Doctors operated on Rosemary Alvarez after she experiencing numbness in her arm and blurred vision.
She went to the emergency room twice and had an x-ray, but everything appeared normal.
It was only when doctors took a closer look at an MRI that they discovered something very disturbing.
Neurosurgeon Dr Peter Nakaji told MyFOXPhoenix.com: "Once we saw the MRI we realised this is something not good. It's something down in her brain stem which is as deep in the brain as you can be."
Alvarez was taken into the operating room where Dr Nakaji and his colleagues were expecting to remove a tumor, but they uncovered a worm instead.
On a video of the surgery, Dr Nakaji can be heard chuckling after he discovered the worm.
"I'm sure this is a very strange response for the people in the operating room," he said. "But because I was so pleased to know that it wasn't going to be something terrible."
Doctors removed the worm and believe Alvarez will not have any lingering health problems.
It is not known where she picked up the worm, but doctors said worms can come from eating undercooked pork or spread by people who don’t wash their hands after using the bathroom.
"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," Dr Nakaji added.
Alvarez, who is now healthy, said she hopes people learn lessons from her story.
"Wash your hands, wash your hands," she noted.
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