Excluding moderate and severe tbi, what may cause concussion symptoms?

The concussion is an immediate and transient loss of neuronal function secondary to trauma. (Neuronal Function = LOC, memory or motor skills).

The impact shakes the brain inside the skull, a wave through brain tissue causes discharge of damaging chemicals; nerve cells can shear, microscopic damage can affect the anatomy and function of brain cells.

It is a mild traumatic brain injury caused by a bump, jolt, or blow to the head.