The vast majority of domestic-violence victims who show signs of traumatic brain injury never receive a formal diagnosis. Temet / Getty

In the first version of her story, Grace Costa says that, on the night after Christmas, in 2012, her ex-boyfriend broke into her house, hid behind her bedroom door, and then attacked her as she and her two grown children—a son and a daughter—were about to eat dinner. In the second version, it’s still the night after Christmas, but it might be 2013, and only her daughter is at home with her. There’s a half-eaten apple on the floor of the kitchen; she remembers asking her daughter if she’d thrown it toward the garbage and missed. She also remembers thinking that she’d left the outside light on and then it was off.

Costa (whose name has been changed) describes the night in disjointed phrases. She cries and then stops. She spirals out from the story into another, and it takes some nudging to get her to return to the original. She knows she somehow got wrapped in a cord, and she comes back to this over and over. It was a phone cord, she thinks. “I don’t know where that cord came from,” she says. Then, later, “I don’t know where he got that cord.” Her hands were bound somehow, and then she fell to the ground. She was inside, and then she was outside. She remembers her ex-boyfriend punching her daughter in the face, blood spurting from her nose.

Local newspapers said the police arrived when she was on the ground. She was down, then up. Maybe down again. Thrown against the car, hard. Punched. Strangled. She was trying not to black out. There was blood, and that cord, and her daughter. The police weren’t there, and then they were. The night comes in flashes, an image at a time—apple, blood, cord—but the pieces never fit together into a whole. Instead, they hang untethered in her mind. “I don’t remember much of anything half the time,” she says.

Costa has a mild brain injury from that night, though she does not recall this exact diagnosis. She also has vertigo, hearing loss, poor memory, anxiety, headaches, ringing in her ears (which she describes as a constant “electrical signal”), and a hip that causes her to limp sometimes, which she believes came from being hurled against her car. In light of her other injuries, she hasn’t had her hip treated.

After the police arrived, Costa, her daughter, and her ex-boyfriend were all taken to the same emergency room. She remembers that the hospital was overwhelmingly busy, and that her attacker was still nearby. She had a sense of being in shock. She was released that same night, but for the next two weeks she had pain in her neck, her head, and her throat. She had difficulty breathing. She was covered in bruises, and her scalp ached. She saw her primary-care doctor in the days after the attack, had CT scans of her head and neck, and took a lethality-assessment screening at a local crisis center, where she was deemed high risk for domestic-violence homicide. Her ex-boyfriend was found guilty of attempted murder and is now in prison. But even with him gone, her life is a constant reminder of that night. She forgets to do things, and when and how things happened: when she lived where, when she moved, when she filed this or that paperwork. Concentration sometimes gives her headaches. She is able to work full time, in health care, but she spends most of her free time alone. Her ex-boyfriend will be out of jail in several years, and she lives in terror of that moment, caught inside her own disquieting anguish.

Fifty per cent of domestic-violence victims are strangled at some point in the course of their relationship—often repeatedly, over years—and the overwhelming majority of strangulation perpetrators are men. Those strangled to the point of losing consciousness are at the highest risk of dying in the first twenty-four to forty-eight hours after the incident, from strokes, blood clots, or aspiration (choking on their own vomit). Such incidents can cause brain injury—mild or traumatic—not only by cutting off oxygen to the brain but because they are often accompanied by blunt-force trauma to the head. Still, victims of domestic violence are not routinely screened for strangulation or brain injury in emergency rooms, and the victims themselves, who tend to have poor recollections of the incidents, are often not even aware that they’ve lost consciousness. This means that diagnoses are rarely formalized, the assaults and injuries are downplayed, and abusers are prosecuted under lesser charges.

Gael Strack, the chief executive officer of the Training Institute on Strangulation Prevention, is one of the domestic-violence community’s most prominent voices on strangulation and its attendant issues. In 1995, when she was the assistant district attorney in San Diego, two teen-age girls were killed “on her watch,” as she puts it. In the weeks before one of the girls’ death—she was stabbed in front of her girlfriends—she had been strangled. The police were summoned, but when they showed up she recanted and no charges were filed. The other girl was strangled and set on fire. Both girls had sought domestic-violence services and had developed safety plans. Strack believed that San Diego was at the forefront of aggressive domestic-violence intervention. They even had a dedicated domestic-violence council and court. “We had specializations everywhere,” Strack says.

Strack and Casey Gwinn, the co-founder of the Training Institute and her boss at the time, felt responsible for the girls’ deaths in some way. What had they missed? What would have kept the girls alive? Strack went back and studied the case files of three hundred non-fatal domestic-violence strangulation cases. Strangulation turned out to be a critical marker. Not only did it dramatically increase the chances of domestic-violence homicide, but only fifteen per cent of the victims in the study turned out to have injuries visible enough to photograph for police reports. As a result, the officers often downplayed the incidents, listing injuries like “redness, cuts, scratches, or abrasions to the neck.” And emergency rooms tended to discharge victims without CT scans and MRIs. What Strack and the domestic-violence community understand today is that most strangulation injuries are internal, and that the very act of strangulation turns out to be the penultimate abuse by a perpetrator before a homicide. “Statistically, we know now that once the hands are on the neck the very next step is homicide,” Sylvia Vella, a clinician and a detective in the domestic-violence unit at the San Diego Police Department, says. “They don’t go backwards.”

In many of those three hundred strangulation cases, Strack also saw that the victims had urinated or defecated—an act she chalked up to their fear. She spoke to an emergency-room physician named George McClane who offered her a very different view. Urination and defecation are physical functions, like sweating and digestion, that happen below our consciousness, and are controlled by the autonomic nervous system. Sacral nerves in the brain stem—the final part of the brain to expire—control the sphincter muscles. So urination and defecation weren’t a sign of fear, McClane showed Strack, but rather evidence that every one of those victims had been mere moments away from death. And each one of those cases had been prosecuted as a misdemeanor.