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In early 2012, a neuropathologist named Daniel Perl was examining a slide of human brain tissue when he saw something odd and unfamiliar in the wormlike squiggles and folds. It looked like brown dust; a distinctive pattern of tiny scars. Perl was intrigued. At 69, he had examined 20,000 brains over a four-decade career, focusing mostly on Alzheimer’s and other degenerative disorders. He had peered through his microscope at countless malformed proteins and twisted axons. He knew as much about the biology of brain disease as just about anyone on earth. But he had never seen anything like this. The brain under Perl’s microscope belonged to an American soldier who had been five feet away when a suicide bomber detonated his belt of explosives in 2009. (Worth, 6/10)

They are among war’s invisible wounds: the emotional and cognitive problems that many troops experience years after combat explosions sent huge shock waves through their brains. Whereas the link between concussions and post-traumatic stress disorder has become clearer in recent years, a specific connection between PTSD and blast waves has remained elusive. Now, a prominent neuropathologist who researches brain injuries among military personnel says his team has identified evidence of tissue damage caused by blasts alone, not by concussions or other injuries. The team’s study was published on Thursday in The Lancet Neurology. (Schwarz, 6/9)