl) Normal

Protein (mg/dl) 40-200

Cell Count 200-500

Differential Mostly lymph & mono

Pressure (cm H2O) N or I

Lumbar Puncture Note

  1. Consent
  2. Indication
  3. Pressure
  4. Color
  5. Amount
  6. Tests
  7. Interspace
  8. Anesthesia
  9. Position
  10. Pt. tolerance