You're not alone. It's not unusual for me to loose the ability to use or understand language during migraines. I've suffered from various forms of migraine for more than 60 years, usually just identified as "atypical migraine" as the symptoms have been too variable to be identified any specific form. Then around 15 years ago I was diagnosed as having hemiplegic migraines, although in my case the pain doesn't seem to be as severe as it should be, and sometimes almost absent, so perhaps they are not really hemiplegic migraines at all - just another variant of "atypical".
My migraine symptoms often mimic a stroke or extreme intoxication so closely that it fools even the experts until the results of an MRI or toxicity screening is seen. I've found myself in ER on a number of occasions when I haven't noticed a pending migraine and been "caught short" so to speak, and I'm seen staggering in the street, one side of my face drooping, and an arm flopping around uselessly, crashing into people and objects and unable to speak coherently or effectively ask for help. I am also autistic and while I'm hypersensitive to external stimuli, it's the opposite for internal sensations, so I usually fail to notice such things as thirst or hunger or low to moderate sense of pain, or signs that I'm experiencing symptoms of a migraine prodrome.
I have had EEGs done but these have been done several hours or a day after being admitted and the results range from normal to "unusual", but not typically what would be seen if it had been a real stroke. I'm guessing the delays might have been because meaningful communication between myself and the clinician wasn't possibly or a shortage of resources, but I'm not really sure.
There are times when I'm also unable to understand what others are saying. I can sort of understand the meaning or broad concept of most individual words, but am unable to understand the meaning of a sentence as a whole. It's bad enough not being able to convey what I wish to communicate, but it's even more distressing when I'm unable to comprehend what others are trying to communicate to me.
The stroke-like symptoms can last for up to a day, and I'm mostly back to normal within a week. Some things such as motor memory do take longer. For example, the ability to tie shoe laces without having to make every move consciously and deliberately might take several weeks to return. And sometimes it has taken me a week or two to be able to walk and at the same time maintain a conversation.