Leptomeningeal metastases (LM) occur when cancerous cells metastasize or spread to the leptomeninges, cerebral spinal fluid (CSF), or both. The meninges are thin layers of tissue surrounding and protecting the spinal cord and brain.

Cerebral spinal fluid is a clear fluid that the brain produces. It appears between the layers of the meninges and provides a cushion for the spinal cord and brain. The symptoms of LM, such as increased pressure in the brain, come from the cancerous cells clogging the usual exit points for CSF, resulting in a fluid buildup.

According to Cancer Research UK, between 5% and 10% of people who have cancer may develop leptomeningeal metastases. It is most common in those who have breast, lung, or melanoma skin cancer.

This article will discuss what happens when LM occurs, including the symptoms and causes. It will also explain how doctors diagnose and treat it.

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Leptomeningeal metastases refer to the spread of cancer cells to the thin layers of tissue that cover the spinal cord, also known as the leptomeninges, and the brain.

According to the National Cancer Institute, it is a serious condition that results in inflammation of the meninges, which are layers that protect the brain. It is a stage 4 disease.

Other names for LM include:

  • neoplastic meningitis
  • leptomeningeal disease
  • leptomeningeal carcinomatosis
  • carcinomatous meningitis

Around 5–8% of people with solid cancerous tumors and 5–15% with hematological or blood cancers develop LM. There are various treatment options for LM, and it usually has a negative prognosis.

People with leptomeningeal metastases may experience one or more symptoms as the cancerous cells affect the flow of nutrients, function, or pressure on the spinal cord and brain. However, some individuals may have no symptoms.

Common symptoms of LM may include:

  • headaches
  • confusion
  • weakness
  • nausea or vomiting
  • hearing problems
  • vision changes, such as loss of sight or double vision
  • facial drooping
  • seizures
  • changes to behavior or mood
  • problems with bowel or bladder control
  • weakness or numbness in the bottom or one or both legs
  • unexplained pain in the neck, legs, or lower back

People develop leptomeningeal metastases when cancerous cells metastasize or spread. In the case of LM, cancerous cells may travel from another part of the body through the bloodstream or tissues and reach the meninges or CSF. Alternatively, they can also spread from secondary cancer that has already developed in the brain.

Most solid tumors can metastasize, but the most common that involve the leptomeninges occur are:

  • breast tumors
  • lung tumors
  • melanoma
  • gastrointestinal tumors
  • primary central nervous system tumors

Only a relatively small percentage of people with cancer develop LM. By some estimates, around 5–10 out of every 100 individuals who have cancer develop LM. On average, there are around 110,00 new diagnoses of LM in the United States annually.

Despite being fairly rare, according to some calculations, LM is the third most common type of metastatic cancer that involves the central nervous system.

The largest risk factor for developing leptomeningeal metastases is a person having cancer.

Overall, the most common cause of LM is metastatic breast cancer, and the next most common are small-cell lung cancer and then melanoma, a type of skin cancer.

The best treatment for leptomeningeal metastases often depends on individual factors, in particular, what primary or secondary type of cancer it developed from.

A range of treatments may include the below.

Chemotherapy

Chemotherapy involves anticancer medications, which come in the form of oral medication, injections into a vein, or injections directly into the CSF using a lumbar puncture.

A ventricular access device called an Ommaya reservoir, a dome-shaped device that doctors insert under the scalp via surgery, may also deliver chemotherapy.

The Ommaya reservoir has tiny tubes that allow doctors to deliver chemotherapy medications directly into the brain ventricles, the fluid-filled spaces between brain matter where CSF fluid resides.

Radiation therapy

Doctors can deliver radiation, often in the form of X-rays, to the whole brain or parts of the brain to shrink or eliminate cancer cells.

Targeted cancer medications

Medications can target the differences in cancer cells that allow them to grow and survive. The specific type of targeted medications often depends on the primary type of cancer someone has.

Some medications for cancer may include:

  • dabrafenib
  • vemurafenib
  • bevacizumab
  • gefitinib
  • erlotinib

Surgery

Surgery can improve the flow of CSF and reduce pressure on the brain and spinal cord. However, doctors rarely perform it.

In most cases, the goal of treating LM is to help reduce symptoms and control the growth rate of cancer. Some people are too ill to undergo treatment for LM, but doctors may administer medication to control their symptoms.

Medications that doctors commonly recommend to manage LM symptoms include:

  • antidepressants
  • pain medications
  • antianxiety medications

The outlook for someone with LM depends largely on individual factors, such as:

  • whether cancerous cells have migrated to additional parts of the body
  • how the cancer responds to treatment
  • how fast the cancer is spreading and growing

Treatments for LM may be able to slow the growth or progression of cancer for a few months to a year or more.

Generally, however, there are fairly limited treatment options for LM, and the outlook for the disease is limited. With treatment, many people with LM only survive around 2–4 months.

People who develop LM from breast cancer tend to live slightly longer, around 5–7 months, compared with people who develop it from skin and lung cancer, who tend to survive for 4 months.

Diagnosing LM can be challenging. Sometimes, a doctor can diagnose the condition using imaging tests, such as an MRI scan.

A doctor may also be able to diagnose LM by looking for cancerous cells in CSF fluid from the spine. To acquire CSF fluid for testing, they will perform a lumbar puncture, a procedure where they insert a long needle through the lower back into the space surrounding the spinal cord.

Before receiving a lumbar puncture, doctors numb the portion of the skin where they insert the needle. A lumbar puncture can also help a doctor determine how much pressure there is on the brain or spinal cord.

Most diagnoses of LM occur 1.2 to 2 years after someone receives a cancer diagnosis of solid cancerous tumors. People who develop LM from blood cancers tend to receive a diagnosis of LM around 11 months after receiving a blood cancer diagnosis.

The only way to prevent LM from developing is to effectively treat the primary or secondary cancer it originates from effectively before it can spread.

Leptomeningeal metastases are a fairly rare complication of other types of cancer, most commonly breast, lung, and skin cancers. It occurs when cancerous cells spread from an initial cancer site to the meninges or CSF.

Diagnosing and treating LM can be challenging. In most cases, the outlook for people with LM is limited, even with proper treatment. Generally, treatments for LM aim to relieve symptoms, improve someone’s quality of life, and extend their lives by a few months to years.