This is a heart breaking video, and reminds me of how I was ( and even worse) for over a year in 1998-99. All of these symptoms can be due to high/abnormal intracranial pressures - which particularly affect the lower brain areas ( cranial nerves included) and pituitary.
Those involuntary jerks and twitches are called myoclonus. I had this. I had no saliva at one point, but when I rolled my head to the right, saliva would flow. ( cranial nerve symptom) He mentions that these can be set off by coughing. Yes, coughing increases intracranial pressure.
Dehydration and drinking all the time - oh yes. Is it due to abnormal ADH secretion by the pituitary, which is also under excess pressure?
Notice his body posture. His left shoulder is tilted to the left, and he most often has head tilted to his right. Classic for mild scoliosis, and resulting functional short leg, pelvis issues. ( Scoliosis will rotate the sacrum and the head.)
Just two weeks ago I had dental work, crown on right front upper palate. Oh my God. Suddenly severe dizziness, nausea, sweating, visual disturbances. My acupuncturist aligned my occiput, atlas and I was almost instantly better.
I have had some of the finest body workers/acupuncturists, and I still have problems and am not well enough to work. Why ???? Small posterior fossa ( brain space at skull base), tethered or short spinal cord attachment, rotated dural/spine/sacrum, neck due to mild scoliosis ?? Cerebellum is hanging low on one side.
May All that is Good and Strong and Beautiful enlightened our researchers, and help us understand these complex structural issues and find a solution.