Ten years after radiation treatment for head and neck cancer, some patients may develop problems speaking and swallowing, a new study finds.

These problems are related to radiation damage to the cranial nerves, the researchers explained. The condition is called radiation-induced cranial neuropathy.

"We had always thought that radiation did not damage cranial nerves because they get treated in every patient with head and neck cancer, and we do not see cranial neuropathy that commonly," said Dr. Thomas Galloway, from the department of radiation oncology at the Fox Chase Cancer Center in Philadelphia.

"What our data is suggesting is that a small percentage of people do get cranial nerve damage from treatment, but it occurs after a long latency period," Galloway said.

For the study, the researchers collected data on 1,100 patients who had radiation for head and neck cancer between 1990 and 2005. Among these patients, 112 were followed for at least 10 years.

Of the 112 patients, 14% developed at least one cranial neuropathy. The median time until the condition was seen was more than seven years. It took some patients more than 10 years to develop the problem, the findings showed.

Curing the initial cancer is the most important concern, Galloway said. But these patients need to be followed for the rest of their lives, if possible, he added.

The report was published recently in the journal Oral Oncology.