Treatment of chronic pain by epidural spinal cord stimulation: a 10-year experience.

Epidural spinal cord stimulation by means of chronically implanted electrodes was carried out on 121 patients with pain of varied benign organic etiology. In 116 patients, the pain was confined to the back and lower extremities and, of these, 56 exhibited the failed-back syndrome. Most patients were referred by a pain management service because of failure of conventional pain treatment modalities. Electrodes were implanted at varying sites, dictated by the location of pain. A total of 140 epidural implants were used: 76 unipolar, 46 Resume electrodes, 12 bipolar, and six quadripolar. Patients were followed for periods ranging from 6 months to 10 years, with a mean follow-up period of 40 months. Forty-eight patients (40%) were able to control their pain by neurostimulation alone. A further 14 patients (12%), in addition to following a regular stimulation program, needed occasional analgesic supplements to achieve 50% or more relief of the prestimulation pain. Pain secondary to arachnoiditis or perineural fibrosis following multiple intervertebral disc operations, when predominantly confined to one lower extremity, seemed to respond favorably to this treatment. Uniformly good results were also obtained in lower-extremity pain secondary to multiple sclerosis. Pain due to advanced peripheral vascular disease of the lower limbs was well controlled, and amputation below the knee was delayed for up to 2 years in some patients. Pain due to cauda equina injury, paraplegic pain, phantom-limb pain, pure midline back pain without radiculopathy, or pain due to primary bone or joint disease seemed to respond less well. Patients who responded to preliminary transcutaneous electrical nerve stimulation generally did well with electrode implants. Notable complications included wound infection, electrode displacement or fracturing, and fibrosis at the stimulating tip of the electrode. Three patients in this series died due to unrelated causes. Epidural spinal cord stimulation has proven to be an effective and safe means of controlling pain on a long-term basis in selected groups of patients. The mechanism of action of stimulation-produced analgesia remains unclear; further studies to elucidate it might allow spinal cord stimulation to be exploited more effectively in disorders that are currently refractory to this treatment modality.

Deep brain stimulation for control of intractable pain in humans, present and future: a ten-year follow-up.

Deep brain stimulation with chronically implanted electrodes has provided satisfactory control of pain in patients with intractable chronic pain syndromes, which have been refractory to medication and other conventional modalities of management. In this series the authors present their experience with 48 patients who have been followed for periods ranging from 6 months to 10 years. Long-term pain control was achieved in 30 patients (63%). Both the periventricular gray and specific sensory thalamic nuclei have been used as targets. Our results indicate that there is an initial 2-year fall-off of pain control caused by idiopathic tolerance, with stable results thereafter, regardless of site of the implant. This is suggestive of some biochemical modification of tissues around the electrode. Patients with failed-back syndrome secondary to multiple disc operations fared well; those with pain secondary to progressive neurological disorders or cancer had only short-term pain relief, and those with thalamic pain, cauda equina injury, or phantom limb pain usually had a poor result. Deep brain stimulation, in selected patients, appears to provide long-term pain control safely with few side effects or complications.

The epidural opioid internalized system.

For several years opioids have been given epidurally with success to control chronic intractable pain. The authors report their 2-year experience with internalization of the epidural catheter and injection port in 18 patients at University Hospital, Saskatoon. In all, 21 devices were used. All patients had metastatic cancer; 16 are now dead. The need for other medications was eliminated with 9 and reduced with 12 devices. In the patients who died, the devices were effective for 82% of their remaining life-span. They were able to spend 46% of this time at home. Blockage of the epidural end of the device was the most common mechanical problem, followed by leakage from the port. One patient suffered meningitis after 11 days as a result of subarachnoid placement of the catheter but responded to removal of the device and antibiotic therapy. The authors have been impressed with the excellent pain relief afforded to many of these patients, and their ability to enjoy life free of the sedative effects of other methods of narcotic administration.

The effect of acetaminophen administration on its disposition and body stores of sulphate.

This investigation was designed to investigate the effects of ingestion of multiple therapeutic doses of acetaminophen on the disposition of the drug and on the cosubstrate, sulfate. Nine healthy volunteers and nine outpatients receiving acetaminophen for chronic pain were involved in the study. Volunteers were given a single 650 mg oral dose of acetaminophen. One week later they were given 650 mg of acetaminophen every six hours for five doses. Patients were maintained on their normal treatment and dosage schedules (600 mg every 3 to 8 h) for the study. In healthy volunteers the half-life of acetaminophen after single and multiple dosing was not significantly different. However, the fraction of acetaminophen recovered in the urine as the sulfate conjugate was less and the glucuronide conjugate greater after multiple dosing than after a single of the drug. There was no difference in the percentage recovered as the parent compound between single and multiple dosing. Serum sulfate levels fluctuated over the 6-h period following administration of single and multiple doses of acetaminophen to volunteers. The mean serum sulfate concentration was less after administration of five sequential 650 mg doses of acetaminophen than after a single dose. The renal clearance of inorganic sulfate showed a corresponding decrease. Unexpectedly, patients on chronic acetaminophen therapy exhibited elevated serum sulfate levels (levels higher than the maximum sulfate concentration seen in volunteers).

Deep brain stimulation for alleviating chronic intractable pain.

The authors present their 4-year experience with 18 patients who had deep brain stimulation. Most were referred because of chronic pain of varied etiology. All conventional modalities of management had failed. Both the paraventricular gray matter and the sensory thalamus were target sites. The 18 patients underwent a total of 21 implants. Follow-up ranged from 6 months to 4 years with moderate relief of prestimulation pain in 14 patients (77%). Patients with failed back syndrome secondary to multiple disc operations fared well. Patients with pain secondary to progressive neurologic disorders or cancer had only short-lived benefits, while those with pain from cauda equina injury or vascular disease had a poor result. Deep brain stimulation appears to be an effective means of controlling chronic pain in selected cases.

Comparison of bupivacaine and lidocaine for intravenous regional analgesia.

In a double blind study, seven volunteers were given lidocaine 0.75 per cent and bupivacaine 0.25 per cent in two trials to compare the agents for use in intravenous regional analgesia. There was no significant difference between the two agents in the duration of analgesia after removal of the tourniquet. Bupivacaine produced fewer side effects. It also consistently produced persistent analgesia on the posterolateral aspect of the forearm.

The role of atropine in electroconvulsive therapy.

The practice of preparing patients about to undergo electroshock treatment with atropine has been re-examined in the light of the great variety of practices which prevail both in terms of dose, route of administration and timing of the drug, as reported in the literature. By using patients as their own controls in the course of a series of treatments, it was determined that there are no appreciable differences between intravenous atropine given in different doses at different times and no atropine at all. Since no evidence was found that atropine contributes to cardiovascular stability or to consistent drying of secretions, and since its omission was not accompanied by untoward effects, it is suggested that the agent is not needed nor even necessarily desirable as a premedicant in electroshock therapy.

Chronic pain syndromes and their treatment. III. The piriformis syndrome.

The piriformis is a deep-seated muscle, most of its muscular portion being part of the dorsal wall of the pelvis. The lateral portion and its insertion is extra-pelvic and lies deep to the glutei. Like more superficially located and therefore more easily accessible skeletal muscles, the piriformis too can be the seat of trigger points, giving rise to symptoms indistinguishable from those of other causes of low backache, unless a deliberate search is made for the signs specific to the piriformis syndrome. Having made a presumptive diagnosis, confirmation is gained by palpating the muscle itself via rectum or vagina and reproducing the pain by digital pressure. If this test also is positive, the muscle is injected, the approach being either through the sciatic notch, from the perineum, or through the vagina. Immediate relief of pain is experienced after the solution of local anaesthetic and steroid has been deposited deep within the fleshy portion of the muscle.

Chronic pain syndromes and their treatment. II. Trigger points.

Trigger points are distinct areas of focal hyperirritability which give rise to areas of refered pain in well-defined areas of the musculo-skeletal system, sometimes remote from the point itself and not related to it by anatomically definable pathways. While the vast majority of pain manifestations from trigger points are related to the musculo-skeletal system, this need not be invariably so, as has been demonstrated in two of the cases cited, where injection of trigger points in the neck relieved chronic tinnitus. In all manifestations of chronic pain it is recommended that a diligent search be made for such trigger points.

Chronic pain syndromes and their treatment. I. Cluster headache.

Cluster headache is a form of unilateral headache which, in the past, has been very resistant to treatment. Lithium carbonate has been shown to be the only reliably effective treatment in this condition and, although only a few cases have so far been reported in the literature they have, with very few exceptions, been successful. Therefore we selected five patients who at one time or another had presented with cluster headache and who had no relief from conventional treatment, and treated them with lithium carbonate. This has been highly successful. Some patients who had suffered from the disease for many years have been completely or almost completely relieved of their affliction, while others have been markedly improved to the point where they can now function normally, both socially and professionally. The possible modes of action of lithium in this condition are discussed.

Chinese acupuncture.

Acupuncture has been described as it is practiced in the People's Republic of China. To understand fully the preoccupation of the Chinese with this mode of treatment one must be familiar with its economic, historical and cultural background. Since conditions in Western countries are totally different from those in China it is obvious that acupuncture cannot be transplanted in toto from country to country, but that it requires reassessment of its usefulness as a treatment modality. Although further basic and clinical studies must be carried out, it would appear at the moment that acupuncture may have a useful place as yet and additional means of treating pain, especially in areas in which present treatment is less than satisfactory. At the moment no clear indication is obvious for acupuncture anaesthesia in countries in which this specialty is well developed and where adequate numbers of trained anaesthetists are available.

Some pharmacological properties of althesin (CT1341) in man.

Althesin in dose ranges of 40, 60 and 80 mul/Kg was administered to six healthy unpremedicated volunteers according to a balanced incomplete block design. Both subjective and objective changes resulting from the administration of the agent were studied and analyzed. In the dose ranges used, Althesin was found to have no deleterious effects on heart rate, respiratory rate or blood pressure and apnoea only occurred in one patient who had an end-expiratory CO2 level lower than normal, due to preanaesthetic hyperventilation. The onset of sleep is prolonged with Althesin at the injection rate of 1 ml/10 secs. The onset of anaesthesia is not influenced by the total dose, but the sleep time is directly proportional to the dose injected. Auditory evoked responses tended to lie on a curve which might indicate that with increasing dose the time to reappearance of these responses is not correspondingly prolonged. However, this last observation must be confirmed by studies on a larger scale.