Cerebrospinal Fluid (CSF)

CSF is produced by the choroid plexus in the lateral third and fourth ventricles of the brain. In normal adults, the total CSF volume is 90–150 mL. Eighty percent of the CSF is contained in the arachnoid space in the cranium and spinal cord, where a small amount can be extracted for examination, most commonly through a lumbar puncture. CSF pressure is measured by a manometer.

Normal values:

• Appearance: clear, colorless

• Normal opening adult pressure: 90–180 mL of water in an adult in the lateral decubitus position with the legs and neck in a neutral position

• Cell count and differential (Table 16.17):

  • Adults: WBC 0–5 cells/mm³, RBC 0/mm³

  • Newborns: WBC 0–30/mm³, RBC 0/mm³

Examination of CSF is required when CNS involvement by inflammatory, infectious, neoplastic, or neurologic complications are suspected. Up to 20 mL of fluid can be removed in the adult.

CSF is divided into three sterile tubes:

• Chemistry and immunology studies

• Microbiology examinations

• Cell count, differential, and cytology (if indicated)

Increased number or red blood cells: either hemorrhagic tap or subarachnoid hemorrhage

Increased number of neutrophils: bacterial or early viral CNS infection, early CNS TB, CNS syphilis, fungal infection, contamination with peripheral blood through traumatic tap, CNS hemorrhage

Increased number of lymphocytes: viral infection of the CNS, CNS TB, acute lymphocytic leukemia or lymphoma of the CNS, cryptococcal infection of the CNS, fungal infection of the CNS, CNS syphilis, parasitic disease infecting the CNS, Guillain-Barré syndrome

Increased eosinophils: parasitic infection of the CNS, fungal infection of the CNS, viral infection of the CNS, CNS syphilis, allergic reaction

Increased basophils: chronic myelogenous leukemia

Tumor cells: primary or metastatic tumors of the CNS

Xanthochromia (yellowish discoloration): marker of previous intracerebral bleeding