Lumbar puncture is indicated for the following purposes:
Diagnosis of meningitis and other infective or inflammatory disorders, subarachnoid hemorrhage, hepatic encephalopathy, meningeal malignancies, paraneoplastic disorders, or suspected abnormalities of intracranial pressure.
Assessment of the response to therapy in meningitis and other infective or inflammatory disorders.
Administration of intrathecal medications or radiologic contrast media.
Rarely, to reduce cerebrospinal fluid (CSF) pressure.
Suspected intracranial mass lesion. In this situation, performing a lumbar puncture can hasten incipient transtentorial herniation.
Local infection overlying the site of puncture. Under this circumstance, cervical or cisternal puncture should be performed instead.
Coagulopathy. Clotting-factor deficiencies and thrombocytopenia (platelet count below 50,000/μL or rapidly falling) should be corrected before lumbar puncture is undertaken to reduce the risk of hemorrhage.
Suspected spinal cord mass lesion. In the case of complete spinal block, only a small quantity of CSF should be removed because fluid removal can produce a pressure differential above and below the block, which can increase the degree of spinal cord compression.
With a cooperative patient, lumbar puncture can generally be performed by a single person. An assistant can be helpful in positioning the patient and handling CSF samples, especially if the patient is uncooperative or frightened.
The following items, which are usually included in preassembled lumbar puncture trays, are required. All must be sterile.
Iodine-containing solution for sterilizing the skin.
Syringe (5 mL).
Needles (22- and 25-gauge).
Spinal needles (preferably 22-gauge) with stylets.
Lumbar puncture is usually performed with the patient in the lateral decubitus position (Figure 2-1), lying at the edge of the bed and facing away from the person performing the procedure. The patient's lumbar spine should be maximally flexed to open the intervertebral spaces. The spine should be parallel to the surface of the bed, and the hips and shoulders should be aligned in the vertical plane.
Lateral decubitus position for lumbar puncture.
Occasionally it is desirable to perform lumbar puncture with the patient seated. In this case, the patient is seated on the side of the bed, bent over a pillow that rests on a bedside table, while the physician reaches over the bed from the opposite side to perform the procedure.
The usual practice is to enter the L3-L4 or L4-L5 vertebral interspace, because the spinal cord (conus medullaris) terminates at approximately the L1-L2 level in adults. Thus the procedure is performed without danger of puncturing the cord. The L3-L4 interspace is located at the level ...