Why should periodic paralysis mean cognitive issues? Classically, it is not a symptom of HypoPP. Based on my own experiences and guesses, there are a couple of contributing factors.
Image from http://curerator.com/remedy/hypokalemic-periodic-paralysis/
After an attack, or during an abortive attack, I get terrible sleep. The amount of pain and cramping after an attack just doesn't work with a nice relaxing lie down. There are frequently severe headaches during this time as well. It would make sense that words get tricky after three to five days of poor sleep. Spacial reasoning gets a little wonky, too.
There's also the likelihood that my electrolytes get all outta whack. When my muscles depolarize and go flaccid, they're retaining a lot of potassium. When they come back, that all gets dumped back out to my blood.
While not normally listed as a symptom, it is commonly reported. You can see in the small, informal survey that a little over half of the respondents have these types of issues. http://hkpp.org/survey-of-64-patients
The good news - like everything else with this whackadoo disorder, it will go away. I'll continue my electrolyte supplements, get better sleep, and feel fresh and new soon enough.
We do what we can with what we have when we have it :)