Doctors in Arizona thought a Phoenix-area woman had a possible brain tumor, but it turned out there was something else penetrating her brain – a worm.

Rosemary Alvarez started experiencing numbness in her arm and blurred vision. She went to the emergency room twice and had a cat scan, but everything came up clear, MyFOXPhoenix.com reported.

Click here for a video.

It wasn’t until doctors took a closer look at an MRI that they discovered something very disturbing.

“Once we saw the MRI we realized this is something not good,” neurosurgeon, Dr. Peter Nakaji told the news station. “It's something down in her brain stem which is as deep in the brain as you can be.”

Alvarez was wheeled into surgery where Nakaji and his colleagues were expecting to remove a tumor, but they uncovered a worm instead.

On a video of the surgery, Nakaji can be heard chuckling after he made the discovery.

“I'm sure this is a very strange response for the people in the operating room,” he told MyFOXPhoenix.com. “But because I was so pleased to know that it wasn't going to be something terrible.”

Doctors removed the worm and don't believe Alvarez will have any lingering health problems. No one knows exactly where she picked up the worm –- doctors said worms can come from eating undercooked pork or spread by people who don’t wash their hands after using the bathroom, according to the report.

“It only takes one person who is spreading it constantly to get a lot of people exposed and some of those people are going to go on to develop this problem,” Nakaji said.

Alvarez, who is now healthy and has resumed normal activities such a playing ball with family in her backyard, said she hopes people learn this lesson from her story.

“Wash your hands, wash your hands,” she added.

Click here to read more and see the video of the surgery from my MyFOXPhoenix.com.