Erica Ortegas has been at the center of one of this season's ongoing storylines, and, frankly, it's been pretty rough on her. It's less that more horrible things have happened to Erica than other members of the Enterprise crew, and more that Erica has been batted around pretty badly by memories of one particular awful experience: her encounter with the Gorn.
A concussion is a form of traumatic brain injury that can occur when a blow to the head or force that shakes your body is strong enough to cause your brain to hit the side of your skull. Myriad symptoms can occur, including headaches, decreases in cognitive function such as confusion or amnesia, sleep difficulties such as prolonged feelings of drowsiness, and emotional dysregulation such as irritability and mood swings.