Aaron Hernandez
Aaron Hernandez looks at the gallery during his murder trial in Fall River, Massachusetts. The former New England Patriots football star hanged himself in the jail cell where he was serving a life sentence for murder REUTERS/Dominick Reuter

Former New England Patriots tight end Aaron Hernandez, who committed suicide in April 2017 while serving a life sentence for murder, was found to have a severe form of the degenerative brain disease CTE.

Researchers who examined Hernandez's brain found it was "the most severe case they had ever seen in someone Aaron's age," one of his lawyers said on Thursday (21 September). Hernandez was 27.

CTE, or chronic traumatic encephalopathy, is linked to repeated head trauma and has been found in more than 100 former NFL players, The New York Times reported. Hernandez joins a long list of former NFL players who have committed suicide and later been found to have CTE.

Those include Dave Duerson, Junior Seau, Andre Waters, Ray Easterling and Jovan Belcher.

Duerson and Sean both shot themselves in the chest after which researchers examined their brain, the Times reported. Hernandez hanged himself in his Massachusetts prison cell.

While Duerson, Seau and Waters were all over the age of 40, Hernandez is one of the youngest former NFL players to have been diagnosed with the disease. Researchers at Boston University released their findings in July that revealed CTE had been found in the brains of 110 of the 111 former NFL players they had examined.

Hernandez's lawyer, Jose Baez, said his client's brain showed a level of damage only seen in players with a median age of 67 years, the Times reported. Hernandez's brain was examined by Dr Ann McKee, the director of the CTE Center at Boston University who developed stages to describe the severity of the disease.

Individuals with stage three of CTE are reported having cognitive impairment and trouble with executive functions, such as planning and organising. Those with the most severe version, stage four, have dementia, difficulty finding words and aggression.

Hernandez was found to have Stage three and had "early brain atrophy," McKee said in a statement.

Baez said he has filed a federal lawsuit against the Patriots and the NFL on behalf of Hernandez's young daughter.

The lawsuit seeks unspecified damages for loss of parental support. It also claims the Patriots and the NFL were "fully aware of the damage that could be inflicted from repetitive impact injuries and failed to disclose, treat or protect him from the dangers of such damage".

According to the Times, Baez did not rule out including the NCAA or the University of Florida, where Hernandez played as a college student, in the suit. He said that in retrospect, the family had witnessed Hernandez act in a manner consistent with a person having CTE "but you don't know".

The NFL told the Times it had not seen the lawsuit and could not comment.