CSF, obtained by lumbar intrathecal puncture, is the main diagnostic tool for neurologic disorders. A lumbar intrathecal puncture is done for the following reasons:
To examine the spinal fluid for diagnosis of four major disease categories:
Meningitis
Subarachnoid hemorrhage
Central nervous system (CNS) malignancy (meningeal carcinoma, tumor metastasis)
Autoimmune disease and multiple sclerosis (MS)
To determine level of CSF pressure, to document impaired CSF flow, or to lower pressure by removing volume of fluid
To identify disease-related immunoglobulin patterns (IgG, IgA, and IgM referenced to albumin) in neurotuberculosis, neuroborreliosis, or opportunistic infections
To introduce anesthetic agents, drugs, or contrast media used for x-ray studies and nuclear scans into the spinal cord
To confirm the identity of pathogens involved in acute inflammatory or chronic inflammatory disorders (e.g., MS and blood–brain barrier dysfunction)
To identify extent of brain infarction or stroke
To formulate antibody index of the IgG class for polyspecific immune response in the CNS. Examples: measles, rubella, and varicella zoster (MRZ) antibodies to viruses in MS; herpes simplex virus antibodies in MS; toxoplasma antibodies in MS; and autoantibodies to double-stranded DNA
To identify brain-derived proteins, such as neuron-specific enolase present after brain trauma
See Figure 5.1 for an example of a CSF analysis report.
Clinical Alert
The MRZ reaction (MRZR) occurs in MS, lupus erythematosus, Sjögren syndrome, and Wegener granulomatosis
Certain observations are made each time lumbar puncture is performed:
CSF pressure is measured.
General appearance, consistency, and tendency of the CSF to clot are noted.
CSF cell count is performed to distinguish types of cells present; this must be done within 2 hours of obtaining the CSF sample.
CSF protein and glucose concentrations are determined.
Other clinical serologic and bacteriologic tests are done when the patient’s condition warrants (e.g., culture for aerobes and anaerobes or tuberculosis).
Tumor markers may be present in CSF; these tests are useful as supplements to CSF cytology analysis (Table 5.2).
Clinical Alert
Blood levels for specific substances should always be measured simultaneously with CSF determinations for meaningful interpretation of results.
Before lumbar puncture, check eyegrounds (fundus of the eye as visualized with an ophthalmoscope) for evidence of papilledema (swelling of the optic disc generally due to an increase in ICP) because its presence may signal potential problems or complications of lumbar puncture.
A mass lesion should be ruled out by computed tomography (CT) scan before lumbar puncture because a mass lesion can lead to brain stem herniation.
If increased pressure is found while performing the lumbar puncture, it should not be necessary to stop the procedure unless neurologic signs are present.