Experimental model of posttraumatic syringomyelia: the role of adhesive arachnoiditis in syrinx formation

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✓ An experimental model was devised to elucidate the role of spinal blockade in posttraumatic syringomyelia. Thirty-eight Japanese White rabbits, each weighing about 3 kg, were used in this study. The animals were divided into four groups: in Group 1, eight animals received traumatic injury only; in Group 2, 12 animals received traumatic injury following injection of 100 mg kaolin suspended in 1 cc normal saline solution into the subarachnoid space at the site of trauma; in Group 3, nine animals received traumatic injury following injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space at the site of trauma; and in Group 4, nine animals without traumatic injury received an injection of 200 mg kaolin in 1 cc normal saline solution into the subarachnoid space.

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 2 cm from the injured site. Syrinx formation was seen in 12.5% (one of eight rabbits) in Group 1, 41.7% (five of 12 animals) in Group 2, 55.5% (five of nine rabbits) in Group 3 and 0% (none of nine animals) in Group 4 (p < 0.05). There was a tendency for the combined trauma/kaolin injection groups to be more prone to develop a syrinx. In the kaolin injection only group (Group 4), no animal showed a definite cyst or an extending cavity during the experimental period. The results suggest that kaolin enhances the extension of multiple small cavities that have already formed at the time of initial injury. The difference between the frequency of syrinx formation and the time of survival was statistically significant well beyond the 0.05% level. The overall difference, relating to the frequency of syrinx development, group, and duration of survival, was also statistically significant. In summary, subarachnoid block secondary to adhesive arachnoiditis is important in initiating the extension of the syringomyelia cavity.

Article Information

Address reprint requests to: Hiroshi Abe, M.D., Department of Neurosurgery, University of Hokkaido School of Medicine, North 15, West 7, Kita-ku, Sapporo, Hokkaido 060, Japan.

© AANS, except where prohibited by US copyright law.

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Figures

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    Drawing illustrating the extension of the syrinx and the relationship between syrinx formation and the distribution of kaolin in 11 rabbits developing syringomyelia after spinal cord injury. For description of groups see text. D = days; W = weeks.

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    Photographs of specimens from the one rabbit in Group 1 that showed syrinx formation. The magnified photographs (right), from areas indicated by a box in the photographs at left, demonstrate an obstructed subarachnoid space (S.A.S.) with strong adhesion.

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    Photographs of specimens from a Group 1 rabbit at 8 weeks after injury showing cystic necrosis with an irregular margin in the gray matter but no definite cystic cavity. The subarachnoid space (SAS, arrows) is well preserved. H & E.

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    Left: Photographs of specimens from a Group 2 rabbit obtained within 1 week after injury showing extension of the cavity and obstruction of the subarachnoid space due to the mixture of kaolin and hematoma. R = rostral; C = caudal to injury. Right: Photographs of specimens from a Group 2 rabbit obtained at 6 weeks after injury presenting a round cavity extending 4 cm rostrally from the injured site and kaolin in the subarachnoid space around the cystic cavity. H & E.

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    Photographs of specimens from a Group 3 rabbit obtained at 2 days after injury showing a cystic cavity and accumulation of kaolin and hematoma in the posterior portion. The necrotic cavity breaks into and communicates with the central canal 3.2 cm rostral to the injured site and then the mixed cavity extends rostrally about 6 cm from the injured site. H & E.

  • View in gallery

    Photographs of specimens from two Group 3 rabbits obtained at 6 weeks after injury showing a large cavity extending rostrally 7 cm in one rabbit (A) and 4 cm in the other (B) from the injured site into the lateral funiculus. H & E.

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    Photographs of specimens from the animals in Group 4 obtained at 4, 6 and 9 weeks after injury showing multiple microcystic formations in the gray matter and numerous spongioses of various sizes caused by stromal edema, but no definite cyst. H & E.

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    Photographs of specimens from a Group 4 rabbit showing some dilatation of the central canal and a decrease in ependymal cells. H & E.

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