Oral health

Masticator Space Abscess Secondary to Oral Trauma

Rajkumar Agarwal, MD, and Usha Sethuraman, MD


Case In Point
An Intriguing Diagnosis

A 7-year-old boy presented to the emergency department with pain and swelling of the right side of his face and difficulty in opening his mouth. Five days before presentation, he had accidentally stuck his inner right cheek with a corndog skewer. This was followed by pain and difficulty in opening his mouth the next morning, with drooling and decreased oral intake. The symptoms progressively worsened over the next few days, and he started to develop swelling over the right face.

He had an upper respiratory tract infection with congestion, runny nose, and cough, which was improving. There was no history of fever. There was no vomiting, diarrhea, otitis, or systemic symptoms. He had no significant past medical or surgical illness, his immunizations were up to date, and the family history was noncontributory.

On physical examination, the patient was awake and alert. His temperature was 37.7°C (99.9°F), heart rate was 130 beats per minute, respiratory rate was 24 breaths per minute, blood pressure was 114/58 mm Hg, and arterial oxygen saturation via pulse oximetry was 97% on room air. He spiked a fever of 38.6°C (101.5°F) within a few hours of presentation. He had dry mucous membranes and was clinically mildly dehydrated. He appeared very uncomfortable because of the pain.

pterygoid muscle

Axial computed tomography image depicting the pus collection in the medial pterygoid muscle (arrow). Also present are small pus pockets in the right pharyngeal mucosal space and swelling of the medial pterygoid muscle on the right side.

A subtle asymmetry was noted over the face with swelling of the right jaw area. An area of induration could be palpated over the right angle of the jaw, with exquisite tenderness all around it. Intraoral examination, limited due to trismus, showed swelling of the cheek mucosa with some mucopurulent discharge. Anterior and posterior cervical lymph nodes were enlarged and tender on palpation. The rest of the systemic examination was unremarkable.

On laboratory evaluation, the white blood cell count was 10.3 × 109/L with 69% neutrophils, 21% lymphocytes, and 10% monocytes, and the C-reactive protein level was 9.51 mg/L. The differential diagnoses included a dental or a peritonsillar abscess. The patient began treatment with intravenous fluids and underwent a computed tomography (CT) scan of the maxillofacial area, which showed an enlarged right medial pterygoid muscle with multiple small abscesses (masticator space abscess), the largest measuring 2.2 × 0.8 × 0.7 cm (Figures). The enlarged muscle was in communication with multiple small abscesses in the right pharyngeal mucosal space, the largest measuring 1.2 × 1.5 × 1.4 cm.

coronal ct

Coronal CT image depicting the pus collection in the medial pterygoid muscle (arrow).

The patient began therapy with ceftriaxone and clindamycin and was scheduled to undergo drainage in the operating room the next morning. Under general anesthesia during drainage, intraoral examination showed a small puncture wound approximately 2.5 cm deep in the right oral cavity, just superior and lateral to the right tonsil. There was no noticeable pus expressed during the procedure. Swabs from wound were sent for culturing, and the wound was irrigated. Since the wound was open and had been drained of all the pus, no further intervention was deemed necessary.

Postoperatively, the patient was continued the antibiotic and pain management regimen. Culture results from the pus showed a polymicrobial growth (Streptococcus viridans, micrococci, group F streptococci, and rare Neisseria species—neither N meningitidis nor N gonorrhoea). On day 4 of admission, the patient had improvement of symptoms, did not require breakthrough pain medication, and was able to eat well. He was discharged home with a 14-day course of cephalexin and clindamycin.


The masticator space is a distinct deep facial space bounded by the superficial layer of the deep cervical fascia. It contains the ramus and posterior body of the mandible, and the 4 muscles of mastication: the medial and lateral pterygoid muscles, the temporalis muscle, and the masseter muscle. The masticator space is separated from adjacent face and neck spaces by a superficial layer of deep cervical fascia on all sides except superiorly, where it freely communicates with the temporal space. The spaces adjacent to the masticator space are the buccal space (anterior), parotid space (posterior), parapharyngeal space (medial) and the sublingual and submandibular spaces (inferior).

A masticator space abscess most likely develops as a complication of an odontogenic infection.1 Rare cases result from hematogenous causes, local spread, or unknown causes.2 Our case resulted from local trauma, which has not been reported in the literature as a cause of masticator space infection in a child.

Clinical examination of the masticator space is difficult, because it is deep and not easily accessible. In a prospective study of patients with severe odontogenic infections, trismus and dysphagia were reported as the presenting symptoms in most patients with masticator space abscess.3 Affected patients complain of facial pain, swelling, and inability to open the mouth, symptoms that can complicate clinical evaluation of the masticator space. Overt signs of infection could be absent in deep masticator space infection.4 In some cases, the presence of severe trismus without overt signs of infection such as fever and leukocytosis has led to cases of masticator space abscess being wrongly diagnosed as a temporomandibular joint disorder.4 Although our patient was afebrile on presentation, his fever spiked soon after admission.

Because trismus can make clinical evaluation difficult, imaging has an important role in the diagnosis and assessment of masticator space infection.1 Computed tomography (CT) is particularly useful in emergency cases, not only for diagnosis but also for formulating the initial therapy. The presence of inflammatory changes in the form of cellulitis mandates medical management, unlike the presence of pus collection, which might require surgical drainage.

Masticator space abscess often involves other facial and deep neck spaces with extension into the parapharyngeal, submasseteric, and parotid spaces and also to the base of the skull and the temporal spaces.1,2 Imaging thus helps determine the route for surgical drainage if it is required. Additionally, CT can reveal signs of osteomyelitis, which necessitates subperiosteal drainage. Magnetic resonance imaging sometimes can reveal early signs of osteomyelitis that otherwise might be missed on a CT scan.1 In the our case, local signs of an abscess and purulent discharge were seen at the buccal mucosa. Nevertheless, the patient’s trismus, largely limited the physical examination, and the diagnosis was made based on the CT scan.

Although extraoral drainage traditionally is required for masticator space abscesses that spread to other spaces, intraoral drainage also has been done in infections confined to the masticator space.4 In our patient, intraoral drainage was selected because of the presence of a puncture wound and the lack of spread of infection to the deep spaces of the neck. The presence of the wound track might have helped drainage of the abscess and restricted its spread to other areas.

The organisms responsible for masticator space abscesses primarily are mixed aerobic and anaerobic organisms, most commonly α-hemolytic streptococci, Peptostreptococcus species, and Bacteroides species.3,5 The initial choice of antibiotic therapy in our patient’s case was a combination of ceftriaxone and clindamycin. For masticator space infections arising from dental complications, clindamycin and penicillin have been used. However, the abscess in this particular patient had developed as a complication of trauma and was at high risk for polymicrobial growth; therefore, empiric broad-spectrum coverage was considered the most appropriate approach.

Although infections of the facial spaces most commonly are odontogenic, they still might arise from other causes such as trauma. In the event of local trauma and the presence of other clinical features of infection, it is imperative to consider the possibility of abscess in one of the deeper structures. CT scan has an important role in detecting infections of the soft tissue of the face, especially in the presence of trismus.


1. Schuknecht B, Stergiou G, Graetz K. Masticator space abscess derived from odontogenic infection: imaging manifestation and pathways of extension depicted by CT and MR in 30 patients. Eur Radiol. 2008;18:1972-1979.

2. Hardin CW, Harnsberger HR, Osborn AG, Doxey GP, Davis RK, Nyberg DA. Infection and tumor of the masticator space: CT evaluation. Radiology. 1985;157(2):413-417.

3. Flynn TR, Shanti RM, Levi MH, Adamo AK, Kraut RA, Treiger N. Severe odontogenic infections, part 1: prospective report. J Oral Maxillofac Surg. 2006;64(7):1093-1103.

4. Hasegawa T, Shibuya Y, Kuroki S, et al. Two cases of masticator space abscess initially diagnosed as temporomandibular joint disorder. Kobe J Med Sci. 2008;54(3):E163-E168.

5. Krishnan V, Johnson JV, Helfrick JF. Management of maxillofacial infections: a review of 50 cases. J Oral Maxillofac Surg. 1993;51(8):868-874.