Girl, 18, battling brain damage after crashing into a cliff during pre-prom ...

An 18-year-old girl was left paralyzed, comatose and needing a breathing tube after hitting her head against a cliff and falling 25 feet in a pre-prom abseiling event. 

Avery Tanner, from Utah, started the day on April 20 by abseiling with her friends, before they were due to have a lunch, an evening dance, and celebratory dinner for finishing school. 

But while abseiling, Avery pinched her hand in the carabiner clips and let go of the rope suspending her, sending her crashing into rock, and free-falling to the ground. 

One of the boys in her group who had already abseiled to the bottom caught Avery in his arms - in a move that likely saved her life. 

But severe damage had already been done by hitting her head. 

Avery Tanner, 18, was excited about her prom when she had an abseiling accident that almost killed her

Avery Tanner, 18, was excited about her prom when she had an abseiling accident that almost killed her

While abseiling, Avery pinched her hand in the carabiner clips and let go of the rope suspending her, sending her crashing into rock, and free-falling to the ground. Pictured: Avery surrounded by machines to keep her alive

While abseiling, Avery pinched her hand in the carabiner clips and let go of the rope suspending her, sending her crashing into rock, and free-falling to the ground. Pictured: Avery surrounded by machines to keep her alive

Avery and her dad at another dance before her prom celebrations

Avery and her dad at another dance before her prom celebrations

Surgeons didn't expect Avery to make a recovery. She had a 90 percent chance of being in a permanent vegetative state

Surgeons didn't expect Avery to make a recovery. She had a 90 percent chance of being in a permanent vegetative state

Avery coded and died momentarily in the helicopter, before being resuscitated. 

Once at the hospital, doctors stabilized Avery and carried out CT scans of her head and spine before placing a monitor in her skull to measure intercranial pressure. 

An MRI revealed that she had suffered a diffuse axonal injury, meaning the wires to the brain were torn from their connections.

Her doctors said 90 percent of patients who suffer this kind of injury never wake up from their coma.

The other 10 percent are left in a permanent vegetative state.

Her father Jesse, 39, recalls the first time he and her mom Caysie, 38, saw Avery after arriving at the hospital as the most painful sight. 

She looked as if she was dead.

'As a physician myself, I've seen this before, but nothing prepares you for seeing your daughter in this position. She looked dead. I've seen dead people, but nothing was more awful than this,' Jesse said. 

'Caysie and I were placed in a small waiting room for what felt like an eternity until they came and told us they were placing a monitor in her skull.

'Avery was taken up to the trauma ICU as the neurosurgeon drilled a small hole in her skull and dropped in a fiber-optic sensor to monitor the intracranial pressure in her skull. 

'We were eventually allowed to go and spend time with Avery who was connected to life support with, what felt like, a million machines surrounding her.'

Even though Avery (pictured before her accident) was nervous about abseiling, she told a younger girl in her group, who was terrified, that she would go first to show her that there was nothing to worry about

Even though Avery (pictured before her

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