Cerebrospinal Fluid Analysis - Specimen Collection, Cerebrospinal Fluid Analysis, Specimen Collection, Graff's Textbook of Urinalysis and Body Fluids
Indications for examination of CSF include CNS malignancy, demyelinating diseases, meningeal infection, and subarachnoid hemorrhage. The procedure for obtaining CSF is known as a lumbar puncture. Contraindication to performing this puncture is the presence of infection at the puncture site. Lumbar puncture through an area of infection may cause the spread of infection into the meninges. However, bacteremia is not a contraindication because CSF examination can confirm or rule out concurrent meningitis.
Figure 9-1. Anatomy of the central nervous system
Figure 9-2. Detail of meninges
The most common site used for lumbar puncture is the intervertebral space between L3 and L4. Using this site avoids damage to the spinal cord in adults because the spinal cord does not extend that far down. The spinal cord may extend that far in small children and infants; therefore the intervertebral space between L4 and L5 is used for them. Figure 9-3 shows placement of the needle for CSF collection between L4 and L5. The lumbar puncture site is thoroughly cleansed and a local anesthetic is applied. The lumbar puncture is made and with the needle seated in the dura mater, CSF pressure is measured using a graduated manometer attached to the syringe. CSF is collected if this pressure is normal and if there is no significant fall in pressure when collection begins. Typically, 10–20 mL of CSF is slowly removed into three or four sterile tubes that are numbered sequentially. What
Figure 9-3. Placement of the needle for CSF collection
tests are performed on which tubes is dependent upon laboratory protocol or physician’s specific request. A common protocol is the performance of chemical and immunologi analysis on tube number one, microbiological procedures on tube number two, and cells counts on tube number three.1 Figure 9-4 shows the typical containers into which CSF is collected. Notice that the tubes are prenumbered.
Figure 9-4. Specimen containers for cerebral spinal fluid specimens
REFERENCES
Lillian A. Mundt and Kristy Shanahan, Graff's Textbook of Urinalysis and Body Fluids, Second Edition 2011
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