Facial Plast Surg 2019; 35(05): 559-560
DOI: 10.1055/s-0039-3399607
Letter to the Editor
Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

Temporalis Muscle Reduction Using Botulinum Toxin Type A for a Desirable Upper Face Circumference

1   Department of Plastic Surgery, GLAD Plastic Surgery Clinic, Daegu, Korea (the Republic of)
› Author Affiliations
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Publication History

Publication Date:
22 October 2019 (online)

The temporal fossa is the concave area below the superior temporal line, which is the part of the temporal bone that forms the floor of the temple. The temporalis muscle originates from the temporal fossa and is surrounded by two fascial planes. The temporalis muscle assists in closing the mouth or keeping it closed and also in chewing. Temporalis muscle hypertrophy can cause prominence and protrusion of the temples with a consequent bulging appearance to the head and the upper face. This condition may also cause twitching of the temples when the mouth is closed or during chewing leading to an undesirable appearance. These issues can be effectively corrected using botulinum toxin (BTX). This study involved the injection of BTX into the temporalis muscle in 20 patients between June and September 2018. Prior to the procedure, the temporalis muscle thickness (TMT) was measured using an ultrasound imaging device (Prosound Alpha7; Hitachi Aloka Medical). TMT was measured at a point located 4 cm horizontally and 5 cm vertically away from the jugale, which was used as the reference point (Point 2 in [Fig. 1]). The upper face circumference was measured using the same reference point. As shown in [Fig. 1], botulinum toxin type A (BTX-A, Botox) (25 units/0.5 mL) was injected at five points using the jugale (an anatomical landmark on the skull that marks the meeting point of the temporal and frontal processes of the zygomatic bone) as the reference point. The TMT and the upper face circumference were measured at the same locations a month after the procedure. The pre- and post-procedure measurements were compared. The TMT was 6.2 ± 2.2 mm before procedure and 2.8 ± 1.7 mm a month after procedure. The upper face circumference was 50.2 ± 9.2 cm before procedure and 49.1 ± 10.7 mm a month after procedure ([Fig. 2]).

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Fig. 1 Botulinum toxin injected into five points using the jugale as the reference point. Temporalis muscle thickness was measured using an ultrasound imaging device at a point 2. The upper face circumference was measured at a point 2 level.
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Fig. 2 Changes in the upper face circumference observed in a 35-year-old man at the following time points: (A) Before the injection; (B) One month after the injection.

BTX-A has been used to treat various conditions including strabismus, blepharospasm, facial wrinkles, cerebral palsy, cervical dystonia, and hyperhidrosis. It is also injected into the temporal fossa to treat chronic migraine. BTX-A injection used to treat chronic migraine must target the sensory neurons in the trigeminocervical complex. The technique described in this study involves a simple direct injection of BTX-A into the temporalis muscle to effectively reduce the TMT. The effect of BTX-A usually lasts over 5 to 6 months, and a similar duration of effect was observed in this study. Although the changes in the TMT and head circumference were minimal, the aforementioned strategy effectively reduced the twitching around the temples and the upper face circumference. Patients presenting with a visibly large or asymmetric temporalis muscle or other symptoms require thorough evaluation of underlying diseases prior to undergoing the aforementioned procedure. Maintaining normal functioning of the temporalis muscle is important. It is necessary to evaluate the risk–benefit ratio of BTX-A administration before injecting this substance for cosmetic purposes. Therefore, it is recommended that the smallest possible dose be used over the longest possible treatment period.