J Korean Neurosurg Soc.  2014 Aug;56(2):121-129. 10.3340/jkns.2014.56.2.121.

Does Intramedullary Signal Intensity on MRI Affect the Surgical Outcomes of Patients with Ossification of Posterior Longitudinal Ligament?

• Choi JH
• Shin JJ
• Kim TH
• Shin HS
• Hwang YS
• Park SK

• KMID: 1956514
• DOI: http://doi.org/10.3340/jkns.2014.56.2.121

Abstract

OBJECTIVES
Patients with cervical ossification of posterior longitudinal ligament (OPLL) are susceptible to cord injury, which often develops into myelopathic symptoms. However, little is known regarding the prognostic factors that are involved in minor trauma. We evaluated the relationship between minor trauma and neurological outcome of OPLL and investigated the prognostic factors with a focus on compressive factors and intramedullary signal intensity (SI).
METHODS
A total of 74 patients with cervical myelopathy caused by OPLL at more than three-levels were treated with posterior decompression surgeries. We surveyed the space available for spinal cord (SAC), the severity of SI change on T2-weighted image, and diabetes mellitus (DM). The neurological outcome using Japanese Orthopedic Association (JOA) scale was assessed at admission and at 12-month follow-up.
RESULTS
Among the variables tested, preoperative JOA score, severity of intramedullary SI, SAC, and DM were significantly related to neurological outcome. The mean preoperative JOA were 11.3+/-1.9 for the 41 patients who did not have histories of trauma and 8.0+/-3.1 for the 33 patients who had suffered minor traumas (p<0.05). However, there were no significant differences in the recovery ratios between those two groups.
CONCLUSIONS
Initial neurological status and high intramedullary SI in the preoperative phase were related to poorer postoperative outcomes. Moreover, the patients with no histories of DM and larger SACs exhibited better improvement than did the patients with DM and smaller SACs. Although the initial JOA scores were worse for the minor trauma patients than did those who had no trauma prior to surgery, minor trauma exerted no direct effects on the surgical outcomes.

Keyword

Ossification of the posterior longitudinal ligament; Spinal cord injury; Surgical treatment; Magnetic resonance imaging

MeSH Terms

Asian Continental Ancestry Group
Decompression
Diabetes Mellitus
Follow-Up Studies
Humans
Magnetic Resonance Imaging*
Orthopedics
Ossification of Posterior Longitudinal Ligament*
Spinal Cord
Spinal Cord Diseases
Spinal Cord Injuries
Surgical Procedures, Minor

Figure

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  Fig. 1 Measurement of maximal spinal canal stenosis (%) and the space available for the spinal cord (SAC) were calculated on the basis of axial computed tomography. Ossified mass diameter (A) and developmental canal diameter (B). Spinal canal stenosis (%)=A/B×100. SAC=B-A, is calculated by subtracting the axial diameter of the ossified mass from developmental canal diameter.

• 

  Fig. 2 Cobb's angle, the cervical lordotic angle is measured from lines that is created parallel to the inferior aspect of the C2 body and parallel to that of the C7 body on lateral views with the patients in neutral positions.

• 

  Fig. 3 The involved length of signal intensity (SI) is measured from one end of the region of altered intensity to the other end on sagittal T2-weighted MR images.

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  Fig. 4 The signal intensity of the spinal cord was assessed as Grade 0, for no change in signal intensity on T2-weighted MR images; Grade 1, for light intensity change; and Grade 2 for a bright signal, clearly distinguishable from that of Grade 1.

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  Fig. 5 A : Preoperative T2-weighted MRI of a 61-year-old male patient with spinal cord compression at C3-4-5-6. Intramedullary high signal intensity, grade 1 was visible at the region of the marked compressed cord. His JOA score was 5. B : Cervical 3D CT showed a mixed type of ossification of posterior longitudinal ligament. Spinal canal stenosis was 46.3%. C : He underwent the cervical laminoplasty at C3-4-5-6. D : MRI of the patient from B, 12 months following the cervical laminoplasty with successful decompression of the spinal cord. The patient's Japanese Orthopedic Association score was 10. The recovery rate was 41.7%.

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  Fig. 6 A : Initial Japanese Orthopedic Association (JOA) score correlated with JOA recovery ratio (clinical outcome). B : JOA recovery ratio correlated with the space available for the spinal cord (SAC). C : The maximal spinal canal stenosis correlated negatively with JOA recovery ratio.

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