Understanding CTE: A Conversation With Tau Pioneer Dr. Khalid Iqbal

The New York City Medical Examiner has confirmed that Shane Tamura, the 27-year-old gunman who killed four people in a Midtown Manhattan office building in July before turning the gun on himself, had chronic traumatic encephalopathy, a neurodegenerative disease linked to repeated brain trauma.

The disease, which can only be diagnosed posthumously, was found at a low stage in Tamura’s brain tissue.

Tamura, a former high school football player, left a suicide note blaming the National Football League for concealing the dangers of CTE. He asked that his brain be studied, echoing other athletes who died by suicide and sought to contribute to science.

The tragedy revived long-standing questions about the dangers of repeated head injuries, even among young athletes who never played professionally.

On the floor of the 2025 Alzheimer’s Association International Conference on Alzheimer’s research, Being Patient’s Deborah Kan spoke with Dr. Khalid Iqbal, a neurodegeneration researcher widely known as the “father of tau.”  Iqbal discovered tau, the protein that tangles inside brain cells and drives neurodegeneration in Alzheimer’s disease, CTE, and other neurodegenerative disorders.

Iqbal is professor and chairman of neurochemistry at the New York State Institute for Basic Research in Developmental Disabilities, where he directs the Chemical Neuropathology Laboratory. He also serves as Chief Scientific Officer of Phanes Biotech, a company developing tau-targeted therapies.

What is CTE?

“CTE is a chronic result of traumatic brain injury,” Iqbal said. While most people experience minor head bumps in life without long-term consequences, severe injuries, particularly those that involve bleeding in the brain or prolonged loss of consciousness, can trigger progressive degeneration. Over time, he explained this cascade becomes CTE.

Did the NYC shooter have CTE?

A definitive diagnosis of CTE can only be made after death, by examining brain tissue under a microscope. While the shooter claimed he had CTE and his symptoms may have aligned with the disease, at the time, there was no confirmed public evidence that he was officially diagnosed. Later, the New York City medical examiner confirmed that yes, Tamura did have low-stage chronic traumatic encephalopathy.

The diagnosis was made posthumously by examining his brain tissue in an autopsy.

Tamura had written in his suicide note that football “gave me CTE” and asked that his brain be studied. The autopsy findings validate his claim, though experts caution that while CTE is associated with mood swings, impulsivity, and aggression, the disease alone cannot fully explain violent acts.

As researchers from the Concussion Legacy Foundation told The New York Times, the presence of CTE “should not be seen as the cause of the tragedy.”

Tau’s role in CTE

In diseases like Alzheimer’s and CTE, abnormal tau is closely linked with brain cell damage and decline. Scientists believe tau plays a driving role in that process. But the story is complicated: Sometimes tau builds up before neurons actually die, and not every case of tau pathology leads to the same level of damage.

In Alzheimer’s disease, Iqbal explained, tau tangles typically begin in the hippocampus, the brain’s memory center. But in CTE, tau starts in the cerebral cortex, the region that governs reasoning, decision-making, and behavior.  This difference in “topography,” as Iqbal puts it, helps explain why CTE so often manifests with agitation, poor impulse control, and an elevated risk of suicide.

“When tau pathology strikes the prefrontal and temporal cortices, you don’t just see memory loss—you see behavioral changes,” Iqbal said. This pattern is common among athletes in contact sports like football or rugby, as well as others who’ve endured repeated brain trauma.

Preventing CTE

Can a single concussion cause CTE? “It’s variable,” said Iqbal. Mild concussions without bleeding usually heal. Severe injuries, however, are “bad news” — the risk of CTE is high.

Protective gear can reduce risk, but there’s currently no proven therapy to stop tau from clumping and killing brain cells. Several pharmaceutical companies are testing tau-targeting drugs, but results remain preliminary.

“Would you let your kids play football or rugby,” Kan asked Iqbal. “I would not prevent people from playing football or rugby,” he answered, “but I would say you have to use all the protective gear. Do not take chances without it.” Even still, as the world has seen in sky-high rates of CTE across players from the NFL, protective gear is often not protective enough.