Intramedullary Lesion Length on Postoperative Magnetic Resonance Imaging is a Strong Predictor of ASIA Impairment Scale Grade Conversion Following Decompressive Surgery in Cervical Spinal Cord Injury

Abstract

Background: Evidence indicates that, over time, patients with spinal cord injury (SCI) improve neurologically in various degrees. We sought to further investigate indicators of grade conversion in cervical SCI.

Objective: To detect predictors of ASIA impairment scale (AIS) grade conversion in SCI following surgical decompression.

Methods: In a retrospective study, demographics, clinical, imaging, and surgical data from 100 consecutive patients were assessed for predictors of AIS grade conversion.

Results: American Spinal Injury Association motor score was 17.1. AIS grade was A in 52%, B in 29%, and C in 19% of patients. Surgical decompression took place on an average of 17.6 h following trauma (≤12 h in 51 and >12 h in 49). Complete decompression was verified by magnetic resonance imaging (MRI) in 73 patients. Intramedullary lesion length (IMLL) on postoperative MRI measured 72.8 mm, and hemorrhage at the injury epicenter was noted in 71 patients. Grade conversion took place in 26.9% of AIS grade A patients, 65.5% of AIS grade B, and 78.9% of AIS grade C. AIS grade conversion had statistical relationship with injury severity score, admission AIS grade, extent of decompression, presence of intramedullary hemorrhage, American Spinal Injury Association motor score, and IMLL. A stepwise multiple logistic regression analysis indicated IMLL was the sole and strongest indicator of AIS grade conversion (odds ratio 0.950, 95% CI 0.931-0.969). For 1- and 10-mm increases in IMLL, the model indicates 4% and 40% decreases, respectively, in the odds of AIS grade conversion.

Conclusion: Compared with other surrogates, IMLL remained as the only predictor of AIS grade conversion.

Keywords: ASIA; Cervical spine; Decompression; MRI; Outcome; Spinal cord injury.

FIGURE 1.

Preoperative midsagittal CT and MRI images (plates A and B) belonging to a 24-yr-old man who sustained a fall and was air lifted to the trauma center 67 min following trauma. His AMS was 12 and AIS grade B. CT of cervical spine showed a C5 teardrop fracture, and MRI indicated spinal cord compressive injury with bleeding at the injury epicenter and spinal cord swelling. He underwent C5 anterior cervical corpectomy and fusion (plate C). Postoperative MRI (plate D) taken 65 h following injury indicated a lesion 46 mm in length and bleeding and myelomalacia at the injury epicenter. At his latest follow-up 13 mo after injury, his AMS was 90 and AIS grade D.

FIGURE 2.

Preoperative midsagittal CT and MRI images belonging to a 17-yr-old male patient who sustained an automobile accident and was transferred to the trauma center tetraplegic. His AMS was 6 and AIS grade A. CT of cervical spine (plate A) indicated C4/C5 unilateral facet dislocation and MRI (plate B) significant discoligamentous and SCI. There was bleeding at the injury epicenter and extensive spinal cord swelling. The patient had realignment of the spinal column and C4/C5 anterior cervical discectomy and fusion 11.5 h following trauma (plate C). Postoperative MRI (plate D) indicated an IMLL of 102 mm (long bracket) with bleeding (short bracket) and myelomalacia (dotted lines) at the injury epicenter. Spinal cord decompression was inadequate, and there was CSF pathway still closed shut by the swollen spinal cord from C3 to C6 motion segments. Six months after injury, the patient remained quadriplegic with an AMS of 6 and AIS grade A.

FIGURE 3.

Bar graph demonstrating the relationship between postoperative intramedullary lesion length (IMLL in mm) and chances of AIS grade conversion at follow-up.