Around 56% of sufferers of cancer-related pain, experience moderate to severe pain and around 10-15% of these patients fail to get adequate pain relief with conventional treatment. Spinal cord stimulators have been used for this refractory group of patients with neuropathic cancer pain. A case report of a seventy-year-old female, who suffered from severe pain from metastasis to her sacrum from renal cell carcinoma, which did not respond to conventional therapy, is presented. On successful implantation of the spinal cord stimulator, she had almost 90% pain relief and improving her mobility and quality of life. A review of the spinal cord stimulators, their indications, contraindications and benefits is also included.
Cancer pain, Neuropathic pain, Spinal cord stimulation
A 70-year-old-lady was referred from hospice to the pain clinic complaining of continuous pain and discomfort which made her bed bound, for most of the time during the day. She had significant burning pain down the back of her thighs to her knees when she sat for 10-15 minutes at a time. She was not getting any relief from conventional analgesic drugs. She was referred in view of considering an intrathecal pump or spinal cord stimulator.
A diagnosis of neuropathic pain in both legs, due to nerve root involvements, secondary to metastasis to sacrum from renal cell carcinoma of right kidney was made. The pain was persistent with a pain score of 8-9 on the Visual Analogue Scale.
A year earlier, she was diagnosed with a renal cell carcinoma or hypernephroma of the right kidney and widespread metastasis in the sacrum. She underwent right radical nephrectomy and was started on chemotherapy.
For the previous 20 years, she has been on anti-hypertensive therapy for essential hypertension. Her other medications included sunitinib malate (SUTENT) for her advanced renal cell carcinoma, and zoledronic acid infusions (to prevent skeletal fractures in patients with cancers. It is also be used to treat hypercalcemia of malignancy and can be helpful for treating pain from bone metastases). Analgesics consisted of paracetamol, gabapentin and oxycontin.
The patient was made aware that before a spinal cord stimulation system is permanently implanted, most physicians recommend a trial period. During this time, a temporary stimulator is surgically implanted to allow the therapy for a while (a minimum of 24 hours, but can be up to several weeks). This trial period is important to determine if the therapy provides satisfactory pain relief and is a good way to find out if the patient is comfortable with the sensations of spinal stimulation. If the system works, a permanent stimulation system can be implanted.
The trial of stimulator was done under full aseptic conditions, x ray guidance with an Octrode electrode (50cm) was placed at the level of T10/11. The patient reported immediate decrease in the VAS score to 1-2 out of 10. She returned to the clinic, a week later and remained relatively pain free and was able to sit out of bed for the first time in years. Her exercise tolerance improved significantly.
Two weeks later, the patient underwent implantation with permanent leads and a pulse generator. The procedure was done in ambulatory surgery, and the postoperative course was uneventful. The patient used the spinal cord stimulator continuously and reported 90% pain relief both at rest and with activities. She decreased her pain relief medications and returned to her pre-neuropathy level of functioning. At two months post-implant, the patient continued to report good pain control (VAS scores 1 to 2 out of 10) and improved functional status.
In a survey for patients suffering from cancer in Europe in 2006-2007, it was found that 69% patients had pain related difficulties with everyday activities and 56% suffered from moderate to severe pain at least monthly1. The World Health Organisation guideline for cancer pain follows a three step ladder. The first step is the use of paracetamol, aspirin and non-steroidal anti-inflammatory drugs. The second step is the use of weak opioids, where as the third step advocates strong opioids2. The use of adjuvants like tricyclic antidepressants and antiepileptics can be done at any step. But the use of this guideline does not result in adequate pain relief in 10% to 15% patients3. The uses of interventional pain relief procedures have been advocated in this group of patients. The use of spinal cord stimulator (SCS) has been reported and is being increasingly used for intractable cancer pain.
Spinal Cord Stimulator as an analgesic
Mechanism of action
Shealy and Colleagues first used the spinal cord stimulator for pain relief in 19674. Melzack and Wall proposed the ‘gate-control theory’ of pain in 19655. The spinal cord stimulator is based on this theory which postulates that it activates the large diameter afferent fibres by applying an external electrical field that closes the gate and stops the transmission of pain. It stimulates the dorsal column, which in turn inhibits transmission through pain conducting spino thalamic tract. Linderoth et al suggested that there is increased release of both GABA and serotonin and suppression of glutamate and aspartate in the dorsal horn of spinal cord6,7. In ischaemic pain, it has been suggested that the mechanism of action is due to sympathetic inhibition and vasodilatation leading to increased oxygen supply8.
- Many studies have shown the benefit of spinal cord stimulators in the management of severe chronic pain in various causes9:
- Back pain in ‘Failed Back Surgery Syndrome (FBS)10,11.
- Radicular pain syndrome or radiculopathies not amenable to operative therapy
- Post-laminectomy pain
- Degenerative disk disease (DDD)/herniated disk pain refractory to conservative and surgical therapies
- Epidural fibrosis, lumbar adhesive arachnoiditis
- Peripheral vascular disease12
- Ischaemic heart disease13
- Complex Regional Pain Syndrome (CRPS), Reflex Sympathetic Dystrophy (RSD), or causalgia14,15
Benefits of using Spinal Cord Stimulator
- Effectively improve pain relief (a majority of patients may experience at least a 50% reduction in pain)2-4
- Increase activity levels2-5
- Reduce the use of narcotic medications3-5
- Lead to reduced hospitalisations and surgical procedures, reduced health care costs, greater independence, and improved quality of life2-4
- Screening trial allows testing of a patient’s response before a full implant
- Patient control within physician-set limits
- Non-destructive procedure compared with surgical alternatives
- Criteria for implanting spinal cord stimulator
- Chronic, intractable pain for more than three months
- Objective evidence of pathology concordant with pain complaint
- Lack of adequate relief from more conventional treatments
- Initial or further surgical intervention not indicated
- Patient stable psychologically
- Patient does not demonstrate drug seeking behaviour
- Patient can understand the technology and operate the system.
- Patient understands risks involved
- Meets implant screening criteria with no contraindications
Implant screening criteria
- Minimum 50% pain reduction during trial phase of spinal cord stimulation
- The area of paraesthesia generated needs to correspond to the main area of pain, and it should not be unpleasant
- There should be evidence of functional and psychological improvement
Limitations of spinal cord stimulation
- It gives 50-60% pain relief in most patients.
- It does not correct any underlying anatomical problem. In patients with a correctable anatomical lesion, treatments to address the source of the pain should be tried first.
- The safety and effectiveness of this therapy has not been established for paediatric use (patients under the age of 18), pregnancy, unborn foetus, or delivery
- Patients should not scuba dive below ten metres of water or enter hyperbaric chambers above 2.0 atmosphere absolute (ATA).
Risks and Potential Complications of Spinal Cord Stimulation
Most of the risks are relatively minor, including:
- Pain at the incision site
- CSF leak leading to headache
- Allergy to the implanted materials
- Weakness, numbness, clumsiness, paralysis
- Electrode migration
- Electrode failure
- Device failure
- Battery failure and/or battery leakage
- Undesirable changes in stimulation due to scar tissue forming around the leads
Contraindications for implant
- Presence of local infection
- Generalised sepsis
- Patient on anticoagulation
Post implant precautions
- Shortwave, microwave or therapeutic ultrasound diathermy should not be used in patients post implantation as can interact with the neurostimulation system.
- MRI examinations of the head only using an RF transmit/receive head coil may be safely performed in a patient with spinal cord stimulator, using a transmit/receive head coil of a 1.5-Tesla horizontal bore MRI. MRI examinations of any other part of the body are not recommended, as these require the use of the MRI RF transmit body coil, which may produce hazardous temperatures at the location of the implanted lead electrodes.
- Rupture or piercing of the neurostimulator can result in severe burns.
- An implanted cardiac device (eg, pacemaker, defibrillator) may damage a neurostimulator, and the electrical pulses from the neurostimulator may result in an inappropriate response of the cardiac device.
The complete system consists of the following
- An implanted programmable neuropulse generator (IPG) with its rechargeable battery which can be charged via a wireless power charger
- Connecting wires
- Leads or electrodes which can be percutaneous or paddle type
- Physician programmer to adjust the stimulation settings
- Handheld patient programmer device to customise the stimulation
In order to be effective the area of paraesthesia induced by the SCS must overlap the area of pain. At present up to 16 electrodes can be stimulated by one system. So a patient may have one 4-lead electrode to up to four 4-lead or two 8-lead electrodes.
Insertion procedures and techniques
SCS implantation involves a trial phase (usually seven days), in which the electrode is placed at the desired level, anchored to the interspinous ligament and connected via the connecting wires to an external stimulator. The stimulation is started to achieve the desired level and the patient is sent home.
When the patient returns and once the screening criteria are met, the IPG is permanently implanted subcutaneously below the rib cage.
Programming involves selecting the electrode stimulating configuration, adjusting the amplitude, width and frequency of electrical pulses.
Amplitude is set within a range of 0–10V according to the type of electrode used and the type of nerves stimulated. Lower voltage is chosen for peripheral nerves and paddle type electrodes. Ideally paraesthesia should be felt between 2 and 4V. Pulse width usually varies from 100 to 400 microsec.
Widening the pulse width will also broaden the area of paraesthesia. Frequency of pulse wave is usually between 20 and 120Hz. It is generally used for 1-2 hours, 3-4 times everyday
Spinal Cord stimulator in cancer pain
The incidence of neuropathic component in cancer pain is estimated to be around 15% to 40%16. Neuropathic pain is often seen to respond poorly to opioid medications. Often patients with cancer pain require interventional pain management procedures as the side effects of opioids and adjuvant medications often become unbearable.
Recently, spinal cord stimulators have been suggested as a safe and effective management of cancer pain. Cata et al17 showed benefit in chemotherapy –induced pain in two patients. Hamid and Haider18 showed improved pain relief in radiatherapy-induced transverse myelitis. Yakovlev et al19 presented two case reports of two similar cancer patients, with uncontrolled neuropathic pain using conventional medications, who benefitted from the implantation of spinal cord stimulator.
A 70-year-old-lady presented with intractable pain due to metastasis to her sacrum from renal cell carcinoma. The pain was predominantly neuropathic that was not well controlled using traditional pain therapy. The pain was significantly affecting her mobility and quality of life. With the implantation of a spinal cord stimulator, her pain relief and activities were significantly improved. In conclusion spinal cord stimulator can be used as a technique for refractory cancer pain, not responding to conventional treatment.
- Breivik H, Cherny N, Collett B, et al. Cancer-related pain: a pan European survey of prevalence, treatment and patient attitudes. Annals of Oncology 2009;20(8):1420-1433
- Schug SA, Zech D, Dorr U. Cancer pain management according to WHO analgesic guidelines. J Pain Symptom Manage 1990;5:27–32.
- Sloan PA, Melzack R. Long-term patterns of morphine dosage and pain intensity among cancer patients. Hosp J 1999;14:35–47.
- Shealy CN. Dorsal column stimulation. Surg Neurol 1977;7:192.
- Melzack RA, Wall PD. Pain mechanisms: a new theory. Science 1965;150:971–979.
- Linderoth B, Foreman R.Physiology of spinal cord stimulation: review and update. Neuromodulation 1999;3:150–164.
- Oakley J, Prager J.Spinal cord stimulation: mechanism of action. Spine 2002;27:2574–2583.
- Dilorenzo, D. J.; and Bronzino, J. D. (2008). Neuroengineering. CRC Press. Chapter 7
- Cameron T. Safety and efficacy of spinal cord stimulation for the treatment of chronic pain: a 20-year literature review. J Neurosurg 2004;100:254–267.
- Struijk JJ, Holsheimer J, Spincemaille GH, Gielen FL, Hoekema R. Theoretical performance and clinical evaluation of transverse tripolar spinal cord stimulation. IEEE Transactions in Rehabilitation Engineering 1998:6:277–285.
- Ohnmeiss DD, Rashbaum RF, Bogdanorffy GM. Prospective outcome evaluation of spinal cord stimulation in patients with intractable leg pain. Spine 1996;21:1344–1350.
- Ghajar AW, Miles JB. The differential effect of the level of spinal cord stimulation on patients with advanced peripheral vascular disease in the lower limbs. Br J Neurosurg 1996;12:402–408.
- Hautvast RW, DeJongste MJ, Staal MJ, van Gilst WH, Lie KI. Spinal cord stimulation in chronic intractable angina pectoris: a randomized controlled efficacy study. Am Heart J 1998;136:1114–1120.
- Kumar K, Toth C, Nath RK. Spinal cord stimulation for chronic pain in peripheral neuropathy. Surg Neurol 1996;46:363–369.
- Tesfaye S, Watt J, Benbow SJ, Pang KA, Miles J, McFarlane IA. Electrical