- Email: [email protected]
Neuromodulation and obstetric anaesthesia
International Journal of Obstetric Anesthesia (2017) xxx, xxx–xxx 0959-289X/$ - see front matter Ó 2017 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ijoa.2017.02.007
EDITORIAL
www.obstetanesthesia.com
Neuromodulation and obstetric anaesthesia Neuromodulation is a rapidly evolving area of medical practice and obstetric anaesthetists are likely to encounter patients with neuromodulatory devices in situ more frequently. Defined by the International Neuromodulation Society as ‘‘the alteration of nerve activity through the delivery of electrical stimulation or chemical agents to targeted sites of the body”,1 neuromodulation is now used to treat a seemingly ever expanding range of conditions.2 Neuromodulation systems have traditionally been reserved as second or third line treatments – generally considered only after other medical and surgical options have failed. In the past, systems have been considered prohibitively expensive and implantation has required major invasive surgery. However, in recent years, new generation systems have become progressively smaller and easier or less destructive to insert. Despite the continuing lack of Class 1 evidence of effectiveness in pain management, the evidence of costeffectiveness of neuromodulation compared with medical treatment alone is likely to support the expansion of use, both in terms of absolute numbers of patients and in the range of indications.3–5 Most neurostimulation systems consist of distal electrode(s) placed adjacent to a target site, with connecting leads tunneled over a variable distance to a subcutaneous Implanted Pulse Generator (IPG). The IPG has an integrated battery, which is either replaced surgically every few years, or more commonly now (especially in younger patients) is charged remotely using an external induction charging system. This device is generally worn intermittently by the patient, typically a few hours per week, in close proximity to the IPG. Common neuromodulation targets include various intracranial and neuraxial sites, as well as peripheral nerves. However, many additional potential targets and modes of neuromodulation are emerging. Deep brain stimulation (DBS) has been used extensively for Parkinson’s disease, and less commonly for a range of other conditions including myotonic syndromes, tremor associated with multiple sclerosis, and psychiatric conditions such as intractable depression, Tourette’s syndrome and obsessive compulsive disorder.6,7 Spinal cord stimulation is most commonly used for failed back (surgery) syndrome (FBSS)8–10 and complex regional pain syndrome (CRPS).11–15 Peripheral nerve stimulators can be used for mononeuropathies
such as occipital or trigeminal neuralgia. Recently, dorsal root ganglion (DRG) stimulators have been used for more localized pain conditions such as post-thoracotomy pain, post-herpetic neuralgia and post-herniorrhaphy pain. Sacral nerve stimulators can be used both for pain conditions and bladder or bowel sphincter dysfunction. In this issue of the journal, Anso´ et al. present a case report of a young patient with a sacral nerve stimulator used very effectively to treat bladder sphincter dysfunction associated with Fowler’s Syndrome.16 The field of neuromodulation also encompasses intrathecal drug delivery therapies, which supply infusions of medications directly into the cerebrospinal fluid (CSF). The infusion is run from a pump, typically implanted over the iliac fossa in the lower abdominal wall. A catheter runs subcutaneously from the pump into the intrathecal space, commonly introduced at either the L2–3 or L3–4 intervertebral space. Intrathecal medications include baclofen to relieve the spasticity of cerebral palsy or spinal cord injury, and analgesics for chronic (especially malignant) pain. Whilst many intracranial systems are used in older patients, there are already case reports of women with DBS systems requiring obstetric care.17,18 There are also multiple case reports (and short case series) of pregnant women with cervical and thoracic spinal8,10–15,19–22 and sacral nerve stimulators23,24 in situ. Several case reports have been published of successful epidural analgesia in the presence of intrathecal infusion pumps.25,26
Management of neuromodulation systems during pregnancy There is currently a lack of meaningful human research to assess the impact of neuromodulation systems on pregnancy (or vice versa) – most particularly, there is a paucity of data on the theoretical implications of the resulting electromagnetic fields on the developing fetus. Some animal data exist, such as studies examining the reproductive health of laboratory rats and dairy cattle exposed to high voltage powerlines.27–29 However, in the absence of good quality human data, current recommendations from all neuromodulation device companies are that devices be switched off for the duration of pregnancy. Accordingly, the Food and Drug Administration (FDA) and similar bodies have not licensed
2 neuromodulation systems for use during pregnancy. Neither the companies – nor the authors of this editorial – can be seen to condone the ‘off label’ use of neuromodulation during pregnancy. However, this should not preclude a rational discussion of the risks and benefits that this may involve, and consideration of research that could potentially be undertaken in the future in order to further delineate these risks. This may represent an example in clinical practice where the theoretical risk of an unknown harm needs to be weighed against the genuine risk of known morbidity. Clearly the consequences of turning off neuromodulation during pregnancy vary depending on the indication for which the device was inserted. Patients with chronic pain will need to take alternative analgesia to replace the pain relief provided by the stimulator, and these analgesics themselves may have adverse effects during pregnancy (e.g. opioid dependence in the newborn). Alternatively, many chronic pain patients choose to endure poor pain control for the duration of the pregnancy, which may have its own psychosocial and physiological consequences. There is little research examining the holistic consequences of chronic pain on outcomes in pregnancy and reproductive health more broadly.30,31 The patient described in Anso´’s case report clearly suffered significant morbidity associated with turning off her device. It is quite conceivable that her repeated episodes of urinary sepsis could have independently threatened the viability of her pregnancy. Many IPG systems are not designed to be turned off for prolonged periods of time and batteries become nonviable if allowed to completely discharge.
Editorial insertion. These electrodes are then tunneled to the IPG, which is typically implanted in the lower flank or upper buttock. One case report describes the use of ultrasound to delineate the exact location of an intrathecal catheter prior to epidural analgesia.26 It is also important to establish what other form of spinal surgery the patient has undergone, particularly in cases of FBSS. The integrity of the epidural space is important for the prospects of successful epidural analgesia. Any open back surgery from a posterior approach, including the insertion of plate electrodes via laminectomy, has the potential to compromise the epidural space at that level, leading to an increased risk of dural puncture and partial or total failure of epidural anaesthesia. Spinal anaesthesia should be safe and effective and the risk to the system is minimised if the approach is made at a level anatomically separate from the location of the leads and electrodes. Whilst not globally recommended, prophylactic antibiotics would seem prudent, given the catastrophic consequences of iatrogenic infection which generally necessitates removal of the entire system. If the patient has chosen to use the device during pregnancy, it would seem advisable to turn the stimulation or drug delivery device off for the duration of labour and birth, including during placement of an epidural catheter or during caesarean section. Neuromodulation systems can be turned off either with the patient’s own control unit or by application of a magnet over the IPG, in a similar way to application of a magnet over a cardiac pacemaker.
Guidelines for the obstetric team Implications of neuromodulation systems for obstetric anaesthetists The most important question for the obstetric anaesthetist is whether neuraxial anaesthesia can be safely conducted and whether it is likely to be effective. There is no absolute contraindication to epidural or spinal anaesthesia. However, there is the theoretical risk of damaging spinal stimulation systems via direct trauma or infection. Pre-anaesthetic assessment should include a detailed record of the exact anatomical location of the entire system, including the electrodes, connecting leads and IPG. This information can be remarkably difficult to obtain, especially after-hours. Ideally, contact with the clinician who implanted the device should be made, with review of the original operation report. Percutaneous spinal systems are commonly inserted via either the L2–3 or L3–4 interspace and then the electrodes are advanced under X-ray guidance to lie at the target location in the low thoracic epidural space. Plate electrodes are generally placed in the low thoracic epidural space via a laminectomy. Leads may be anchored adjacent to the interspinous ligament at the point of
In addition to the considerations for anaesthetists, there are also important considerations for the obstetric team. Early involvement of a specialist pain physician may assist the obstetric team, and the woman herself, to weigh the relative risks and benefits of alternative analgesic options including continuing to use neuromodulation throughout the pregnancy. The physiological changes of pregnancy can theoretically result in stretching, dislodgement or damage to electrodes and connecting leads. Previously, IPGs were commonly placed in a suprapubic or iliac fossa location where they could be damaged during caesarean delivery. Intrathecal pumps are also often located in this area. Implanted Pulse Generators are now typically located in the upper anterior chest wall or in the upper buttock or flank, and are at far less surgical risk. Surgeons are advised to avoid monopolar diathermy in the vicinity of neurostimulatory systems as it may cause damage to the IPG. There is also potential for diathermy to heat the electrodes and this thermal energy maybe be transferred along the length of the electrode, resulting in burns to distant neural structures.
Editorial Another major consideration is Magnetic Resonance Imaging (MRI) compatibility. Magnetic resonance imaging has become an important imaging modality for investigating many obstetric conditions, for example placental implantation disorders. Many older neuromodulation systems are incompatible with MRI. The induced electromagnetic field may dislodge implanted components, damage the device electronics or generate voltage within the leads. Some newer systems may be MRI ‘conditional’, whereby MRI is possible but specific guidance is required from the manufacturer prior to scanning.
Future directions This is such a rapidly evolving area of medicine that, even if quality evidence were available to support the safety of current neuromodulation systems in pregnancy, inevitably new technology will supersede the old. For example, there is now Class II evidence to indicate the superiority of burst stimulation (pulsed wave) systems and high frequency (10 kHz) rather than tonic (60–200 Hz) stimulation in pain management.32,33 These new systems appear to provide superior pain relief for back pain and a patient experience that is free from the paraesthesia common to low frequency, tonic stimulation. Paraesthesia-free systems should enable placebocontrolled trials and thus help improve the quality of evidence available about their continued use.
Conclusion Subject to further supportive evidence from high level randomised trials, neuromodulation is likely to become increasingly common. As in many other conditions, safe obstetric management relies on excellence in communication between the entire treating team, including the obstetrician, pain physician, neurosurgeon and anaesthetist. Further research is needed to weigh the potential risks and benefits from neuromodulation in pregnant women and their offspring. James Griffiths Royal Women’s Hospital, Melbourne, Victoria, Australia E-mail address: [email protected] Peter Teddy Department of Neurosurgery, Royal Melbourne Hospital, Department of Surgery, The University of Melbourne, Melbourne, Victoria, Australia
3
References 1. International Neuromodulation Society. Available from http:// www.neuromodulation.com/ [accessed 2 Nov 2016]. 2. Levy RM. The evolving definition of neuromodulation. Neuromodulation 2014;17:207–10. 3. Kumar K, Malik S, Demeria D. Treatment of chronic pain with spinal cord stimulation versus alternative therapies: cost-effectiveness analysis. Neurosurgery 2002;51:106–15. 4. Kumar K, Rizvi S. Cost-effectiveness of spinal cord stimulation therapy in management of chronic pain. Pain Med 2013;14:1631–49. 5. Taylor RS, Ryan J, O’Donnell R, Eldabe S, Kumar K, North RB. The cost-effectiveness of spinal cord stimulation in the treatment of failed back surgery syndrome. Clin J Pain 2010;26:463–9. 6. Hariz M, Blomstedt P, Zrinzo L. Future of brain stimulation: new targets, new indications, new technology. Mov Disord 2013;28:1784–92. 7. Pereira EA, Green AL, Nandi D, Aziz TZ. Deep brain stimulation: indications and evidence. Expert Rev Med Devices 2007;4:591–603. 8. Das B, McCrory C. Spinal cord stimulation in pregnancy with failed back surgery syndrome. Ir Med J 2014;107:117–8. 9. Gredilla E, Abejon D, Del Pozo C, Del Saz J, Gilsanz F. Failed back surgery, spinal cord stimulation and pregnancy: presentation of a case. Rev Esp Anestesiol Reanim 2012;59:511–4. 10. Fedoroff IC, Blackwell E, Malysh L, McDonald WN, Boyd M. Spinal cord stimulation in pregnancy: a literature review. Neuromodulation 2012;15:537–41. 11. Ahmed S, Lindsay JM, Snyder DI. Spinal cord stimulation for complex regional pain syndrome: a case study of a pregnant female. Pain Physician 2016;19:E487–93. 12. Hanson JL, Goodman EJ. Labor epidural placement in a woman with a cervical spinal cord stimulator. Int J Obstet Anesth 2006;15:246–9. 13. Ito S, Sugiura T, Azami T, Sasano H, Sobue K. Spinal cord stimulation for a woman with complex regional pain syndrome who wished to get pregnant. J Anesth 2013;27:124–7. 14. Segal R. Spinal cord stimulation, conception, pregnancy, and labor: case study in a complex regional pain syndrome patient. Neuromodulation 1999;2:41–5. 15. Yoo HS, Nahm FS, Yim KH, Moon JY, Kim YS, Lee PB. Pregnancy in woman with spinal cord stimulator for complex regional pain syndrome: a case report and review of the literature. Korean J Pain 2010;23:266–9. 16. Anso´ M, Veiga-Gil L, De Carlos J, Hualde A, Pe´rez-Cajaraville J. Neuraxial analgesia in a pregnant woman with Fowler’s syndrome and sacral neuromodulation. Int J Obstet Anesth. http://dx.doi. org/10.1016/j.ijoa.2016.11.008. [Epub ahead of print]. 17. Paluzzi A, Bain PG, Liu X, Yianni J, Kumarendran K, Aziz TZ. Pregnancy in dystonic women with in situ deep brain stimulators. Mov Disord 2006;21:695–8. 18. Ziman N, Coleman RR, Starr PA, et al. Pregnancy in a series of dystonia patients treated with deep brain stimulation: outcomes and management recommendations. Stereotact Funct Neurosurg 2016;94:60–5. 19. Bernardini DJ, Pratt SD, Takoudes TC, Simopoulos TT. Spinal cord stimulation and the pregnant patient-specific considerations for management: a case series and review of the literature. Neuromodulation 2010;13:270–4. 20. Patel S, Das S, Stedman RB. Urgent cesarean section in a patient with a spinal cord stimulator: implications for surgery and anesthesia. Ochsner J 2014;14:131–4.
4 21. Sommerfield D, Hu P, O’Keeffe D, McKeating AK. Caesarean section in a parturient with a spinal cord stimulator. Int J Obstet Anesth 2010;19:114–7. 22. Young AC, Lubenow TR, Buvanendran A. The parturient with implanted spinal cord stimulator: management and review of the literature. Reg Anesth Pain Med 2015;40:276–83. 23. Wiseman OJ, v d Hombergh U, Koldewijn EL, et al. Sacral neuromodulation and pregnancy. J Urol 2002;167:165–8. 24. Yaiesh SM, Al-Terki AE, Al-Shaiji TF. Safety of sacral nerve stimulation in pregnancy: a literature review. Neuromodulation 2016;19:770–9. 25. Ali Sakr Esa W, Toma I, Tetzlaff JE, Barsoum S. Epidural analgesia in labor for a woman with an intrathecal baclofen pump. Int J Obstet Anesth 2009;18:64–6. 26. Badve M, Shah T, Jones-Ivy S, et al. Ultrasound guided epidural analgesia for labor in a patient with an intrathecal baclofen pump. Int J Obstet Anesth 2011;20:370–2. 27. Kim SH, Song JE, Kim SR, et al. Teratological studies of prenatal exposure of mice to a 20 kHz sawtooth magnetic field. Bioelectromagnetics 2004;25:114–7. 28. Martin FB, Bender A, Steuernagel G, et al. Epidemiologic study of Holstein dairy cow performance and reproduction near a high-
Editorial
29.
30.
31.
32.
33.
voltage direct-current powerline. J Toxicol Environ Health 1986;19:303–24. Rommereim DN, Rommereim RL, Sikov MR, et al. Reproduction, growth, and development of rats during chronic exposure to multiple field strengths of 60-Hz electric fields. Fundam Appl Toxicol 1990;14:608–21. Souzdalnitski D. Analgesia for the parturient with chronic nonmalignant pain. Tech Reg Anaesth Pain Manag 2014;18:166–71. Trikha AB, Baidya KD, Singh PM. Complex regional pain syndrome and pregnancy. J Obstet Anaesth Crit Care 2012;2:69–73. North JM, Hong KJ, Cho PY. Clinical outcomes of 1 kHz subperception spinal cord stimulation in implanted patients with failed paresthesia-based stimulation: results of a prospective randomized controlled trial. Neuromodulation 2016;19:731–7. Schu S, Slotty PJ, Bara G, von Knop M, Edgar D, Vesper J. A prospective, randomised, double-blind, placebo-controlled study to examine the effectiveness of burst spinal cord stimulation patterns for the treatment of failed back surgery syndrome. Neuromodulation 2014;17:443–50.
EDITORIAL
www.obstetanesthesia.com
Neuromodulation and obstetric anaesthesia Neuromodulation is a rapidly evolving area of medical practice and obstetric anaesthetists are likely to encounter patients with neuromodulatory devices in situ more frequently. Defined by the International Neuromodulation Society as ‘‘the alteration of nerve activity through the delivery of electrical stimulation or chemical agents to targeted sites of the body”,1 neuromodulation is now used to treat a seemingly ever expanding range of conditions.2 Neuromodulation systems have traditionally been reserved as second or third line treatments – generally considered only after other medical and surgical options have failed. In the past, systems have been considered prohibitively expensive and implantation has required major invasive surgery. However, in recent years, new generation systems have become progressively smaller and easier or less destructive to insert. Despite the continuing lack of Class 1 evidence of effectiveness in pain management, the evidence of costeffectiveness of neuromodulation compared with medical treatment alone is likely to support the expansion of use, both in terms of absolute numbers of patients and in the range of indications.3–5 Most neurostimulation systems consist of distal electrode(s) placed adjacent to a target site, with connecting leads tunneled over a variable distance to a subcutaneous Implanted Pulse Generator (IPG). The IPG has an integrated battery, which is either replaced surgically every few years, or more commonly now (especially in younger patients) is charged remotely using an external induction charging system. This device is generally worn intermittently by the patient, typically a few hours per week, in close proximity to the IPG. Common neuromodulation targets include various intracranial and neuraxial sites, as well as peripheral nerves. However, many additional potential targets and modes of neuromodulation are emerging. Deep brain stimulation (DBS) has been used extensively for Parkinson’s disease, and less commonly for a range of other conditions including myotonic syndromes, tremor associated with multiple sclerosis, and psychiatric conditions such as intractable depression, Tourette’s syndrome and obsessive compulsive disorder.6,7 Spinal cord stimulation is most commonly used for failed back (surgery) syndrome (FBSS)8–10 and complex regional pain syndrome (CRPS).11–15 Peripheral nerve stimulators can be used for mononeuropathies
such as occipital or trigeminal neuralgia. Recently, dorsal root ganglion (DRG) stimulators have been used for more localized pain conditions such as post-thoracotomy pain, post-herpetic neuralgia and post-herniorrhaphy pain. Sacral nerve stimulators can be used both for pain conditions and bladder or bowel sphincter dysfunction. In this issue of the journal, Anso´ et al. present a case report of a young patient with a sacral nerve stimulator used very effectively to treat bladder sphincter dysfunction associated with Fowler’s Syndrome.16 The field of neuromodulation also encompasses intrathecal drug delivery therapies, which supply infusions of medications directly into the cerebrospinal fluid (CSF). The infusion is run from a pump, typically implanted over the iliac fossa in the lower abdominal wall. A catheter runs subcutaneously from the pump into the intrathecal space, commonly introduced at either the L2–3 or L3–4 intervertebral space. Intrathecal medications include baclofen to relieve the spasticity of cerebral palsy or spinal cord injury, and analgesics for chronic (especially malignant) pain. Whilst many intracranial systems are used in older patients, there are already case reports of women with DBS systems requiring obstetric care.17,18 There are also multiple case reports (and short case series) of pregnant women with cervical and thoracic spinal8,10–15,19–22 and sacral nerve stimulators23,24 in situ. Several case reports have been published of successful epidural analgesia in the presence of intrathecal infusion pumps.25,26
Management of neuromodulation systems during pregnancy There is currently a lack of meaningful human research to assess the impact of neuromodulation systems on pregnancy (or vice versa) – most particularly, there is a paucity of data on the theoretical implications of the resulting electromagnetic fields on the developing fetus. Some animal data exist, such as studies examining the reproductive health of laboratory rats and dairy cattle exposed to high voltage powerlines.27–29 However, in the absence of good quality human data, current recommendations from all neuromodulation device companies are that devices be switched off for the duration of pregnancy. Accordingly, the Food and Drug Administration (FDA) and similar bodies have not licensed
2 neuromodulation systems for use during pregnancy. Neither the companies – nor the authors of this editorial – can be seen to condone the ‘off label’ use of neuromodulation during pregnancy. However, this should not preclude a rational discussion of the risks and benefits that this may involve, and consideration of research that could potentially be undertaken in the future in order to further delineate these risks. This may represent an example in clinical practice where the theoretical risk of an unknown harm needs to be weighed against the genuine risk of known morbidity. Clearly the consequences of turning off neuromodulation during pregnancy vary depending on the indication for which the device was inserted. Patients with chronic pain will need to take alternative analgesia to replace the pain relief provided by the stimulator, and these analgesics themselves may have adverse effects during pregnancy (e.g. opioid dependence in the newborn). Alternatively, many chronic pain patients choose to endure poor pain control for the duration of the pregnancy, which may have its own psychosocial and physiological consequences. There is little research examining the holistic consequences of chronic pain on outcomes in pregnancy and reproductive health more broadly.30,31 The patient described in Anso´’s case report clearly suffered significant morbidity associated with turning off her device. It is quite conceivable that her repeated episodes of urinary sepsis could have independently threatened the viability of her pregnancy. Many IPG systems are not designed to be turned off for prolonged periods of time and batteries become nonviable if allowed to completely discharge.
Editorial insertion. These electrodes are then tunneled to the IPG, which is typically implanted in the lower flank or upper buttock. One case report describes the use of ultrasound to delineate the exact location of an intrathecal catheter prior to epidural analgesia.26 It is also important to establish what other form of spinal surgery the patient has undergone, particularly in cases of FBSS. The integrity of the epidural space is important for the prospects of successful epidural analgesia. Any open back surgery from a posterior approach, including the insertion of plate electrodes via laminectomy, has the potential to compromise the epidural space at that level, leading to an increased risk of dural puncture and partial or total failure of epidural anaesthesia. Spinal anaesthesia should be safe and effective and the risk to the system is minimised if the approach is made at a level anatomically separate from the location of the leads and electrodes. Whilst not globally recommended, prophylactic antibiotics would seem prudent, given the catastrophic consequences of iatrogenic infection which generally necessitates removal of the entire system. If the patient has chosen to use the device during pregnancy, it would seem advisable to turn the stimulation or drug delivery device off for the duration of labour and birth, including during placement of an epidural catheter or during caesarean section. Neuromodulation systems can be turned off either with the patient’s own control unit or by application of a magnet over the IPG, in a similar way to application of a magnet over a cardiac pacemaker.
Guidelines for the obstetric team Implications of neuromodulation systems for obstetric anaesthetists The most important question for the obstetric anaesthetist is whether neuraxial anaesthesia can be safely conducted and whether it is likely to be effective. There is no absolute contraindication to epidural or spinal anaesthesia. However, there is the theoretical risk of damaging spinal stimulation systems via direct trauma or infection. Pre-anaesthetic assessment should include a detailed record of the exact anatomical location of the entire system, including the electrodes, connecting leads and IPG. This information can be remarkably difficult to obtain, especially after-hours. Ideally, contact with the clinician who implanted the device should be made, with review of the original operation report. Percutaneous spinal systems are commonly inserted via either the L2–3 or L3–4 interspace and then the electrodes are advanced under X-ray guidance to lie at the target location in the low thoracic epidural space. Plate electrodes are generally placed in the low thoracic epidural space via a laminectomy. Leads may be anchored adjacent to the interspinous ligament at the point of
In addition to the considerations for anaesthetists, there are also important considerations for the obstetric team. Early involvement of a specialist pain physician may assist the obstetric team, and the woman herself, to weigh the relative risks and benefits of alternative analgesic options including continuing to use neuromodulation throughout the pregnancy. The physiological changes of pregnancy can theoretically result in stretching, dislodgement or damage to electrodes and connecting leads. Previously, IPGs were commonly placed in a suprapubic or iliac fossa location where they could be damaged during caesarean delivery. Intrathecal pumps are also often located in this area. Implanted Pulse Generators are now typically located in the upper anterior chest wall or in the upper buttock or flank, and are at far less surgical risk. Surgeons are advised to avoid monopolar diathermy in the vicinity of neurostimulatory systems as it may cause damage to the IPG. There is also potential for diathermy to heat the electrodes and this thermal energy maybe be transferred along the length of the electrode, resulting in burns to distant neural structures.
Editorial Another major consideration is Magnetic Resonance Imaging (MRI) compatibility. Magnetic resonance imaging has become an important imaging modality for investigating many obstetric conditions, for example placental implantation disorders. Many older neuromodulation systems are incompatible with MRI. The induced electromagnetic field may dislodge implanted components, damage the device electronics or generate voltage within the leads. Some newer systems may be MRI ‘conditional’, whereby MRI is possible but specific guidance is required from the manufacturer prior to scanning.
Future directions This is such a rapidly evolving area of medicine that, even if quality evidence were available to support the safety of current neuromodulation systems in pregnancy, inevitably new technology will supersede the old. For example, there is now Class II evidence to indicate the superiority of burst stimulation (pulsed wave) systems and high frequency (10 kHz) rather than tonic (60–200 Hz) stimulation in pain management.32,33 These new systems appear to provide superior pain relief for back pain and a patient experience that is free from the paraesthesia common to low frequency, tonic stimulation. Paraesthesia-free systems should enable placebocontrolled trials and thus help improve the quality of evidence available about their continued use.
Conclusion Subject to further supportive evidence from high level randomised trials, neuromodulation is likely to become increasingly common. As in many other conditions, safe obstetric management relies on excellence in communication between the entire treating team, including the obstetrician, pain physician, neurosurgeon and anaesthetist. Further research is needed to weigh the potential risks and benefits from neuromodulation in pregnant women and their offspring. James Griffiths Royal Women’s Hospital, Melbourne, Victoria, Australia E-mail address: [email protected] Peter Teddy Department of Neurosurgery, Royal Melbourne Hospital, Department of Surgery, The University of Melbourne, Melbourne, Victoria, Australia
3
References 1. International Neuromodulation Society. Available from http:// www.neuromodulation.com/ [accessed 2 Nov 2016]. 2. Levy RM. The evolving definition of neuromodulation. Neuromodulation 2014;17:207–10. 3. Kumar K, Malik S, Demeria D. Treatment of chronic pain with spinal cord stimulation versus alternative therapies: cost-effectiveness analysis. Neurosurgery 2002;51:106–15. 4. Kumar K, Rizvi S. Cost-effectiveness of spinal cord stimulation therapy in management of chronic pain. Pain Med 2013;14:1631–49. 5. Taylor RS, Ryan J, O’Donnell R, Eldabe S, Kumar K, North RB. The cost-effectiveness of spinal cord stimulation in the treatment of failed back surgery syndrome. Clin J Pain 2010;26:463–9. 6. Hariz M, Blomstedt P, Zrinzo L. Future of brain stimulation: new targets, new indications, new technology. Mov Disord 2013;28:1784–92. 7. Pereira EA, Green AL, Nandi D, Aziz TZ. Deep brain stimulation: indications and evidence. Expert Rev Med Devices 2007;4:591–603. 8. Das B, McCrory C. Spinal cord stimulation in pregnancy with failed back surgery syndrome. Ir Med J 2014;107:117–8. 9. Gredilla E, Abejon D, Del Pozo C, Del Saz J, Gilsanz F. Failed back surgery, spinal cord stimulation and pregnancy: presentation of a case. Rev Esp Anestesiol Reanim 2012;59:511–4. 10. Fedoroff IC, Blackwell E, Malysh L, McDonald WN, Boyd M. Spinal cord stimulation in pregnancy: a literature review. Neuromodulation 2012;15:537–41. 11. Ahmed S, Lindsay JM, Snyder DI. Spinal cord stimulation for complex regional pain syndrome: a case study of a pregnant female. Pain Physician 2016;19:E487–93. 12. Hanson JL, Goodman EJ. Labor epidural placement in a woman with a cervical spinal cord stimulator. Int J Obstet Anesth 2006;15:246–9. 13. Ito S, Sugiura T, Azami T, Sasano H, Sobue K. Spinal cord stimulation for a woman with complex regional pain syndrome who wished to get pregnant. J Anesth 2013;27:124–7. 14. Segal R. Spinal cord stimulation, conception, pregnancy, and labor: case study in a complex regional pain syndrome patient. Neuromodulation 1999;2:41–5. 15. Yoo HS, Nahm FS, Yim KH, Moon JY, Kim YS, Lee PB. Pregnancy in woman with spinal cord stimulator for complex regional pain syndrome: a case report and review of the literature. Korean J Pain 2010;23:266–9. 16. Anso´ M, Veiga-Gil L, De Carlos J, Hualde A, Pe´rez-Cajaraville J. Neuraxial analgesia in a pregnant woman with Fowler’s syndrome and sacral neuromodulation. Int J Obstet Anesth. http://dx.doi. org/10.1016/j.ijoa.2016.11.008. [Epub ahead of print]. 17. Paluzzi A, Bain PG, Liu X, Yianni J, Kumarendran K, Aziz TZ. Pregnancy in dystonic women with in situ deep brain stimulators. Mov Disord 2006;21:695–8. 18. Ziman N, Coleman RR, Starr PA, et al. Pregnancy in a series of dystonia patients treated with deep brain stimulation: outcomes and management recommendations. Stereotact Funct Neurosurg 2016;94:60–5. 19. Bernardini DJ, Pratt SD, Takoudes TC, Simopoulos TT. Spinal cord stimulation and the pregnant patient-specific considerations for management: a case series and review of the literature. Neuromodulation 2010;13:270–4. 20. Patel S, Das S, Stedman RB. Urgent cesarean section in a patient with a spinal cord stimulator: implications for surgery and anesthesia. Ochsner J 2014;14:131–4.
4 21. Sommerfield D, Hu P, O’Keeffe D, McKeating AK. Caesarean section in a parturient with a spinal cord stimulator. Int J Obstet Anesth 2010;19:114–7. 22. Young AC, Lubenow TR, Buvanendran A. The parturient with implanted spinal cord stimulator: management and review of the literature. Reg Anesth Pain Med 2015;40:276–83. 23. Wiseman OJ, v d Hombergh U, Koldewijn EL, et al. Sacral neuromodulation and pregnancy. J Urol 2002;167:165–8. 24. Yaiesh SM, Al-Terki AE, Al-Shaiji TF. Safety of sacral nerve stimulation in pregnancy: a literature review. Neuromodulation 2016;19:770–9. 25. Ali Sakr Esa W, Toma I, Tetzlaff JE, Barsoum S. Epidural analgesia in labor for a woman with an intrathecal baclofen pump. Int J Obstet Anesth 2009;18:64–6. 26. Badve M, Shah T, Jones-Ivy S, et al. Ultrasound guided epidural analgesia for labor in a patient with an intrathecal baclofen pump. Int J Obstet Anesth 2011;20:370–2. 27. Kim SH, Song JE, Kim SR, et al. Teratological studies of prenatal exposure of mice to a 20 kHz sawtooth magnetic field. Bioelectromagnetics 2004;25:114–7. 28. Martin FB, Bender A, Steuernagel G, et al. Epidemiologic study of Holstein dairy cow performance and reproduction near a high-
Editorial
29.
30.
31.
32.
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voltage direct-current powerline. J Toxicol Environ Health 1986;19:303–24. Rommereim DN, Rommereim RL, Sikov MR, et al. Reproduction, growth, and development of rats during chronic exposure to multiple field strengths of 60-Hz electric fields. Fundam Appl Toxicol 1990;14:608–21. Souzdalnitski D. Analgesia for the parturient with chronic nonmalignant pain. Tech Reg Anaesth Pain Manag 2014;18:166–71. Trikha AB, Baidya KD, Singh PM. Complex regional pain syndrome and pregnancy. J Obstet Anaesth Crit Care 2012;2:69–73. North JM, Hong KJ, Cho PY. Clinical outcomes of 1 kHz subperception spinal cord stimulation in implanted patients with failed paresthesia-based stimulation: results of a prospective randomized controlled trial. Neuromodulation 2016;19:731–7. Schu S, Slotty PJ, Bara G, von Knop M, Edgar D, Vesper J. A prospective, randomised, double-blind, placebo-controlled study to examine the effectiveness of burst spinal cord stimulation patterns for the treatment of failed back surgery syndrome. Neuromodulation 2014;17:443–50.