EVALUATION OF THE TEMPORAL EVOLUTION OF ACUTE SPINAL-CORD INJURY

RATIONALE AND OBJECTIVES. After receiving a controlled injury to the t horacic cord, five rats were examined on a 1.5-T magnetic resonance (M R) imaging system at regular intervals over 1 month to assess evolutio n of the injury. METHODS. After the rats received pentobarbital anesth esia, a T10 laminectomy was performed on them, which exposed the dura over the dorsal surface of the spinal cord. With the animal placed in a New York University weight-drop device, a 10-g rod with a flat brass tip was dropped (free-fall) from a height of 50 mm to impact the cord . After injury, the incision was closed with suture material. Each ani mal was imaged on the day of injury, and at 7, 14, and 28 days after i njury. Before contrast injection was administered, sagittal sections w ere obtained with T2 fast-spin echo and T1-spin echo technique. Each r at then received 0.3-mmol/kg gadoteridol (Gd HP-DO3A or ProHance) intr avenously, with the T1 scan repeated. At 28 days, the animals were kil led, and the cord was fixed and embedded in paraffin for histologic ev aluation. RESULTS. The intensity of cord enhancement in the region of injury, after intraveous (IV) contrast injection, was at a maximum on the day of injury, and it decreased in a steady fashion thereafter. Th e intensity was 11.7 +/- 0.6 on the day of injury, 9.7 +/- 2.6 on day 7, 6.3 +/- 5.3 on day 14, and 0.0 +/- 2.3 on day 28. The results on da y 0 and 7 were statistically significant in terms of a difference from that on day 28, with a P value < 0.001. The length of cord injury, as sessed postcontrast, also decreased in a steady fashion from the day o f injury. The length of injury (in cm) was 1.1 +/- 0.1 on the day of i njury, 0.5 +/- 0.2 on day 7, 0.3 +/- 0.1 on day 14, and 0.1 +/- 0.1 on day 28. The results on day 0 and 14 were statistically significant in terms of a difference from those at the next time point, with P value s from < 0.01 to < 0.001. Visually, on T2 images, substantial edema wa s noted on day 0, with progression to focal cord atrophy and gliosis b y day 28. CONCLUSIONS. Acute spinal cord injury in a rat model is well visualized on pre- and postcontrast MR scans at 1.5 T. Observation of T2 changes and disruption of the blood-spinal cord barrier provide ma rkers for temporal assessment of spinal cord injury in the rat model.