In terms of hair restoration, shock loss means that the scalp undergoes a trauma that causes the hairs to fall out in response. There are two classifications for when this happens – temporary, and permanent.
This is the result of trauma to the scalp, and can occur due to a number of different reasons. The most important characteristic of temporary shock loss is that the hair regrows after a certain period of time, regardless of the original causation. The most common forms of temporary hair loss occur:
During follicular unit strip surgery (FUSS), a portion of the occipital scalp is removed so that the hairs can be dissected and prepared into new grafts that are ready for transplantation. The occipital scalp is the back of the scalp, also known as the donor zone. Once the donor zone has been removed, the surgeon must close the wound using either sutures or staples. If there is too much tension on the wound closure, the disruption of blood flow from this tension and traumatize the hairs in the immediate vicinity of the closure. Hairs surrounding the donor zone will fall out as a result. This is temporary, and once the wound heals (and once staples are removed if they were chosen), the hair will eventually grow again. This type of hair loss can manifest itself along the entire wound closure, or sometimes be as small as a quarter.
Permanent shock loss is the result of a sustained trauma to the follicle that does not allow it to properly regrow hair. Typically, these hairs were already being affected by dihydrotestosterone (DHT), the hormone responsible for causing hair loss and baldness, and were going to be permanently lost within a number of years. Permanent shock can also occur due to transection, which is where important structures of the hair, such as the bulb, are damaged by the transplantation. Follicular units on the scalp can contain anywhere from one-to-four hairs. However, a high transection rate means that a follicular unit that is supposed to contain four hairs could actually contain as little as one viable hair. The overall hair density is lessened, and the transplant will not look natural as a result.