cervical spine spondylolysis is the most commonly caused by high energy trauma to the upper cervical spine in the form of a " hangman 's " fracture of c2 vertebrae7 ) . however , congenital cervical spine spondylolysis is discovered by incidental radiographic finding , neck pain after minor trauma , a clunking or clicking neck and rarely neurologic compromise1 - 3,6,8,10 ) . this rare condition potentially signifies an unstable cervical spine . we will report a case of congenital isthmic defect of cervical spine and describe a cause of cervical isthmic defect , diagnostic radiographic finding and appropriate treatment of cervical spondylolysis or spondylolithesis a 23-year - old female suffered from a hyperextension injury to cervical spine after a traffic accident . following this injury , she experienced mild to moderate degree of nuchal and back pain . plain radiograph of the cervical spine showed bilateral pars interarticularis defect at the c6 level with cleft - bow - tie configuration , hypoplastic pedicle , grade i spondylolisthesis of c6 on c7 and spinal bifida at c6 ( fig . 1 ) . computed tomography of the c6 vertebrae showed bilateral corticated defects of the c6 articular mass , bilateral hypoplastic pedicles , lamina and spinal bifida of c6 and apparent neural foraminal enlargement at c6 - 7 ( fig . the magnetic resonance image of spine showed grade i spondylolisthesis c6 - 7 , degenerative change of c6 - 7 disc and acute compressed fracture at 4 thoracic vertebrae . she was subjected to controlled flexion - extension views of the cervical spine , which confirmed stability of the segment with less than 10 degrees of anterior angulations ( fig . she was treated with the semihard - orthosis brace immobilization for 8 weeks followed by repeated lateral cervical spine radiography . after 10 months to injury , she was symptom free with full range of motion of cervical spine . reported cervical spondylolysis are incidentally discovered except the " hangman 's " fracture1 - 3,6,8,9,10 ) . cervical spondylolysis is less prevalent than lumbar spondylolysis , only about 100 cases have been reported in the literature worldwide , mainly in adults1 ) . there is often no clear uniform mechanism of the injury , or the force causing the injury is often not strong enough to explain all of observed cervical anomaly . incidentally discovered cervical spondylolysis could combine with another anomaly like spinal bifida , dysplastic lamina or transverse process ( table 1 ) . the etiology of cervical spondylolysis is unknown , but congenital basis is asserted because no history of trauma is elicited in the majority of cases2,3,5 ) . another basis is nonunion of vertebra after birth , infantile fracture or repetitive microtrauma1,6,9 ) . the vertebral body will articulate with the vertebral arch at the neurocentral joints at birth , with fusion occurring between the ages of 5 and 8 years5,7 ) . if congenital defect is invalid , problem of ossification or chondrification might occur during vulnerable period from birth to fusion at neurocentral joint . proposed that this condition was caused by repetitive microtrauma resulting in stress fractures to the pars region similar to the process proposed in lumbar spondylolysis5 ) . they further proposed c6 to be the commonest site to be affected as , this being a transitional vertebra , it was subjected to stress more often . some of these theories can be put together and it may be suggested that a dysplastic spine is more susceptible to trauma or stress and leads to spondylolysis6 ) . we could clarify that our case was associated with congenital basis because of well corticated margin in defected area combined with another congenital lesion and no trauma history . congenital cervical spondylolysis , an embryologic developmental defect , occurs the most commonly at c61,2,6,9,10 ) . the overall frequency is unknown , and most cases are detected incidentally ( table 1 ) conventional radiolographic findings of cervical spondylolysis included a deformed articular mass , hypoplastic or dysplastic pedicle , spinal bifida and anterolisthesis1 - 3,6,8 - 10 ) . the computed tomography is the most useful image modality , because it shows the exact bony structures and three dimensional images . the magnetic resonance image can aid identification of combined soft tissue damage , cord injury and bony contusion at trauma lesion . however , magnetic resonance image is not useful for diagnosis of cervical spondylolysis . in our case , cervical magnetic resonance image showed acute compressive fracture at 4 thoracic vertebrae and degenerative disc change . misdiagnosis occurred for traumatic unilateral interfacet dislocation , a chronic nonunited articular mass fracture or congenitally absent pedicle4,10 ) . for example , unilateral interfacet dislocation is characterized by spondylolisthesis greater than 3 mm , rotation without a superimposed articular mass , and misalignment of the spinous process4 ) . the cervical spondylolysis can cause variable symptoms like neck pain , muscle spasm or neurologic deficit . symptomatic cervical spondylolysis need adequate treatment because previously existing cervical spondylolysis is vulnerable to trauma . the treatment of cervical spondylolysis depends on instability . if the cervical spine is stable , conservative approach is desirable for treating symptomatic cervical spondylolysis . our case was stable but needed hard orthosis because of the fracture of 4 thoracic vertebrae .
we report a case of rare cervical isthmic spondylolisthesis of c6 - 7 combined occult spinal bifida at c6 , and review the radiologic finding , different diagnosis and treatment . a 23-year old female presented nuchal , back pain after traffic accident . 
 radiologic finding showed the 6th cervical isthmic defect , spondylolisthesis and dysplasia . 
 the patient was conservatively treated about 8 weeks , and 10 months after injury , she was symptom free with full range of motion of cervical spine and she was followed up . 
 cervical spondylolysis is a very rare condition . 
 this clinical importance is vulnerable to trauma . for whatever reasons , 
 symptomatic patients need to be treated by conservative or surgical option .