March 6, 2013 -- Actress Valerie Harper, best known for her role as Rhoda Morgenstern on The Mary Tyler Moore Show and Rhoda in the 1970s, has learned she has leptomeningeal carcinomatosis.

The condition happens when cancer spreads to the brain and spinal cord.

Now 73, Harper told People magazine she received the diagnosis in January.

The American Cancer Society has no specific statistics on this complication. Some research estimates it happens in about 5% to 10% of patients with cancer.

WebMD asked Henry S. Friedman, MD, deputy director of The Preston Robert Tisch Brain Tumor Center at Duke University, for more details. He does not treat Harper.

Q: What is leptomeningeal carcinomatosis?

It is also called neoplastic meningitis. They mean the same thing. There are tumor cells that are in the spinal fluid.

They come from either a primary brain tumor or an extraneural [outside the brain] cancer.

The extraneural cancer in this case might have been the lung cancer [reportedly diagnosed in Harper in 2009].

Q: How do the cancer cells spread?

They enter the spinal fluid, usually through the blood vessels in the brain.

Once in the spinal fluid, the cells have a great roadway up and down the brain and the spine.

Q: Is there a typical age for getting this?

You can get neoplastic meningitis as a little child all the way up to adulthood.

Q: What are the symptoms?

There are many symptoms.

There can be vision problems, movement problems, problems in movement of your face, and speech and swallowing problems.

Q: Harper is reportedly getting chemotherapy. Is that standard?

Yes. Chemo can be given to the spinal fluid directly, but not always.

Radiotherapy can be used.

There are newer things, like monoclonal antibody [a lab-produced molecule that attacks cancer cells]. It's too early to say about the long-term results for monoclonal antibody therapy.

I'm not aware of any alternative therapy that has produced a meaningful benefit in treatment.

Q: What are the causes or risk factors?

There is no specific cause other than having either a primary or extraneural tumor [such as breast cancer, melanoma, and others] that has a propensity to spread to the spinal fluid.

Q: What is the outlook?

In general, patients do not do well. While the spread of cancer into the spinal fluid is considered lethal, there are always surprises that have better outcomes.

It's not an optimistic diagnosis. But I hate to use the word terminal because there are always patients who surprise you.