There are many forms of TIA's. Many are not severe enough to seek medical attention due to their transient nature. They can happen during sleep and feel like a foggy brain when one wakes up. The ischemia can be due to restricted blood flow from an embolism or just a lack of proper oxygen from apnea or other Hypoxic-Anoxic events which is otherwise known as a HAI (Hypoxic-Anoxic Injury). A vasovagal attack can also cause a momentary TIA.

In my brain injury support group, there is a young man who suffered a concussion then a TIA on the sidelines. Sometimes, a vascular accident in the carotid or vertebral arteries can release a clot or plaque that coincides with the trauma to the head.

TIAs that are not imageable are as difficult to diagnose and understand as concussions and PCS.