Medical Terms

Alopecia

The medical term for hair loss. There are numerous types of alopecia. Alopecia can be classified as diffused or localized, and by presence or absence of scarring. The most common form of surgically treatable alopecia is androgenic alopecia (AGA).

Alopecia Areata (AA)

Although the exact pathophysiology of AA is not clear, it has been determined that it is a T-lymphocyte mediated autoimmune condition that occurs in genetically susceptible individuals. It typically presents itself with sharply demarcated coin-sized patches of alopecia. The scalp is the most commonly affected area, but any hair-bearing area can be involved. Spontaneous remissions and recurrences are common. A common non-scarring alopecia. 

Alopecia Universalis

A loss of all hair on the body.

Androgenic Alopecia (AGA)

A heritable androgen and age-dependent process resulting in a progressive decline in visible scalp hair density in a sex-dependent defined pattern.

Body Hair Transplant

Donor follicles that are harvested from any region of the body except the traditional scalp donor area. Body hair includes all hair inferior to and inclusive of the neck and beard. Body hair has an unpredictable and variable yield.

Catagen

The catagen phase is a brief transitional phase between anagen and telogen that lasts only a few weeks.

Cicatricial Alopecias

Uncommon and clinically diverse disorders that result in permanent and irreversible loss of scalp hair. These disorders may be primary, with the follicle itself being the target of the disease process, or secondary, where hair follicles are destroyed as part of a more generalized tissue-damaging event (e.g. deep skin infection, thermal burn, trauma, or ionizing radiation). Clinically it is characterized by the disappearance of visible follicular ostia within an area of alopecia.

Choi Implanter Pen

Is a tool that hair transplant specialists are beginning to use more often. It allows doctors to implant individual hairs one by one with precision carefully.

Direct Hair Implantation (DHI) 

Is a hair transplant technique that involves extracting hair follicles from a donor area and implanting them into recipient areas. It’s a minimally invasive procedure that’s often used to treat hair loss in the scalp.

Densitometer (Trichoscope)

A tool that gives a rapid, accurate and reproducible assessment of donor hair density.

Densitometry

Analyzes the scalp under high-power magnification to give information on hair density, follicular unit composition and degree of miniaturization.

Density

The number of hairs in a specific area.

Diffuse Patterned Alopecia (DPA)

The term used to describe diffused hair loss that involves thinning. The occipital donor area is spared.

Dihydrotestosterone (DHT)

The most potent natural androgen in humans. Testosterone is converted to DHT by the enzyme 5-alpha reductase. It is believed that DHT is the key androgen required for the induction of MPHL.

Donor Area

The fringe above the ears and around the back of the head where hair follicles are genetically programmed to remain intact and grow throughout life.

Donor Density

The number of hairs in the donor area measured per square centimeter. In general, patients require a donor density of at least 40 FU/cm2 to be considered for transplants.

Drug-Induced Alopecia

A form of alopecia usually presented as a diffused, non-scarring variety most commonly involving the scalp. In almost all cases, there is recovery of hair loss after the discontinuation of the medication.

Dutasteride

An inhibitor of both type I and type II 5a-reductase that was approved by the FDA for the treatment of benign prostatic hyperplasia. Dutasteride has been shown to significantly increase hair counts and hair weight, improve the ratio of anagen and telogen hairs and improve scalp coverage.

Effluvium

Active hair loss denoted by the hair loss of > 100 hairs daily over a longer time period of 2/4 weeks.

Follicular Density

A term that refers to the number of follicular units per square centimeter.

Follicular Unit

The majority of human hair shafts that emerge from the scalp as single, 2, and 3-hair groupings. These are the visible superficial portion of a distinctive histologic structure known as the follicular unit the follicular unit consists of one to four, and occasionally five terminal hair follicles, one, or rarely two vellus follicles, the ions of the arrector pili muscles, its neural and vascular plexuses and the fine adventitial collagen that surrounds and defines the unit.

Follicular Unit Dissection

A technique in which naturally occurring, individual follicular units are dissected from donor tissue that has been removed as a single strip. Stereo-microscopic dissection is required.

Follicular Unit Extraction (FUE)

A method of graft harvest whereby punches of various types are used to remove follicular units from the donor region one at a time.

Follicular Unit Graft

A graft consisting of a single follicular unit.

Frontal Area

The scalp area that lies between the anterior hairline and a line initially drawn vertically from the left and right tragus and then gently curve anteriorly.

FUT (Follicular Unit Transplantation)

A method of hair restoration surgery whereby parallel incisions are made in the donor scalp area to remove a strip. The length and width of the excision depend on the amount of grafts. From this strip, individual follicular units are then dissected under the stereo microscope.

Hair

Hair itself has few physical functions but they include defense against the effects of UV radiation, suppression of heat loss and tactile sensation. The various hair types consist of terminal, intermediate, and vellus hairs. Hair has two separate structures: the follicle in the skin and the hair shaft that is visible on the body surface.

Hair Additions

Any external hair-bearing device that is added to existing hair or scalp to give the appearance of a fuller head of hair, i.e.: hair weaves, hair extensions, hair pieces, toupees, non-surgical hair replacements, partial hair prostheses, hair wefts. 

Hair density

A product of the concentration of hairs and the size or caliber of each individual hair.

Hair Follicle

A strand of hair and its root that is extracted from the donor area and transplanted into the recipient area during hair restoration surgery.

Hair Grafts

Hair follicles that have been harvested from the donor area and are ready for transplantation into the recipient area of the scalp.

Hair Transplant procedure

A surgical technique that transfers hair follicles from the donor area to the recipient area. The hair transplantation process consists of two parts: 1) removing the donor follicles and 2) placing them back into the skin.

Hairline

A prominent part of the largest visible feature of the face. Creating a natural hairline is one of the most important elements of a successful hair transplant. The goal is to achieve the age-appropriate look that will sustain a natural appearance with the future progression of hair loss.

Harvesting

The term used to describe removing hair from the donor area.

Ludwig Scale

A common scale used for describing a type of female pattern hair loss in which there is centralized diffused loss of hair. The Ludwig I scale demonstrates mild hair thinning throughout the central scalp. The Ludwig II scale exhibits moderate with notable thinning in the central scalp. The Ludwig III scale shows severe hair loss and thinning in the central scalp.

 Miniaturization

A primary pathological process in androgenetic alopecia resulting in the conversion of large (terminal) hairs into small (vellus) hairs. Miniaturized follicles still have the capacity to produce hairs and retain cycling ability.

Minoxidil

Originally developed as an antihypertensive agent, it was approved by the FDA for treatment of MPHL as a 2% and 5% scalp lotion. The action mechanism of minoxidil on hair growth is still unclear. Recent studies suggest that it also enhances hair growth by increasing the production of prostaglandin E2. Topically applied, minoxidil increased hair weight with a less dramatic increase in hair counts. Adverse effects of minoxidil include skin irritation, hypertrichosis on the face and hands and tachycardia.

Overharvesting:  

Hair transplant overharvesting happens when too many hair follicles are removed from the donor area during surgery. This can lead to permanent thinning or scarring.

Platelet-Rich Plasma (PRP)

An autologous preparation of plasma with platelets that is capable of secreting growth factors and cytokines that stimulate stem cells. Some hair transplant surgeons have used PRP in hair transplantation procedures either by storing the grafts in PRP until they are placed on the scalp or by injecting PRP into the scalp prior to placement of grafts. The results of studies pertaining to the use of PRP as an adjunctive modality in hair transplantation remain controversial.

Punch

A surgical instrument used to obtain small samples of tissue.

Recipient Área

An area where hair loss has occurred and hair follicles will be implanted during a hair transplant procedure. There are many methods of creating recipient sites including lightning blades, minded blades, custom-cut razor blades, and various needles.

Reductase enzyme

The enzyme that converts testosterone to the potent androgen dihydrotestosterone (DHT). It exists as three isozymes whose tissue distribution varies.

Sapphire Surgical Blade:

It is a sharp sterile instrument that allows the opening of origins on the scalp of the recipient area to implant the grafts manually with tweezers, and generally the final density obtained with this tool is lower compared to the choi pen. 

Saw Palmetto (Serenoa Repens)

An over-the-counter herb. It Inhibits 5-a reductase conversion of testosterone to DHT.

Shedding:

(also Shock loss) Is a natural part of the hair growth cycle, while shock loss is a temporary hair loss that occurs after a stressful event like surgery.

Spironolactone

An aldosterone antagonist employed in clinical practice as a potassium-sparing diuretic. It reduces adrenal androgen production and exerts a competitive blockade on androgen receptors in target tissues. This medication has been used off-label in female pattern hair loss. 

Strip harvesting

A technique for harvesting donor hair that involves the excising of a horizontal section of safe donor hair from the occipital, parietal and occasionally temporal regions. The resulting wound is sutured or stapled and leaves a linear scar

Telogen Effluvium

Refers to the excessive loss of telogen hairs due to an abnormality in hair cycling. It may occur in response to a number of triggers including fever, hemorrhage, severe illness, stress, childbirth, crash dieting and iron deficiency. It typically occurs approximately 3 months from the time of the precipitating event.

Traction Alopecia

A condition that is caused by excessive stretching of the hair shafts through hair-styling practices. Thinning and recession involve the frontal area, but may extend into the temporal regions. Prolonged traction alopecia can scar the new hair follicle and cause permanent hair loss. Hair transplantation is successful in lowering the receded frontal hairline and re-establishing the appropriate density.

Trichoscopy

A dermatoscopy of the hair and scalp. It can be performed with a handheld dermatoscope or a digital videodermatoscopy system. It may be applied in the differential diagnosis of multiple hair and scalp diseases.

Vertex (crown)

The most posterior area of male pattern baldness that is characterized by a whorl arrangement of hair direction. It extends from the posterior border of the mid-scalp to the posterior curved parieto-occipital fringe of hair.