In addition to blood tests, there are two other procedures that many children
will require to check for the presence of cancer cells. These two procedures are
bone marrow aspirations and lumbar punctures (spinal taps). These procedures can
be frightening for children. They are regularly done with sedation and pain medication
so children experience minimal discomfort and often have no recall of the procedure.
Technically these procedures are often quite simple to perform and are usually
done in the treatment room. Your doctor will discuss both of these procedures
with you and your child in more detail. Please ask questions or feel free to discuss
any concerns you have with them.
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Bone Marrow Examination
The bone marrow, which is in the cavity present in the center of bones,
is the organ responsible for the production of red blood cells, white
cells and platelets. Most leukemias originate in the bone marrow. A marrow
sample is usually necessary to make a correct diagnosis and determine
the type of leukemia present. Some solid tumors also spread to the bone
marrow, so a bone marrow sample may be necessary to determine how much
the tumor has spread (the stage of the cancer). Infants have active blood
production in the cavities of many bones, but with age, active bone marrow
becomes localized to the sternum (breast bone), spine, pelvis (hip bones),
and the top part of the femurs (thigh bones). Bone marrow tests usually
consist of obtaining an "aspirate" which is about 1/2 teaspoon sample
of blood-like bone marrow fluid, or (less often) a biopsy which is a small
solid piece of the marrow. These samples are usually obtained from the
prominent bones over the back hip (posterior iliac crest) or front hip
(anterior crest).
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At least one hour prior to the procedure, a cream (EMLA) can be placed on the
skin to help numb it.
The procedure generally involves sedating your child. After the child is sedated,
the skin over the area where the sample is to be taken from is numbed with lidocaine,
and the deeper sensitive covering of the bone (periosteum) is also numbed. This
procedure is done under sterile conditions. Despite the numbing of these areas,
the test can be momentarily painful when the actual sample is drawn. The bone
marrow fluid sample will be stained, and the physician will then look at the
sample under the microscope. The results may be available the same day. The
testing of biopsy samples may take three days.
A sample may also be sent for cytogenetic testing. This test studies the chromosomes
which are often abnormal in leukemias. It also helps doctors monitor for rejection
by determining if the marrow is from the donor and helps doctors monitor for
he recurrence of disease after transplant.
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Spinal Taps (Lumbar Punctures, LPs)
The brain and spinal cord is surrounded by fluid called cerebrospinal
fluid (CSF). This fluid is made by the brain itself and serves to protect
it from sharp impacts. (The fluid acts as a "shock absorber" for the brain).
Cancer cells may circulate in the bloodstream and gain access to the fluid
surrounding the brain, or in the case of brain tumors may directly extend
to this area from the tumor itself. The cerebrospinal fluid and the blood
are separated by a natural barrier. This natural barrier prevents the
chemotherapy injected into the bloodstream from reaching the CSF area.
This barrier creates a problem since it is known that a large number of
leukemias and lymphomas are particularly likely to spread to the covering
of the brain and spinal cord. Therefore, it is important to check the
CSF for the presence of malignant cells. It may be necessary to administer
chemo to the CSF before the transplant even if no cancer cells are detected
because it is known that the cancer could spread to this region.
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Spinal taps are usually done with the child lying in a curled position (the
"fetal" position) on his/her side. This opens up a space between each vertebrae
(spinal bones) along the spine. Like bone marrow exams, these procedures are
done under sterile conditions, with the skin numbed with EMLA cream and/or lidocaine.
A small needle is inserted through the space between adjacent vertebrae in the
lower back area. The spinal cord stops well above this area so there is no danger
of contacting the cord itself during this procedure. A small amount of clear
fluid is withdrawn and medications may be given through the same needle. The
fluid sample is studied under the microscope by your doctor in order to detect
any malignant cells. Some patients may experience headaches or nausea after
an LP, especially if medications are given into the fluid. Therefore, an anti-emetic
(a drug that prevents vomiting) is usually given to avoid these side effects.
In general, LP procedures go easily, but in some cases it may require a longer
period of time to insert the needle into the proper position.
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