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Spinal cord stimulation for patients with chronic pain conditions

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Carol Banks, MSc (Pain Management), RN, Dip.

Nurse Specialist, Pain Management-Basildon and Thurrock General Hospitals NHS Trust, Orsett Hospital, Orsett

Chronic pain is a complex and multidimensional experience both for the person in pain and for the health-care team treating that person. It is for this reason that a multidisciplinary, biopsychosocial approach is used in chronic pain management clinics.

Chronic pain is a complex and multidimensional experience both for the person in pain and for the health-care team treating that person. It is for this reason that a multidisciplinary, biopsychosocial approach is used in chronic pain management clinics.

 


 

The diagnosis and pathology of chronic pain, particularly back pain, is still poorly understood, which is why most pain clinics have an armoury of interventions, both invasive and non-invasive, that can be used both therapeutically and diagnostically to help sufferers of chronic pain.

 


 

The International Association for the Study of Pain (IASP) recommends that chronic pain clinics take a multidisciplinary approach (1997). Most chronic pain clinics employ staff from a number of disciplines including medicine, nursing, psychology and physiotherapy, and offer a variety of different interventions ranging from cognitive behavioural pain management programmes to the implantation of pain-management devices such as spinal cord stimulation (SCS) devices.

 


 

A pain clinic assessment of a person with chronic pain begins with a biopsychosocial assessment in order to understand the person who is in pain and not just the pain itself. This involves an assessment not only of the intensity of pain and the patterns, but an understanding of these in the context of the person and his or her environment. Patients with a surgically remedial condition can be referred appropriately. Others with chronic pain can enter the pain clinic treatment continuum. This continuum is not linear and can be entered and exited at any point.

 


 

Invasive techniques in pain management are an important addition to conservative treatment, but only when the pain is localised. Before any invasive procedure is undertaken patients should always be fully informed regarding complications and side-effects and any limited duration of action of the treatment that is planned.

 


 

This paper will look at SCS for the treatment of chronic, non-malignant pain, within a multidisciplinary chronic pain service.

 


 

What is spinal cord stimulation?
SCS is a reversible non-destructive treatment for some types of chronic pain. SCS is an electrical device consisting of implanted electrodes, connected by a lead to a receiver or pulse generator. The lead is inserted into the epidural space percutaneously or as an open operation. The receiver or pulse generator is usually implanted in the abdominal wall; it can then be connected to the lead via an extension cable, which is inserted subcutaneously.

 


 

A pulse generator (internal power source) will last for five to seven years, depending on how it is used and the parameters required. The pulse generator is replaced surgically. A receiver (external power source) should last indefinitely. Potentially, a patient will require the device for the rest of his or her life, although on occasions the patient’s pain may improve and the device can be removed.

 


 

The overall aim of SCS is to reduce the severity of pain in order to improve function and enhance quality of life and pain-management coping strategies; it is not a curative treatment. A reduction in pain intensity may improve sleep and mobility, reduce malaise and increase alertness by allowing a reduced drug intake. This will increase morale, reduce depression and enhance the ability to cope with residual pain (Simpson, 1994).

 


 

Because of the intricate interaction between physiological and psychological factors in chronic pain, SCS therapy cannot be considered as a standalone treatment. Therefore, a full complement of disciplines experienced in treating the patient in chronic pain is necessary. A patient-centred biopsychosocial model to understand pain is used that involves the patient and a multidisciplinary pain management team. The team consists of:

 


 

- Consultant pain specialist

 


 

- Nurse specialist in pain management

 


 

- Psychologist specialising in pain management

 


 

- Physiotherapist specialising in pain management.

 


 

How is SCS done?
Most physicians who perform SCS implantation for chronic pain perform the operation in two stages. The first stage involves the placing of the lead containing the electrodes into the epidural space using X-ray control to guide the lead placement. This is usually performed under local anaesthetic to enable the patient to feed back to the doctor operating where the tingling is felt. The aim is to produce stimulation-induced paresthesia (tingling) in the area of pain.

 


 

The patient then has the opportunity to trial SCS for one to four weeks at home. If the outcome of the trial is positive and the patient reports a reduction in pain greater than 50% and an improvement in his or her quality of life, the patient proceeds to the second stage and a pulse generator or receiver is implanted. The patient is able to control the system using a hand-held programmer, or a transmitter attached to the implanted receiver. The Medtronic website provides more information (see ‘Useful websites’ box). Figure 1 shows SCS systems in place with external and internal power sources.

 


 

How does SCS work?
SCS, along with other pain-management techniques such as TENS (Transcutaneous Electrical Nerve Stimulation), developed as a direct consequence of the gate control theory. This theory was proposed by Melzack and Wall in 1965 and suggests that pain is influenced by internal factors in the central and peripheral nervous systems and by external factors such as emotions and cognition (Bonica 1990).

 


 

Both small- and large-diameter nerve fibres carry sensory input to the dorsal horn of the spinal cord, where a notional ‘pain gate’ is thought to occur. The gate control theory describes a scenario in which the stimulation of large-diameter fibres leads to impulses from those fibres overriding those from small-diameter fibres, with the result that pain is diminished.

 


 

In simplistic terms, SCS achieves the same aim by stimulating large-diameter fibres but other mechanisms are also involved. SCS seems to activate several different mechanisms to treat different types of pain. In ischaemic pain, for example, animal experiments demonstrate that inhibition of afferent activity in the spinothalamic tracts, long-term suppression of sympathetic activity and antidromic effects on peripheral reflex circuits may take place to alleviate the pain of the condition (Linderoth and Foreman, 1999). The first SCS system was implanted in 1967 (Shealy et al, 1967); since then technology and the technique have been refined.

 


 

Indications for SCS
It is important that an accurate diagnosis of the underlying pain aetiology and type are made before SCS is considered for a patient. There is general agreement that SCS is a treatment for severe neuropathic pain and ischaemic pain. These include radiculopathy, complex regional pain syndromes type 1 and 2, peripheral nerve lesions, and ischaemic pain conditions such as peripheral vascular disease and, most recently, refractory angina (confirmed by a European Federation of IASP Chapters’ (EFIC) consensus statement) (Gybels et al, 1998). The European consensus statement on neuromodulation and more information regarding SCS for refractory angina are available. See ‘Useful websites’.

 


 

Assessment and selection process for SCS
Over the many years that SCS has been in clinical use criteria to aid the selection process have gradually evolved. These criteria include both physiological and psychological issues, and the performance of a trial screening period. The selection process for SCS is a multi-step process. Increased refinement of patient-selection criteria has been an important focus to improve SCS outcome, and throughout the history of SCS application there has been a search to refine patient-selection criteria (Nelson et al, 1996). The goal of the selection process has developed in order to select those patients for whom SCS will be most effective, while also assuring that resources are not expended unnecessarily.

 


 

Patients with chronic pain who are seen in a pain clinic have often already undergone numerous failures of treatment. Yet another failure could be potentially damaging to the individual. Therefore the benefits of adequate patient selection are threefold:

 


 

- Identifying those patients who are most likely to benefit from SCS

 


 

- Preventing unsuitable candidates from undergoing a costly, invasive procedure

 


 

- Redirecting patients for whom SCS would be unsuitable to more appropriate treatments.

 


 

The criteria are clearly defined in the EFIC European consensus statement (Gybels, 1998). This highlights the importance of psychological screening and a clear diagnosis of the pain condition before proceeding to SCS implantation (Kupers, 1994). An experienced clinical/ counselling psychologist assesses all patients being considered for SCS implantation. The aim of the psychological assessment is: ‘To assess the appropriateness and timing of the intervention according to the individual person’s needs’ (Nelson, 1996). General inclusion and exclusion criteria are listed in Table 1.

 


 

Patient education and preparation
In order to make an informed choice about the appropriateness of SCS as a treatment for their pain it is crucial that patients are armed with relevant information. Patient education should address all aspects of SCS treatment, including expectations of outcome, complications and the possibility of treatment failure. This issue is of particular importance as these patients have often already undergone many treatment failures - failure of other forms of pain relief, including medication, is usually the main reason why they are being considered for SCS.

 


 

Referral for SCS is often viewed as a last resort by both patient and referring doctors. Patients can be apprehensive, fearful and hesitant about their forthcoming SCS trial. They need to know that there is never a 100% guarantee that SCS will provide even partial relief. Anecdotal evidence suggests that successful outcomes are often related to expectations met. Therefore the primary goal of SCS patient education is to ensure the patient has realistic expectations regarding outcome. SCS implantation involves patient participation not only during the procedure and the trial period, but also with respect to ongoing pain management and rehabilitation. Preparation and education of this group of patients is usually the role of the pain nurse specialist.

 


 

Review of treatment
Patients are routinely reviewed in the outpatient clinic for wound care, programming and assessment and have open access to the nurse specialist for advice and trouble-shooting (Box 1).

 


 

Conclusion
SCS is only one of the possible treatment options and should not be seen as a last resort but as an option for certain patients who fit the criteria and undergo a detailed physiological and psychological assessment. New indications for SCS are emerging all the time. Nurses need to be aware of these new developments in order to be able to care for patients with chronic pain.

 


 

Useful websites
- Manufacturer’s website: www.medtronic.com

 


 

- European Journal of Pain website: www.harcourt-international.com

 


 

- For information on SCS in angina: www.angina.org

 

 

Bonica, J.J. (1990) History of pain theories, in: The Management of Pain, Bonica, J.J. (Ed.). Philadelphia: Lea and Febiger.


Gybels, J., Erdine. S., Maeyaert, J. et al. (1998) Neuromodulation of pain: a consensus statement prepared in Brussels 16-18 January 1998 by the task force of the European Federation of IASP Chapters (EFIC). European Journal of Pain 2: 3, 203-209.


International Association for the Study of Pain. (1997) Provision of Pain Services. London: Association of Anaesthetists of Great Britain and Ireland and IASP.


Kupers, R., Vanden Oever, R. Van Houdenhove, B. et al. (1994) Spinal cord stimulation in Belgium: a nationwide survey on the incidence, indications and therapeutic efficacy by the health insurer. Pain 56: 211-216.


Linderoth, B., Foreman, R.D. (1999) Physiology of spinal cord stimulation: review and update. Neuromodulation 2: 3, 150-164.


Melzack, R., Wall, P. (1965) Pain mechanisms: a new theory. Science 150: 971-973.


Nelson, D.R., Kennington, M., Nory, D.M., Sqriten, P. (1996) Psychological selection criteria for implantable spinal cord stimulation. Pain Forum 5: 93-103.


Shealy, C.N., Mortimer, J.T., Reswick, J.B. (1967) Electrical inhibition of pain by stimulation of the dorsal columns: preliminary clinical report. Anaesthesia and Analgesia 46: 489-491.


Simpson, B. (1994) Spinal cord stimulation. Pain Reviews 1: 199-230.


van Buyten, J.P., Zundert, J.V., Vueghs, P., Vanduffel, L. (2001) Efficacy of spinal cord stimulation: 10 years’ experience in a pain centre in Belgium. European Journal of Pain 5: 299-307.
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