One of the rarer complications of acute myeloid leukemia (AML) is the involvement of the central nervous system (CNS). This complication can occur in both children and adults. Children will undergo regular testing for CNS involvement from diagnosis. Adults may undergo testing after a relapse.

AML is a type of blood cancer that starts in bone marrow cells, where blood cells develop. The cells, known as leukemic blasts, develop abnormally and do not function properly. The cells can survive and grow better than healthy cells and can block the production of healthy cells.

Leukemia is the most common form of childhood cancer. Studies have shown that 6–29% of children with AML will have CNS involvement at the time of diagnosis.

Most adults with a new diagnosis of AML are over the age of 65 years. However, it is more common for children with AML to have CNS involvement than it is for adults. Adults do not undergo routine testing for this condition at diagnosis unless a doctor suspects CNS involvement.

This article will explain what the CNS is and how AML can impact its function. It will also list the symptoms, outlook, and treatment options for AML with CNS involvement.

AML can sometimes involve the central nervous systemShare on Pinterest
Tomekbudujedomek/Getty Images

The human CNS carries out many functions at the same time. For instance, it controls intentional, or voluntary, movement, including walking and speech.

The CNS also controls involuntary movement, such as breathing and blinking. Moreover, it can shape a person’s perceptions, emotions, and thoughts.

The brain is the central processing unit that receives information and makes sense of it. The spinal cord is the communication system through the nerves that reach out to other parts of the body.

The vertebrae of the spine make up different sections, and each section communicates with a different body part.

Learn more about the CNS here.

AML can affect the CNS in both adults and children. However, CNS involvement occurs more frequently in people with acute lymphoblastic leukemia, which is another type of leukemia.

Doctors will confirm CNS involvement if they discover leukemic cells in the cerebrospinal fluid. This can also present with tumors in the cerebrum in the brain, or in the meninges, which are the layers of membrane that protect the brain and spinal cord.

Researchers suggest that several specific factors may lead to a higher risk of AML with CNS involvement:

Children rather than adults

One 2021 review states that children are at greater risk of developing CNS involvement with AML than adults. This is because the AML is more likely to spread to the CNS and grow tumors there.

However, children are more likely than adults to undergo routine testing for the condition after receiving an AML diagnosis. Therefore, many more adults may also have CNS involvement, but it may go undiagnosed.

The review also suggests that CNS involvement in adults with AML may be asymptomatic. However, the researchers recognize that this was a small review and that more research is necessary.

Learn more about AML in children here.

After relapse

A relapse is when a person experiences AML again after a period of remission.

The authors of a 2017 study found that CNS involvement occurred in 0.6% of AML cases, or in less than 1 in 100 people. Those who experienced a relapse had a higher prevalence of CMS involvement, which occurred in 2.6% of relapse cases, or in less than 1 in 300 people.

Cell counts

A 2015 review involving 395 participants aged over 18 years found that 20 of the participants had CNS involvement. Seven individuals had initial CNS condition, and four had an isolated relapse of CNS.

The people with CNS involvement were more likely to be under the age of 45 years, have higher cell counts of leukocytes, platelets, and immature cell blasts, and have a specific chromosomal abnormality.

The review authors observe that more research is necessary to determine whether these are specific risk factors for AML with CNS involvement.

Symptoms will depend on the area of the nervous system that has become affected.

CNS involvement in AML usually does not cause any symptoms. However, nervous system symptoms may include:

Rarer symptoms

Other, rarer symptoms may suggest the involvement of the cranial nerves. These symptoms include:

Spinal cord involvement may cause symptoms such as:

Survival rates for adults who are living with AML with CNS involvement are low when compared with other blood cancer conditions or with AML without CNS involvement. However, studies emphasize that treatment options are improving with medical advances.

Survival rates for people living with leukemia have improved more than fourfold since the 1960s. For AML, the 5-year survival rate is 29.8% overall, and 70.6% for children under the age of 15 years.

People with AML with CNS involvement will receive treatment for the condition if it presents. This can include:

  • Chemotherapy: This treatment may be intensive and could include a drug called cytarabine. Maintenance chemotherapy afterward may involve using a drug called tioguanine.
  • Intrathecal therapy: This type of treatment can help with severe chronic pain or spasticity. It also helps reduce cancer cells. Doctors use a pump to deliver this treatment directly into the spinal cord. It involves chemotherapy drugs.
  • Cranial irradiation: This is a type of radiation therapy that can help prevent further spreading of cancer cells in the brain.
  • Stem cell transplants: Some people with AML and CNS involvement may be eligible for a stem cell transplant. This can involve taking stem cells from the same person who will be receiving them, or taking the cells from a donor.

Treatment may depend on a number of factors, such as:

  • age
  • overall health, including other health conditions
  • previous cancer treatment
  • type of AML
  • CNS involvement at diagnosis

Learn more about treatment for AML here.

AML with CNS involvement is rare, but it is more likely to occur in children with AML, who undergo routine screening for this condition. Intrathecal chemotherapy treats the nervous system and protects it from leukemia cells. Treatment may include stem cell transplants.

Adult CNS involvement with AML will also require more complex treatment. Adults do not receive routine testing for CNS involvement unless they have symptoms.

Scientists continue to test new therapies to improve survival rates for individuals with AML with CNS involvement.