They kill more people than cancer, and New Zealand has the highest rates per capita in the world.
Yet brain injuries are still a "silent epidemic", says Whangarei-based Brain Injury Association Northland (BIAN) chairman Iain Watkins.
"More people die from brain injuries than die of cancer, but it's not something you outwardly see," he said.
June marks the Worldwide Head Injury Awareness Month and Mr Watkins hopes to both raise awareness and fundraise for the service, which receives its funding mostly from ever-diminishing grants.
"People just do not have awareness of [brain injuries] and it's not an area people donate," he said.
An AUT study late last year found the number of New Zealanders with traumatic brain injuries has reached epidemic levels, with a new injury occurring on average every 15 minutes.
The research, published in November in international medical journal The Lancet, and led by Professor Feigin from AUT's National Institute for Stroke and Applied Neuroscience, found most were due to falls (38 per cent), followed by mechanical forces, transport accidents, and assaults.
But Mr Watkins said they were also dealing with people who had brain injuries as a result of strokes.
"We get anyone who's had any sort of brain trauma."
Symptoms of brain injury include extreme fatigue, cognitive difficulties, memory problems, sensory disabilities and personality changes, yet still some health professionals are skeptical of the effects of brain trauma, he said. "If it hasn't affected you then it's very hard to know what it's like. But just have a think about what is under your hat."
BIAN liaison officer Vikki Herdman helps brain injury sufferers with day-to-day tasks, and often helps them deal with government bodies such as ACC, WINZ, and Corrections, and with health professionals such as doctors - tasks that brain injury sufferers can find daunting.
"New Zealand has the highest brain injury rate per capita - and it's a lifetime for a lot of people - it's not going to go away."
There are supposed to be two liaison officers to carry out the work she does, but funding cuts means she is the only person within the organisation in her role helping brain injury sufferers from Wellsford through to the Far North.
A client, who wishes to remain anonymous, sustained a brain injury after having a stroke five years ago. Prior to the stroke, she was a regional manager in charge of over 30 people, but now she can't work due to symptoms of her brain injury, such as extreme fatigue, forgetfulness and generally not coping - a marked change compared with before the stroke.
"Because it's such a hidden illness you learn people look at you and think you're a hypochondriac because they can't see a physical disability."
BIAN help her cope.
"They are a huge support in dealing with things and in advocacy. I wouldn't like to think where I'd be without these guys."
To contact BIAN, phone 459 5013. For donations, the account number is 12-3093-0207556-00.