Craniofacial Muscles

312 J. Park et al.
16.9.5 Treatment
BoNT injection into the orbicularis oculi muscle and other affected muscles is now
the most widely used treatment. In cases with obvious compression at the exit zone of
the facial nerve root or refractory hemifacial spasm, a second line of treatment might
be provided by microvascular decompression (MVD) (Kemp and Reich 2004 ) .
16.9.5.1 BoNT Injection
Since Elston fi rst reported the use of BoNT in the successful treatment of patients
with hemifacial spasm, various publications report that BoNT injections reduce
symptoms in 80–90% of patients with hemifacial spasm (Park et al. 1993 ; Soulayrol
et al. 1993 ; Chen et al. 1996 ; Elston 1986, 1992 ; Jedynak et al. 1993 ) . Periodic
BoNT injection is now considered the treatment of choice for hemifacial spasm.
Interestingly, the effect of BoNT injection tends to persist longer in hemifacial
spasm patients, often 4–6 months, than in essential blepharospasm or Meige’s syndrome
patients.
The dose and injection sites of BoNT should be individualized based on the
symptoms and response to BoNT treatment. The treatment regimen is similar to that
of blepharospasm. BoNT can be injected unilaterally or bilaterally into the eyelids
to reduce iatrogenic facial asymmetry. Additional injections may be given to lower
facial muscles using low doses; however, the orbicularis oris muscle should be
avoided because of the risk of causing problems with eating and drinking. Sometimes
the platysma muscle, whose abnormal contractions are often unsightly, is injected
with higher doses. This muscle is easily identi fi able by asking the patients to clench
their teeth keeping the lips open. As long as the anterior fi bers are not injected, the
injections do not cause swallowing problems.
The typical BoNT/A dose injected into each treatment site is 2.5–5 units, and the
total dose for the fi rst session should range between 17.5 and 45 units. In the second
session, if the patient is not satis fi ed with the duration of ef fi cacy or complains of
persisting spasms, doses can be increased to a maximum of 50 units.
Like in BEB, a relatively low dose of BoNT for hemifacial spasm does not appear
to lead to systemic side effects. Local side effects are often caused by the toxin’s
diffusion to other muscles. In addition to the complications described for BoNT in
the treatment of BEB, excessive lower facial weakening especially the orbicularis
oris muscle is a problem. These adverse effects are not common, and more importantly,
they are short-lived.
16.9.5.2 Oral Medication
Antiseizure or antianxiety drugs were used in the past with limited effectiveness and
poorly tolerated side effects, especially drowsiness. Some oral medications including