Treatment of Male Pattern Baldness with
Botulinum Toxin: A Pilot Study
Sir:
We would like to present the results of an openlabel
pilot study using botulinum toxin type A
(Botox; Allergan, Inc., Irvine, Calif.) for the treatment
of androgenetic alopecia. This form of alopecia is believed
to be caused by a genetically predisposed sensitivity
of hair follicles to the toxic effects of dihydrotestosterone,
ametabolite of testosterone. Medical treatment
of androgenetic alopecia has previously only been moderately
effective using systemic drugs such as finasteride,
a 5-reductase inhibitor.1
In this ethically approved study, 50 male subjects aged
between 19 and 57 years with Norwood/Hamilton ratings
of II to IV participated.2 The study was 60 weeks in duration,
with 12 weeks of run-in followed by two treatment
cycles of 24 weeks each. Subjects were injected with 150
units of Botox (5 units per 0.1 ml saline) into the muscles
surrounding the scalp, including frontalis, temporalis,
periauricular, and occipitalis muscles in equally divided
doses over 30 injection sites. The primary outcome measure
was a change in hair count in a fixed 2-cm area using
a method described by Canfield.3 Secondary outcome
measures included hair loss, measured by having subjects
collect loose hair from their pillow with a sticky lint roller,
and subjective efficacy using a validated questionnaire.
Statistical analysis entailed paired t tests of group means.
Forty subjects completed the study, and no adverse
effects were reported. The treatment response rate was
75 percent. Mean hair counts for the entire group
showed a statistically significant (p 0.0001) increase
of 18 percent between baseline and week 48 (Table 1),
similar to the results reported with Propecia (Merck,
Whitehouse Station, N.J.).1 Hair regrowth was objectively
visible in some subjects (Fig. 1). Secondary outcome
measures were also significantly improved. The
reduction in hair loss and increase in hair count did not
show a statistically significant correlation. This suggested
that longer retention of terminal hairs did not
account for the increase in hair count.
Mechanistically, the scalp behaves like a drum skin with
tensioning muscles around the periphery. These muscle
groups—the frontalis, occipitalis, and periauricular muscles
and to a minor degree the temporalis—can create a
“tight” scalp when chronically active. Because the blood
supply to the scalp enters through the periphery, a reduction
in blood flow would be most apparent at the distal
ends of the vessels, specifically, the vertex and frontal
peaks. Areas of the scalp with sparse hair growth have
been shown to be relatively hypoxic, have slow capillary
refill, and to have high levels of dihydrotestosterone.4
Conceptually, Botox “loosens” the scalp, reducing pressure
on the perforating vasculature, thereby increasing
blood flow and oxygen concentration. The enzymatic
conversion of testosterone to dihydrotestosterone is oxygen
dependent. In low-oxygen environments, the conversion
of testosterone to dihydrotestosterone is favored;
whereas in high-oxygen environments, more testosterone
is converted to estradiol.4 Blood flow may therefore be a
primary determinant in follicular health. Strategically
placed Botox injections appear able to indirectly modify
this variable, resulting in reduced hair loss and new hair
growth in some men with androgenetic alopecia.
DOI: 10.1097/PRS.0b013e3181ef816d
Brian J. Freund, D.D.S., M.D.
Marvin Schwartz, D.D.S., M.Sc.
Crown Institute
Pickering, Ontario, Canada
Correspondence to Dr. Freund
49 Main Street South
Uxbridge, Ontario L9P 1J4, Canada
freund@crowninstitute.com
This clinical trial has been registered as “Treatment of
Male Pattern Baldness with Botulinum Toxin” at
http://www.clinicaltrials.gov/ClinicalTrials.gov
Copyright ©2010 by the American Society of Plastic Surgeons with identifier NCT00965640
