One of the most common forms of this is Amyotrophic Lateral Sclerosis, also known as Motor Neurone Disease or Lou Gehrig's Disease. If you have Lou Gehrig's Disease, your motor neurons, which are responsible for triggering actions, gradually decay away while the rest of your nervous system (including your brain) remains perfectly intact. You can still feel pain and boredom but cannot move to avoid it. Clumsiness is one of the first symptoms. Poor Stephen Hawking gets more of a taste of this than anyone ever wants, living like this for years, though he at least gets sight, hearing and enough eye movement to control his computer (which does the communicating for him), along with retaining his incredible mind. The fact that Hawking is not only able to maintain a positive attitude, but still focus his brilliant mind, is testament to hissheer willpower.
Fibrodysplasia ossificans progressiva (FOP). A horrible, horrible genetic disease where, if your muscles are damaged in any way at all, your body decides to replace the damaged muscle- not with more muscle, but with bone. By the time you're thirty, most, if not all of your joints have been locked into place by newly-grown bones and you die of starvation/suffocation because you can't move your jaw or ribs. And trying to remove the bone growths with surgery only results in the body "healing" the surgical cuts with even more bone.
A bad experience with the psychoactive herb salvia divinorum can cause horrifying sensations of being trapped in an eternal loop or transformed into an inanimate object.
Not just salvia, but almost any dissociative drug. Time dilation plus ego death equals this trope becoming very, very real.
During surgery, hospital patients are supposed to receive neuromuscular blocking agents (which keep them paralyzed so they don't twitch and mess up the surgery), sedatives (to keep them asleep and give them amnesia), and an anesthetic (to numb them so they don't feel anything). There are numerous reports of patients who have had the sedatives and anesthetics wear off during/after surgery but KEPT ON the neuromuscular blocking agent. So essentially they are completely paralyzed and wide awake and have no possible way to give the doctors a sign that they are in excruciating pain. Luckily, the autonomous systems keep functioning and react to the pain as normal (quickened breathing and pace, heightened blood pressure, sweat), so a good doctor would probably be able to tell and administer more anesthetic. Hopefully.
Modern anesthesia machines include an "entropy sensor" to make sure the patient is unconscious. The problem is that quite often it is removed for being in the way
Polio often caused paralysis. Sometimes of limbs. Sometimes of the various breathing mechanisms. Iron lungs, for a very long time, meant lying down in a sort of cylinder, with only the head outside◊. That's a nonintrusive way to keep someone breathing, and it's fine and dandy as a temporary thing. Most people who needed them only needed them for a week or two. But some polio patients were never able to breathe on their own again, and it was years before smaller long-term breathing machines were invented. Why We Immunize has a good article on that.
I did some volunteer work in a children's hospital. There was only one polio patient: one of the last cases, then a teenager, in an iron lung. By then there were no more specialty polio centers, no more polio wards, in which at least the inhabitants could talk to someone who understood. In a ward for children, where the other patients were kids who'd had some other treatable illness or injuries, there was his iron lung. He wanted no part of the cheerfulness we tried to bring to the ward. And no wonder. Unless he could adapt to one of the smaller respiratory assists that came later, he was stuck for life in a huge, unwieldy, scary case... immobile, having to be tended by people who reached in through portholes on the side to clean him up, change his diaper... and who, increasingly, would not have a clue what his life was like because people like him were so few now. He could not see his body, engulfed in the machine that kept him alive. He could see only what was directly above him or reflected in the mirror over his head. None of the electronic aids for the disabled existed then... or for another decade or two. There were, and are, more lethal diseases than polio: those with a higher mortality, and greater infectivity as well. But polio had a special horror to it.
This is the gist of Locked in syndrome, wherein you appear comatose, but are actually 100% aware of everything going on. This can go undiagnosed, everyone thinking they're just plain comatose.
When former editor of Elle magazine Jean-Dominique Bauby was struck by locked-in syndrome after a stroke, he managed to communicate through a system of eyeblinks, and wrote a book about his experiences called The Diving-Bell and the Butterfly, later made into a film.
Empress Dowager Lüi of the Han Dynasty, after having the young prince Ruyi murdered as a perceived threat to her son Hui's throne, tortured his mother, Consort Qi, by hacking off her hands and feet, putting out her eyes, deafening her, and tossing her in a pig pen to live out the rest of her life. Emperor Hui was so traumatized by his mother's unspeakable and pointless cruelty that he took to drink and died.
In the book "Musicophilia", Oliver Sacks describes the sad case of conductor Clive Wearing, who suffers from an acute case of both retrograde and anterograde amnesia (i.e. he has lost almost all memories of his past, and is also unable to form new long-term memories, like the protagonist in the film Memento). Wearing is aware that something is terribly wrong with him, but he has no way to learn what has happened or come to terms with it, and is left only with a constantly recurring realization of having been robbed of all past experience. At one point, Wearing's therapist suggested that he might try keeping a diary...
But his journal entries consisted, essentially, of the statements "I am awake" or "I am conscious," entered again and again every few minutes. He would write, "2.10 pm: this time properly awake... 2.14 pm: this time finally awake... 2.35 pm: this time completely awake," along with negations of these statements: "At 9.40 pm I awoke for the first time, despite my previous claims." This in turn was crossed out, followed by "I was fully conscious at 10.35 pm, and awake for the first time in many, many weeks." This in turn was canceled out by the next entry. This dreadful journal, almost void of any other content but these passionate assertions and denials, intending to affirm existence and continuity but forever contradicting them, was filled anew each day, and soon mounted to hundreds of almost identical pages." (pp. 203-204)
Wearing has been keeping this diary for more than twenty years.
Heartwarmingly, one of the few things Wearing can always recognize and remember is his wife.
This experiment involving MRIs implies that people in persisted vegetative states may be completely aware of their surroundings, even going so far as to answer complicated questions. What's worse, the BBC broadcast talking about this implied the moral and legal obligations of such a claim, that someone stuck in this state and capable of asking for it would not be legally allowed assisted suicide.
However, several other methods of determining if someone in this state is aware are prone to problems. To wit, facilitated communication (where allegedly the comatose is able to communicate through another person "guiding" his hand to a keyboard) does not work (tests where different facilitators are used and where a test object is hidden from the facilitator, but not the PVS). The most prominent case of this is Rom Houben, a man who was thought to be completely aware for his 23 years in a coma, but was determined to still be out when the facilitated communication used to stake the claim failed.
Sleep paralysis is a condition in which the normal REM atonia that normally prevents the body from moving during REM sleep persists after one regains consciousness. Though generally this is experienced for only a few minutes at a time, the body is generally unable to accurately perceive the passage of time, and it can feel like hours. If it's not bad enough you're in a state of panic because you can't move, the subject can also experience terrifying hallucinations.
Thankfully, it's possible to learn to recognize what's going on and teach oneself ways to stay calm. Some sufferers are also able to break out of it faster by wiggling their toes, gradually regaining the ability to move at a somewhat quicker rate than if one stayed perfectly still. For some people, sleep paralysis can be triggered by various environmental factors (some are more likely to experience it if they sleep in a hot room, for example), so figuring out and avoiding these factors may reduce the chances of it happening.
Some people experience sleep paralysis mostly as a result of sleep deprivation. That means that whenever you try to go to sleep, you get paralyzed, and once you escape, you're exhausted and have to try to go asleep again, which leads to more sleep paralysis... The saddest part about this phenomenon is that it is not uncommon. It is where the word for nightmare originated from.
The leukodystrophies, a family of disorders in which the fatty sheath covering the nerves slowly dissolves, oftentimes lead to the sufferer becoming paralyzed, blind and deaf.
The WNYC program Radiolab reported the story of Emilie Gossiaux, who suffered a traumatic brain injury that left her unable to communicate with the outside world. Or was she? It was unusually hard to tell, since Emilie was deaf, and the accident robbed her of her sight. You can listen to it here; it's absolutely riveting.
Tetrodotoxin, a potent neurotoxin found in newts and puffer fish, can induce muscular paralysis and a comatose stupor that lasts for several days—while leaving you fully conscious. It's believed by some to be the active ingredient in real-life zombie powder.
When you try to kill a bug, but it barely survives and you don't notice. That poor fly is lying on the pavement, unable to fly or do anything other than wiggle its legs, until either someone kills it properly or it dies on its own of starvation. Luckily for bugs, they have very simple nervous systems and don't feel pain the way humans do — but try telling that to your imagination.
Curare, a toxin that causes full-body paralysis without affecting the mind or the feeling of pain, was used as an "anesthetic" for surgeries in the 1940's. On patients which included babies.
Some types of wine involve pickling a live viper in a bottle for months. Usually the snakes die but sometimes, they survive. There are even instances of snakes coming back to life and biting people who try to open the bottle.
Because of reptiles' slow metabolisms, decapitation can take hours or days to kill them, though they feel every bit of it the whole time.
There are a number of parasites that take control of insects or small animals and then force them, sometimes against their will, to allow themselves to be eaten by predators. For example, the Dicrocoelium infects an ant and then forces the ant to crawl to the tip of a blade of grass where it can easily be eaten by a bird, thus allowing the parasite to continue its cycle inside a bird. Even worse, the Spinochordodes larvae enter grasshoppers that drink the water they reside in and then after growing inside the grasshopper, they take control and force the grasshopper to jump into a body of water and drown itself. Imagine being unable to stop your body from drowning itself.
Encephalitis lethargica. A disease that reached epidemic levels in the 1920s, it started as a simple headache, fever, and sore throat. If it killed you, you were lucky, as many people in the late stages of the disease were left totally unable to move or speak, despite possibly still being conscious.
Some strokes can cause enough damage that they can leave you in such a state. An example is John Paul Getty III, grandson of oil baron J. Paul Getty. In 1981, years after his infamous kidnapping by Italian gangsters, Getty tried a cocktail of various drugs. He suffered a stroke and came out of it quadriplegic '''and''' blind. Up until his death in 2011, all Getty could do to communicate was scream.