Disturbances of cerebrospinal fluid flow attributable to arachnoid scarring cause interstitial edema of the cat spinal cord

OBJECTIVE: Spinal arachnoid scarring may be caused by trauma, inflammation, surgery, spinal instability, degenerative diseases, or malformations and m ay lead to progressive neurological deficits and syringomyelia. We wanted t o investigate the effects of focal arachnoid scarring in the cervical spina l canal of cats on pressures in the subarachnoid space and spinal cord tiss ue, as well as on spinal cord histological features. METHODS: Twenty-nine adult cats were used for this study. Nine animals serv ed as control animals, whereas 20 animals received a focal arachnoid scar a t C1-C2, which was produced by placement of a kaolin-soaked fibrin sponge o n the posterior surface of the spinal cord. After 4 months, pressure record ings above and below the scar, in the subarachnoid space and spinal cord, w ere performed. Elasticity measurements were performed with small bolus inje ctions. Morphometric analyses of brain and ventricle volumes, sizes of the central canal, and sizes of the perivascular spaces in gray and white matte r were also performed. RESULTS: No animal developed clinical or neurophysiological evidence of neu rological symptoms at any time. In the kaolin-treated group, pressure recor dings revealed a significant increase in the subarachnoid pressure at C1, b ecause of the cerebrospinal fluid flow obstruction. Pressure gradients tend ed to increase at all measuring points. A significant difference was detect ed between the spinal cord and subarachnoid space at C2, where the intramed ullary pressure exceeded the subarachnoid pressure. Elasticity was signific antly increased in the spinal cord at C2. Intracranially, no evidence of hy drocephalus was observed. In the spinal cord, perivascular spaces were sign ificantly enlarged in the posterior white matter above the arachnoid scar a nd in the central gray matter below the area of scarring in the cervical co rd. CONCLUSION: Arachnoid scarring at. C1-C2 produces an interstitial type of e dema ire the central gray matter below the area of scarring in the cat cerv ical cord, because of altered cerebrospinal fluid and extracellular fluid f low dynamics. These changes may be interpreted as the initial stage in the development of syringomyelic cavities.