Milan P. Stojanovic

Human brain activation under controlled thermal stimulation and habituation to noxious heat: An fMRI study

Brain activity was studied with functional magnetic resonance imaging (fMRI) following thermal stimulation. Two groups (n = 6/group) of human male volunteers were given up to four noxious (46°C) and four non‐noxious (41°C) stimuli. In the 46°C experiment, positive signal changes were found in the frontal gyri, anterior and posterior cingulate gyrus, thalamus, motor cortex, somatosensory cortex (SI and SII), supplementary motor area, insula, and cerebellum. Low‐level negative signal changes appeared in the amygdala and hypothalamus. All regions activated by 46°C were also activated by 41°C. However, except for SI and thalamus, significantly more activation was observed for the 46°C stimulus. A significant attenuation of the signal change was observed by the third stimulus for the 46°C, but not for 41°C experiment. Similar findings were replicated in the second group. These fMRI findings specify differences between somatosensory and pain sensation and suggest a number of rich avenues for future research. Magn Reson Med 41:1044–1057, 1999.

Acute plasticity in the human somatosensory cortex following amputation.

WE studied a patient after amputation of an arm and found that in less than 24 h stimuli applied on the ipsilateral face were referred in a precise, topographically organized, modality-specific manner to distinct points on the phantom. Functional magnetic resonance imaging (fMRI) performed one month later showed that brush-evoked activity in the brain demonstrates objective signal changes which correlate with perceptual changes in the phantom hand. This finding in humans corresponds to the observations of immediate plasticity in cortical pathways described in animals, including primates. The results suggest that reorganization of sensory pathways occurs very soon after amputation in humans, potentially due to the unmasking of ordinarily silent inputs rather than sprouting of new axon terminals.

The Role of Fluoroscopy in Cervical Epidural Steroid Injections : An Analysis of Contrast Dispersal Patterns

Study Design. A multicenter, retrospective analysis of cervical epidurograms. Objectives. To determine the effectiveness of the loss of resistance (LOR) technique in identifying the cervical epidural space. To delineate the pattern of epidural contrast spread during cervical epidural steroid injections. Background. Previous studies have shown that if performed without fluoroscopy, the LOR technique can result in inaccurate needle placement in up to 30% of lumbar epidural steroid injections. To date, no study has examined accuracy of LOR technique and pattern of radiographic contrast spread in cervical epidural levels. Methods. Epidurograms of 38 cervical epidural steroid injections in 31 patients were reviewed. The number of LOR attempts and pattern of contrast spread was analyzed. The effects of age, gender, MRI results, previous cervical laminectomy, and the physician’s level of training were correlated with results. Results. The authors found a 53% rate of false LOR during the first attempt to enter the epidural space. Unilateral epidural contrast spread was found in 51% and ventral epidural spread was found in 28% of cases. The average number of cervical vertebral levels covered with 2 mL of contrast was 3.14, with significantly wider spread noted in those patients who had not undergone previous cervical laminectomy. Other variables did not influence the accuracy of needle placement and pattern of epidural contrast spread. Conclusions. The loss of resistance technique may not be an adequate method for ensuring accurate needle placement in blindly performed cervical epidural injections. The use of epidurography can improve the accuracy of needle placement and medication delivery to targeted areas of pathology.

The Technical Aspects of Epidural Steroid Injections: A National Survey

UNLABELLED Although epidural steroid injections (ESIs) are a common treatment for chronic pain conditions, it is not clear whether there is consensus on their technical aspects. The current literature suggests that variations in technical aspects may affect ESI outcomes. The goal of the survey was to help establish a standard frame of reference for the performance of ESIs. We analyzed survey results from 68 academic anesthesia programs and 28 private practices in the United States. The main finding in this survey is that there is no clear-cut consensus as to the ideal method to perform ESI. There is a wide variation among individual practices in almost every technical aspect of ESI. Private practices use significantly more fluoroscopy than academic centers. The large difference was found in the cervical region where 73% of private practices and only 39% of academic institutions polled perform the ESIs with fluoroscopic guidance (P = 0.005). A similar discrepancy was found in approaches to the epidural space after laminectomy where 61% of private practices, but only 15% of academic centers, use the transforaminal approach. The study results indicate that there is no consensus, and that there is a wide variation in current practices. IMPLICATIONS A national survey of practices performing epidural steroid injections was conducted. The purpose was to establish whether consensus exists on technical aspects of this procedure. The study results indicate that there is no consensus, and that there is a wide variation in current practices.

Clinical predictors of success and failure for lumbar facet radiofrequency denervation.

ObjectiveTo determine the clinical factors associated with the success and failure of radiofrequency denervation of the lumbar facet joints. MethodsClinical data were garnered from 3 academic medical centers on 192 patients with low back pain who underwent radiofrequency denervation after a positive response to diagnostic blocks. Success was defined as ≥50% pain relief lasting at least 6 months. Factors evaluated for their association with outcome included duration of pain, opioid use, symptom location, paraspinal tenderness, pain exacerbated by extension/rotation (ie, facet loading), MRI abnormalities, diabetes, smoking, scoliosis, obesity, prior surgery and levels treated. ResultsThe only factor associated with a successful outcome was paraspinal tenderness. Variables that correlated with treatment failure were ‘facet loading,’ long duration of pain, and previous back surgery. ConclusionsIt is counterproductive to use ‘facet loading’ as the sole basis for choosing patients for facet interventions. In patients at high risk for treatment failure, taking additional steps to reduce the rate of false-positive screening blocks may improve outcomes.

Lumbar discography: A comprehensive review of outcome studies, diagnostic accuracy, and principles

Background and Objectives: Since its advent more than 50 years ago, the use of discography has been mired in controversy. The purpose of this review is to provide a clinical overview of lumbar discography and discogenic back pain, with special emphasis on determining the accuracy of discography and whether or not the procedure improves outcomes for surgery. Methods: Material for this review was obtained from a MEDLINE search conducted from 1951 thru September 2004, bibliographic references, book chapters, and conference proceedings. Results: Based on a large number of comparative studies, plain discography is less accurate than magnetic resonance imaging in diagnosing lumbar herniated nucleus pulposus and comparable or slightly more sensitive in detecting degenerative disc disease. For disc degeneration, CT discography remains the gold standard for diagnosis. There are very few studies comparing surgical outcomes between patients who have undergone preoperative provocative discography and those who have not. What little evidence exists is conflicting. Before disc replacement surgery, approximately half the studies have used preoperative discography. A comparison of outcomes did not reveal any significant difference between the 2 groups but none of the studies was controlled, and they used different outcome measures, follow-up periods, and surgical techniques. Because all intradiscal electrothermal therapy (IDET) studies have used discography before surgery, no conclusions can be drawn regarding its effects on outcome. Conclusions: Although discography, especially combined with CT scanning, may be more accurate than other radiologic studies in detecting degenerative disc disease, its ability to improve surgical outcomes has yet to be proven. In the United States and Europe, there are inconsistencies in the use of lumbar discography such that it is routinely used before IDET, yet only occasionally used before spinal fusion.

Risk factors for failure and complications of intradiscal electrothermal therapy: a pilot study.

Study Design. A bi-institutional, retrospective clinical data analysis. Objectives. To determine risk factors for failure and complications of intradiscal electrothermal therapy, a treatment for discogenic back pain. Summary of the Background Data. Intradiscal electrothermal therapy is a relatively new treatment for discogenic back pain. Though previous studies have shown it to be an effective treatment, there are few published studies examining complications and none examining risk factors for failure. Methods. The authors treated 79 patients with discogenic back pain using intradiscal electrothermal therapy. Complications were assessed by patient report and, when indicated, further diagnostic testing. Success or failure was determined by visual analogue pain scores at 6-month follow-up. Variables examined for their relationship to failure and complications were age, sex, duration of pain, number of levels heated, smoking history, diabetes, obesity, leg pain, and previous back surgery. Results. Forty-eight percent of patients reported more than 50% pain relief at their 6-month follow-up. There were eight complications (10%), most of which were self-limited and transient. The only risk factor associated with intradiscal electrothermal therapy failure was obesity (P = 0.01). Whereas 54% of nonobese patients reported good pain relief at 6 months, only one out of 10 obese patients had successful intradiscal electrothermal therapy. The obese patients in our study were more likely to have a complication from intradiscal electrothermal therapy than they were to obtain pain relief. Conclusion. The only risk factor found to be associated with IDET outcome was obesity, which was a strong predictor of failure. Obesity should be considered a relative contraindication to performing IDET.

The effect of opioid dose and treatment duration on the perception of a painful standardized clinical stimulus.

Background and Objectives: The concept of opioid‐induced hyperalgesia has recently gained prominence as a contributing factor for opioid tolerance and long‐term treatment failure. But whereas the preclinical data for this phenomenon are strong, the mixed clinical data derive primarily from experimental pain models conducted in volunteers and heroin addicts, and nonstandardized clinical stimuli, e.g., surgery. The primary objective of this study is to delineate the effect of opioid dose and treatment duration on pain intensity and unpleasantness ratings following a standardized clinical pain stimulus. Methods: Three hundred and fifty‐five patients, on a steady regimen of analgesic medications and scheduled for an interventional procedure, received a standardized subcutaneous injection of lidocaine prior to a full dose of local anesthetic. Before and immediately following the injection, subjects were asked to rate pain and unpleasantness intensity on a 0 to 10 numerical rating scale. Subjects were stratified into 6 groups based on opioid dosage. A control group of 27 volunteers who had no pain and were taking no analgesics were also injected. Results: Both opioid dose and duration of treatment directly correlated with pain intensity and unpleasantness scores. Baseline pain intensity was also positively associated with both outcome variables. Gender was found to be associated with pain intensity and unpleasantness, with females scoring higher in both categories than males. Compared with patients not receiving opioid treatment, patients receiving opioid therapy were more likely to rate the standardized pain stimulus as being more unpleasant than painful. Conclusions: The results of this study bolster preclinical and experimental pain models demonstrating enhanced pain perception in subjects receiving opioid therapy. This simple clinical model may provide a useful tool in examining opioid‐induced hyperalgesia.

Single needle approach for multiple medial branch blocks: A new technique

Background and ObjectivesMedial branch blocks are an important tool for the diagnosis of facet joint arthropathy. The most commonly used technique involves multiple needle placements, one for each nerve blocked. This multiple needle technique may require a large amount of local anesthetic for anesthetizing the skin, thereby increasing the rate of false-positive blocks. TechniqueDiagnostic lumbar medial branch blocks are usually performed using multiple needles, one for each branch. The authors describe a different technique using a single needle for all levels. Initially, the needle is directed toward the medial branch located at the level of the affected facet joint in the antero–posterior view. After anesthetizing this nerve with local anesthetic, the same needle is withdrawn to the skin with the tip still in the subcutaneous tissue and repositioned to block the medial branch above, and thereafter below, while continuing to use only the antero–posterior view, thereby using only one entry site. ConclusionsWhen performed correctly, the single needle technique provides accuracy similar to the more conventional multiple needle approach during the performance of diagnostic facet joint nerve blocks. Because only one skin entry point is needed, however, this technique may afford several advantages over the multiple needle approach. These may include less patient discomfort, less time required and less radiation exposure since only one C-arm position is used, a smaller volume of local anesthetic, and possibly a lower incidence of false-positive blocks.

Does needle insertion site affect diskography results? A retrospective analysis

Study Design. A retrospective clinical data analysis was performed. Objectives. To determine the effect of needle insertion site on provocative diskography results, and to ascertain whether performing diskography ipsilaterally to a patient’s reported pain leads to a higher rate of false-positives. Summary of Background Data. In certain groups of patients, provocative diskography is associated with a significant false-positive rate, which can lead to misdiagnosis and inappropriate treatment. Although purported by some to be a cause of false-positive diskogram results, the effect of needle insertion site on diskography results has yet to be determined. Methods. The charts of 127 patients who underwent diskography were evaluated to determine the relationship between the location of pain, needle insertion site, and diskography results. Results. Performing diskography on the side ipsilateral to a patient’s pain did not result in a higher incidence of positive diskogram results. Conclusion. False-positive diskography results are unlikely to result from performing the procedure on the same side as a patient’s reported pain.