Multiple myeloma is a cancer originating in plasma cells, a type of white blood cell found primarily in the bone marrow. These abnormal plasma cells, also called myeloma cells, accumulate in the bone marrow, disrupting normal blood cell production and forming tumors in bones throughout the body. While multiple myeloma predominantly affects the bone marrow, it can, in rare instances, spread to other areas of the body, including the central nervous system (CNS), which encompasses the brain and spinal cord. This brain involvement is an uncommon occurrence in multiple myeloma.
How Multiple Myeloma Affects the Brain
The brain is protected from substances in the bloodstream by the blood-brain barrier (BBB), a protective network of cells. Despite this barrier, myeloma can reach the brain or spinal cord. One way is direct extension from bone lesions, especially from the skull, where myeloma cells can grow into adjacent brain tissue.
Another pathway is hematogenous spread, where myeloma cells travel through the bloodstream. While less common due to the BBB, some aggressive myeloma cells may bypass this barrier. Myeloma can also involve the meninges (membranes surrounding the brain and spinal cord), a condition called leptomeningeal carcinomatosis. These CNS occurrences are categorized as extramedullary plasmacytomas when forming a mass, or leptomeningeal disease when affecting the membranes.
Recognizing Brain Involvement
The signs and symptoms of multiple myeloma affecting the brain vary depending on the affected brain or spinal cord area. Headaches are a common symptom, often persistent and severe. Seizures can also occur, indicating brain tissue irritation or damage.
Cognitive changes, including confusion, memory problems, or difficulty concentrating, may develop. Vision disturbances, such as blurred or double vision, can also occur. Weakness, numbness, or personality changes might be observed.
Cranial nerve palsies, affecting nerves controlling facial movement, eye movement, or sensation, are another manifestation. These symptoms are not specific to multiple myeloma and can mimic other neurological conditions, making diagnosis challenging. Therefore, any new or worsening neurological symptoms in a multiple myeloma patient warrant prompt investigation.
Confirming Brain Involvement
Confirming multiple myeloma involvement in the brain involves a combination of diagnostic methods. Magnetic Resonance Imaging (MRI) of the brain and spine is a primary imaging technique to identify lesions or abnormalities. MRI can reveal extramedullary plasmacytomas (tumor masses) or signs of leptomeningeal involvement.
Cerebrospinal fluid (CSF) analysis, obtained via lumbar puncture (spinal tap), plays a significant role. This procedure allows examination of CSF for myeloma cells or elevated protein levels, indicating meningeal disease. In some instances, a biopsy of a suspected lesion may be necessary to confirm diagnosis through pathological examination.
Managing Brain Involvement
Treatment approaches for multiple myeloma affecting the brain are aggressive due to the serious nature of CNS involvement. Systemic therapies, including certain chemotherapies and novel agents, are chosen based on their ability to cross the blood-brain barrier and target myeloma cells. Some immunomodulatory drugs, like lenalidomide and pomalidomide, are thought to have some ability to cross the BBB.
Intrathecal chemotherapy involves delivering medication directly into the cerebrospinal fluid, bypassing the blood-brain barrier to reach cancer cells in the meninges. This is often a triplet regimen including hydrocortisone, methotrexate, and/or cytarabine. Radiation therapy is another important modality, often used for localized lesions or to manage symptoms like pain or neurological deficits. This can involve focal brain radiation or craniospinal irradiation.
In some cases, high-dose chemotherapy followed by autologous stem cell transplant may be considered for eligible patients. This intensive treatment aims to eliminate cancer cells and then rescue the bone marrow with the patient’s own previously collected stem cells. The treatment plan is highly individualized, taking into account the extent of brain involvement, the patient’s overall health, and prior treatments. The goal of treatment is to control the disease, alleviate symptoms, and improve quality of life.