The death of Archie Battersbee, who was at the centre of a legal battle between his parents and doctors, was a "tragedy", a coroner said.
The inquest into the death of the 12-year-old from Southend-on-Sea, Essex, was opened on Friday at Essex Coroners Court.
It heard he died of a brain injury secondary to strangulation.
Lincoln Brookes, senior coroner for Essex, adjourned the inquest until 7 February 2023.
The hearing was told Archie was found unresponsive on 7 April.
Paramedics who attended found him in cardiac arrest and tried to resuscitate him.
He was taken to Southend University Hospital before he was transferred to Royal London Hospital where he died on 6 August after his life support was withdrawn.
The inquest heard the cause of death was catastrophic hypoxic ischemic brain injury secondary to strangulation.
Mr Brookes said Archies death was a "tragedy" and expressed his condolences to his loved ones.
Archies parents had battled through the courts to continue his life-sustaining treatment but judges ruled continuing was "futile".
His family then wanted Archie to be moved to a hospice but the High Court, on hearing medical evidence, ruled he was too unstable to be transported by ambulance.
Archie died at 12:15 BST surrounded by friends and family.
His mum Hollie Dance said he was "such a beautiful little boy and he fought right until the very end and Im so proud to be his mum".