EditorIgarashi and colleagues have presented their series of epiduroscopies in a most interesting way,1 and Richardson has written a highly supportive editorial.2 They have focused on the visual findings as well as outcome, and have not made comparison with other treatments, apart from epidural steroid injection. Their paper raises a number of questions.
Patients with radicular (monosegmental) pain had a greater amount of fatty tissue and vascularity within the epidural space than those with more widespread (multisegmental) pain. We are told that both groups received epidural blocks 214 weeks before epiduroscopy with local anaesthetic, either with or without steroid. The number of epidural blocks was not specified. Diagnosis of spinal stenosis was made either by computed tomography with myelography or by magnetic resonance imaging. Can the authors ascertain that a previous epidural or epidurals at various time points, whether with or without steroid, would not affect the amount of vascularity? Epidural steroid injection is often reserved for those primarily with radicular pain and this group may have had a greater number of epidurals, thus affecting the epiduroscopy findings.
Using failure of response to epidural steroid injection as a ratification of efficacy of epiduroscopically applied steroid can only be made with a full account of the approach used for epidural steroid injection before epiduroscopy. It is known that up to 36% of caudal injections are inaccurately positioned when checked with fluoroscopy, and 69% of lumbar injections are similarly inaccurately positioned.3 4
It has already been documented that targeted steroid injection for sciatic radicular pain can produce a good response. Lutz5 showed that transforaminal epidural steroid injection produced greater than 50% relief of pain in 75% of patients for an average of 80 (28144) weeks, and 78% were satisfied with the final outcome. These results appear to compare very favourably with those of the authors.1 Kraemer has shown similar results with perineural and epidural steroids.6 My own experience with epiduroscopy suggests that those with problematic fibrosis around the nerve root were unlikely to respond to targeted steroid infiltration. Problematic fibrotic scar tissue is of such density that little can at present be offered through the epiduroscope, and this paper does not convince me that epiduroscopy as a means of applying steroid to nerve roots has advantages over simpler methods. It may have advantages once further epiduroscopic interventions are possible, and as a diagnostic aid, but first we need to understand what we are seeing. The authors clearly are trying to advance this knowledge.
Liverpool
EditorWe would like to thank Dr Nash for his letter regarding our article. Dr Nash's comments raise several questions: (i) influence of the previous epidural block on the epidural structure; (ii) therapeutic outcome compared with other treatments; and (iii) possibility of incorrect placement of epidural injectates owing to heavy fibrosis around the involved nerve roots.
First, as it was pointed out by Dr Nash, we also recognize that previous epidural blocks might affect epiduroscopic findings, as previously published literature suggests that previous epidural blocks may increase the amount of fibrosis or the degree of adhesion of epidural space.7 8 In this study, the mean numbers of epidural blocks before epiduroscopy were 4.9 and 4.6 times in the monosegmental and the multisegmental groups, respectively. We did not find a difference between the two groups. However, some patients already received epidural blocks in other clinics before they came to our clinic, and therefore details of previous epidural blocks were unknown. Although we would like to resolve the question with further research, we believe that the variability in epiduroscopic findings could be related to the different pathological processes producing spinal stenosis.9
Second, we do not agree with Dr Nash's interpretation in making comparison of our patients' outcome with Lutz's and Kraemer's studies referring to perineural fibrosis and epidural steroids injection. It is important to note that both studies included patients with lumbar nucleus prolapse and radiculopathy, whereas all of our patients were suffering from spinal stenosis. We anticipated the therapeutic effect of the perineural and epidural steroids injections would be more pronounced in patients with a herniated disk because of the benign natural history of this disease. As there are few data available to discuss superiority or inferiority of epiduroscopy to other treatments, we will conduct further comparative studies on homogenous patients' groups.
Lastly, we also experienced difficulties in targeted infiltration through the epiduroscopy owing to heavy fibrosis in patients with failed back surgery syndrome. As mentioned in our article, our patients did not have previous back surgery, and therefore the fibrosis around nerve roots was not as serious. In our study, we performed epidurography during the epiduroscopy and confirmed that the contrast medium reached the affected nerve root at the end of procedures. We therefore suppose that the most important mechanisms for pain relief after epiduroscopy is correct placement of epidural injectates in the involved region in patients with spinal stenosis. Additional mechanisms, such as modification of blood flow to the nerve root after epiduroscopy, may contribute to long-term pain relief.
Tochigi, Japan
References
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