When Neurologic Complications of Cancer Occur
by Lisa M. DeAngelis, MD
Neurologic complications occur frequently in people with cancer. They can affect the brain, spinal cord, nerves, or muscles, causing weakness, seizures, or confusion. Neurologic complications can be divided into two main groups: those due to metastatic spread of the cancer to nervous system structures (e.g., brain metastases), and those due to indirect effects from cancer or its treatment, such as damage to the peripheral nerves from chemotherapeutic drugs. Neurologic complications are important to address because they can cause disability if untreated, but early diagnosis and effective therapy can reduce their impact on a person’s quality of life.
The most common site of metastasis to the nervous system is the brain. Brain metastases may cause confusion, headache, seizures, or weakness affecting one side of the body. They are easily diagnosed by an MRI or CT scan of the head.
When one or a few metastases are evident, effective treatment may include surgery or stereotactic radiosurgery, a highly focused single radiotherapy treatment that can be performed by a gamma knife, Cyberknife®, or standard radiotherapy machines. For people with multiple metastases, standard radiotherapy of the whole brain can be effective. Chemotherapy is sometimes used to treat brain metastases, but only after other approaches have been used first.
Neurologic complications are important to address because they can cause disability if untreated, but early diagnosis and effective therapy can reduce their impact on a person’s quality of life.
Tumors that spread to the bony structures of the spine may grow and cause pressure on the spinal cord, resulting in back pain, leg weakness, trouble walking, and sometimes, difficulty urinating or defecating. When a tumor is exerting pressure on the spinal cord, urgent treatment is required. Treatment often involves radiotherapy, but increasingly, surgery is used and may be associated with better neurologic function in some people. New technologies employing multiple doses of highly focused radiation, called intensity-modulated radiotherapy (IMRT), may be an additional option. People with progressively severe back pain must alert their doctors so they can be evaluated for possible spread of their cancer to the spine, which is easily identified by an MRI.
The two most common neurologic complications in people with cancer that are not caused by metastases are peripheral neuropathy and confusion. Peripheral neuropathy refers to damage of the nerve endings in the fingers and toes and usually involves the toes first. In people with cancer, peripheral neuropathy is usually caused by chemotherapeutic agents, especially vincristine, cisplatin, paclitaxel, docetaxel, and newer agents such as bortezomib. Each drug causes a slightly different type of damage, but the first symptom is usually numbness or tingling in the toes and fingers. This may be followed by weakness of the feet and hands, particularly with vincristine, or progressive numbness and difficulty walking, particularly with cisplatin and paclitaxel.
Peripheral neuropathy tends to be cumulative and worsens with increasing doses of chemotherapy. Furthermore, people who have pre-existing nerve damage from another injury or illness, such as diabetes mellitus, are more sensitive to the nerve-damaging effects of these drugs. While some symptoms are particularly bothersome, they usually improve when the drug is stopped. However, people receiving cisplatin may actually experience worsening symptoms for several months after the drug is stopped before any improvement begins.
Recovery is often, but not always, complete. No treatment is available to accelerate improvement of damaged nerve endings, but if tingling or pain interferes with function, medications are available to help relieve it. Experimental drugs are being developed to protect the nerve endings during chemotherapy administration so this damage does not develop.
Confusion, poor memory, and other cognitive abnormalities are common in people with cancer and may be due to many causes. Drugs taken in addition to curative treatments, such as pain medications, may cause confusion or sedation. Memory loss and diminished cognitive function may be a result of radiation to the brain or systemic chemotherapy, but this is usually mild when present. Some people may develop a short-lived period of disorientation after a major surgical procedure. Frequently, people with cancer have more than one cause of confusion, and pinpointing that cause requires brain imaging, as well as blood tests and other evaluations. Recognizing and correcting these multiple causes usually leads to restoration of normal mental function.
Oncologists, radiation oncologists, oncologic surgeons, and neurologists are all sensitive to the common causes of neurologic dysfunction in people with cancer. Early recognition and treatment can preserve neurologic function, and in people with metastases, help control their cancer, both leading to longer life and improved quality of survival.
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Dr. Lisa DeAngelis is chair of the department of Neurology at Memorial Sloan-Kettering Cancer Center and professor of Neurology at Weill Medical College of Cornell University.
This article was originally published in Coping® with Cancer magazine, May/June 2009.