Pathologic Findings of Experimental Post-traumatic Syringomyelia

ABSTRACT

An experimental model was devised to elucidate the role of spinal blockade in post-traumatic syringomyelia. 38 White adult rabbits were divided into four groupsin Group 1, eight animals received traumatic injury only to the midthoracic area via the weight-drop method but no further treatment;in Group 2, 12 animals received a traumatic injury following injection of 100mg kaolin suspended in 1cc normal saline into subarachnoid space at the midthoracic trauma level;in Group 3, nine animals received traumatic injury following injection of 200mg kaolin in 1cc of normal saline into subarachnoid space;in Group 4, nine animals without injury received an injection of 00mg kaolin in 1cc normal saline solution into subarachnoid space at the midthoracic level. The subjective criteria for syrinx formation were the presence of a definite round cyst having a smooth margin and an upper or lower extension of more than 2cm from the injured site. Syrinx formation was seen in 12.5% in Group 1, 41.7% in Group 2, 55.5% in Group 3 , and 0% in Group 4(p<0.05). In subarachnoid space, the specimen of trauma and kaolin groups showed neutrophils infiltration and obstruction of subarachnoid space on acute stage. The pathologic changes in subarachnoid space on chronic stage were infiltration of kaolin-laden macrophages and chronic arachnoiditis. In parenchyma, hemorrhagic necrosis of the cord, edema, microinfarcts and liquefaction of hematoma were found on acute stage, and multiple cysts in white mater, cell-debris-laden macrophages in the cyst, formation of foam cells, microcysts, and large yst were shown. In Group 4, the same findings as other groups were shown in the subarachnoid space, but in the parenchyma there was no cyst formation. The results suggest that subarachnoid block secondary to adhesive arachnoidities is important in initiating the extension of the syringomyelia cavity that have already formed at the time of initial injury.