Radiographic Analysis of the Cervical Spine in Patients With Retro-Odontoid Pseudotumors

Abstract

Retro-odontoid pseudotumors were not always associated with radiographic atlantoaxial instability. Our data indicate that extensive OALL and ankylosis of the adjacent segments are risk factors for the formation of the pseudotumor. Retro-odontoid pseudotumors may develop as an "adjacent segment disease" after altered biomechanics of the cervical spine, especially those in the adjacent segments. Posterior fusion was effective even in cases without radiographic atlantoaxial instability.

C1 laminectomy for retro-odontoid pseudotumor without atlantoaxial subluxation: review of seven consecutive cases

“…In our study no patient had atlantoaxial subluxation. However, five of the seven patients had risk factors which Chikuda et al [10] reported, ankylosis of the segments adjacent to the atlantoaxial joint and cervical kyphosis below the atlantoaxial joint. The results of our study support Chikuda's hypothesis.…”

“…The pathomechanism for pseudotumor formation has been postulated to the result of atlantoaxial instability that induces repeated tears and subsequent hypertrophy of the transverse ligaments [8,20]. Chikuda et al [10] found that retro-odontoid pseudotumor was not necessarily associated with overt atlantoaxial instability, but that excessive stress concentration to the atlantoaxial complex caused by altered biomechanics of the cervical spine due to OALL, OPLL and cervical kyphosis may cause repeated damage to the transverse ligament. In our study no patient had atlantoaxial subluxation.…”

“…Because previous reports identified retro-odontoid pseudotumor as a reactive mass caused by mechanical stress due to atlantoaxial instability or ankylosis in the mid and lower cervical spine, posterior fusion, such as O-C2 fusion or O-C4 fusion, has been considered to be the appropriate procedure for preventing further progression of the pathology. Additionally, posterior fusion resulted in regression of the retro-odontoid pseudotumor and improvement of neurological deficits [8,10].…”

“…Neurological and symptomatic improvement can be expected following posterior fusion [8,11,12]. Furthermore, spontaneous regression of pseudotumors following posterior fusion has been reported [10,13]. On the other hand, Suetsuna et al [14] reported spontaneous regression of retro-odontoid pseudotumors following C1 laminoplasty.…”

“…However, retro-odontoid pseudotumors not associated with any apparent atlantoaxial (AAS) subluxation are occasionally encountered [9]. Ten cases of retro-odontoid pseudotumor without AAS were reported by Chikuda et al They found that extensive ossification of the anterior longitudinal ligament (OALL) and ankylosis of the adjacent segments were risk factors for the formation of pseudotumors [10]. More specifically, the altered biomechanics of the upper cervical spine due to ankylosis caused by OALL, ossification of the posterior longitudinal ligament (OPLL) and cervical kyphosis might load mechanical stress on the atlantoaxial joint, leading to development of a retro-odontoid pseudotumor without atlantoaxial subluxation.…”