CSF analysis

Cerebrospinal Fluid

CSF Formation 140 ml spinal and cranial CSF 30 ml in the spinal cord Production is approx. 0.35 ml/min

Location of CSF Two lateral ventricles Third ventricle Fourth ventricle Spinal cord central canal Subarachnoid space

Formation of CSF Choroid plexuses of lateral, third and fourth ventricles Ependymal lining of ventricular system Blood vessels

Circulation of CSF Due to pulsation of blood in choroid plexus Due to pulsation of ependymal cells Lateral ventricles Interventricular Foramen of Monro third ventricle Mesencephalic Aqueduct (Aqueduct of Sylvius) fourth ventricle spinal cord central canal through the Median Foramen of Magendie; also, out the Lateral Apertures of Luschka to the subarachnoid space. 6

Absorption of CSF Through the arachnoid villi, a protrusion of arachnoid membrane into the central venous sinus and other sinuses A valve opens when CSF pressure exceeds venous pressure Absorption by veins and capillaries of CNS

Specimen Collection

Lumbar Puncture

Indications for Lumbar Puncture Primary indication for emergent spinal tap is possibility of CNS infection The second indication for an emergent spinal puncture is a suspected spontaneous subarachnoid hemorrhage.

Infectious Indications Fever of unknown origin Children 1mo to 3yrs: fever, irritability, and vomiting. Cannot comfort child Over age 3yrs: nuchal rigidity, Kernig’s sign, and Brudzinski’s sign Petechial rash in a febrile child Partially treated children are less likely to be febrile or exhibit an altered mental status

Contraindications for LP Absolutely contraindicated in the presence of infection in the tissues near the puncture site. Relatively contraindicated in presence of increased ICP. Caution advised when lateralizing signs.

Indications 1. Suspected CNS infection 2. Suspected subarachnoid hemorrhage 3.Sampling of CSF for any other reason Contraindications 1. Local skin infections over proposed puncture site (absolute contraindication) 2. Raised intracranial pressure (ICP) 3. Suspected spinal cord mass or intracranial mass lesion (based on lateralizing neurological findings or papilledema) 4. Uncontrolled bleeding diathesis 5. Spinal column deformities

Equipment Spinal needle Three-way stopcock Manometer 4 specimen tubes Local anesthesia Drapes Betadine

Procedure Performed with the patient in the lateral recumbent position. A line connecting the posterior superior iliac crest will intersect the midline at approx. the L4 spinous process. Spinal needles entering the subarachnoid space at this point are well below the termination of the spinal cord.

Procedure Almost all patients are afraid of an LP. Explaining the procedure in advance and discussing each step aids in reducing anxiety. Inquire about allergies to anesthetics. Informed consent.

Procedure Sterile gloves MUST be used. Wash back with antiseptic solution. Sterile towel under hips. The skin and deeper subcutaneous tissue are infiltrated with local anesthetic.

Procedure The patient should be told to report any pain and should be informed that he or she will feel some pressure. The needle is placed into the skin in the midline parallel to the bed.

Procedure The ligaments offer resistance to the needle, and a “pop” is often felt as they are penetrated. Clear fluid will flow from the needle when the subarachnoid space has been penetrated.

Procedure If bone is encountered, withdrawal into subcutaneous tissue and redirect. Attach a manometer and record opening pressure. Turn stopcock and collect fluid. Withdrawal needle and place a dressing. Instruct patient to remain lying down for 1-2 hours before getting up

Procedure Tube 1 is used for determining protein and glucose Tube 2 is used for microbiologic and cytologic studies Tube 3 is for cell counts and differential Tube 4 reserve tube for any special tests

Interpretations Opening pressure Cloudiness / Turbidity Cells Glucose Protein

Interpretations Opening Pressure Opening pressure is taken promptly, avoiding falsely low values due to leakage through and around the needle Normal pressure is between 80 and 180 mm Hg

Normal = 80-180 mmHg If elevated, likely due to cerebral edema from intracranial pathology

Interpretation Appearance (Cloudiness / Turbidity) If CSF is not crystal clear, a pathologic condition of the CNS should be suspected Compare fluid to water Fluid may be clear with as many as 200 WBCs/mm3

A simple test of CSF turbidity is to see if normal print can be read easily through the sample – CSF should be crystal clear. Cloudiness usually appears at CSF WBC counts > 200 WBCs/mm3

Interpretation Cells WBC counts over 5 cells/mm3 should be taken to indicate the presence of pathologic condition Polymorphonuclear leukocytes are never seen in normal adults

Infections: PMN predominance: likely bacterial meningitis. Lymphocytic predominance: likely viral meningitis.

Interpretation Cells Neutrophilic pleocytosis is commonly associated with bacterial infections or early stages of viral infections. Eosinophils are always abnormal and most commonly represent a parasite infestation.

Interpretation Cells Normal CSF RBCs are less than 5/mm3. Counts that are otherwise unexplained may be due to a traumatic tap.

The Traumatic Tap It should not be difficult to distinguish between subarachnoid hemorrhage and a traumatic tap. In traumatic taps, the fluid generally clears between 1st and 3rd tubes.

Interpretation Glucose Low CSF glucose concentration indicates increased glucose use in the brain and the spinal cord. The normal range of CSF glucose is between 50 and 80 mg/dl 50-70% of serum glucose concentration Only low concentrations of glucose are significance

Hypoglycorrhachia: Decreased sugar level in CSF Decreased glucose transport by the inflamed meninges. Due to increased glucose utilization by the cerebral tissue.

Interpretation Protein Increase in CSF total protein levels are a nonspecific abnormality associated with many disease states. Levels > 500mg/dl are uncommon and are seen mainly in meningitis, in subarachnoid bleeding, and with spinal tumors.

Raised CSF protein levels are due to increased vascular permeability of the blood-brain barrier and the loss of albumin-rich fluid from the capillaries.

CSF Analysis with Infections Bacterial Infections The Gram stain is of great importance, because this often dictates the initial choice of antibiotic. Gram-negative intracellular or extracellular diplococci are indicative of Neisseria meningitidis Small Gram-negative bacilli may include Haemophilus influenza, especially in children. Gram-positive cocci indicates Streptococcus pneumoniae, other Streptococcus species, or Staphylococcus. 20% of Gram stains may be falsely negative.

CSF Analysis with Infections Bacterial Infections While the culture is pending, one may suspect a bacterial infection in the presence of an elevated opening pressure and a marked pleocytosis ranging between 500 and 20,000 WBCs/mm3. The differential count is usually chiefly neutrophils. A count above 1000 cells/mm3 seldom occurs in viral infections.

CSF Analysis with Infections Bacterial Infections CSF glucose levels less than 40 mg/dl or less than 50% of a simultaneous blood glucose level should raise the question of bacterial meningitis. The CSF protein content in bacterial meningitis ranges from 500 to 1500 mg/dl.

CSF Analysis with Infections Viral Studies The organisms most commonly isolated in viral meningitis are enteroviruses and mumps. Enteroviruses: summer and fall Mumps: winter and spring

CSF Analysis with Infections Viral Studies WBC count in viral meningitis and encephalitis usually: 10 to 1000 cells/mm3. The differential count is predominantly lymphocytic and mononuclear in type. Protein levels are usually mildly elevated

CSF Findings >1000 >50 50-80 ½ - 2/3 serum <30 < ½ serum Component Normal Children Bacterial Meningitis Viral Meningitis Leukocytes/ mm3 WBC 0-5 >1000 100-500 Neutrophils (%) >50 < 40 Glucose (mg/dL) 50-80 ½ - 2/3 serum <30 < ½ serum < 30 - 70 Protein (mg/dL) 20-30 >100 50-100 Erythrocytes/mcL 0-2 0-10

Complications Headache After Lumbar Puncture Most common complication Occurs 5-30% of all spinal taps Usually starts up to 48 hours after to procedure. Usually lasts 1-2 days (occas 14 days)

Meningitis Meningitis is an inflammatory process of the leptomeninges and CSF