Doctors typically see a spike in head injuries and concussions during the winter season due to sports like skiing and snowboarding and falls from some of the hottest holiday sellers like hoverboards, bicycles and skateboards.

"I woke up in an ambulance," said Kristie Holt, who doesn't remember much from the pivotal night of her bicycle accident. "My friend turned right, I turned left," she recalled. "And then it came to me - I got into a bike accident so they're taking me to the hospital."

Holt blacked out before hitting the right side of her face.

"It impacted the right side of my brain," she said. "I hit my head so hard that my eyes weren't connecting to my brain."

She had a concussion.

"What happens is the brain sloshes back and forth when there's a concussion," said Dr. Nimesh Patel, neurosurgeon with Methodist Brain & Spine Institute. "And remember, a concussion doesn't require the head to be hit. It can be the body blow as well."

This is the time of year doctors most often see head injuries and concussions.

A study in the American Journal of Sports Medicine found the number of head injuries doubled with the start of snowboarding season.

After the impact, Dr. Patel said signs to watch for include: nausea, headache, feeling imbalanced and blurry vision.

"I think about that day all the time and if I wouldn't have been wearing a helmet, I would've not been here," said Holt.

Sean Clancy with Local Hub Bicycle Company in Deep Ellum said all helmets have to be certified. It's important to check inside the helmet for two labels: CPSC (Consumer Product Safety Commission) and MIPS.

"The multi-directional impact protection system… is what MIPS stands for," explained Clancy, who said MIPS helmets offer an added layer of protection by reducing rotational forces on the brain if you fall at an angle.

They cost roughly $20 more than regular helmets.

"I slowly got back on the bike," said Holt, who spent three months in therapy following her accident to regain focus in her right eye. A faint scar on her right cheek is one of the few reminders she has left of that blurry night.

Dr. Patel adds that helmets don't prevent concussions, but they do help to protect the brain. There are different helmets for different sports, and they should fit snugly, covering the entire head.