an atlanto - axial synovial cyst is very rare . since the first report of this lesion by onofrio and mih1 ) in 1988 , to our knowledge
. however , the current report described a patient with a large hemorrhagic cystic mass which was seen around prevertebral space of the atlantoaxial joint on the left side and the obstruction of the nasopharyngeal cavity on cervical magnetic resonance image ( mri ) . we report a symptomatic case associated with rheumatoid atlanto - axial subluxation , which regressed after the surgical management .
a 72-year - old woman presented with sudden severe headache in her left occipital area with dyspnea .
a laboratory examination of the patient 's blood revealed no remarkable abnormality indicative of inflammation , but high - titer of rheumatoid factor ( 95.9 iu / ml ) .
seven months ago before visiting to our department , she checked brain mri due to sudden attack of severe headache on left occipital area , which revealed non - specific lesion except rheumatoid pannus with small prevertebral cyst of c1 - 2 junction ( fig .
, there was a large hemorrhagic cystic mass around prevertebral space of the atlanto - axial joint on the left side , obstructing the nasopharyngeal cavity on cervical mri ( fig .
the cystic mass was connected to atlanto - axial joint capsule on axial view of computed tomography ( ct ) .
multiple bony erosion , rheumatoid atlanto - axial instability including left tilted c1 - 2 subluxation and cranial settling were demonstrated .
and there were loss of lordosis and retrolisthesis in c 3 - 4 , 4 - 5 ( fig .
3 ) . in the first operation stage , considering patient 's dyspnea , aspiration of the cystic lesion was performed via transoral approach with otolaryngology surgeon ( fig .
after 0.5 cm - sized mucosal incision on left side oropharyngeal wall , residual material of the cyst was squeezed by forceps and removed by suction tools . in the second operation stage , there were rheumatoid atlanto - axial instability and retrolisthesis in c 3 - 4 , 4 - 5 , so it was followed by posterior occipito - cervical fusion that connected from occiput to c5 , using vertex screw & rod system and iliac bone graft ( fig . 5 ) .
the patient was tolerable on her postoperative course and showed good respiration and relieved headache .
cervical synovial cysts are rare and located at the c1 - 2 junction or lower cervical spine . only 24 cases of synovial cysts of the c1 - 2 junction have been reported in the literature5 ) . moreover ,
the pathogenesis of spinal synovial cysts remains unclear but is thought to be attributable to degenerative changes of the facet joints or excessive joint motion2,3,5,7 ) .
it revealed multiple bony erosions and a large pannus formation of c1 - 2 junction on this case .
this patient also showed atlanto - axial instability caused by rheumatoid arthritis , such as left tilted antlanto - axial subluxation and basilar impression .
the atlantoaxial articulation is a true synovial joint and is responsible for a large proportion of normal cervical mobility .
the etiology of articular cysts is unclear , but they are assumed to be degenerative because minor chronic damage to articular surfaces produces a reactive proliferation of synovium or fibrocartilage that includes loculated collections of mucinous fluid .
so , we hypothesized that hemorrhagic event was developed as a result of microtrauma caused by rheumatoid atlantoaxial instability .
it is known that the higher titer of rheumatoid factor , the more destructive manifestations of joint occur1 ) .
the patient was in the controlled state in serologic inflammatory marker , such as esr(erythrocyte sedimentation rate ) and crp ( c - reactive protein ) .
however , the high titer of rheumatoid factor , in spite of long standing medication of rheumatology , was related factor of progressive destruction of joints .
we report a rare case of large hemorrhagic cyst on prevertebral space of left side c1 - 2 area associated with rheumatoid arthritis causing airway obstruction and left occipital pain , successfully managed anterior and posterior approach .
we suggest repeated microtrauma due to atlanto - axial subluxation associated with rheumatoid arthritis as a main cause of hemorrhagic event on the cyst .
 synovial cyst on prevertebral space of c1 - 2 joint is rare but may be associated hemorrhagic event . 
 we describe a case of a 72-year - old woman who presented with sudden severe headache in her left occipital area with dyspnea . 
 she had rheumatoid arthritis for 14-years . 
 large hemorrhagic cystic mass was seen around prevertebral space of the atlantoaxial joint on the left side on cervical mri ( magnetic resonance image ) and it obstructed the nasopharyngeal cavity . 
 aspiration of the cystic lesion was performed via transoral approach , followed by posterior occipito - cervical fusion . 
 the specimen was xanthochromic , suggesting old hemorrhage . 
 the patient was tolerable on her postoperative course and showed good respiration and relieved headache . 
 we suggest that repeated microtrauma due to atalantoaxial subluxation associated with rheumatoid arthritis as a main cause of hemorrhagic event on the cyst . 
INTRODUCTION
CASE REPORT
DISCUSSION
CONCLUSION