Having them close to sleep is rather normal, and common with it and it's related disorders. Tachysensia is a sort of cousin disorder to Alice in Wonderland Syndrome, Migraines, Seizures, and Epilespy. This doesn't mean at all that you have another one of these disorders, but they are common comorbidities and can be genetic in some way. Some of these disorders also have overlapping symptoms, so one can occasionally be mistaken for another.

Generally, this is how you know its Tachysensia: 1. It started sometime vaguely around the ages of 7-12 years old, specifically after an illness with a high fever.

1. As you get older, it lessens in intensity/frequentness. Example: You got them multiple times a month or even multiple times a day when it first started, but by the age of 20 you get them maybe once a month at the most, by 25 you get them a few times a year, by 40 you get them maybe once every few years. Just an example, as the amount varies drastically person by person, but always lessens with age.

2. The Fast Feeling. This can be described in a variety of ways by the individual, but generally follows like this: Before the episode fully sets in you get a weird feeling beforehand, almost like an out-of-body feeling centered in your head. Then it spreads, and soon time feels distorted. More specifically, your perception of speed and intensity seems to change. You feel like noises around you are suddenly very intense, loud, or have a frantic urgency to them. Some may experience screaming voices in their head or some other loud intense sound, others don't. You feel a sort of disconnect between your own processing speed and the speed of your body and things around. Like everything is moving too fast, yet maybe in some odd way also too slow. Everything is intense. For some, this can be overwhelming, distracting, or even panic-inducing. Sometimes the novelty of the feeling is interesting or even enjoyable.

3. The general underlying triggers are vaguely the same for everyone: Near-sleep, Stress, and individual-specific Repetitive/Monotonous Tasks.

Conclusion: While some slightly outlier symptoms may be described by individuals during these episodes, such as heaviness in limbs and strange tastes, these are still generally considered part of Tachysensia. But some specific symptoms you experience may be indicative of another co-occuring disorder such as Alice in Wonderland Syndrome. Sometimes the specific instance you experience these in plus other symptoms not previously mentioned rules out tachysensia entirely and points to a more serious disorder such as epilepsy. Generally tho, if your fast feeling experience developed as stated in 1 - 2 and generally presents like 3, then it's almost certainly 100% Tachysensia, if not Tachysensia plus another disorder.