gms | German Medical Science

Objective: Even with timely and adequate decompression of the spinal cord motor function does not improve in a considerable number of patients with spinal metastasis. The reason for this is obscure but certainly in part is due to the fact that several fundamental questions regarding the histopathological changes that occur within the cord still remain unanswered. The purpose of this paper is therefore to present the histopathological findings obtained in a study of experimental subacute spinal cord compression.

Methods: Paraparesis of various degrees was produced in 22 white rabbits using a dynamic model for experimental spinal cord compression. 8 animals served as control. Following medullar decompression outcome was considered as favourable in case of retrieval of gait function whereas non-improvement without restoration of gait function meaning a motor grade of III or worse was regarded as unfavourable. Serial sections of the medullar tissue containing the former compression site were produced, stained, and examined microscopically. Additionally all sections were analyzed morphometrically, and the mean value of cells was correlated with outcome.

Results: Animals with favourable outcome had a normal morphologic structure of the spinal cord but showed a decrease of neurons in the anterior grey horn and a rarefaction of glial cells compared with animals of the control group. Morphometric analysis revealed that there were no significant differences between animals with initially severe paresis (motor grades I – III) and animals with only slight paresis (motor grade IV). On the other hand animals with unfavourable outcome showed a destruction of the normal configuration of the spinal cord and morphometrically a further decrease in number of neurons.

Conclusions: Despite timely operative decompression subacute medullar compression may be followed by pronounced irreversible lesions of the spinal cord elucidating why in some cases neurological recovery can not happen any more. In animals with favourable outcome the medullar tissue is affected above all functionally through the compression effectuating paresis of various degrees, it does not sustain, however, such a structural damage that recovery of neurological function can not occur nevertheless and this regardless of the initial degree of paresis. These findings moreover evince that the preoperative degree of paresis does not allow for an individually valid prediction of functional outcome.