The keto diet, from my understanding, was originally used for children with epilepsy. There were large successes with it and many of these children "grew out" of their seizures.
Years later, I've seen more studies popping up, or at least more sources saying the keto diet is beneficial for adults as well.
I do believe the keto diet would be effective for most epileptics.
It is true that the keto diet restricts carbs to a low amount (I believe it's something like no more than 10-12 carbs a day or so). It does use high healthy fats and also a moderate to high amount of protein.
What happens when a person goes into ketosis is they are no longer relying on carbs for energy, but instead they are using healthy/good fats for their energy source.
The majority of the brain is fat - it needs good fats to function, too. When the brain is trained to run itself off of fats, it uses energy in the body pretty efficiently - doesn't leave excessive fat stores in your body. This is what has also made the keto diet more and more common for weight loss or emergency weight loss programs.
The good fats that are more common to use are coconut oil, avocado, bacon, and other animal fats (pork, duck, etc). These are often used generously at every meal.
I don't know much about the keto diet increasing LDL cholesterol or why it would do that.
However, what I do know is that some people do the keto diet and they have no guidance or resources for doing so. I've known people that have gone on the keto diet because they believe that is the best diet for them and then get dehydrated while on it because they're not consuming enough liquids or having issues because they haven't had enough fats.
It's also possible to get what's called the "keto flu". It's believed that what this really is is sugar withdrawals from carbs and the body is acting out because this is out of routine.
I should technically be on a keto diet. Kind of wished I would have been as a kid, perhaps my outcome would've been better. Although, I gave my mom a hard time. I couldn't have chocolate cake so I decided it was a "no go." Back then, we didn't have all the alternatives we do now for carby foods.
Even now, I am sensitive to most grains and I am allergic to rice. If I have rice, I almost have a seizure - it's that awful. I honestly think it's neurotoxic pesticides and not the rice itself. Same goes for the grains. Our food is treated so much different than it used to be. Either way, in my case, if I go without the grains that bother me, my diet is pretty close to low carb - at least paleo.
Although, I drop pounds like crazy when I drop wheat 100% that I try to have some complex carbs like sweet potato, carrots, pumpkin, nut butters, etc. to keep some weight on. I will get terribly thin. I am pretty sure I have gut damage from the amount of wheat I've had over my life time and I know it bothers me badly over the long run, but I was never checked for celiacs or gluten sensitivity growing up. It wasn't a huge thing like it is now.
I do believe the keto diet can be helpful and can reduce the amount of medication used to control seizures in most people.