cavernous sinus thrombosis ( cst ) , which was first described by dease in 1778 , is a rare disease associated with high mortality and morbidity rates if not treated immediately1 . cst can result from infection of the paranasal sinus or any of the anatomic structures drained by the cavernous sinus , including the mid - face , orbit , and oral cavity2 . deep neck infection containing lateral pharyngeal , pterygomandibular and infratemporal space that patient are presenting symptom of the limited mouth opening can cause infection of the cavernous sinus from the pterygoid plexus3,4 . in this study , we report a patient with cst who initially presented with limited mouth opening . a 55-year - old male visited our department with a chief complaint of limited mouth opening , which began suddenly on august 13 , 2013 . on physical examination , mouth opening was limited to approximately 10 mm , with mild pain on opening . however , body temperature was normal and signs of infection including odynophagia , dyspnea , swelling and tenderness were absent . in the transcranial view of the temporomandibular joint , the translation of both temporomandibular joints was limited.(fig . 2 ) the provisional diagnosis was myospasm of the masticatory muscles ; we prescribed a muscle relaxant and analgesic with physiotherapy . three days later , on august 16 , 2013 , the patient was admitted to the department of ophthalmology complaining of orbital swelling and pain . clinical examination revealed ptosis , proptosis , moderate chemosis , diplopia , and complete ophthalmoplegia of right side.(fig . 3 ) peripheral sensation around the right orbit was good and cranial nerves vii through xii were intact . 4 ) computed tomography ( ct ) and magnetic resonance imaging ( mri ) revealed proptosis and engorgement of the right superior ophthalmic vein that was accompanied by enhancement of retrobulbar tissues and swelling of the lateral pterygoid muscle with pus formation . also , contrast enhancement and dilation indicative of inflammation of the cavernous sinus was noted.(fig . 5 ) the paranasal sinuses , including the ethmoid and maxillary sinus of the ipsilateral side , exhibited mucosal thickening and retention of purulent material.(fig . 6 ) initially , the patient was empirically treated with intravenous cephalosporin . on hospital day 3 , he was prepared for incision and drainage under general anesthesia . a large amount of pus was drained from the lateral pharyngeal , pterygomandibular and infratemporal spaces . the wound was irrigated with copious saline through silastic drains placed in the abscess cavity . repeated ct 10 days after surgery demonstrated improvement in the engorgement of the superior ophthalmic vein and dilation of the cavernous sinus.(fig . 7 ) over the following 11 months , his orbital symptoms resolved completely and his range of mouth opening returned to normal.(fig . the cavernous sinus , which is located to the rear of the optic canal and the superior orbital fissure , is an important structure containing the internal carotid artery and cranial nerve iii , iv , v , and vi . thus , if infection or thrombosis occurs in the cavernous sinus , various symptoms referred to as ' cavernous sinus syndrome ' can appear , including ophthalmoplegia , diplopia and ptosis due to impairment of cranial nerve iii , iv , and vi . involvement of the ophthalmic nerve and maxillary nerve can cause paresthesia around the orbital cavity5 . thus , proptosis and chemosis can cause drain blockages of ophthalmic veins to the cavernous sinus6 . there are also connections between the contralateral cavernous sinus , the intercavernous sinus , facial veins that have not valve , and the pterygoid plexus , which is located very close to the cavernous sinus . given the complex anastomosis of veins with the cavernous sinus , sometimes orbital symptoms appear on both sides , or on the opposite side7,8 . childs and courville11 reported that an odontogenic source was responsible in up to 10% of cases . pavlovich et al.2 presented two cases with different mechanisms : sinusitis and dental infection . in our case , chronic periodontitis of the maxillary posterior teeth and mucosal thickening of the right ethmoidal sinus were observed . because the initial clinical symptom was the limitation of mouth opening , however , the infection was assumed to be from an odontogenic source . mazzeo4 reported that mandibular infections may spread directly to the dural sinuses through the pterygoid plexus . in our case , the patient exhibited symptoms of the proptosis , ptosis , and ophthalmoplesia , accompanied by swelling of the face and neck due to what appeared to be a deep neck infection . the infection was thought to originate around the pterygoid muscle , since trismus preceded orbital symptoms . the route of infection to the cavernous sinus was deemed to be via the pterygoid plexus . numerous causes of superior orbital fissure syndrome including trauma , infection of the cavernous sinus , neoplasm , aneurysm of the internal carotid artery , carotid cavernous fistula or idiopathic etiology have been reported in the literature12,13 . imaging studies such as ct , mri , and magnetic resonance angiography should be employed in patients with findings consistent with a cst . if a vascular lesion of the cavernous sinus is suspected , cerebral angiography may be necessary5 . typical radiographic signs of cst include expansion of the cavernous sinus , convexity of the normally concave lateral wall , irregular filling defects , and asymmetry ; indirect signs include venous obstruction , dilation of the superior ophthalmic vein , proptosis , and thrombus in the veins14,15 . our patients underwent angiography with simultaneous ct and mri to distinguish the clinical signs from the vascular lesion . on angiography , abnormal blood vessels were not observed , but direct and indirect radiographic signs of cst were demonstrated on ct and mri . the treatment of cst includes the use of antibiotics directed at the causative organism and surgery to remove the primary source of infection . the role of steroid and anticoagulant therapy for the treatment of cst remains controversial14 . in summary , cst is a rare disease that can cause life threatening complications . infections of the pterygoid plexus from an odontogenic source can present as trismus , and clinicians should consider the potential for progression to cst . prompt diagnosis and appropriate treatment are essential for preventing serious complications .
in the department of oral and maxillofacial surgery , patients with trismus can be easily identified . 
 if the cause of trismus is infection of the masticatory space near the pterygoid plexus , the possibility of cavernous sinus thrombosis should be considered . 
 we report the case of a patient who presented with limited mouth opening and progressed to cavernous sinus thrombosis , along with a review of the relevant literature .