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Varied clinical presentation of os odontoideum a case report.


Os odontoideum is the most common anomaly of the odontoid process. (1) The term os odontoideum was first coined by Giacomini in 1886 and is defined as "... an ossicle with smooth circumferential cortical margins and no osseous continuity with the body of C2". (2) Debate within the literature continues regarding the congenital or traumatic etiology of os odontoideum. Regardless of etiology, both types of os odontoideum can lead to instability of C1 on C2, placing the spinal cord at significant risk of injury. (3) This paper presents a case of os odontoideum in a fiftyfour year old male presenting to a chiropractic clinic with longstanding neck pain. Clinical presentations, diagnosis and management are discussed. Manual therapists treating neck complaints need to be aware of this anomaly considering that instability of the atlanto-axial joint secondary to an os odontoideum can have serious consequences.

Case Presentation

A fifty-four year old male presented to a chiropractic clinic with a longstanding complaint of a stiff and achy neck and upper back without headache. The neck pain was focused primarily on the left and the patient reported significant right rotational restriction, especially with shoulder checking. The patient reported one previous episode of neck pain in 2009 and two previous motor vehicle accidents; a roll-over accident in the 1970s and a minor accident in the 1980s. No medical attention was sought following either accident.

On examination, an alordotic cervical curve was present with mild anterior head carriage. Upper limb neurological screening was unremarkable bilaterally (upper deep tendon reflexes, muscle testing and sensory examination). Active and passive cervical range of motion was globally limited with pain whereas resisted cervical spine range of motion was unremarkable and graded 5/5. Static and motion palpation demonstrated bilateral paraspinal muscle tension and tenderness as well as global segmental restrictions from C3-7. The differential diagnoses after the history and physical exam included Grade II mechanical neck pain, cervical spine degenerative disc disease and cervical spondylosis.

The patient brought his cervical radiographs (AP, lateral) which showed moderate degenerative disc disease at the C5-C7 segments. The patient had additional radiographic views ordered in 2009 by his previous chiropractor along with a MRI ordered by his medical doctor for his prior neck complaint. A request was sent to obtain the cervical spine radiographs and the MRI report. That day cervical long axis distraction mobilizations and cervical spine manipulation were administered with consent and no adverse effects were reported.

Several days later the requested radiographic and MRI reports were received by the treating chiropractor. The radiographic report, read by a chiropractic radiologist, gave the following information "Dystopic os odontoideum with dynamic stenosis at C1-C2 and lateral hypermobility with secondary degenerative joint disease of the left lateral atlanto-axial joint. Dynamic narrowing of the spinal cord space from 16.8 mm in extension to 15.3 mm in flexion". (See figure 1) The MRI report stated the following "There is a remote fracture noted at the dens of C2. There is still some edema within this area. Suggest clinical correlation. If the fracture is recent then a CT scan of this area will be helpful to further assess the extent of healing at the fracture line".


The patient returned to the chiropractic office a few days later and the results of the imaging reports were reviewed. The patient mentioned that the results of the 2009 imaging studies were never discussed with him. The patient was educated on the os odontoideum condition, advised that cervical spine manipulation was no longer a treatment option, and referred back to his medical doctor for further evaluation and surgical considerations. The patient was not seen by an orthopaedic specialist as he was not interested in surgical intervention.


The exact incidence and prevalence of os odontoideum is unclear within the literature as many cases remain clinically silent. Considering the issues with instability and the risk of morbidity which arise in patients with os odontoideum, it is imperative that manual therapists are aware of potential clinical indicators of the condition. The clinical presentation of os odontoideum is quite varied within the literature and can differ significantly between patients. Although os odontoideum cannot be diagnosed without the use of imaging, the following clinical presentations have been noted



Many patients with os odontoideum are often delayed in their diagnosis or the os odontoideum is found as an incidental finding on radiographs because patients are often asymptomatic. (3) The majority of asymptomatic individuals are neurologically intact and only some present with incidentally discovered atlanto-axial instability. (4)

Neck Pain

Neck pain is one of the most common symptoms in patients with a diagnosed os odontoideum. In a review of seventy eight patients identified with an os odontoideum, neck pain was the most commonly reported symptom in 64% of patients. (2) It has also been reported that in some cases, pain in the occipital or cervical region may be the only symptom. (4) However, with an already high prevalence of neck pain in the general population and a lack of prospective studies, the link between neck pain and the presence of os odontoideum is a difficult association to make.


Headaches, a common condition treated by manual therapists, have been reported as a symptom of os odontoideum in the literature however not to a great extent and mostly within case reports. In a 2011 review of seventy eight patients with os odontoideum, only 2 patients presented with headaches. (2) The estimated lifetime prevalence of headache (including all headache types) has been reported to be between 93% and 98%. (5) Given such a high prevalence of headache in the general population, the association between os odontoideum and headache is unclear.

History of Trauma

The association between os odontoideum and previous history of trauma is debated within the literature. However, a large portion of evidence currently points towards a traumatic etiology in the majority of reported cases. (4) There is a proposed theory that trauma may be an instigating event for the development of symptoms from a preexisting os odontoideum. In a case series by Spierings and Braakman, approximately 43% of patients presented with a history of trauma. (6) Other authors maintain that previous traumatic events may not be responsible for an os odontoideum. These authors have proposed that a traumatic event could result in a soft tissue injury that may increase the degree of instability and thus cause a pre-existing os odontoideum to become symptomatic. (7) The effect trauma has on developing or exasperating a pre-existing os odontoideum is still unknown. However, given the amount of evidence pointing towards a traumatic etiology, inquiring about previous trauma during a patient history may offer valuable information to warrant further investigation.

Congenital Syndromes

Os odontoideum are commonly associated with a number of congenital syndromes. It is important to keep this differential in mind in patients presenting with Down syndrome, Klippel-Feil syndrome, Morquio's disease, multiple epiphyseal dysplasia, pseudoachondroplasia, achondroplasia, Larson syndrome, and chondrodystrophia calcificans. (4) It is proposed that ligament hyperlaxity and incomplete ossification of the odontoid process in these syndromes may predispose individuals to the development of a traumatic os odontoideum. (4)

Neurological Signs and Symptoms

Patients with os odontoideum can be asymptomatic however, many have also presented with a wide array of neurological symptoms. In a review of seventy eight patients with os odontoideum, eighteen patients (23%) had neurological signs or symptoms at presentation and an additional fifteen (19%) had a history of intermittent or prior neurological symptoms. (2,8) Patients with an os odontoideum may have abnormal atlanto-axial motion anteriorly, posteriorly or in both directions. Flexion of the cervical spine can cause anterior translation of C-1 leading to impingement on the dorsal aspect of the spinal cord whereas extension can cause the anterior ring of C1 and ossicle to impinge on the ventral aspect of the cord. (8) Therefore, a wide variety of neurological signs and symptoms may present in patients with os odontoideum ranging from subtle transient myelopathy to more explicit signs such as tetraplegia, paresis, bulbar sign and central cord syndrome. (4)


The proper management of os odontoideum still remains uncertain due to the fact that it is a rare condition. The majority of the literature consists of case reports and case series making it difficult to offer evidence-based guidelines and practice recommendations. Also, there remains a gap in knowledge of the long term natural history of untreated os odontoideum. The majority of reports indicate that patients tend to remain asymptomatic after a follow-up between one and seven years. (2) However, one study reported that symptomatic atlanto-axial instability can develop over time, even after a diagnosis of a 'stable' os odontoideum is made. (9)

The following recommendation has been given for patients with incidental os odontoideum "Patients with os odontoideum, either with or without C1-2 instability, who have neither symptoms nor neurological signs may be managed with clinical and radiographic surveillance. (10) However, other authors have advocated for surgical intervention for all patients with radiographically unstable os odontoideum, whether symptomatic or not. (2) Although there are inconsistencies within the literature and a lack of high quality evidence, Table 1 lists recommendations that have been noted within the literature.


There remains a lack of consensus within the literature regarding best practices for os odontoideum and the long term prognosis is unknown. With this uncertainty and the risk of cervical instability, it is imperative that health care professionals, particularly manual therapists who treat neck pain patients, become familiar with the signs and symptoms of potential cervical instability. These health care providers must also remain diligent in their patient histories, physical exams, and imaging studies. This case highlights the importance of following up on imaging studies to rule out diagnoses and not simply relying on the fact that they were performed. Whether or not surgical fixation is warranted is outside the scope of practice for manual therapists. However, the role of manual therapists should be to recognize signs and symptoms of os odontoideum, refer patients for a medical opinion and surgical consultation, and properly educate their patients on the nature and potential risks of their condition.


(1.) Fielding JW, Hensinger RN, Hawkins RJ. Os Odontoideum. J Bone Jt Surg Am. 1980;62(3)376-83.

(2.) Klimo P, Kan P, Rao G, Apfelbaum R, Brockmeyer D.

Os odontoideum presentation, diagnosis, and treatment in a series of 78 patients. J Neurosurg Spine. 2008;9(4)332-42.

(3.) Choit RL, Jamieson DH, Reilly CW. Os odontoideum a significant radiographic finding. Pediatric Radiology. 2005;35(8)803-7.

(4.) Arvin B, Fournier-Gosselin MP, Fehlings MG. Os odontoideum etiology and surgical management. Neurosurgery. 2010;66(3 Suppl)22-31.

(5.) Mintken PE, Metrick L, Flynn TW. Upper cervical ligament testing in a patient with os odontoideum presenting with headaches. J Ortho Sports Phys Ther. 2008;38(8)465-75.

(6.) Spierings EL, Braakman R. The management of os odontoideum. Analysis of 37 cases. J Bone Jt Surg Br. 1982;64(4)422-8.

(7.) Brecknell JE, Malham GM. Os odontoideum report of three cases. J Clinical Neuroscience. 2008;15(3)295-301.

(8.) Klimo P, Coon V, Brockmeyer D. Incidental os odontoideum current management strategies. Neurosurgical Focus. 2011;31(6)E10.

(9.) Clements WD, Mezue W, Mathew B. Os odontoideum-congenital or acquired?--that's not the question. Injury. 1995;26(9)640-2.

(10.) Hadley M. Os odontoideum. Neurosurgery. 2002;50(3 Suppl)S148-55.

(11.) Anderson-Peacock E, Blouin J-S, Bryans R, Danis N, Furlan A, Marcoux H, et al. Chiropractic clinical practice guideline evidence-based treatment of adult neck pain not due to whiplash. J Can Chiropr Assoc. 2005;49(3)158.

(12.) Qureshi MA, Afzal W, Malik AS, Ullah JS, Aebi M. Os-odontoideum leading to atlanto-axial instability--report of surgery in four cases. J Pakistan Med Assoc. 2008;58(11)640-2.

(13.) Wang S, Wang C. Acquired os odontoideum a case report and literature review. Child's Nervous System. 2012 ;28(2)315-9.

Karen Chrobak, (Hons) B.H.Sc, DC (a,b)

Ryan Larson, BSc, DC (c)

Paula J. Stern, BSc, DC, FCCS(C) (a,d)

(a) Canadian Memorial Chiropractic College, 6100 Leslie Street, Toronto, Canada

(b) Division of Graduate Studies, Clinical Sciences, Canadian Memorial Chiropractic College, 6100 Leslie Street, Toronto, Ontario, Canada

(c) Private Practice, 537 Frederick St, Kitchener Ontario Canada

(d) Director, Graduate Education, Canadian Memorial Chiropractic College, 6100 Leslie Street, Toronto, Ontario, Canada Disclaimers None

Patient consent was obtained for the use of clinical information and imaging with respect to this case report.

Sources of financial support none

Corresponding Author Dr. Karen L. Chrobak

T (416) 482-2340 ext. 286 F (416) 482-2560

6100 Leslie Street, Toronto, Ontario, Canada M2H 3J1
Table 1.

Recommendations for os odontoideum

* A detailed history, physical exam and
neurological exam should be completed on all neck
pain patients to look for clinical indicators
of instability and detect subtle myelopathies. (3)

* If instability is suspected, initial imaging
should include cervical radiographs consisting of
an open-mouth odontoid view, a lateral cervical
view and flexion/extension views. (34)

* An unstable os odontoideum is an absolute
contraindication to cervical spine manipulation
and possibly cervical spine mobilization. (11)

* Atlanto-axial instability has been defined as
greater than three millimeters of motion at C1C2
on flexion/ extension films. (12)

* A MRI and surgical consultation is indicated
if significant instability is seen on flexion/
extension radiographs or if myelopathy is detected
on clinical examination. (3,4,13)

* All patients with an os odontoideum should be
educated on potential instability. (2)

* Patients deemed 'stable' upon surgical consult
or who choose not to undergo surgery are
encouraged to have flexion-extension radiographs
taken every year and a MRI of the cranio-cervical
junction every five years. These patients should
also be educated regarding the risks
of participation in contact sports. (4)
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Author:Chrobak, Karen; Larson, Ryan; Stern, Paula J.
Publication:Journal of the Canadian Chiropractic Association
Article Type:Author abstract
Geographic Code:1CONT
Date:Jul 1, 2014
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