Why stammer happens, what kind of lacking is involved in this, which results anybody different from a common person, is it a brain related disease?

Neurogenic stutter-: Ing may occur if signals between the motor speech area of the brain & the nerves to tongue & cheek muscles are disrupted during fetal brain development from exposure to toxins or infections or post-natal ""stroke" or trauma. Family history (many genes are suspected), age of onset > 3.5 yrs., duration > 6 mos., social anxiety & being male ⬆risk. See: http://www.Stammering.Org/watkins.Html.