There’s a glimmer of hope now for soldiers who worry that they may be suffering long-term effects of battlefield concussions.

Previously, the only way to know if concussions were progressing into degenerative brain diseases like Alzheimer’s or Parkinson’s was to autopsy the brain of a dead soldier or athlete. So that wasn’t much good for the living victim.

But researchers at UCLA used PET (positron emission tomography) scans on five retired NFL players, all 45 years or older and suffering from mood swings, depression, or difficulty in thinking and remembering – all potentially early signs of CTE (chronic traumatic encephalopathy).

All of the players’ scans showed signs of tau protein deposits, which is consistent with the autopsied brains of other pro football players and combat vets suffering from CTE.

Tau is a protein that occurs naturally in brain cells, but it’s the bunches or tangles that are abnormal. Normally tau links together to bring nutrition to brain cells, and that long supply line also helps hold up cell walls. When tau proteins clump up, the supply of nutrition is interrupted, and the cell walls may collapse, letting in external salts and/or calcium.

So researchers may be able to use brain scans to tell living athletes and combat vets whether they are beginning to develop CTE.

There are a couple of caveats, however, which is why I said a “glimmer of hope.”

First, five players is a sample size so small that it’s easily subject to error; we need a much larger sample, and then we need to be able to replicate it. Second, we don’t know yet whether the players actually are suffering from CTE so the tangled tau proteins can’t prove anything yet. And third, if this is an early indicator of degenerative brain diseases, we still don’t know how it progressives or how we can stop that progression.

However, several studies at Boston University and the Boston VA Heathcare System have demonstrated that brain injuries, and particularly repeated brain injuries, can progress into CTE. So all we can do is watch – and hope – as researchers attempt to understand how a brain injury progresses into the massive death of brain cells.

As I said, it’s a glimmer of hope. But it’s still more than we had before.