A 18-year-old male was referred to the Oral and Maxillofacial Surgery Department of the State University of Rio de Janeiro for evaluation of bilateral swelling in his temporal and mandibular region. The patient had been aware of the swelling for many years and complained about his facial appearance.

The clinical evaluation showed a marked bilateral swelling involving the temporalis and masseter muscles (Figures 1-3). The bulksgrow to be more prominent during the clenching and the palpation reveals a soft mass at rest and a rigid mass during contraction (Figure 4). There was no pain during palpation or function. The mandibular angles showed significant enlargementresulting in square-jaw appearance. No bruxism, clenching or further parafunctional habit was identified and there were no relevant findings at medical history.

Computed tomography showed a homogeneous enlargement of both masseter and temporal muscles (Figures 5). Panoramic radiograph showed marked enlargement of both mandibular angles (Figure 6).

Treatment was carried out by bilateral resection of the deep portion of the temporalis muscle through coronal approach and surgical recontouring of the mandibular angles with an oscillatory saw through intra-oral approach (Figures 7-9). Caution must be taken to avoid excessive muscular removal at the anterior aspect of the temporal fossae because it could cause a depression in this area. The author’s recommendation is to begin the resection by the posterior region and gradually progress anteriorly. Moreover, proper closure of the detached tissues is critical to produce optimal esthetic results. Suture resuspension of the temporalis fascia to the pericraniumis necessary once the temporalis muscle is detached.

Six months following the procedure, the patient-showed a harmonic facial appearance without evidence of depression, recurrence, dysfunction or asymmetry (Figures 10-14).

The bilateral hypertrophy of the masseter and temporalis muscles is a relative rare condition and its origin is widely discussed. It has previously been referred as the Minotaur Syndrome in some reports because of their harsh facial physiognomy. Bruxism, clenching, and gum chewing are feasible causes of masticatory muscle enlargement. Psychological factors, particularly emotional stress, anxiety, and personality disorders, has been also related to these muscular hyperactivity. Nevertheless, the etiology cannot always be verified [1-8]. In the case reported, we could not identify any parafunctional habit or psychosocial disturbance and for that reason, the muscle

hypertrophy may be regarded as idiopathic.

Traditionally, surgical procedures have beenthe treatment of choice for reduction of masticatory muscle hypertrophy [4,9,10]. The first surgical technique used to treat the masseteric hypertrophy was published in 1947 and consists in partial resection of the muscle bulk through extra-oral approach [9]. Later, additional bony removalat the mandibular angle was advocated [5]. Even though provides good access, the extra-oral approach produces an external scar and presents the risk of damage to the mandibular branch of the facial nerve [5,9,11]. By the time the intraoral approach was first described, in 1959, it was extremely difficult to remove bone at the mandibular angle due to the limited view [12]. With development of surgical saws, specific retractors (e.g. Bauer and Merrill-Lavasseur retractors), and the publication of new surgical techniques, the intraoral approach has become routine [11-14]. Intraoral removal of the mandibular angle without removing any parts of the masseter muscle has then become one of the most commonsurgical technique to treat the masseteric hypertrophy. The disadvantages of this surgical technique are the same presented by most oral surgical procedures performed under general anesthesia (i.e. postoperative haemorrhage, haematoma, edema, infection, anesthesia complications) [11,14].

Few case reports and technical notes of surgical treatment of the temporalis hypertrophy are available [1-3, 15,16]. Fractional resection of the muscle is the most common surgical technique indicated. Partial removal by a modified liposuction has been suggested [15]. The disadvantages of the surgical treatment include the need for coronal flap under general anesthesia and, sometimes, requirement of closed suction drains for 48 hours.

The botulinum toxin A has been used successfully to correct temporalis and masseteric hypertrophy [10]. It is an established drug for the treatment of a variety of neuromuscular disorders and its effect of paralysis and subsequent muscle atrophy has been beneficial to treat this condition [17]. However, these effects are temporary and, for that reason, hypertrophic muscles could regain their original size after few months [10,17,18]. It can be a non-invasive option to treatpatients with muscle hypertrophy, butthis therapy has showed a variable rate of recurrence and lack of long-term follow-up studies.