Doctors have described how a teenage boy has “survived against the odds” after suffering a rare clot on the brain.

Warrick Allon, 15, was rushed into emergency surgery at Southampton Children’s Hospital (SCH) after he collapsed and became unresponsive after complaining of a headache at his home in Andover, Hampshire, in April.

Scans showed he had an arteriovenous malformation (AVM) – an abnormal tangle of blood vessels – that had ruptured causing a large blood clot to form and bleed on his brain.

Neurosurgeon Aabir Chakraborty led the team in the operation to reduce the pressure build-up, which included draining fluid that was surrounding the brain and removing the blood clot and some of the abnormal vessels that had caused the haemorrhage.

The operation also involved removing part of Warrick’s skull, which was stitched into his back during surgery to allow for the swelling around the brain to reduce and to preserve the bone.

He survived the six-hour surgery but was left unable to talk, walk or eat after developing a syndrome common with invasive surgery close to the brain.

But now, after working with a specialist neurological rehabilitation team at SCH, Warrick is able to walk and communicate again and has returned to school part-time.

It all happened so quickly but I remember telling Mr Chakraborty that my boy wasn’t going to die. It wasn’t denial, it was determination – he wasn’t going to die that day

Mr Chakraborty said: “I could see that this was an unusually large blood clot that had caused considerable pressure around Warrick’s brain stem, the lower part of the brain that is connected to the spinal cord.

“I was very concerned that he was at high risk of imminent brain death, and so it was imperative we got him into surgery as quick as possible.”

Warrick’s mother Krissie said: “I will remember that moment forever. We asked what Warrick’s chances of survival were and were told it was 50/50.

“It all happened so quickly but I remember telling Mr Chakraborty that my boy wasn’t going to die. It wasn’t denial, it was determination – he wasn’t going to die that day.”

Mr Chakraborty added “I am so happy to see how far Warrick has come – he really has survived against the odds. He and his family are some of the most remarkable people I have ever met. I look forward to seeing his positive progress.”

Warrick’s father, Dave Allon, who lives in Andover with his wife Lisa, said: “We can’t thank Mr Chakraborty and the amazing team at Southampton Children’s Hospital enough.

“What they have done is nothing short of miraculous, they didn’t just save his life, they have returned him home to us and we will be forever grateful for that.”

Warrick will now continue his outpatient rehabilitation programme and aims to work towards taking his GCSE exams and attending college in 2023.