November 2017

A 13-year-old male with lower extremity weakness | Sub-classification: Spine


A 13-year-old male presents with a six month history of difficulty walking. There is no history of trauma, malignancy, or other medical problems. He states that his legs feel “tight” and that the left leg is numb. He does not endorse upper extremity problems or incontinence of bowel or bladder.   


Cranial nerves II-XII are intact

DTRs – 3+ upper and lower extremities

Strength- 5/5

+ Clonus left lower extremity

Decreased sensation in left lower extremity

Mildly spastic gait


Figure 1

Figure 2

1. What is the likely pathophysiology responsible for this condition?
2. What is the next step in treatment?
3. What further studies would you obtain?
4. Which of the following describes you?
5. I practice in one of the following locations.

Case Explanation:

Question 1: The imaging demonstrates a severe case of os odontoideum. Based on the patients young age and lack of any trauma history the likely cause of the malformation is congenital, although the origin (trauma vs congenital nonunion) of os odontoideum in the broader population is debatable. Laxity of ligamentous structures can be seen in Ehler Danlos patients. Inflammatory pannus can be seen in patients with Rheumatoid arthritis.

Question 2: The patient needs reduction, decompression and fixation. The next step should be traction, likely using a halo ring in preparation for later halo placement. Posterior occipitocervical fusion and decompression is required given the amount of basilar invagination. A biopsy will not be helpful because imaging does not show an obvious tumor and this will not improve the neural compression. An anterior decompression will not result in stabilization of the spine, although an anterior decompression followed by a posterior fusion is an option. Traction with just C1-2 fusion is unlikely to be stable due to the degree of basilar invagination. External orthosis will not remove neural compression.

Question 3: A CT-angiogram can help to demonstrate the location of the vertebral arteries and any associated abnormality since a posterior OC fusion is being planned. The other options would not change the management of the patient.

Please subit your answers to see the case explanation.


  • Zhao D, Wang S, Passias PG, Wang C.Craniocervical instability in the setting of os odontoideum: assessment of cause, presentation, and surgical outcomes in a series of 279 cases. Neurosurgery. 2015 May;76(5):514-21.
  • Weng C, Tian W, Li ZY, Liu B, Li Q, Wang YQ, Sun YZ. Surgical management of symptomatic os odontoideum with posterior screw fixation performed using the magerl and harms techniques with intraoperative 3-dimensional fluoroscopy-based navigation. Spine (Phila Pa 1976). 2012 Oct 1;37(21):1839-46.
  • Klimo P Jr, Kan P, Rao G, Apfelbaum R, Brockmeyer D. Os odontoideum: presentation, diagnosis, and treatment in a series of 78 patients. J Neurosurg Spine. 2008 Oct;9(4):332-42. doi: 10.3171/SPI.2008.9.10.332.
  • Arvin B, Fournier-Gosselin MP, Fehlings MG.Os odontoideum: etiology and surgical management.Neurosurgery. 2010 Mar;66(3 Suppl):22-31. 
  • Leng LZ, Anand VK, Hartl R, Schwartz TH. Endonasal endoscopic resection of an os odontoideum to decompress the cervicomedullary junction: a minimal access surgical technique. Spine (Phila Pa 1976). 2009 Feb 15;34(4):E139-43
  • Qiuhang Z, Feng K, Bo Y, Hongchuan G, Mingchu L, Ge C, Feng. Transoral endoscopic odontoidectomy to decompress the cervicomedullary junction. L.Spine (Phila Pa 1976). 2013 Jun 15;38(14):E901-6. ​

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SANS Pediatric Module 

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SANS Spine Module

SANS Spine Module for Residents

SANS Spine Exam