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CSF: How certain can we be?

CSF: How certain can we be?. Meira Louis PGY1. Objectives. Present a published case highlighting the difficulties in CSF diagnosis Understand the objective evidence for the tests ordered on CSF Understand where clinical judgement falls in the spectrum of certainty. Sheila. PMX:

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CSF: How certain can we be?

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  1. CSF: How certain can we be? Meira Louis PGY1

  2. Objectives • Present a published case highlighting the difficulties in CSF diagnosis • Understand the objective evidence for the tests ordered on CSF • Understand where clinical judgement falls in the spectrum of certainty

  3. Sheila • PMX: • Childhood asthma • Hyperthyroidism • Meds: • None 21yo female 1 day history: • non-specific lethargy • Fever and rigors • Generalized headache • Nausea, vomiting Huynh et al, 2007

  4. On exam: • Vitals: 38°C • Alert, oriented • Normal neuro • Bloodwork • WBC: 19.5 • CRP: 185 • Lytes, LFTs, glucose • Imaging: • Chest X-ray • Urinalysis • CT head

  5. CSF – for what? • Cell count • Gram’s Stain • Turbidity • Xanthochromia • Glucose • Protein • India Ink • Cryptococcal Antigen • Lactic Acid • Bacterial Antigen tests • Acid Fast Stain

  6. Sheila’s CSF • Clear and colourless • Protein: 0.38 mg/dL • Glucose: 3.6 mmol/L • 12x106 RBC • 1x106 WBC (all mononuclear) • Negative gram stain

  7. What would you do? • What’s your diagnosis? • How confident are you? • How confident should you be?

  8. Cell Count and Differential • How many leuks are too many leuks? • Does it matter what kind? • Monomorphic vs polymorphic • lymphocytosis • Does prior abx change your cell count? Thomson et al, 2001.; Van de Beek, 2004.

  9. What happens with a traumatic tap? Predicted WBC = CSF RBC x serum WBC serum RBC • If WBC was more than 10x normal was 48% predictive of bacterial meningitis • If less than 10x was 99% predictive of it NOT being meningitis Mayefsky et al. 1987

  10. Glucose • Hypoglycorrhachia • If normal serum glucose: • Ratio of CSF:serum is 0.6:1 • Abnormal when less than 0.5 • If elevated serum glucose: • Ratio of CSF:serum is 0.4:1 • Abnormal when less than 0.3

  11. Protein • Normal range in CSF: 15-45 mg/dL • Greater than 150 is probably bacterial • Greater than 1000 should suggest fungal • Other causes? • Any meningitis • Subarachnoids • CNS vasculitis • Syphilis • Viral encephalitis • neoplasms

  12. Gram Stain What’s the sensitivity for bacteria? All common etiologies-no previous antibiotics 75-90% All common etiologies-antimicrobial therapy prior to LP 40-60% Streptococcus pneumoniae 90% Neisseria meningitidis 75% Haemophilus influenzae 86% Listeria monocytogenes <50% Gram-negative bacilli 50% Gray et al, 1992

  13. Other tests Lactic Acid • Non-specific • Elevations over 35 mg/dL may indicate bacterial meningitis • Lactate may rise before glucose drops Serum Procalcitonin • Very sensitive • Not available for up to 24 hours

  14. Back to the case… • The following morning: • Diplopia, worsening headache • Temp increase to 40°C • GCS of 9 • No rash, no nuchal rigidity, no focal neuro • Repeat CT scan with contrast • IV ceftriaxone, gentamicin, and acyclovir were started • Blood and CSF came back positive for N. meningitidis

  15. On a reassuring note… Ray et al, 2006

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