Question: Which could be some of the possible causes of hypersomnia?

Context:
Sleep-wake disturbances (SWD) are common after traumatic brain injury (TBI). In acute TBI, we recently found decreased CSF levels of hypocretin-1, a wake-promoting neurotransmitter
Hypocretin levels 6 months after TBI were significantly lower in patients with post-traumatic EDS
These results suggest that sleep-wake disturbances, particularly EDS, fatigue and hypersomnia are common after TBI, and significantly impair quality of life
When sleepiness is excessive, undesirable, inappropriate or unexplained, it often indicates a clinical disorder that is generically termed hypersomnia. One of the leading causes of hypersomnia is sleep apnea
A clinically relevant sleep-wake disturbance is found in up to half the patients with dementia, and the sundowning agitation is a common cause of institutionalisation of demented geriatric patients. The circadian rhythm of demented patients is levelled off with increased daytime sleep and disrupted night sleep. Particularly in vascular dementia, Korsakow syndrome, Parkinson's disease, and depression the alteration of sleep architecture may be pronounced, whereas in Alzheimer's disease prominent hypersomnolence or insomnia is typically only found in later stages of the diseases
We report on an 83 yr old man with hypersomnia and central sleep apnoea (CSA)
One of the leading causes of hypersomnia is sleep apnea.
In this article, the causes of hypersomnia are detailed following the conventional classification of hypersomnic syndromes: narcolepsy, idiopathic hypersomnia, recurrent hypersomnia, insufficient sleep syndrome, medication- and toxin-dependent sleepiness, hypersomnia associated with psychiatric disorders, hypersomnia associated with neurological disorders, posttraumatic hypersomnia, infection (with a special emphasis on the differences between bacterial and viral diseases compared with parasitic diseases, such as sleeping sickness) and hypersomnia, hypersomnia associated with metabolic or endocrine diseases, breathing-related sleep disorders and sleep apnea syndromes, and periodic limb movements in sleep.
In the absence of sleep deprivation (either because of behavioral or medical causes) or pharmacologically induced sleepiness, hypersomnia is a manifestation of one of the central disorders of hypersomnolence, such as narcolepsy types 1 and 2, idiopathic hypersomnia, and recurrent hypersomnias such as Kleine-Levin syndrome.
Sleep apnea syndrome (SAS), narcolepsy, chronic sleep deprivation (insufficiency), and restless legs/periodic limb movements in sleep syndrome (RLS/PLMS) represent the most common causes of hypersomnia.
Hypocretin (orexin) deficiency in narcolepsy and primary hypersomnia.
One of the leading causes of hypersomnia is sleep apnea.

Answer: Sleep-wake disturbances (SWD) with hypersomnia are common after traumatic brain injury (TBI), with decreased CSF levels of hypocretin-1, a wake-promoting neurotransmitter, in cases of sleep apnea, as well as in up to half the patients with dementia, particularly in vascular dementia, Korsakow syndrome, Parkinson's disease, and depression, where the alteration of sleep architecture may be pronounced, whereas in Alzheimer's disease prominent hypersomnolence or insomnia is typically only found in later stages of the diseases.
Exact answer: traumatic brain injury (TBI)
sleep apnea
dementia