Can a blast (brain)injury cause hypersomnia? how can we figure out what's the issue when my fianc can't complete an mslt?

Yes: A study found that compared with the noninjured controls, participants with traumatic brain injury tbi reported significantly poorer sleep quality and higher levels of daytime sleepiness; sleep diaries revealed longer sleep onset latency, poorer sleep efficiency, longer sleep duration, and more frequent daytime napping in the tbi group, as well as earlier bedtimes and greater total sleep duration.

Yes: An injury to the brain causes damage to the structure and normal mechanisms of the brain. This causes an energy mismatch as the brain struggles to perform daily activities while also pulling from the same pool of energy to heal. You should have her rest- physically and cognitively- no cell phone, tv etc- and get evaluated by a health care professional trained in concussion/brain injury management.