Pseudosubluxation or the real thing?

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A 6 year old female was taken to a rural emergency department with a complaint of neck pain. Her behaviour was described as slightly different. She didn’t want to walk around and she was not moving her head much. The only history of trauma that was obtained was being thrown into a swimming pool about 32 hours ago.

 

Exam findings and investigations

She was difficult to examine but she was noted to have some tenderness over her posterior neck.

An cervical spine series was obtained.

c spine

 

Read radiologist report on lateral c-spine

AP and odontoid views were also done, but they are not shown here. This lateral view shows a malalignment of the vertebral bodies of C2-C3.

 

Further Case Progress

A stiff collar was applied, she was placed on a spine board, and transferred to a children’s hospital. During transport, she fell asleep and the transport took place without incident.

Upon arrival, she awoke and became very agitated despite the presence of her mother. She complained that she couldn’t breathe and the back of her head hurt. She was moving her head around excessively despite the immobilization measures.

The physician on duty examined the radiographs and felt that the C2-C3 malalignment represented a normal finding, pseudosubluxation. An opinion with a radiologist was sought via teleradiology, who agreed that this was a pseudosubluxation.

Because of her agitation, she was taken out of cervical spine immobilization. The risk of cervical spine injury was felt to be low because of the normal radiographs, the relatively benign mechanism of injury, and her delayed ambulatory presentation.

After the cervical spine immobilization was removed, the examination of her neck revealed mild tenderness on palpation of the spinous processes in the mid portion of her neck. Range of motion was limited in all directions and associated with some pain. It was difficult to assess the degree of muscle spasm in her neck. There were no complaints of paresthesia. Motor and sensory functions were fully intact.

A CT scan of the cervical spine was obtained to rule out rotary subluxation given her unwillingness to move her neck. This study was normal. Her behavior appeared to normalize and she was ambulating well. Her neck symptoms persisted. She was discharged from the emergency department. She recovered spontaneously without any complications.

 

Teaching Points

  • Rotary subluxation of one of the cervical spine elements (usually C1-C2) can be a difficult diagnosis to make. Plain films are often difficult to interpret. The patient may present with torticollis, which is usually due to benign muscle spasm often following a viral infection. Although most patients with torticollis do not have rotary subluxation, the task of deciding whom to evaluate further is difficult. CT scanning the cervical spine can more definitively assess the rotational relationships of the cervical spine elements and more effectively rule out rotary subluxation.
  • Developmental variants of the cervical spine in young children can be difficult to deal with when interpreting radiographs using measurement parameters based on adults. The space between the atlas and the odontoid can be 4 to 5 mm in children up to age 15 years, compared to 2 mm for adults. This is because the odontoid is not fully ossified. The radiograph shows only the ossified core, while the outer layers of the odontoid are still cartilaginous and not visible on radiographs.
  • Depending on the positioning of the child’s neck, it is not unusual to see a straight cervical spine on the lateral view without the usual lordosis. In adults, the absence of lordosis is an indirect sign of muscle spasm, possibly due to an occult fracture. However, in children, the absence of lordosis is not indicative of muscle spasm.
  • In children up to age 10 years, flexion and extension are greatest about C2 and C3. C2 may appear to be anterior relative to C3 by as much as 5 mm. This pseudosubluxation is increased if the radiograph is taken with the neck flexed. This finding may be present in as many as one-third of all lateral cervical spine films in children.
  • It is extremely important to distinguish true subluxation from pseudosubluxation. It would be unwise to assume the presence of pseudosubluxation until this is certain. This pseudosubluxation phenomenon may result in a delay in establishing the diagnosis of a true subluxation. Such patients should be treated conservatively with cervical spine immobilization until the true diagnosis has been ascertained.
  • The two most common causes of C2-C3 malalignment are pseudosubluxation and a hangman’s fracture. To distinguish these two, Swischuk defined a posterior cervical line drawn from the cortex of the posterior arch of C1 to the cortex of the posterior arch of C3. This line should pass through or be less than 1 mm anterior to the posterior arch of C2. If this distance is greater than 1 mm (possibly up to 1.5 or 2 mm may be normal), this indicates a fracture of the arch of C2 (The vertebral body moves anteriorly, while the arch and the spinous process move posteriorly).
  • Additionally, pseudosubluxations are most pronounced with the neck flexed. C2/C3 malalignment should not persist if the neck is placed in a more neutral or extended position. Persistence of the subluxation in extension is felt to be due to injury (non-physiologic).

 

References

Fassier F. C1-C4 Fractures and Dislocations. In: Letts RM (ed). Management of Pediatric Fractures. New York, Churchill Livingstone, 1994, pp. 807-831.

Ozonoff MB. The Spine. In: Ozonoff MB. Pediatric Orthopedic Radiology. Philadelpha, W.B. Saunders Company, 1992, pp. 1-7.

Woodward GA. Neck Trauma. In: Fleisher GR, Ludwig S. Texbook of Pediatric Emergency Medicine, third edition. Baltimore, Williams & Wilkins, 1993, pp. 1124-1142.

Swischuk LE. Anterior Displacement of C2 in Children: Physiologic or Pathologic? A Helpful Differentiating Line. Radiology 1977;122:759-763.

Chung SMK. The Neck. In: Handbook of Pediatric Orthopedics. New York, Van Nostrand Reinhold, 1986, pp. 43-52.

 

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Prof Loren Yamamoto MD MPH MBA. Professor of pediatrics at the University of Hawaii and a practising pediatric emergency doctor in Honolulu. | Contact | View Loren’s DFTB posts

Author: Loren Yamamoto

Prof Loren Yamamoto MD MPH MBA. Professor of pediatrics at the University of Hawaii and a practising pediatric emergency doctor in Honolulu. | Contact | View Loren’s DFTB posts