CEREBROSPINAL-FLUID FISTULAS IN A CANINE MODEL

Various diagnostic techniques currently are used to detect the presenc e of a cerebrospinal fluid fistula. High resolution computerized tomog raphy scanning with the Instillation of an intrathecal nonionic contra st medium yields the most accurate diagnostic results. Occasionally, e ven with optimal conditions, little information is gained other than t he confirmation of the presence of a fistula. Intrathecal fluorescein can provide accurate information on the exact location of the fistula. The current study was designed to refine the clinical examination for cerebrospinal fluid fistulae with the use of intrathecal fluorescein. The canine model that we used also served as a vehicle to investigate the histopathologic effects of fluorescein on the central nervous sys tem. We modified a commonly used xenon light source to enable examinat ion with 490 nm light. In the canine model, this allowed accurate visu alization of surgically created fistulae using very low doses of intra thecal fluorescein. An examination of the histopathologic features of the central nervous system of the canine model after acute instillatio n of a higher dose of fluorescein revealed microscopic changes consist ent with the introduction of an irritant material. The changes induced by the chemical trauma may explain the serious neurologic sequelae so metimes seen in patients after the instillation of intrathecal fluores cein. Recommendations on the correct dosage of intrathecal fluorescein for diagnosis of cerebrospinal fluid fistulae are proposed.