From the Guidelines
Cerebrospinal fluid (CSF) analysis is a crucial diagnostic tool that typically reveals a mild mononuclear pleocytosis, elevated protein concentration, and presence of oligoclonal bands in patients with encephalitis.
Key Findings
- CSF analysis is essential for diagnosing encephalitis, and it should be performed unless contraindicated 1, 2.
- Common CSF findings in encephalitis include: + Mild to moderate lymphocytic pleocytosis (20-200 cells) 1 + Hyperproteinorrachia 1 + Elevated IgG index and/or IgG synthesis rate 1 + Positive intrathecal oligoclonal bands (unmatched in the serum) 1
- The detection of virus-specific IgM in CSF indicates an intrathecal antiviral immune response, which is especially useful for flaviviruses and other RNA viruses 3.
- CSF PCR can detect various viral and bacterial pathogens, including herpes simplex virus, varicella zoster virus, and cytomegalovirus 2.
Diagnostic Approach
- A lumbar puncture (LP) should be performed to collect CSF for analysis, unless there is a significant contraindication, such as risk of herniation on brain imaging 1, 4.
- CSF analysis should include cell count and differential, protein, glucose, CSF/serum glucose ratio, albumin quotient, IgG index and synthesis rate, oligoclonal bands, and broad viral studies, including PCR and IgG/IgM testing 1.
- The results of CSF analysis should be interpreted in the context of clinical presentation and other diagnostic findings, such as brain MRI and serologic tests 1, 2.
From the Research
Cerebrospinal Fluid (CSF) Analysis Findings
The findings of a cerebrospinal fluid (CSF) analysis can be useful in the evaluation of various neurologic conditions, including:
- Suspected central nervous system infection or subarachnoid hemorrhage 5
- Spontaneous intracranial hypotension, idiopathic intracranial hypertension, multiple sclerosis, Guillain-Barré syndrome, and malignancy 5
- Bacterial meningitis, which has a high mortality rate and characteristic effects on CSF white blood cell counts, CSF protein levels, and the CSF:serum glucose ratio 5, 6
- Viral meningitis, which can present similarly to bacterial meningitis but usually has a low mortality rate 5, 6
CSF Analysis Parameters
CSF analysis parameters that can be useful in differentiating between various conditions include:
- CSF white blood cell counts 5, 6, 7
- CSF protein levels 5, 6, 7, 8
- CSF serum glucose ratio 5, 6
- CSF lactate measurement 5, 6
- CSF culture and antibiotic sensitivities 5, 6
- Oligoclonal gamma immunoglobulins (IgG) in the CSF, which can be helpful in establishing a diagnosis of multiple sclerosis (MS) 9
- Other biological molecules in the CSF, such as neurofiliment, myelin basic protein (MBP), glial fibrillary acidic protein (GFAP), tau, neuronal cell adhesion molecule (NCAM), and the growth associated protein (GAP-43) 9
Diagnostic Value of CSF Analysis
The diagnostic value of CSF analysis can be enhanced by:
- Correlating CSF findings with clinico-radiologic findings 8
- Using adjunctive tests, such as latex agglutination, immunological assays, and molecular reactions 5, 6
- Evaluating basic CSF parameters, such as neutrophils, lymphocytes, and the coefficient of energy balance (KEB) 7
- Performing cytospin examination and culture in cases where malignancy is suspected 8