Hospital diagnosis

[DiagnosisKnow]

My cousin was admitted to hospital with what appears to the uninformed as dementia, but with the apparent onset almost overnight cannot seemingly be the cause. Hes a very fit 67 year old, vegatarian, daily gym attendance and cycled everwhere. No overseas visits, uk based, living on his own for 30 yrs. hospital have been unable to diagnose during last 2 weeks having had head CT, MRI, and body CT scan. Only physical abnormality seems to be bladder thickening.
He will not take anything by mouth and now refusing to cooperate with a drip. Most of the time hes silent and is able to talk, especially when being held down for injections, inclusing anti viral drugs, but mostly very confused conversation.
Can anyone suggest anything?

[DiagnosisKnow]

Thanks for the reply. He hit his head on a rock in August diving into the sea and had some headaches subsequently. not sure theyve looked for an aneurysm. how do they diagnose that?

[allmymarbles]

Has he been involved in an accident recently? Has he been ill lately? Have they looked for an aneurysm?