Decompression surgery may only go so far in relieving pressure on cord

I’m a fan of translational models; one can do, and has done, a lot using rodents, but no one model is ideal. At the very least there is the concern that what works in one species doesn’t in another, so alternative models begin to give one a feel for the robustness of a therapeutic effect.  Likewise, the scale and proportion of humans and rodents is very different. This matters because distribution of the cell or drug of interest may be dependent on such things. And outcomes that we measure to demonstrate effect (positive or adverse, alike) are inevitably dictated by the species you choose.

A number of groups are now working on pig models. While they (pigs that is, not the researchers) are not perhaps the best to measure “hand” function, they do offer distinct features which I see as advantages. Perhaps the major one is the obvious size. Working on pigs allows techniques to be developed and refined which inform how these might be done on humans – surgery, intra-operative monitoring etc. Kwon and others are using the greater accessibility to cerebral spinal fluid (CSF) that pigs offer to profile changes in molecules found in this fluid after injury which offers up the possibility of using this information to aid diagnosis, prognosis and treatment strategy – standard stuff in other areas of medicine and greatly needed in SCI.

A poster by R Tabanfar [629.17] examined the consequences of decompression after SCI. Decompression – surgically realigning displaced bony structures to relieve the pressure being exerted on the cord – is a common procedure in SCI treatment. The assumption is that in doing so blood will flow more freely, stop the tissue from being starved of oxygen and reduce further damage. The group inserted pressure probes into the cord and then applied a sustained compression on the cord to simulate the conditions experienced  following injury. Pressure was maintained for a few hours to replicate the real world scenario and released to mimic decompressive surgery.

As expected, the pressure markedly dropped on release and imaging confirmed the return of gap between the cord and the surrounding dura (the membrane that surrounds the cord and retains CSF that bathes the cord). However, due to the damage sustained by the cord, it begins to swell over the next few hours and expands until it hits the dura. The dura then restricts further expansion and the pressure in the cord begins to rise once more and appears to remain high for some time. Further studies will examine just how long this elevated pressure persists and hopefully answer whether this prolonged elevation of pressure post decompressive surgery has an impact on outcome.