The manometric pressure of the CSF is measured at the beginning and at the end of the procedure. With the patient in the lateral decubitus position, the opening pressure of the CSF is normally 70 to 200 mm H2O. If lumbar puncture is performed with the patient in the sitting position, the CSF usually rises in the manometer to about the level of the foramen magnum but not higher. If the patient coughs, sneezes, or strains during lumbar puncture, there is usually a prompt rise in CSF pressure because of congestion of spinal veins and resultant increased pressure of the contents of the subarachnoid epidural spaces; the CSF pressure subsequently falls to the previous level.
After determination of the initial CSF pressure, four tubes of CSF are withdrawn (usually containing 2–3 mL each) under sterile conditions. Routine CSF examination usually includes cell counts, measurement of total protein, glucose, and gamma globulin levels. Cells are usually cultured, and, when appropriate, spinal fluid electrophoresis is performed to determine whether there are oligoclonal bands. (These are present in a variety of inflammatory disorders, most notably multiple sclerosis but also neurosyphilis, subacute sclerosing panencephalitis, and some cases of viral encephalitis.)
Table 24–1 illustrates the profile of the CSF after lumbar puncture in a number of neurologic disorders.
TABLE 24–1Characteristic Cerebrospinal Fluid Profiles. ||Download (.pdf) TABLE 24–1 Characteristic Cerebrospinal Fluid Profiles.
|Variable ||Appearance ||Opening Pressure (mm H2O) ||RBCs ||WBCs ||Protein (mg/dL) ||Glucose (mg/dL) ||IgG Index ||Oligo-clonal Bands ||Smear ||Culture |
|Normal ||Clear, colorless ||70–180 ||0 ||0–5 lymphocytes (0 PMN) ||<50 ||50–75 ||<0.77 ||Neg ||Neg ||Neg |
|Traumatic ||Bloody; supernatant, clear ||Normal ||↑ ||Proportional to RBCs ||4 mg/dL rise per 5000 RBCs || || || || || |
|Subarachnoid hemorrhage ||Bloody or xanthro-chromic (yellow) ||↑ ||↑ or ↑↑ ||0 or present resulting from secondary irritative meningitis ||↑ ||Normal ||Normal ||Neg ||Neg ||Neg |
|Bacterial meningitis ||May be cloudy or purulent ||↑ ||0 ||↑↑ (PMNs) ||↑↑ ||↓ ||May be ↑ ||Usually neg ||Gram stain may be + ||+ |
|Fungal meningitis ||Normal or cloudy ||Normal or ↑ ||0 ||Normal or ↑ (mono-nucleated) ||↑ ||↓ ||May be ↑ ||Usually neg ||India ink + ||+ |
|Tuberculous meningitis ||Normal or cloudy ||↑ ||0 ||Normal or ↑ (mono-nucleated) ||↑ ||↓ ||May be ↑ ||Usually neg ||AFB + ||+ |
|Viral encephalitis ||Normal ||Normal or ↑ ||0 ||Normal or ↑ (mono-nucleated) ||Normal or ↑ ||Normal ||May be ↑ ||May be present ||Neg ||Neg |
|Brain abscess ||Normal ||↑ ||0 ||Normal or ↑ ||↑ ||Normal ||Normal ||Neg ||Neg ||Neg |
|Brain tumor ||Normal ||↑ ||0 ||0 ||↑ ||Normal ||Normal ||Neg ||Neg ||Neg |
|Spinal cord tumor; partial block ||Normal ||Normal ||0 ||Normal ||Slightly ↑ ||Normal ||Normal ||Neg ||Neg ||Neg |
|Spinal cord tumor; complete block ||Yellow ||Normal or low ||0 ||Normal or slightly ↑ ||↑↑ (200–600 mg/dL) ||Normal ||Normal ||Neg ||Neg ||Neg |
|Epilepsy ||Normal ||Normal ||0 ||0 ||Normal ||Normal ||Normal ||Neg ||Neg ||Neg |
|Mutliple sclerosis ||Normal ||Normal ||0 ||Normal or slightly ↑ ||<80 (often normal) ||Normal ||↑ ||Present ||Neg ||Neg |
|Guillain–Barré syndrome ||Normal ||Normal ||0 ||0 ||↑ or ↑↑ (can be 1,000 mg/dL) ||Normal ||May be ↑ ||May be present ||Neg ||Neg |
Box 24–1 Essentials for the Clinical Neuroanatomist After reading and digesting this chapter, you should know and understand:
Indications and contraindications for lumbar puncture
Principles of analysis of CSF
Characteristic CSF profiles (Table 24–1)