On Feb. 28, 2016, applicant Anthony Dene, 38, a cashier’s assistant with a seizure disorder, returned to work at a Costco store, in Woodland Hills, after recovering from a previous work injury. While in the course and scope of his employment, Dene was loading a metal staircase onto a flatbed truck. However, as he was lifting the staircase, a piece of steel fell and struck him on the head, alleging him. Dene filed a workers’ compensation claim against his employer, Costco Wholesale Corp., whose claims administrator was Helmsman Management Services LLC. He brought a claim against Costco in an attempt to collect workers’ compensation benefits., Dene did not lose consciousness after the incident, but his coworkers sent him to the Kaiser Permanente Woodland Hills Medical Center, in Woodland Hills, where Dene underwent a CT scan of his head. The CT scan showed a known, pre-existing cavernous angioma (or cavernoma) — an intracranial developmental malformation of the vascular bed that frequently enlarges over time — in the right temporal lobe. Dene claimed the blunt force trauma to his head resulted in a concussion, post-concussion syndrome, an aggravation of his pre-existing epilepsy, and issues with executive function in the frontal lobe. Dene treated with a neuropsychologist, who diagnosed him with post-concussion syndrome, and underwent extensive neurorehabilitation. He also claimed that he undergoes home health care and that he requires a structured day as part of his treatment. Dene was already on a dosage of Keppra, an anticonvulsant, but he claimed that he had to have this dosage increased after the subject incident. Dene, who worked for Costco since 1996, claimed that he has not been able to return to work because of his disability. He claimed that although he is conscious and has improved, his treatment aims to make sure he does not introvert. The respondent’s counsel contended that all of Dene’s symptoms were due to his pre-existing epilepsy, and not caused by the subject incident.