The likelihood of a positive Gram stain ranges from 25% to 97% and is highly correlated with the concentration of bacterial colony-forming units in the CSF a negative stain therefore cannot exclude this diagnosis. A meta-analysis reported that a CSF lactate of ≥35 mg/dL had 93% sensitivity and 99% specificity for bacterial meningitis 3, 5. CSF lactate is helpful in distinguishing bacterial from non-bacterial meningitis. The CSF-to-blood glucose ratio may be less helpful in hyperglycaemic patients. When a ratio of ≤0.23 is used, specificity improves to 99%, but at the cost of sensitivity. A ratio of ≤0.5 has 100% sensitivity for bacterial meningitis, but specificity of only 57%. CSF glucose varies proportionally to blood glucose, with a normal CSF-to-blood glucose ratio being 0.6. Low CSF glucose is another helpful pointer towards bacterial meningitis, although it is also seen in TBM and cryptococcal meningitis.
This elevation is typically greater in bacterial and TBM than in viral meningitis, with the exception of meningitis due to the herpes simplex virus (HSV) or varicella zoster virus (VZV). CSF protein is usually elevated in meningitis of both bacterial and viral etiology due to increased permeability of the blood-brain barrier as a consequence of inflammation. monocytogenesis an important exception, with approximately 60% of cases having a leukocyte count of <1000 cells/μL, which may be lymphocytic. A leukocyte count of ≥1000 cells/μL with a neutrophilic predominance is highly suggestive of bacterial meningitis, whereas <1000 cells/μL with a lymphocytic predominance is more consistent with viral meningitis, tuberculous meningitis (TBM) or cryptococcal meningitis. Meningitis is confirmed when the leukocyte count in the CSF exceeds 5 cells/μL. For the majority of patients who do not require CT prior to lumbar puncture (LP) and do not have another clinical contraindication to LP, CSF analysis should be performed as soon as possible, before CSF is rendered sterile by broad-spectrum antibiotics 3, 4.ĬSF leukocyte count is often helpful in distinguishing bacterial from non-bacterial meningitis. Adjunctive tests such as latex agglutination, different immunological assays and molecular reactions have great specificities and increasing sensivities 2.ĪCUTE AND CHRONIC MENINGITIS AND MENINGOENCEPHALITISĬSF analysis is of vital importance in suspected meningitis as clinical characteristics alone are unable to distinguish meningitis from other diagnoses, and bacterial from non-bacterial etiologies. CSF direct examination and cultures can identify causative organisms and antibiotic sensitivities. Despite having low specificity, CSF white blood cell counts, CSF protein levels, CSF serum glucose ratio and CSF lactate measurement are useful in differentiating infections caused by distinct groups of pathogens. Table 2 presents conditions that indicate CT scan prior to LP 1, 2.
#CSF FINDINGS IN BACTERIAL AND VIRAL MENINGITIS SKIN#
Clinical contraindications to LP include anticoagulation, clinical evidence of disseminated intravascular coagulation and local infection or loss of skin integrity at the puncture site ( Table 1). LP is contraindicated if the risk of the procedure outweighs the potential benefit. LP indications: Quincke described an LP in 1891, being used therapeutically to relieve increased intracranial pressure in children with meningitis. This procedure involves introducing a needle below the termination of the spinal cord, passing through the dura mater of the spinal cord, and permitting access to the subarachnoid space.
A lumbar puncture (LP) is an invasive technique that accesses the restricted compartment of the subarachnoid space in order to sample CSF. Since the end of the eighteenth century, cerebrospinal fluid (CSF) analysis has been used as an important diagnostic tool for many conditions affecting the central nervous system (CNS), especially CNS infectious diseases.
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