Hair Restoration

Anatomy

• Two types of hairs
• Terminal (larger, coarse, pigmented)
• Villous (peach fuzz)
• Hair follicles are the layer surrounding and supporting the growth of the hair shaft
• The follicles themselves are found in the subcutaneous layer of the scalp
• Follicular units includes from the skin down:  a sebaceous gland, a stem cell bulge, an arrector pili muscle, and a bulb at the base of the follicle and the neurovascular bundle that enters through the bulb. 
• The just under the skin from the epidermis to the sebaceous unit is called the infundibulum 
• Just under the epidermis is the sebaceous unit. 
• Below that is the bulge which houses the stem cells for the hair  and the arrector pili muscle inserts here 
• At the base is the dermal papilla or bulb. The vascular supply enters the bulb. 

• The shaft of the hair is primarily composed of keratin protein
• Cellular growth extends downward from the bulge, upwardly displacing the prior progeny
• Cellular production of keratin and continual displacement of the cells produces the hair shaft
• Outermost layer called cuticle, (composed of hard keratin), responsible for anchoring hair in place

• Growth  (This is a testing favorite) 
• Anagen phase: active hair growth (lasts 3 years) 
• 90% of scalp hairs involved in this phase
• Catagen phase: is the transition phase at the end of the anagen phase or active growth before the hair falls out. This lasts about 2-3 weeks. During this phase the bulb where the vascular supply enters the hair follicle is destroyed and keratinized which cutes off blood flow.
• Telogen phase: This is the terminal phase of hair growth where the follicle becomes inactive and 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 leading to overall miniaturization of the follicles 
• Inheritance = most common cause of hair loss (X linked dominant)
• Mechanism: increased 5-a reductase leads to conversion of testosterone in the epidermis to dihydroxytestosterone  (DHT) which contributes to increases the telogen phase and conversion of terminal hair fibers to villous leading to less pigmentation and more difficult to visualize (bald scalp and hairline)
• Hamilton’s grading for male pattern baldness
• Vortex, typical, and anterior patterns
• Generally proceeding from hairline receding to crown balding

• Medical Treatment
• Minoxidil (vasodilator) first line recommended treatment
• Increases hairs and diameters of hairs (mild to moderate baldness)
• Finasteride (5-a reductase inhibition) 
• Prevents conversion of testosterone into DHT
• Prevents further hair loss and increases hair counts

• Female pattern alopecia (androgenetic alopecia) 
• 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
• 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

Treatment
Remember alopecia from medical causes are less likely to respond to surgical hair restoration

• 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 transferring 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 grow 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
• Minigrafts: 3-4 hairs
• Macroscopic hair transplantation: hair plugs with multiple hair follicles, skin, sq, epicranial and subepicranial tissue (can look unnatural)

• Donor Site: 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