G. Okubadejo and K.D. Riew reply:
We thank Drs. Wainger and Rathmell for their comments regarding our paper. This study demonstrated a 100% correlation between injection of the particulate steroid in the vertebral artery and eventual mortality in the animal (pig) model used in the study. Nonparticulate steroids did not demonstrate such morbid outcomes.
Drs. Wainger and Rathmell raise the question of whether the findings of this study can be extrapolated to make long-term prognoses. Our animals were kept on ventilator support for only four to six hours after the insult to the brain, with none of the four animals in the methylprednisolone group being able to maintain appropriate oxygenation without ventilator support. No formal neurological examination could be performed on these obtunded animals. They were killed after the four to six-hour recovery period, which was deemed to be appropriate for postoperative recovery. In marked contrast, all animals in the nonparticulate group were able to walk and appeared completely normal.
As Drs. Wainger and Rathmell point out, it is certainly possible that, had we kept the animals alive for a longer period, they might have recovered. We agree that our results with pigs should not be used to prognosticate the long-term outcome in humans who suffer an immediate complication following particulate steroid injections; human beings are capable of overcoming and recovering from serious neurological injuries, given enough time and proper rehabilitation. Nevertheless, there have been several troubling case reports of catastrophic clinical outcomes following inadvertent injection of particulate steroids into the vertebral artery1-3. In almost all instances, the patients sustained serious neurological deficits or ultimately died. These reports suggest, unfortunately, that human correlates of our study do exist.
We also agree that, in theory, it may be possible for artifacts related to tissue processing to produce histological findings similar to what we found. However, as the data in this study were so consistent and reproducible and had correlations with magnetic resonance imaging and clinical findings, we believe that it is reasonable to conclude that the radiographic and histological changes that were observed are indeed representative of true pathological changes as opposed to being artifact.
In conclusion, we agree with Drs. Wainger and Rathmell that, on the basis of our short-term animal study, we cannot judge the permanency of the neural injury following the injection of particulate steroids. We believe that our study should serve as a cautionary note regarding the use of particulate steroids for injections. Finally, we agree that there needs to be further study regarding the safety and effectiveness of nonparticulate steroids before recommending their use.
These letters originally appeared, in slightly different form, on . They are still available on the web site in conjunction with the article to which they refer.