What I didn't have were the "weird" symptoms that are reported in Osler's Web. I was able to stand up whenever I wanted to and didn't have to crawl to the bathroom, even though I didn't have enough energy to stand up for very long and felt light-headed. I never forgot the name of my own town. I didn't try to make telephone calls by using a parking meter. I didn't have seizures caused by watching TV. I didn't have severe heart pains that made me feel like I needed to go to the emergency room. I didn't have random moments when the desire to commit suicide was overwhelming. I often was too tired to read or do math, but I never lost the ability to absorb a sentence or add 2+2 when I focused on it. I never went into a blank state where I was unable to (say) remember what an actress was and then 30 seconds later forget what the question was. I never had to be taken to the emergency room because I'd suddenly passed out. I never (well hardly ever) got excruciating headaches that made me pray to die.
I didn end up in ER with labored breathing and chest pain that had gone on for days. I began to make notes by my bedside to write down my childrens names just in case.. and to write down the meds I took before bed because I would wake up in a panic thinking I had not taken them and it was not a huge deal if I had not.So I dont know this is cyano or not but I also see where you are coming from with the environmental element and it happening so quickly. Those symptoms though may not be only due to cyano.
I think you are right that biotoxins may be a huge factor for some of us and makes sense that something environmental can take people out like that.. starting the cascade. When my brain becomes inflammed, whatever the cause (thinking metals moving lately) I can drop deep into depression, lose my ability to think, memory would drop off a cliff.. but this is temporary.. my brain calms down. The memory issues I had.. forgetting my childrens names cold.. thinking to no avail to remember them.. passed though happened several times.
Brain inflammed I bet everytime. Always starting with sinuses.