Medical Health Encyclopedia

Normal bone marrow contains 5% or less blast cells (the immature cells that ordinarily develop into healthy blood cells). In leukemia, abnormal blasts constitute between 30 - 100% of the marrow.

Spinal Tap

If bone marrow examination confirms ALL, a spinal tap may be performed, which uses a needle inserted in to the spinal canal. The patient feels some pressure and usually must lie flat for about an hour afterward to prevent severe headache. This can be difficult, particularly for children, so parents should plan reading or other quit activities that will divert the child during that time. Parents should also be certain that the professional administering this test is highly experienced.

Click the icon to see an image of a spinal tap.

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A sample of cerebrospinal fluid with leukemia cells is a sign that the disease has spread to the central nervous system. In most cases of childhood ALL, leukemia cells are not found in the cerebrospinal fluid.