How a mum’s fight for answers led to a devastating diagnosis

Theo Arrowsmith was two years old when his mum first noticed something was wrong.
Daisy Hamilton, an early childhood teacher of 12 years, said her toddler had always met his developmental milestones. He had crawled early, fed himself at 12 months, walked by one and was toilet trained by 18 months.
“He was two when we started seeing behaviours that were unusual for him,” Hamilton said.
At first, Hamilton, of Queensland’s Gold Coast, thought maybe it was because she had just welcomed a second child, daughter Lily.
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When the behaviour, including aggression, worsened, Theo was assessed for autism, which was ruled out. In fact, tests showed he was well ahead in his development, measuring as a four-year-old in most areas.
But over the next few months, Hamilton grew more alarmed.
“We really noticed the changes that were happening to him,” she said, adding Theo soon started suffering ‘absence seizures,’ which are a symptom of epilepsy.
When Theo was again assessed for autism just six months later, his mobility, social, cognitive skills and speech had dropped significantly.
Alarmed, Hamilton’s GP sent Theo to a neurologist who conducted an EEG and MRI to rule out a brain tumour.
Hamilton was told the MRI was clear. Based on the EEG results, Theo was diagnosed with epilepsy and put on medication.
But his condition continued to worsen. “He would not walk two steps without falling over,” she said.
“He stopped eating because he couldn’t hold a fork or spoon. When he talked, he would say the wrong words or miss out words.”
On at least two occasions, falls resulted in a gashed head and a trip to hospital, where Hamilton would share her concerns with doctors.
She also began phoning the neurologist “every week,” only to be told the same thing. ”They told me it was a side effect of the epilepsy medication,” she said.
Then during another trip to hospital after a fall, Hamilton showed a doctor videos she had taken of Theo at home.
“It took me saying, ‘We are not going to leave until you do something about it,’ before a doctor finally listened and agreed medication should not make him go backwards and regress like this,” she said.
“The next day we were asked to go to Queensland Children’s Hospital [in Brisbane] for an overnight EEG.”
While they were at the hospital, another neurologist, who was also a metabolic specialist, reviewed the previous MRI.
“He noticed it was showing some atrophy in his brain,” Hamilton said.
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She said the doctor had been involved in a similar case involving another Queensland boy and later told her he recognised the symptoms straight away.
But it would take two genetic tests before they finally got an answer in April 2022. Theo had Batten disease, a form of childhood dementia.
Hamilton said she knew it was bad news when she entered the room to find four or five people waiting and another doctor on a video call.
“It’s a very weird feeling because you are relieved to finally have an answer, but at the same time it was devastating.”
Batten disease is a rare and fatal disorder of the nervous system that begins in childhood. It is part of a group of neuronal ceroid lipofuscinoses (or NCLs) disorders, according to Australia’s Brain Foundation.
A number of genetic problems cause the condition. Theo is one of just three children in Queensland living with the CLN2 variant of Batten disease.
Both Theo’s parents unknowingly carried the gene. Tests later showed their daughter Lily, now three, did not inherit the condition but she is a carrier.
“They said immediately there is no cure,” Hamilton recalled. “However, we are lucky that for this particular type there is one treatment.
“But it will not cure it and it will not halt the progression. It only works on two areas, mobility and speech.”
Hamilton said there was “a big difference” in Theo straight after starting treatment, including some that were not expected.
“We noticed a difference in his emotional state and behaviour. He is no longer aggressive unless he is really frustrated. He is more social,” she said.
Sadly, Theo became non-verbal prior to starting treatment and his speech has not returned.
Two years on, Theo, now six, is doing better than doctors predicted.
“We were told he would most likely be bed-ridden at five or six. We were told he would lose his sight by five or six,” Hamilton said.
“He is still able to see, [and] is still able to move around.
“I do think that part of it is that he is very determined. He is very, very, very stubborn.”
Theo is assessed each year and if his condition worsens past a certain point the medication will probably be withdrawn.
Hamilton holds out some hope that new research may provide a cure one day. Trials of gene therapy treatment are now taking place on animals.
While childhood dementia is rare, 91 children die from the condition in Australia each year — about the same number of cancer deaths in children aged 0 to 14, according to the State of Childhood Dementia in Australia 2024 report.
The report, released this month, found delayed diagnoses such as Theo’s were common, while many families struggled to get necessary healthcare and support.
Less than 2 per cent of childhood dementia sufferers in Australia can access a clinical trial. 
Childhood Dementia Initiative chief executive Megan Maack wants a coordinated national approach to improve quality of life for sufferers.
“We are facing a situation where children are dying without receiving the necessary healthcare and support,” she said.
She said one baby is born with a childhood dementia disorder “every few days” yet there had been “no improvement in survival rates.”
The prognosis for children with childhood dementia is dire. Half die before the age of 10, while 70 per cent [die] before reaching adulthood.
As the disease progresses, children lose the ability to speak, walk, hear and see, and often suffer from debilitating seizures.
Neuroscientist Professor Peter Schofield said childhood dementia was a “uniquely cruel” disease, with progression marked by chronic pain and distress.
“In my practice, I see firsthand how childhood dementia is different from other chronic childhood diseases,” he said.
“Survival rates for children with cancer have risen to 84 per cent. Childhood dementia in comparison sits at zero per cent survival.”
While Theo’s future is unclear, Hamilton said “we focus on positives and not negatives.”
“But it is still very difficult. We are grieving a child every day even though they are here.”
She wants to raise awareness after terrible experiences in the community, at childcare, school and among medical professionals.
As part of Theo’s condition, he feels and processes pain as soon as it it happens but not after that.
During a recent trip to hospital after another fall, Hamilton said the doctor, knowing about Theo’s history, gave him three stitches in his head without local anaesthetic as Theo screamed in pain, arguing he “would forget about it in five minutes.”
“It’s things like that [that upset me]. You go to medical professionals for help and you do not get the help you need,” she said.
“There is not enough information and support. Not a lot of people know what it is.”