My Great Pyrenees dog began to have seizures at 3 years old. I have no experience which suggests this breed is in any way predisposed to this; any dog of any age and of any breed can be afflicted, and it's an interesting disease to familiarize yourself with.
Seizures are one of the most baffling, sad, and frustrating things an owner can deal with. Many dogs can have 1 seizure in their life and never another one, while others suffer from them considerably, and it can be challenging to manage them. They are harder on the owner in many ways, as they can be difficult to watch, especially knowing we are relatively helpless in the moment. The reality is, your dog *doesn't know* he or she is having them; it's not a painful event.
Many seizures are "idiopathic" (we don't know why they have them), and this can be so frustrating for an owner who just wants to "fix" the problem, but if they are truly idiopathic, there is no cure, only medical management. We monitor and watch them, and while veterinarians will have different approaches, my experience is that you begin medication when they have more than 1 a month.
Outside of idiopathic seizures, there are many things which can cause seizures. Younger dogs, dogs around ages 2-3 typically are assumed to have idiopathic epilepsy in lieu of an MRI to confirm it, and in the absence of toxin exposure or blood abnormalities. Older dogs with their first seizure are prime suspects for a brain tumor, but again, without an MRI it is speculative. Electrolyte imbalance, low glucose (blood sugar), and toxin exposure can also lead to seizures.
MRIs can be performed on our dogs. They are not cheap but the diagnostic is the only way to truly understand if their seizures are idiopathic or cancer when other factors are ruled out. If your dog presents to your vet with seizures, they should recommend this diagnostic. You can treat the seizures without, but it is the gold standard of care. The MRI will enable you to know if cancer is responsible, enabling you to have the option to consider treating the cancer.
Often times owners are challenged to understand if it even was in fact a seizure they witnessed. It can be easy for a person to struggle to differentiate between fainting, collapse, or seizure. If you are unsure, and able, record the event on your phone so you can show the doctor. Most owners, if uneducated or inexperienced, mistake seizures for syncope (fainting) and vice verse. While all dogs are unique, there tend to be some helpful differences.
Most seizures happen at night, while the dog was sleeping. You may hear them yelp out, they may fall out of your bed, etc. The typical dog may paddle fiercely, while drooling excessively and potentially urinating and defecating. The key is that after the episode, they are not "themselves" right away. They have a phase described as "post-ictal" where they are neurologically inappropriate for many minutes. My dog isn't himself for about an hour. They may seem blind, bump into things, or have other unusual behavior.
Syncopal dogs tend to have fainting episodes with moments of excitement. They may yelp out, become very rigid, fall over, and owners report "he seemed dead". After a few seconds or minutes, they rebound quickly and are immediately themselves again. Like seizures, they may also urinate and defecate, but they may not paddle, and they certainly shouldn't appear neurologically appropriate afterward.
Is there anything you can do for your dog, at home, should they suffer a seizure? The short answer is no. If you have drugs on hand because you already know they suffer, then naturally you can give those as advised. To elaborate, dogs with a history of seizures may have owners who have a drug at home to give rectally for seizures lasting over 3 minutes. There is nothing you should try to "do" to stop the seizure short of those medications, and certainly there is no "home remedy" or "over-the-counter/human" medication you can give.
If you have a giant breed such as a Pyrenees, you need to be careful not to injure yourself, and you need to be prepared for the phase following the seizure where their behavior may be strange and unpredictable. Let them have the seizure, do not get bit! They don't know it's you.. don't try to comfort them, hold them.. move things away from them which may injure them but that is all.
Seizures are an emergency (and these guidelines vary slightly) when they have more than 1 in a 12 hour period, or any seizure lasting longer than 3 minutes. I've heard various guidelines quoted, ie. more than 1 in 24 or seizures longer than 5 minutes.. but, you get the point.
If you are not too freaked out to do so, try to take note of the time the seizure started, and how long it lasted for. If they have multiple seizures, likewise. Before you jump in the car to get them to the doctor, also access if they had any potential exposure to toxins which may be to blame. It's hard to concentrate when our pets are suffering, but in the least try to watch how long the seizure lasted.
Neurological diseases can be very serious and your dog should be seen by a neurologist if they have a persistent condition. It's very important we feel confident it's idiopathic (via your vet) versus other reasons. As with all diseases and abnormalities, never put things off. And most of all, never be an armchair veterinarian. Neurology is a very complex subject, and the items I touch on in this article likely just scratch the surface.
My understanding is that a vast majority of dogs respond well to seizure medication. I meet too many dogs who've been taken off their seizure meds because the dog had more, and the owners assumed it meant "the drug isn't working". It's not a disease you give up on, and like many diseases medications require fine-tuning to manage our dogs.
My dog was well-controlled on 1 medication for a year. He began to have "break through" seizures, and we tweaked his first drug. Time went by, and we needed to add a 2nd drug. I recently had to begin a 3rd seizure medication for him, and so far so good. It's a process, and we just have to watch them and commit to partnering with our doctors to manage their seizures.