The primary method for diagnosing meningitis is a lumbar puncture (LP), commonly known as a spinal tap. During this procedure, a clinician inserts a needle into the subarachnoid space of the lower spine to collect cerebrospinal fluid (CSF).
1. CSF Analysis and Chemistry
Once the fluid is collected, it undergoes immediate "macroscopic" inspection and laboratory analysis:
Appearance: Normal CSF is crystal clear. Cloudy or turbid fluid often indicates an abundance of white blood cells (WBCs) or bacteria, typical of bacterial meningitis.
WBC Count & Differential: High levels of neutrophils usually point toward a bacterial cause, while a predominance of lymphocytes often suggests a viral origin.
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