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Epidural space and chronic pain
European Journal of Pain Supplements 4 (2010) 269–272
Contents lists available at ScienceDirect
European Journal of Pain Supplements journal homepage: www.EuropeanJournalPain.com
Epidural space and chronic pain William Raffaeli ⇑, Donatella Righetti, Jessica Andruccioli, Donatella Sarti Chief Dept. of Palliative Care and Pain Therapy, Infermi Hospital, via Ovidio n.5, 47900-Rimini, Italy
a r t i c l e
i n f o
Keywords: Epidural space Chronic pain FBSS Epiduroscopy Raffaeli-technique Resaflex
a b s t r a c t Epidural fibrosis, flogosis, hyperemia and stasis, are some of the pathological morphologies that can be found in the epidural space (ES) of patients affected from failed back surgery syndrome (FBSS), stenosis and other chronic painful pathologies, usually grouped in the class of low back pain (LBP) syndrome. As a consequence of lumbar spine surgery fibrotic tissue commonly replace epidural fat, and large amounts of scar tissue are found around nerve roots. The diagnostic tools currently available, magnetic resonance imaging (MRI) and computer tomography (CT) are dramatically poor, and allow only the definition of pathological structural contents. The only method for monitoring the dura anatomy is during the epiduroscopy, which has been revalued only recently for the diagnosis and the treatment of FBSS. In 2001 we introduced a new endoscopic technique (the Raffaeli method) for the lysis of adhesions under direct imaging, and the study of normal and pathological morphologies of the dura. Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
1. Introduction
2. Raffaeli endoscopic method
The morphology of the ES has been extensively studied in anesthesiology and especially in the practice of regional anesthesia, in relation to the placement and distribution of injected solutions in the ES (De Andrés et al., 2009). The study of ES morphology, however, has an important role also in algology. Thanks to the advances in microscopy and technological tools, it has been recently possible to show the involvement of dura morphologic anomalies in chronic pain insurgence. Different rachid structures are involved in chronic pain: intervertebral disk, nerve roots of the dura, articular facets, ligaments and muscles (Kuslich et al., 1991), whereas the dura has been neglected in the study of chronic pain. The direct visualization of the dura is allowed only during the epiduroscopy, using a video guide inside the ES. The introduction of a new tool, the Resascope, allowed us to demonstrate that epidural morphology in patients with rachid pain is more complex and heterogeneous than what it appears from traditional investigation, and to perform a better lysis of the adherence. We report in this paper a technical short topical review of our experience with epiduroscopy, and describe the several pathological morphologies of the dura that we observed.
At the begging of the procedure, we perform the distension test: opening of the Fogarty ballon and saline solution injection, rising the intracranial pressure. If pain is evoked by the test, then there is traction on the dura, suggesting the presence of some structures blocking the sliding of the dura pannus. This test helps identifying the causes of pain. The Raffaeli endoscopic method (Raffaeli and Righetti, 2005; Raffaeli et al., 2007) can be divided in two phases (phase I and II). Phase I (exploration): an initial mechanical dissection of the connective structures was performed, to visualize the pannus and pathological areas by isolating the fibrotic structures and/or pathological adhesions and to avoid blind advancement and exploration (visualization of the lumbosacral canal). Phase II (lysis): the resection with the Resaflex probe was performed, after that the individual fibrous septa or the connective tissue adhering to the dura was identified with the Fogarty. The innovation of this procedure is the property of the Resaflex (Fig. 1A), which uses radiofrequency molecular quantum to lyse tender tissues, lyse and coagulate at the same time or only coagulate, keeping the temperature at <50 °C. Resascope is a video guided catheter for the exploration and interventions in the epidural space; which has been designed, with all its components for the contemporary use of a Fogarty ballon and Resaflex (Fig. 2). The Resablator 50 (Fig. 1B) is connected to the Resaflex and generates an alternating current with especially combined high frequency waves, the main was is at 4 MHz and subsequent waves are at 8, 12 and 16 MHz. These waves of energy
⇑ Corresponding author. Tel.: +39 339 541 705250; fax: +39 339 541 705686. E-mail address: [email protected] (W. Raffaeli).
1754-3207/$36.00 Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.eujps.2010.09.014
270
W. Raffaeli et al. / European Journal of Pain Supplements 4 (2010) 269–272
3.2. Stenosis
Fig. 1. The Resaflex and the Resablator. The Resaflex has an angled tip in order to be placed within the visual field of the optic fiber. (A) Characteristics of the Resaflex: 0.80 mm diameter steel ball at the tip, working depth 1 mm beyond the tip, depth gauge, stem with a 495 mm plastic insulation, extra flexible silicone cable, connector for quick push–pull. (B) The Resablator is a high frequency waves generator.
break molecular bonds without increasing the kinetic energy of atoms and molecules and therefore there is no increase in temperature.
Spinal stenosis is a narrowing of the spinal channel with intrusion on the neural structures by surrounding bone and soft tissue, resulting in radicular leg pain or neurogenic claudication (Weinstein et al., 2008). Spinal stenosis in one of the three most common diagnosis of LBP and leg pain, together intervertebral disc herniation and degenerative spondylolisthesis with stenosis, which have indication for spinal surgery (Cummins et al., 2006). As concerning the stenosis morphology, there can be patients with a similar radiological morphology, but have different clinical conditions, such as painful or non-painful state, different type of pain (nociceptive or neuropathic), and presence or absence of neurogenic claudication. In the genesis of back/radicular pain, the role of neuroinflammatory factors is increasingly believed to be relevant, even in the absence of any apparent compressive cause (Rang et al., 1991).
4. Causes of chronic pain 3. Chronic pain: LBP, FBSS and stenosis In Europe, 30–40% of adults (Deyo et al., 1991) suffer from LBP, requiring treatments and temporary or permanent suspension from work activities (Cassidy et al., 1998). LBP treatment has great invalidity costs (Frymoyer and Cats-Baril, 1991), derived from the persistence of an ‘‘intense” chronic pain and disk disorders (Hillman et al., 1996; Santos-Eggimann et al., 2000; Waddell, 1996), and is considered the most expensive benign pathology of the North American healthcare system (Engel et al., 1996). FBSS and stenosis are the better-characterized LBP pathologies. 3.1. FBSS FBSS is a severe, long-lasting and disabling complication of rachid surgery, resulting in chronic back and/or leg pain (Ross et al., 1996). Despite the improvement of surgical techniques, there are still high percentages (10–40%) of pain recurrence after surgical procedures (Schofferman et al., 2003). Hernia recurrence, postoperative instability, scarring entrapment of the spinal nerve roots, arachnoiditis, or psychological causes (depressive syndromes, etc.) are some of the several causes of FBSS (Frymoyer and CatsBaril, 1991). The physiopathology of FBSS can be related both to an extensive fibrosis (20–36%), and to an immune reaction against antigens located within the arachnoid membrane (North et al., 1991; Linhart et al., 2003). The fibrosis is often originated from the rearrangement of post-surgical hematoma with fibrous tissue from the periosteum and the paravertebral muscles (Ross et al., 1996; Fritsch et al., 1996).
The fibrosis distribution within the ES and the constraints generated on the surrounding tissues is an indication of the type of pain. Recurrence of pain-free intervals, moreover, suggest involvement of a biochemical phenomenon in an area which is made anatomically sensitive by adhesion fimbria (Raffaeli and Righetti, 2005). We therefore postulated that there are several alterations of the dura pannus that result in chronic pain, and we classified the factors involved in these alterations in three groups: vascular, mechanical and biochemical factors. 4.1. Vascular factors Intrinsic vascularization, hyperemia (Fig. 4B); and vascular stasis (Fig. 4A) are often associated to fibrotic structures, and contribute to pain insurgence. Evoked pain (similar-neuropathic pain and dura allodynia), as a consequence of fluid injection during the distension test, is a good indicator of the presence of the vascular anomalies above reported; and we called this phenomenon: ‘‘regional rachidian compartmental syndrome”. This morphology was found in 43% and 75% of FBSS and stenosis subjects, respectively. 4.2. Mechanical factors Mechanical factors are the origin of pain when there is wide connective fibrosis; in this case pain is responsive to opioid therapy.
Fig. 2. The Resascope. 2 anterior tube for the insertion of (B) an optic fiber and (A) fluid injection in one channel, smaller volume of saline solution is required, and there is no waste of saline solution, the ocular and optic fiber are separated, the optic fiber is connected with a special and tighter valve to the resascope channel. 2 posterior tubes for the insertion of (C) Fogarty and (D) Resaflex, this allow to work with two instruments together, without the need extract one first, time saving, work ability in 4 directions. The use of the fogarty ballon in the epidural space allows to have a better visualization and hence a better use of the resaflex, helps to detach scar fibers, and a smaller fluid volume is required. The resascope allows a direct visualization of the epidural space, and optimizes the use of surgical interventions on the pathological structures of the epidural space.
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4.3. Biochemical factors The physiopathology of FBSS pain can be related both to an extensive fibrosis, estimated roughly 24% of FBSS cases, and to an immune reaction against antigens located within the arachnoid membrane (North et al., 1991a). This immune reaction is mediated by several neuroinflammatory factors, such as bradykinin (BK), serotonin (5-HT), prostaglandin E2 (PG E2), adenosine triphosphate (ATP), protons H+ (Mense, 2001). Chronic nerve injury or inflammation acts in conjunction with mechanical compression to generate and maintain the combination of radicular, axial, and lower extremity pain (Linhart et al., 2003). The involvement of inflammation can be identified during the distension test, at the beginning of the Epiduroscopy. When pain and allodynia (thermal and mechanical origin) are evoked at the minimum fluid injection and opening of the ballon with only 0.2 ml of solution, and injection of 1 ml of saline solution. When pain is caused by inflammation and neurochemical alterations, there is no the need to perform a complete lysis. The Fogarty, indeed, can easily remove the microfibrosis. This biochemical component is correlated to the presence of a painful pathology with vessel stasis and flogosis/nociceptive reaction. We defined this condition as compartmental syndrome, which is similar to Complex Regional Pain Syndrome (CRPS) type II, and is characterized by a neuropathic peripheral pain with a small nociceptive component, and respond to SCS treatment. The endoscopic morphology of distal sections, from the painful site, are normal and do not present any alterations.
Fig. 4. Vascular factors. (A) Fibrosis and vascular stasis, blood vessels (in red) are entrapped in the fibrosis; (B) fibrosis and hyperemia, the blood vessels (bottom right corner) are separated from the fibrosis (top left corner), the yellow arrow indicates the Fogarty.
5. ES Morphological findings The Raffaeli endoscopic method allows removing completely the connective tissue, under direct vision, and thanks to the video guide is possible to study the anatomical, morphological and pathological characteristics of the epidural space. Pathological morphologies of the dura included: false septa (Fig. 3B) and fibrosis (Figs. 4 and 5) as it can be noticed when compared to normal dura (Fig. 3A). Fibrosis is found in 55% and 54% of FBSS and stenosis cases respectively. Fibrosis has different morphologies that are grouped in two classes: reactive fibrosis in stenosis patients, and cicatricial (scar)+ reactive fibrosis in FBSS patients. Stenosis patients did not underwent any previous surgical procedure, for this reason their fibrosis is interpreted as reactive fibrosis, due to the suffering of the structures in the peridural compartment, whereas, in FBSS patients there is also scar tissue. Notwithstanding the type of fibrosis, the fibrotic elements have different consistence and distribution in the ES. According to macroscopic and organizational characteristics of the fibrosis filaments, 4 different fibrotic classes are identifiable: Jagged or cotton-candy-like structures; Organized fibrous structures of hard
Fig. 5. Morphological features. (A) jagged or cotton-candy-like structures of transparent nature, the fibrosis occludes the majority of the ES (from Raffaeli et al., 2007); (B) organized fibrous structures with vessel ecstasy and almost complete obstruction of the ES, the yellow arrow indicates a blood vessel entrapped in the fibrosis (from Raffaeli et al., in press); (C), Fibroid bridles with multiple cords forming a deformed transversal network, the yellow arrow indicates the tip of the Resaflex; (D), Blind compartmentalization, the fibrosis occludes completely the ES with no vascular factor involved (from Raffaeli et al., in press).
consistency; Fibroid bridles, Blind compartmentalization of dura channel. 5.1. Jagged or cotton-candy-like structures These fibrosis structures appear as transparent and bluish flaps, adhering tightly on surrounding tissues and loosely on the dura. (Fig. 5A), and forming a partial and segmented stenosis. This morphology is found in 75–80% of the cases. 5.2. Organized fibrous structures
Fig. 3. Dura. (A) normal dura (B) dura with false septa from Raffaeli et al. (2007).
These fibers have hard consistency, with signs of intrinsic vascularization and vascular stasis (Fig. 5B). They adhere onto the dura (exerting traction on it) and are mostly distributed laterally to dura canal sectors, reducing ES diameter of at least 2/3 (anatomical stenosis). The distension tests evoked pain, indicating that there was a mechanical nature of the painful pathology.
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Raffaeli method. We also show that this method enlightens paintriggering mechanisms otherwise unrevealed and justifies the onset of some painful pathology; because, differently to the classic resonance, the epiduroscopy allows a direct morphological sight. Raffaeli method is also useful for confirming different ES pathological morphologies: adhesive fibrosis (prevalent in FBSS), and neuroinflammation (prevalent in stenosis). Given the variability of pathological features identified, we believe that the technique can be useful for morphological diagnosis; further studies are necessary to determine its diagnostic and in particular its therapeutic value. Conflict of interest statement Fig. 6. Subdural space. Image of the subdural space from Raffaeli et al. (2007).
The authors declare that they have no conflict of interest.
5.3. Fibroid bridles Acknowledgements Multiple fibrotic cords formed a transversal, often paraforamenal, network, which was associated with multiple inflammatory sites (Fig. 5C). The distention test evokes pain hence, suggesting that primary pain in these cases is of nociceptive nature. During epiduroscopy, these painful features are often the reason for the suspension of the procedure. 5.4. Blind compartmentalization The morphology of phenotype is characterized by a thick fibrosis that occludes the ES at different levels, resulting in a complete stenosis, however, it does not result in painful adhesions at the base of the dura (Fig. 5D). 5.5. Morphology of the subdural space During the endoscopy is also possible to insert the Resascope with the optic fiber in the subdural space without complications (Fig. 6) and explore (opening the Fogarty balloon with 40–50 ml of saline solution) the different compartment: the arachnoid and nerve root. In the subdural space we did not find any scar tissue adhering to the arachnoids. 6. Functional instability and stable stenosis We showed several patterns of fibrosis, resulting in different degree of ES occlusion: bridles, adherences, organized or cottoncandy-like fibrous elements adhering to the dura or perineural structures. We defined the presence of dynamic instability when the fibrosis adheres to the dura, resulting in painful distension of meninges, perineural tissue, and nerve roots as a consequence of flexion, traction or other dura strains (e.g. increased SCF pressure). On the contrary, we defined the presence ‘‘stable stenosis” when fibrosis adheres onto inert elements, not eliciting pain under traction. Dynamic instability and stable stenosis can both be found in the same patients. We noted, moreover that different morphologic alterations may induce similar clinical patterns; whereas fibrosis resulting in similar degree of ES occlusion may not always be correlated with same pain patterns. 7. Conclusions In the present technical short topical review we show and describe the pathologic morphological features of ES in FBSS and stenosis patients, as monitored during the epiduroscopy with the
We acknowledge the Foundation ISAL for the sponsorship. References Cassidy JD, Carroll LJ, Cote P. The Saskatchewan health and back pain survey. The prevalence of low back pain and related disability in Saskatchewan adults. Spine 1998;23(17):1860–6. Cummins J, Lurie JD, Tosteson TD, Hanscom B, Abdu WA, Birkmeyer NJ, et al. Descriptive epidemiology and prior healthcare utilization of patients in the Spine Patient Outcomes Research Trial’s (SPORT) three observational cohorts: disc herniation, spinal stenosis, and degenerative spondylolisthesis. Spine (Phila Pa) 2006;31(7):806–14. De Andrés J, Reina MA, Prats A. Epidural space and regional anesthesia. Eur J Pain Suppl 2009;3:55–63. Deyo RA, Cherkin D, Conrad D, Volinn E. Cost, controversy, crisis: low back pain and the health of the public. Annu Rev Public Health 1991;12:141–56. Engel CC, von Korff M, Katon WJ. Back pain in primary care: predictors of high health-care costs. Pain 1996;65(2-3):197–204. Fritsch EW, Heisel J, Rupp S. The failed back surgery syndrome, reasons, intraoperative findings, and long-term results, are port of 182 operative treatments. Spine (Phila Pa) 1996;21(5):626–33. Frymoyer JW, Cats-Baril WL. An overview of the incidences and costs of low back pain. Orthop Clin North Am 1991;22(2):263–71. Hillman M, Wright A, Rajaratnam G, Tennant A, Chamberlain MA. Prevalence of low back pain in the community: implications for service provision in Bradford, UK. J Epidemiol Community Health 1996;50(3):347–52. Kuslich SD, Ulstrom CL, Michael CJ. The tissue origin of low back pain and sciatica: a report of pain response to tissue stimulation during operations on the lumbar spine using local anesthesia. Orthop Clin North Am 1991;22(2):181–7. Linhart O, Obreja O, Kress M. The inflammatory mediators serotonin, prostaglandin E2 and bradykinin evoke calcium influx in rat sensory neurons. Neuroscience 2003;118(1):69–74. Mense S. [Pathophysiology of low back pain and the transition to the chronic state – experimental data and new concepts]. Schmerz 2001;15(6):413–7. North RB, Kidd DH, Campbell JN, Long DM. Dorsal root ganglionectomy for failed back surgery syndrome: a 5-year follow-up study. J Neurosurg 1991;74(2):236–42. Raffaeli W, Righetti D. Surgical radio-frequency epiduroscopy technique (RResAblator) and FBSS treatment: preliminary evaluations. Acta Neurochir Suppl 2005;92:121–5. Raffaeli W, Righetti D, Andruccioli J, Sarti D. Epiduroscopy and radiofrequency technique: the Raffaeli–Righetti technique. Pain Clinic 2007;19(4):185–91. Rang HP, Bevan S, Dray A. Chemical activation of nociceptive peripheral neurones. Br Med Bull 1991;47(3):534–48. Ross JS, Robertson JT, Frederickson RC, Petrie JL, Obuchowski N, Modic MT, et al. Association between peridural scar and recurrent radicular pain after lumbar discectomy: magnetic resonance evaluation. ADCON-L European Study Group. Neurosurgery 1996;38(4):855–61. Santos-Eggimann B, Wietlisbach V, Rickenbach M, Paccaud F, Gutzwiller F. One-year prevalence of low back pain in two Swiss regions: estimates from the population participating in the 1992-1993 MONICA project. Spine 2000;25(19):2473–9. Schofferman J, Reynolds J, Herzog R, Covington E, Dreyfuss P, O’Neill C. Failed back surgery: etiology and diagnostic evaluation. Spine J 2003;3(5):400–3. Waddell G. Low back pain: a twentieth century health care enigma. Spine 1996;21(24):2820–5. Weinstein JN, Tosteson TD, Lurie JD, Tosteson AN, Blood E, Hanscom B, et al. Surgical versus nonsurgical therapy for lumbar spinal stenosis. N Engl J Med 2008;358(8):794–810.
Contents lists available at ScienceDirect
European Journal of Pain Supplements journal homepage: www.EuropeanJournalPain.com
Epidural space and chronic pain William Raffaeli ⇑, Donatella Righetti, Jessica Andruccioli, Donatella Sarti Chief Dept. of Palliative Care and Pain Therapy, Infermi Hospital, via Ovidio n.5, 47900-Rimini, Italy
a r t i c l e
i n f o
Keywords: Epidural space Chronic pain FBSS Epiduroscopy Raffaeli-technique Resaflex
a b s t r a c t Epidural fibrosis, flogosis, hyperemia and stasis, are some of the pathological morphologies that can be found in the epidural space (ES) of patients affected from failed back surgery syndrome (FBSS), stenosis and other chronic painful pathologies, usually grouped in the class of low back pain (LBP) syndrome. As a consequence of lumbar spine surgery fibrotic tissue commonly replace epidural fat, and large amounts of scar tissue are found around nerve roots. The diagnostic tools currently available, magnetic resonance imaging (MRI) and computer tomography (CT) are dramatically poor, and allow only the definition of pathological structural contents. The only method for monitoring the dura anatomy is during the epiduroscopy, which has been revalued only recently for the diagnosis and the treatment of FBSS. In 2001 we introduced a new endoscopic technique (the Raffaeli method) for the lysis of adhesions under direct imaging, and the study of normal and pathological morphologies of the dura. Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
1. Introduction
2. Raffaeli endoscopic method
The morphology of the ES has been extensively studied in anesthesiology and especially in the practice of regional anesthesia, in relation to the placement and distribution of injected solutions in the ES (De Andrés et al., 2009). The study of ES morphology, however, has an important role also in algology. Thanks to the advances in microscopy and technological tools, it has been recently possible to show the involvement of dura morphologic anomalies in chronic pain insurgence. Different rachid structures are involved in chronic pain: intervertebral disk, nerve roots of the dura, articular facets, ligaments and muscles (Kuslich et al., 1991), whereas the dura has been neglected in the study of chronic pain. The direct visualization of the dura is allowed only during the epiduroscopy, using a video guide inside the ES. The introduction of a new tool, the Resascope, allowed us to demonstrate that epidural morphology in patients with rachid pain is more complex and heterogeneous than what it appears from traditional investigation, and to perform a better lysis of the adherence. We report in this paper a technical short topical review of our experience with epiduroscopy, and describe the several pathological morphologies of the dura that we observed.
At the begging of the procedure, we perform the distension test: opening of the Fogarty ballon and saline solution injection, rising the intracranial pressure. If pain is evoked by the test, then there is traction on the dura, suggesting the presence of some structures blocking the sliding of the dura pannus. This test helps identifying the causes of pain. The Raffaeli endoscopic method (Raffaeli and Righetti, 2005; Raffaeli et al., 2007) can be divided in two phases (phase I and II). Phase I (exploration): an initial mechanical dissection of the connective structures was performed, to visualize the pannus and pathological areas by isolating the fibrotic structures and/or pathological adhesions and to avoid blind advancement and exploration (visualization of the lumbosacral canal). Phase II (lysis): the resection with the Resaflex probe was performed, after that the individual fibrous septa or the connective tissue adhering to the dura was identified with the Fogarty. The innovation of this procedure is the property of the Resaflex (Fig. 1A), which uses radiofrequency molecular quantum to lyse tender tissues, lyse and coagulate at the same time or only coagulate, keeping the temperature at <50 °C. Resascope is a video guided catheter for the exploration and interventions in the epidural space; which has been designed, with all its components for the contemporary use of a Fogarty ballon and Resaflex (Fig. 2). The Resablator 50 (Fig. 1B) is connected to the Resaflex and generates an alternating current with especially combined high frequency waves, the main was is at 4 MHz and subsequent waves are at 8, 12 and 16 MHz. These waves of energy
⇑ Corresponding author. Tel.: +39 339 541 705250; fax: +39 339 541 705686. E-mail address: [email protected] (W. Raffaeli).
1754-3207/$36.00 Ó 2010 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.eujps.2010.09.014
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W. Raffaeli et al. / European Journal of Pain Supplements 4 (2010) 269–272
3.2. Stenosis
Fig. 1. The Resaflex and the Resablator. The Resaflex has an angled tip in order to be placed within the visual field of the optic fiber. (A) Characteristics of the Resaflex: 0.80 mm diameter steel ball at the tip, working depth 1 mm beyond the tip, depth gauge, stem with a 495 mm plastic insulation, extra flexible silicone cable, connector for quick push–pull. (B) The Resablator is a high frequency waves generator.
break molecular bonds without increasing the kinetic energy of atoms and molecules and therefore there is no increase in temperature.
Spinal stenosis is a narrowing of the spinal channel with intrusion on the neural structures by surrounding bone and soft tissue, resulting in radicular leg pain or neurogenic claudication (Weinstein et al., 2008). Spinal stenosis in one of the three most common diagnosis of LBP and leg pain, together intervertebral disc herniation and degenerative spondylolisthesis with stenosis, which have indication for spinal surgery (Cummins et al., 2006). As concerning the stenosis morphology, there can be patients with a similar radiological morphology, but have different clinical conditions, such as painful or non-painful state, different type of pain (nociceptive or neuropathic), and presence or absence of neurogenic claudication. In the genesis of back/radicular pain, the role of neuroinflammatory factors is increasingly believed to be relevant, even in the absence of any apparent compressive cause (Rang et al., 1991).
4. Causes of chronic pain 3. Chronic pain: LBP, FBSS and stenosis In Europe, 30–40% of adults (Deyo et al., 1991) suffer from LBP, requiring treatments and temporary or permanent suspension from work activities (Cassidy et al., 1998). LBP treatment has great invalidity costs (Frymoyer and Cats-Baril, 1991), derived from the persistence of an ‘‘intense” chronic pain and disk disorders (Hillman et al., 1996; Santos-Eggimann et al., 2000; Waddell, 1996), and is considered the most expensive benign pathology of the North American healthcare system (Engel et al., 1996). FBSS and stenosis are the better-characterized LBP pathologies. 3.1. FBSS FBSS is a severe, long-lasting and disabling complication of rachid surgery, resulting in chronic back and/or leg pain (Ross et al., 1996). Despite the improvement of surgical techniques, there are still high percentages (10–40%) of pain recurrence after surgical procedures (Schofferman et al., 2003). Hernia recurrence, postoperative instability, scarring entrapment of the spinal nerve roots, arachnoiditis, or psychological causes (depressive syndromes, etc.) are some of the several causes of FBSS (Frymoyer and CatsBaril, 1991). The physiopathology of FBSS can be related both to an extensive fibrosis (20–36%), and to an immune reaction against antigens located within the arachnoid membrane (North et al., 1991; Linhart et al., 2003). The fibrosis is often originated from the rearrangement of post-surgical hematoma with fibrous tissue from the periosteum and the paravertebral muscles (Ross et al., 1996; Fritsch et al., 1996).
The fibrosis distribution within the ES and the constraints generated on the surrounding tissues is an indication of the type of pain. Recurrence of pain-free intervals, moreover, suggest involvement of a biochemical phenomenon in an area which is made anatomically sensitive by adhesion fimbria (Raffaeli and Righetti, 2005). We therefore postulated that there are several alterations of the dura pannus that result in chronic pain, and we classified the factors involved in these alterations in three groups: vascular, mechanical and biochemical factors. 4.1. Vascular factors Intrinsic vascularization, hyperemia (Fig. 4B); and vascular stasis (Fig. 4A) are often associated to fibrotic structures, and contribute to pain insurgence. Evoked pain (similar-neuropathic pain and dura allodynia), as a consequence of fluid injection during the distension test, is a good indicator of the presence of the vascular anomalies above reported; and we called this phenomenon: ‘‘regional rachidian compartmental syndrome”. This morphology was found in 43% and 75% of FBSS and stenosis subjects, respectively. 4.2. Mechanical factors Mechanical factors are the origin of pain when there is wide connective fibrosis; in this case pain is responsive to opioid therapy.
Fig. 2. The Resascope. 2 anterior tube for the insertion of (B) an optic fiber and (A) fluid injection in one channel, smaller volume of saline solution is required, and there is no waste of saline solution, the ocular and optic fiber are separated, the optic fiber is connected with a special and tighter valve to the resascope channel. 2 posterior tubes for the insertion of (C) Fogarty and (D) Resaflex, this allow to work with two instruments together, without the need extract one first, time saving, work ability in 4 directions. The use of the fogarty ballon in the epidural space allows to have a better visualization and hence a better use of the resaflex, helps to detach scar fibers, and a smaller fluid volume is required. The resascope allows a direct visualization of the epidural space, and optimizes the use of surgical interventions on the pathological structures of the epidural space.
W. Raffaeli et al. / European Journal of Pain Supplements 4 (2010) 269–272
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4.3. Biochemical factors The physiopathology of FBSS pain can be related both to an extensive fibrosis, estimated roughly 24% of FBSS cases, and to an immune reaction against antigens located within the arachnoid membrane (North et al., 1991a). This immune reaction is mediated by several neuroinflammatory factors, such as bradykinin (BK), serotonin (5-HT), prostaglandin E2 (PG E2), adenosine triphosphate (ATP), protons H+ (Mense, 2001). Chronic nerve injury or inflammation acts in conjunction with mechanical compression to generate and maintain the combination of radicular, axial, and lower extremity pain (Linhart et al., 2003). The involvement of inflammation can be identified during the distension test, at the beginning of the Epiduroscopy. When pain and allodynia (thermal and mechanical origin) are evoked at the minimum fluid injection and opening of the ballon with only 0.2 ml of solution, and injection of 1 ml of saline solution. When pain is caused by inflammation and neurochemical alterations, there is no the need to perform a complete lysis. The Fogarty, indeed, can easily remove the microfibrosis. This biochemical component is correlated to the presence of a painful pathology with vessel stasis and flogosis/nociceptive reaction. We defined this condition as compartmental syndrome, which is similar to Complex Regional Pain Syndrome (CRPS) type II, and is characterized by a neuropathic peripheral pain with a small nociceptive component, and respond to SCS treatment. The endoscopic morphology of distal sections, from the painful site, are normal and do not present any alterations.
Fig. 4. Vascular factors. (A) Fibrosis and vascular stasis, blood vessels (in red) are entrapped in the fibrosis; (B) fibrosis and hyperemia, the blood vessels (bottom right corner) are separated from the fibrosis (top left corner), the yellow arrow indicates the Fogarty.
5. ES Morphological findings The Raffaeli endoscopic method allows removing completely the connective tissue, under direct vision, and thanks to the video guide is possible to study the anatomical, morphological and pathological characteristics of the epidural space. Pathological morphologies of the dura included: false septa (Fig. 3B) and fibrosis (Figs. 4 and 5) as it can be noticed when compared to normal dura (Fig. 3A). Fibrosis is found in 55% and 54% of FBSS and stenosis cases respectively. Fibrosis has different morphologies that are grouped in two classes: reactive fibrosis in stenosis patients, and cicatricial (scar)+ reactive fibrosis in FBSS patients. Stenosis patients did not underwent any previous surgical procedure, for this reason their fibrosis is interpreted as reactive fibrosis, due to the suffering of the structures in the peridural compartment, whereas, in FBSS patients there is also scar tissue. Notwithstanding the type of fibrosis, the fibrotic elements have different consistence and distribution in the ES. According to macroscopic and organizational characteristics of the fibrosis filaments, 4 different fibrotic classes are identifiable: Jagged or cotton-candy-like structures; Organized fibrous structures of hard
Fig. 5. Morphological features. (A) jagged or cotton-candy-like structures of transparent nature, the fibrosis occludes the majority of the ES (from Raffaeli et al., 2007); (B) organized fibrous structures with vessel ecstasy and almost complete obstruction of the ES, the yellow arrow indicates a blood vessel entrapped in the fibrosis (from Raffaeli et al., in press); (C), Fibroid bridles with multiple cords forming a deformed transversal network, the yellow arrow indicates the tip of the Resaflex; (D), Blind compartmentalization, the fibrosis occludes completely the ES with no vascular factor involved (from Raffaeli et al., in press).
consistency; Fibroid bridles, Blind compartmentalization of dura channel. 5.1. Jagged or cotton-candy-like structures These fibrosis structures appear as transparent and bluish flaps, adhering tightly on surrounding tissues and loosely on the dura. (Fig. 5A), and forming a partial and segmented stenosis. This morphology is found in 75–80% of the cases. 5.2. Organized fibrous structures
Fig. 3. Dura. (A) normal dura (B) dura with false septa from Raffaeli et al. (2007).
These fibers have hard consistency, with signs of intrinsic vascularization and vascular stasis (Fig. 5B). They adhere onto the dura (exerting traction on it) and are mostly distributed laterally to dura canal sectors, reducing ES diameter of at least 2/3 (anatomical stenosis). The distension tests evoked pain, indicating that there was a mechanical nature of the painful pathology.
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Raffaeli method. We also show that this method enlightens paintriggering mechanisms otherwise unrevealed and justifies the onset of some painful pathology; because, differently to the classic resonance, the epiduroscopy allows a direct morphological sight. Raffaeli method is also useful for confirming different ES pathological morphologies: adhesive fibrosis (prevalent in FBSS), and neuroinflammation (prevalent in stenosis). Given the variability of pathological features identified, we believe that the technique can be useful for morphological diagnosis; further studies are necessary to determine its diagnostic and in particular its therapeutic value. Conflict of interest statement Fig. 6. Subdural space. Image of the subdural space from Raffaeli et al. (2007).
The authors declare that they have no conflict of interest.
5.3. Fibroid bridles Acknowledgements Multiple fibrotic cords formed a transversal, often paraforamenal, network, which was associated with multiple inflammatory sites (Fig. 5C). The distention test evokes pain hence, suggesting that primary pain in these cases is of nociceptive nature. During epiduroscopy, these painful features are often the reason for the suspension of the procedure. 5.4. Blind compartmentalization The morphology of phenotype is characterized by a thick fibrosis that occludes the ES at different levels, resulting in a complete stenosis, however, it does not result in painful adhesions at the base of the dura (Fig. 5D). 5.5. Morphology of the subdural space During the endoscopy is also possible to insert the Resascope with the optic fiber in the subdural space without complications (Fig. 6) and explore (opening the Fogarty balloon with 40–50 ml of saline solution) the different compartment: the arachnoid and nerve root. In the subdural space we did not find any scar tissue adhering to the arachnoids. 6. Functional instability and stable stenosis We showed several patterns of fibrosis, resulting in different degree of ES occlusion: bridles, adherences, organized or cottoncandy-like fibrous elements adhering to the dura or perineural structures. We defined the presence of dynamic instability when the fibrosis adheres to the dura, resulting in painful distension of meninges, perineural tissue, and nerve roots as a consequence of flexion, traction or other dura strains (e.g. increased SCF pressure). On the contrary, we defined the presence ‘‘stable stenosis” when fibrosis adheres onto inert elements, not eliciting pain under traction. Dynamic instability and stable stenosis can both be found in the same patients. We noted, moreover that different morphologic alterations may induce similar clinical patterns; whereas fibrosis resulting in similar degree of ES occlusion may not always be correlated with same pain patterns. 7. Conclusions In the present technical short topical review we show and describe the pathologic morphological features of ES in FBSS and stenosis patients, as monitored during the epiduroscopy with the
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