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Spinal tap for diagnostic purposes and intrathecal administration of chemotherapy in children


Medical editor Bernward Zeller MD
Pediatric Oncologist
Oslo University Hospital

General

A spinal tap is performed to examine spinal fluid. The test provides information about intrathecal pressure, cell counts, and cell types. A spinal tap is also used for intrathecal administration of chemotherapy for leukemia and lymphoma. This is done either either prophylactically or for treatment of cancer in the brain membranes (meninges).

Children undergoing this procedure are usually given general anesthesia.

Indications

  • Suspicion of disease in the central nervous system.
  • Intrathecal chemotherapy administration for most leukemias and certain non-Hodgkin lymphomas

Contraindications

  • Thrombocyte values < 20,000 (first give thrombocyte transfusion). For diagnostic spinal tap for leukemia/lymphoma, the number of thrombocytes should be at least > 50,000.
  • INR values > 1.8. If necessary, give fresh frozen plazma or cryoprecipitate first. This should be considered in view of the risk of inadequate anticoagulation.
  • Low molecular weight heparin combined with more than one platelet inhibiting factor.
  • Disseminated intravascular coagulation (DIC).
  • Untreated acute promyelocytic leukemia
  • Fibrinolytic treatment ongoing, or where treatment is finished less than 2 days earlier.

Goal

  • Diagnose disease in the spinal fluid
  • Treat and prevent disease and/or CNS involvement

Equipment

  • Equipment and supplies for spinal tap.

Preparation

  • Prior to the examination, the child and parents should be thoroughly informed about the purpose of the test and how it will be carried out.  
  • The child should fast for 4-5 hours before the examination. Breastfed children need only fast for 2 hours before the exam.
  • The examination is performed by a doctor and takes about 10 minutes.
  • The child is put under general anesthesia. The parents should stay with the child until he/she is asleep.
  • Mixing of chemotherapy should be done immediately before the tap.

Implementation

  • The child should lay on the side with the back flexed on a flat surface. This position makes the thecal sac more easily accessible.
  • Wash the area with chlorhexidine from the puncture point and out.
  • Palpate and find the desired invertebral space (L4-L5 or L3-L4) and place one finger on the adjacent spinous process. 
  • Puncture the invertebral space L4-L5 or L3-L4. This is at the level of the iliac crest or right above. The bevel of the needle should be facing up to minimize damage to the ligament and dura. The direction of the needle should be perpendicular to the skin on small children and directed more caudad on larger children. 
  • There should be constant resistance in the tissue until the flaval ligament is met, which will increase the resistance.
  • When the needle reaches the epidural space, less resistance will be met.
  • Carefully press further past the arachnoid, many times one feels the membrane puncture.
  • Carefully pull out the stylet and check if spinal fluid drains. This should be done sterile so it can be repeated if the needle is in the wrong location. 
  • The drop rate of spinal fluid is rarely above 1 drop/second. 
  • After the desired amount of spinal fluid is drained for testing, the chemotherapy can be injected.
  • Remove the needle and apply a bandage.

Cell count and test for total protein and glucose

  • 1 tube with a minimum of 20 drops (1 ml) marked for spinal fluid for protein and glucose.
  • 1 tube with 9 drops for cell count. This should be taken at the end since bleeding caused by the puncture can give a higher cell count.
  • An extra tube should always be filled with at least 30 drops at the time of diagnosis. This is sent to pathology for cytology testing. Flow cytometry on the fluid may not be possible due to a low number of white blood cells in the fluid.

The spinal fluid is drained into tubes without anything added.


Follow-up

Older children should lie flat for 2 hours after the tap to avoid a headache. All children having received chemotherapy via spinal fluid (most often methotrexate) should lie flat for a few hours after the spinal puncture. This is to improve distribution of the drug up to the brain. In small children, remaining flat is often not possible.

For headache

  • Bedrest until the headache subsides.
  • Increase fluid intake.
  • Paracetamol for pain relief (unless contraindicated). Caffeine may also be helpful.
  • Duration >2-4 days: seal dural leakage with an epidural "blood patch" (contact anesthesiologist)

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