Abstract
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.
Keywords
Cancer pain, Neuropathic pain, Spinal cord stimulation
Case Presentation
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.
Discussion
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.
Indications
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 healthcare costs, greater ind