Acute myeloid leukemia (AML) is the most common type of acute leukemia that develops in adults, according to the National Cancer Institute (NCI). It also makes up about 15% to 20% of acute leukemias in children.

“Acute” means that the cancer tends to develop quickly and requires aggressive treatment. “Chronic” leukemias tend to develop slower.

AML develops in the blood-producing cells in your bone marrow and quickly moves to your blood. It can spread to other parts of your body, such as your:

  • lymph nodes
  • liver
  • spleen
  • testicles
  • cerebrospinal fluid and central nervous system (brain and spinal cord)

It’s less common for AML to spread to your spinal fluid and central nervous system (CNS) than another type of cancer called acute lymphocytic leukemia (ALL).

In this article, we take a closer look at how acute myeloid leukemia in your spinal fluid and CNS affects AML symptoms, treatment, and outlook.

Cancer cells spreading to the spinal fluid and CNS is reported in about 3 percent of people with AML. Although, some researchers think this might be an underestimation. CNS involvement seems to be more common in children.

Research involving European pediatric AML study groups reported CNS involvement affecting 6% to 29% of children with AML.

In a 2017 study, researchers found that CNS involvement was more common in people with relapsed AML than in newly diagnosed AML. In a group of 3,261 people with AML, 0.6% had CNS involvement at initial diagnosis, while 2.9% had it at relapse.

Researchers are still trying to understand how leukemia cells reach your cerebrospinal fluid.

In a 2018 study, researchers found evidence in mice that leukemia cells grasp proteins on the outside of blood vessels and ride them from bone marrow to your spinal fluid.

Risk factors for CNS involvement

Risk factors associated with the development of CNS involvement include:

  • high pretreatment levels of lactate dehydrogenase and white blood cells
  • chromosome 16 inversion and chromosome 11 abnormalities
  • having subcategories of AML called acute myelomonocytic leukemia or acute monocytic leukemia
  • younger age

AML in your spinal fluid or other parts of your CNS usually doesn’t cause symptoms. If symptoms are present, they depend on where cancer cells are found. They can include:

If your cranial nerves are affected, you may develop:

In rare cases, sudden onset of obesity can develop from changes in a part of your brain called the hypothalamus.

More typical symptoms of AML include:

To check to see if leukemia has spread to your cerebrospinal fluid, your doctor can test your fluid using a procedure called a lumbar puncture or spinal tap.

During this procedure, a small amount of your spinal fluid is removed from your lower back with a needle. The procedure is normally performed with local anesthesia and shouldn’t cause much pain.

A lumbar tap isn’t typically used for AML in adults unless you have symptoms that suggest that cancer has spread to your spinal fluid. It’s part of routine evaluation for children.

Treatment for AML with CNS involvement depends on factors such as:

  • your age
  • your overall health
  • the subcategory of AML you have
  • the degree and location of CNS involvement
  • whether you’ve received previous cancer treatment

Induction therapy

An initial round of chemotherapy called induction chemotherapy is used to kill leukemia cells in your bone marrow. Induction therapy often includes a combination of cytarabine and an anthracycline drug such as daunorubicin or idarubicin.

Some people with certain genetic mutations may also receive the targeted therapy drugs midostaurin or gemtuzumab.

Consolidation therapy with stem cell transplant

If you achieve remission after induction therapy, you’ll receive another round of chemotherapy to kill any remaining cells. Consolidation therapy often includes several cycles of chemotherapy with a regimen called high dose cytarabine.

You may also receive a bone marrow transplant during this stage of treatment if you’re eligible.

People who received targeted therapy drugs during induction therapy may continue to receive them.

Intrathecal chemotherapy

If doctors find evidence of CNS involvement after a lumbar puncture, you’ll likely receive intrathecal chemotherapy, a procedure where chemotherapy drugs are injected directly into your spinal fluid. Usually, the drugs methotrexate or cytarabine are used.

Intrathecal chemotherapy may also be combined with radiation therapy.

CNS involvement is associated with a poorer outlook in people with AML. Research suggests that about half of people with CNS involvement live less than about 3 months, and the reported 5-year overall survival rate is 11%.

Despite a generally poor outlook, treatment options are improving, and the survival rate for AML is likely to improve in the future. Since 1975, the overall 5-year relative survival rate has improved from 5.5% to 30.3%, according to the NCI.

In a 2021 study, researchers found no significant difference in survival between people with newly diagnosed AML with or without CNS involvement.

Here are some questions people frequently ask about AML in the spinal fluid.

How fast does AML spread?

Leukemias are classified as acute or chronic. Acute leukemias like AML tend to spread quickly and require aggressive treatment. Symptoms of AML tend to develop over a few weeks and continue to get worse.

Is a bone marrow test similar to a lumbar puncture?

A bone marrow biopsy involves having a small amount of bone marrow taken from one of your bones with a long, thin needle. Often the sample is taken from your pelvic bone.

A lumbar puncture involves inserting a needle into your lower spine. The needle is inserted into the subarachnoid space where spinal fluid circulates between the protective layers of your spinal cord.

Can AML start in the spinal fluid or does it typically spread there from bone marrow or peripheral blood?

AML starts in cells that produce blood cells. Most of the cells that produce blood cells in your body are in your bone marrow. Abnormal blood cells produced by your bone marrow quickly circulate throughout your body and can reach your spinal fluid.

Acute myeloid leukemia (AML) can spread to your spinal fluid and other parts of your CNS. Involvement of the CNS seems to be more common in children than adults. Another type of leukemia called ALL seems to spread to the CNS more frequently than AML.

AML that has spread to the CNS often does not cause symptoms. A lumbar puncture is only performed in adults when CNS involvement is suspected.

It’s critical to let your doctor know if you have any symptoms that may indicate that the cancer has spread to your CNS. Symptoms include unexplained headaches, nausea, or vomiting.