Aaron Hernandez “had a horrendous existence” as a result of chronic traumatic encephalopathy (CTE), a degenerative brain disease resulting from repeated head trauma, the former football player's lawyers claimed in the refiling of a lawsuit against National Football League (NFL) and its former helmet manufacturer.

Hernandez’s estate has claimed that the former New England Patriot sustained multiple blows to the head while wearing Riddell helmets because of which he suffered from Stage 3 CTE — a rarity in football players his age, People magazine reported Wednesday.

“Aaron experienced a chaotic and horrendous existence in many respects, due to his undiagnosed brain injury,” the estate alleges in its complaint. In another part of the lawsuit, the estate says that CTE causes “aggression, explosive behavior, loss of concentration, mood swings, depression, apathy, and cognitive impairment.”

According to a statement from Boston University’s CTE Center, Hernandez “had early brain atrophy and large perforations in the septum pellucidum, a central membrane.” This means that the Hernandez's brain had started to shrink and two holes where formed the membrane that divides the two cerebral hemispheres. His family lawyer said last month that the advanced stage 3 of CTE is normally found in the median age of a 67-year-old man.

Hernandez, who was serving a life sentence for killing semi-pro football player Odin Lloyd, was found hanging in his prison cell at the Souza-Baranowski Correctional Center in Shirley, Massachusetts, in April. The 27-year-old took his life just a week after he was acquitted of the double homicide of Daniel de Abreu and Safiro Furtado outside a Boston nightclub in July 2012.

His lawyer, Jose Baez and his fiancée, Shayanna Jenkins-Hernandez filed the lawsuit last month against NFL and the Riddell on behalf of the couple’s 4-year-old daughter, Avielle Janelle Hernandez.

“Aaron had Stage III CTE usually seen in players with a median age of death of 67 years,” the initial lawsuit stated. “Aaron played football in the National Football League for the New England Patriots for three seasons starting in 2010. By the time Aaron entered the NFL, in 2010, [the Patriots and 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.”

The lawsuit seeks $20 million for “redress for the loss of parental consortium she has experienced based on the negligent conduct of [Hernandez’s daughter] that deprived her of the companionship and society of her father.”

Late last month, the NFL vowed to “vigorously” fight the lawsuit against the league and the New England Patriots filed by Hernandez’s family.

“We intend to contest the claim vigorously,” NFL spokesman Joe Lockhart told reporters on a conference call at the time. “Any attempt here to paint Aaron Hernandez as a victim, we believe is misguided. His personal story is complex and doesn’t lend itself to simple answers.”

A spokesman for Riddell said the company will fight the lawsuit, stating that it started efforts to “enhance concussion mitigation [in helmets] and awareness” more than 15 years ago, the New York Post reported.