"They thought I was stressed out and gave me a week off work, but I went back struggling to talk, read and function with some of the most basic tasks," she said.
Encephalitis, a brain inflammation, is widely misunderstood and it wasn't until she was given a lumbar puncture that she got the correct diagnosis.
Theberge, of One Tree Point, and her team of three other women are competing alongside two other teams in the Northland Spirited Women Race next month, to raise money for the Encephalitis Society.
She told friends they were "insane" when they first encouraged her to join their team and compete in the race two years ago.
They persisted, telling her 'we think you're great, you need to come'.
''That's how we got started on these races,'' she said.
This year, Theberge is competing in the medium course which will take six to 12 hours and includes 15-25km of mountain biking, a 10-15km trek, and up to 2km of paddling.
Completion time and distance depend on the route taken by the team and navigation is part of the challenge.
The UK based Encephalitis Society supports sufferers and their whānau from all over the world, promotes awareness and provides resources for medical professionals.
Symptoms vary widely between patients and can mimic better-known conditions such as strokes and meningitis, making it tough for GP's to pin down.
Theberge said her speech is affected but not her mobility, whereas others could be the opposite.
"An acquired brain injury is an invisible illness, affecting your functioning in lots of different ways. Your mental health is put through extreme challenges, but we [may] look fine on the outside," she said.
Theberge has become a board member of the Northland Brain Injury Association and writes a blog to help others going through similar challenges.
World Encephalitis day is today, February 22, and teams in the Northland Spirited Women Race will have maps and start times handed out to them in a briefing on Friday, March 12.
The exact location of the course, near Whangārei, will remain secret until then, so teams will have equal time to plan their navigation.
The races, of varying difficulty levels, will take place on March 12 and 13.
To support Theberge and her team, visit www.givealittle.co.nz/cause/weird-wonderful-brain-following-encephalitis
What is Encephalitis:
Encephalitis (en-sef-uh-LIE-tis) is inflammation of the brain. There are several causes, but the most common is a viral infection.
Encephalitis often causes only mild flu-like signs and symptoms — such as a fever or headache — or no symptoms at all. Sometimes the flu-like symptoms are more severe.
Encephalitis can also cause confused thinking, seizures, or problems with movement or with senses such as sight or hearing.
In some cases, encephalitis can be life-threatening. Timely diagnosis and treatment are important because it's difficult to predict how encephalitis will affect each individual.
