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the masticator space is defined by the superficial layer of the deep cervical fascia and is composed of a suprazygomatic ( temporal fossa ) portion and a deep nasopharyngeal ( infratemporal fossa ) portion .
the medial part includes the medial pterygoid muscle ; the lateral part contains the masseter muscle , which communicates with the lateral pterygoid muscle1,2 .
similar to temporomandibular disorder ( tmd ) , the initial symptoms are trismus and temporomandibular joint ( tmj ) pain .
orofacial pain and limitation of jaw movement without obvious odontogenic infection commonly lead to the diagnosis of tmd . for an accurate early diagnosis of unusual infection in the masticator space , clinicians need to be aware of case reports of masticator - space abscess ( msa ) without odontogenic origins .
this report describes a case of abscess formation in the masticator space after an acupressure massage .
a 66-year - old male visited the emergency room ( er ) complaining of acute pain in the left cheek and pre - auricular area three days after receiving a facial acupressure massage .
he had tenderness in the left masseter and pain when clenching his teeth , opening his mouth , and moving his mouth laterally .
2 ) he had no history of systemic symptoms or fever . during his first visit to the
after five days , he returned to the er because his pain increased and expanded beyond the left tmj area , decreasing his ability to open his mouth . during his second visit , he was again diagnosed with tmd and discharged with an intravenous analgesic .
two days after his second visit to the er , he presented with severe pain and trismus . at this time , his maximum mouth opening distance had decreased to 25 mm .
he also had tenderness in his left masseter , temporalis , and pre - auricular area .
contrast - enhanced facial computed tomography ( ct ) was performed to identify the pain source .
the ct scan illustrated a 4.21.92.3 cm collection of lobulated fluid with peripheral enhancement ; we suspected an abscess or an organized hematoma in the left masticator space.(fig .
3 ) the patient was admitted to the hospital and administered empirical antibiotics , including intravenous cefoperazone / sulbactam , metronidazole , and aminoglycoside .
needle aspiration was performed to check for an abscess or hematoma in the masticator space and confirmed pus .
4 ) at admission , the following laboratory results were obtained ; erythrocyte sedimentation rate , 59 mm / hour ; c - reactive protein , 3.1 mg / dl ; and white blood cell count , 11,390/l .
additionally , extra - oral incision and drainage were performed to access the temporal space .
after these treatments , his symptoms subsided , and he was discharged without any clinical symptoms .
the final ct scan before discharge revealed that the peripheral enhancing fluid collection in the left masticator space had decreased in size.(fig .
the masticator space lies deep within the skull and consists of a suprazygomatic portion and a nasopharyngeal portion .
the space contains four masticator muscles : the temporalis , the masseter , and the lateral and medial pterygoids .
abscess formation in the masticator space is relatively rare , and odontogenic causes account for most msas .
odontogenic causes include periodontitis , pericoronitis , dental caries , suppurative pulpitis , and post - tooth extraction infection3,4 .
in addition to these common causes , sinusitis5 , sinus fracture6 , posttraumatic osteomyelitis of the maxilla7 , temporomandibular arthroscopy8 , and trauma3,9 can also cause msa4,10 .
typical clinical symptoms of msa include trismus and tenderness in the masticator muscles ; these symptoms are similar to those of tmd .
these symptoms , in the absence of clear odontogenic infection , might lead to a diagnosis of tmd .
matsumura et al.11 reported a patient with a peri - temporomandibular abscess that was a complication of acupuncture treatment and was tentatively diagnosed as tmj arthritis .
first , a patient was diagnosed with tmd after extraction of an upper second molar due to severe periodontitis .
second , a patient who had class iv caries in the lower left second molar and pericoronitis in the lower left third molar tooth was first diagnosed with tmd .
kim et al.9 reported three cases of msa that did not have an odontogenic origin .
of these , one patient had no specific etiology , one had an upper respiratory infection , and the other had experienced trauma to the chin .
these cases demonstrate the difficulty of differential diagnosis between msa and tmd , especially when there is no clear etiology .
the patient in the present report complained of trismus and facial pain after receiving an acupressure massage with particularly strong pressure .
he had not received dental treatment prior to the massage . at his first er visit
the analogical cause of this case was a closed trauma , which is rarely reported in the literature .
goldschmidt et al.12 described a mechanism by which closed trauma can increase the chance of tmj infection .
microorganisms can invade an infection site via three inoculation routes : direct , contiguous , or hematogenous13 .
finally , hematogenous inoculation involves intravenous seeding of microorganisms from a distant primary infectious site9 ; hematogenous inoculation is rare in msa cases14 .
direct inoculation , such as post - extraction complications , is common among msa cases .
closed injury increases the risk of secondary infection through a hematogenous route ; however , the mechanism for this is unclear .
there are three possible etiological explanations for tmj infection : 1 ) hyperemia increases the chance of exposure to microorganisms ; 2 ) damage to local anatomy allows bacteria easy access to the focal site ; and 3 ) hematoma formed by trauma provides a local culture medium for bacterial growth15 .
ct scan and clinical findings also showed no inflammation in the tissue around the masticator space .
there were no systemic predisposing factors , but there were potential local infection sources development of msa .
a panoramic radiography of the infection site showed a fractured root in the right lower first molar with an infectious state .
s. intermedius , a member of the streptococcus milleri group , was detected in the cultured pus sample .
the s. milleri group constitutes normal flora of the mouth that have the ability to cause suppurative infection16 . of the s.
milleri group members , s. intermedius is frequently isolated from dental plaque17 and is most likely to be associated with head and neck infection18 .
another study found that abscesses caused by s. intermedius infection are associated with hematogenous spread and deep - tissue infection19 .
based on these findings , it is possible that a blunt trauma to the head caused the hematoma within the masticator space , allowing s. intermedius to spread hematogenously from an intra - oral primary infection source
. however , the exact source or route of the infection was not confirmed , and more research is needed .
as with other facial abscess , antibiotic therapy combined with surgical drainage successfully resolved the msa . to obtain optimum results , appropriate antibiotic selection based on culture sensitivity and a specific early diagnosis via ct or magnetic resonance imaging are needed .
typical symptoms of msas , which are similar to those of tmd , include trismus and pain in the masticator muscles .
the clinical symptoms might mislead clinicians to a wrong diagnosis , especially when the etiology is unusual .
delayed treatment of msa increases the infection extent and severity . to prevent this , clinicians must bear in mind that rarely reported etiologies , like facial massage , are capable of initiating an infection .
clinical features of masticator - space abscess ( msa ) are very similar to those of parotitis or temporomandibular disorder ( tmd ) , making early differential diagnosis difficult . 
 local causes of msa include nerve block anesthesia , infection after tooth extraction , and trauma to the temporomandibular joint ( tmj ) ; the systemic cause is immunodeficiency . 
 odontogenic causes account for most etiologies , but there are also unusual causes of msa . 
 a 66-year - old male patient visited the emergency room ( er ) presenting with left - side tmj pain three days after receiving an acupressure massage . 
 he was tentatively diagnosed with conventional post - trauma tmd and discharged with medication . 
 however , the patient returned to the er with increased pain . at this time , his tmd diagnosis was confirmed . 
 he made a third visit to the er during which facial computed tomographic ( ct ) images were taken . 
 ct readings identified an abscess or hematoma in the left masticator space . 
 after hospitalizing the patient , needle aspiration confirmed pus in the infratemporal and temporal fossa . 
 antibiotics were administered , and the abscess was drained through an incision made by the attending physician . 
 the patient 's symptoms decreased , and he was discharged .