A teenager who temporarily regressed to a child-like state after an operation to 'switch off' half her brain in order to stop her having seizures or developing dementia has said her first word again - "mum".

Imogen Golder, 16, has suffered with seizures since she was four years old and was diagnosed with a rare neurological disease 18 months ago, writes John Bett, SWNS

She has rasmussen's encephalitis - which can cause dementia - and the decision was made to perform a hemispherectomy.

The operation disconnected the left hand side of Imogen's brain, temporarily returning her to a child-like state - having to learn to walk and talk again.

Imogen's mum, Karen, a special needs coordinator, says she has said the word mum for the first time again.

Karen, from Penzance, said: "The operation is quite rare in the UK.

"Your brain is in two halves, two hemispheres, and each side is plugged into your neurology and your vascular system.

"Imogen has damage on the left side of her brain, so they've disconnected all the connections from that side to everywhere else in her body - so functionally she has half a brain.

"We're still in hospital at the minute, it was only two weeks ago, the hope is that she will be seizure free but having said that she has already had two breakthrough seizures.

"Pre operation she had uncontrollable seizures. We'd put her on a ketogenic diet which is used to control epilepsy but that didn't work - nothing worked.

"Surgery was the only option. She also had a weakness in the right side of her body, and had a cognitive delay.

"This operation should stop the seizures, she'll still have the weakness - she'll have to learn to talk and walk again.

"It takes away the field of vision on the right hand side of both eyes, so she had just 50 per cent of her sight.

"But hopefully she'll be seizure free, or at least have far less seizures, she'll have more energy and be able to enjoy life. She was sleeping pretty much all the time."

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Imogen in hospital recovering from the operation. Picture: Golder family/ SWNS

Imogen is currently recovering in Birmingham Children's Hospital, after the operation on November 4, and has now said "mum" twice.

Kaken said that Imogen is showing promising signs, but it could still be years before life returns to some degree of normality.

She continued: "We're in Birmingham Hospital Childrens at the minute and she will be transferred to Bristol Children's unit when she is able to - it's led by her needs and abilities.

"There are little bits of progress every day, she's learning new words every day. This time last week she was like a baby and couldn't hold her head up.

"It's like retrieving things, rather than relearning, the first thing she said was mum - then I think it was 'dog'. Mum was the first thing she said as a baby too.

"She's also said little instinctual phrases that are stuck in her brain, so 'wait a minute' came out.

"We're having speech and language therapy and we queue her up so say things like 'when we're tired we have to lie...' and she thinks of the next word.

"It's like when you have a word on the tip of your tongue but you can't retrieve it."

Imogen started showing symptoms of her disease when she was just four years old, but wasn't officially diagnosed until 18 months ago.

This is because a series of criteria need to be met, and rigorous checks performed, before a patient can be recognised as having rasmussen's encephalitis.

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Imogen before the operation. Picture: Golder family/ SWNS

Karen continued: "She first had symptoms when she was four years old, so 12 years ago. She lost use of one of her arms and then started having seizures.

"They finally diagnosed a year and a half ago.

"For someone to be diagnosed with rasmussens, they have to have a weakness on one side, a cognitive delay, and the seizures have to be coming from just one hemisphere of the brain.

"You have MRI and EEGs, after an EEG they do what's called a surgical EEG where electrodes are put through the skull into the brain so they can pinpoint where the seizures is coming from within the brain.

"Then they took a biopsy of her brain and it was confirmed that she had R - that's when the decision was made to act.

"With rasmussen's it pretty much always ends up with this procedure, if she was diagnosed sooner maybe her rehab may have been easier, but it wouldn't have made much difference.

"It will be at least two years before life goes back to normal, until she's self sufficient again."

Karen, who is also a part-time Baptist minister alongside her husband, Murray, 50, has shared Imogen's story to help raise awareness for the condition.

Rasmussen's encephalitis is a rare inflammatory neurological disease that generally occurs in children under the age of 15.

Sufferer's experience frequent and severe seizures, loss of motor skills and speech, weakness on one side of the body, inflammation of the brain, and dementia.

Imogen, who goes to a special needs school, lives in her family home with her brother, 18-year-old Jed.

The family are currently accepting donations to help pay for Imogen's rehabilitation, and anyone looking to donate should visit https://www.gofundme.com/f/25yrh7oqeo