- Anatomy
- Hair follicles found in the subcutaneous layer; primarily composed of keratin protein, shaft is produced by matrix which is in turn produced by follicle –> follicles are indentations of the epidermis located in the SQ layer of the scalp
- Individual hairs develop from the base of the follicle, progeny displaces below and produces keratin
- Infundibulum is the upper portion of the hair follicle able the sebaceous duct
- Outermost layer called cuticle, (composed of hard keratin), responsible for anchoring hair in place
- Individual hair follicle: dermal papillae bulb (dermal/epidermal coat)
- Anagen phase: active hair growth (lasts 3 years –> actively grows through division and keratinization of follicular cells) (90% of scalp hairs involved in this phase)
- Catagen –> follicular bud destroyed and base of hair is keratinized (lasts 2-3 weeks)
- Telogen phase: follicle inactive and hair is shed
- 10% of hairs at any given time are in telogen phase; catagen phase the follicular bulb atrophies and degrades
- In general, hair loss occurs when anagen phase shortens and telogen phase is prolonged
- Alopecia
- Male pattern alopecia (androgenetic alopecia) associated with prolonged telogen phase
- Inheritance
- Inheritance is the most common cause of hair loss (X linked dominant)
- increased 5-a reductase which increases testosterone to DHT
- Conversion of terminal hair fibers (larger and pigmented) to villous: less pigmentation and more difficult to visualize (bald scalp and hairline)
- Medical Treatment:
- Minoxidil first line recommended treatment, increases hairs and diameters of hairs (mild to moderate baldness)
- Finasteride inhibits 5-a reductase: converts testosterone into dihydroxytestosterone
- Prevents further hair loss and increasing hair counts
- Hamiltons grading for male pattern baldness
- Female pattern hair loss: androgenetic alopecia in females –> reduction in hair density over the crown and frontal scalp (frontoparietal), relative sparing and preservation of the frontal hairline
- Typically hyperandrogenic–> menstrual irregularities, acne, PCOS!
- Can treat medically with minoxidil and finasteride
- Anagen effluvium: occurs after insult to hair follicle that impairs its mitotic activity (associated with chemotherapy) –> physical exam reveals narrow hair shafts, fractured hair shafts at the site of narrowing
- Growth will restart after cessation of insult
- Telogen effluvium: result stress on body (childbirth, malnutrition, infection, major surgery, extreme mental stress)
- Can lose 90% of hair at this time
- Phenomenon is self limited and hair growth typically recurs
- Do not perform hair transplantation on these patients
- Traction alopecia from tight hairstyles
- Alopecia areata: inflammatory condition thought to result from immune system attacking the hair follicles. Results in nonscarring hair loss, T cell mediated autoimmune condition
- Treated with corticosteroids
- Trichotillomania: an impulse control disorder. Likely associated with change in social situations or acute stress
- Treatment is referral to a psychiatrist to address the underlying condition
- Body Dysmorphic Disorder: an obsessive compulsive disorder related to the preoccupation with perceived appearance of lows for at least an hour a day, repetitive behaviors related to preoccupation, and significant stress
- Remember alopecia from medical causes are less likely to respond to surgical hair restoration
- Treatment:
- Androgenetic alopecia:
- Follicular unit hair transplantation is gold standard –> preserves the natural architecture of the hair units and gives natural results
- Includes 1-4 terminal hair follicles; perifollicular plexi
- Has better growth than single hair micrografts which break up the follicular unit
- Micrograft: 1-2 hairs
- Micrografting is hair follicles with dermal elements: 2-4 hairs with their own associated neurovascular bundles, sebaceous glands, sweat glands, piloerectile muscles surrounded by collagen
- Micrograft survival is 85%- can grown in areas of fibrosis and burn scars and STSG; 95% if unscarred in healthy tissues
- Not as great because it breaks up the follicular unit (see above)
- Minigrafts 3-4 hairs
- Macroscopic hair transplantation: hair plugs with multiple hair follicles, skin, sq, epicranial and subepicranial tissue (can look unnatural)
- Occipital scalp most appropriate donor site- donor dominance –> each hair follicle possesses its own individual pre-determined lifespan
- Occiput has longest lifespan; baldness can occur at frontal, parietal, or vertex regions
- After hair transplantation, hair shaft loss is expected after the first month following implantation as the hair follicles enter into the telogen phase
- Catagen first (grow 3-4mm) –> then enter telogen phase which lasts for 3-4 months (expect almost every hair to fall out) –> finally anagen phase –> hair will grow thicker with time
- Miscellaneous:
- Laser and intense pulsed-light hair reduction: melanin is target chromophore (absorbs wavelengths of 250-1200nm)
- Less effective hair reduction for those with lighter hair
