What cause it?

Scarring alopecia —or cicatricial alopecia— is caused by an existing injury, be it a traumatic injury or a surgical one. This causes the hair follicle to get damaged permanently by the trauma or by the scarring process (fibrosis).

Scars develop from traumatisms such as blows or burns, but they can also arise from surgical procedures such as a craniotomy, the Follicular Unit Transplant technique, forehead surgery, rhytidectomy, and more.

Craniotomies are usually emergency procedures attending brain injuries or encephalic traumatisms, and they are done through incisions on the scalp.