Clinicoanatomical study of thalamic stimulation for pain relief

Our small experiences with electrical stimulation in the VPL and VPM for dysesthetic pain show that it provoked only paresthesia and induced some relief of pain. It does not increase the beta-endorphin level in CSF. To clarify the anatomical substrata in VPL stimulation, neuroanatomical studies were done about the inputs to VPL in man, monkey and cat by the Fink-Heimer method. The spinothalamic tract terminates in VPL in a patchy fashion in the monkey. The corticothalamic fibers from SI and SII cortex project to VPL and VPM in somatotopical organization in the cat. SI and SII cortices have reciprocal connections, in addition to projections to area 5 or SIII cortex. The corticofugal fibers to the magnocellular and gigantocellular tegmental fields are suggested in addition to the dorsal column nuclei, spinal trigeminal nuclei and spinal posterior horn in cat. The medial lemniscus input to VPL and the above neural circuits are thought to be associated with VPL stimulation.     

Chronic stimulation of the septal area for the relief of intractable pain

Although brain stimulation techniques have changed the treatment of pain, their rationale has not yet been fully proved, and their clinical results are still frequently erratic or contradictory. In an attempt to provide alternate sites for stimulation, 10 patients were, in addition to conventional targets, chronically implanted at the septal area. Satisfactory relief of dysesthetic pain was induced by septal stimulation in 60% of the cases overall, without untoward effects. The follow-up ranged from 1 to 42 months. The available data conceivably suggest other mechanisms than the presumed exclusive activation of opiomimetic structures. They also seem to indicate that the septal area may be a suitable target for chronic stimulation.     

Transcranial magnetic stimulation for the treatment of central post-stroke pain

Transcranial magnetic stimulation (TMS) is a new technique that results in neuron excitation using alternating magnetic fields. According to recent reports, high-frequency TMS could be an effective treatment for drug-resistant central post-stroke pain (CPSP). The present case report describes the clinical observation of two patients with CPSP with different lesion localisations and volumes. High frequency (10 Hz) TMS of the primary motor cortex of the affected hemisphere was used in each patient. After stimulation, we recorded a significant reduction in pain on a visual analogue scale (VAS). However, after the end of treatment with TMS, pain gradually returned to previous levels after 3–4 months.     

Percutaneous central gray stimulation for cancer pain.

Electrical stimulation of the periventricular and periaqueductal gray matter via a percutaneous electrode appears to be a useful method for relieving cancer pain with midline and bilateral distribution. Due to the nondestructive character and the minor surgical risks involved in this procedure it may be tried before considering bilateral cordotomy or myelotomy. A possible mechanism of action or at least a contributive factor to the pain relief is the activation of endorphins.     

Spinal cord stimulation in peripheral vascular pain

Results in 12 patients suffering from pain due to peripheral vascular pathology and treated with spinal neurostimulation are reported. The best results were obtained in stage III of vascular disease; however, our results indicate that regression of the pain symptom and healing of trophic lesions do not always correspond to any variation in blood flow.     

Vasopressin responses to peripheral and central osmotic pulse stimulation

To determine the relative importance of central and peripheral osmoreceptors in the osmotically-induced vasopressin secretion, osmosensitive areas of pentobarbital-anaesthetized rats were exposed for 5 sec to an osmotic pulse (130 μmoles NaCl in 200 μl). The hepatic portal receptors were stimulated by superfusion of the portal vein, and the central receptors by infusion into one common carotid artery. Portal stimulation was 2.14±0.25 (mean±SEM, 4 groups of 5 rats) more effective than central osmotic pulse stimulation in elevating, within 1 minute, the plasma vasopressin level (measured by RIA). The central stimulus was not effective when introduced into the freely perfused vessel, although the hypothalamic extracellular NaCl concentration rose transiently (6 sec) to 2.6±0.3 w/v% (mean±SEM, n=6 rats). The results show that brief osmotic pulses preferentially stimulate portal osmoreceptors to cause the release of vasopressin, and suggest that portal osmoreceptors may be involved in the dynamic regulation of plasma osmolality.     

Electrical stimulation of the posterior limb of the internal capsule for treatment of thalamic pain

Electrical stimulation of the posterior limb of the internal capsule was performed in 7 patients with thalamic pain who had developed dysesthesia, hyperpathia and/or spontaneous burning pain. Ramped bipolar stimulation elicited sensory responses, such as warm or comfortable sensation. Follow-up from 9 months to 2 years and 7 months showed that 3 patients had a good result, two had fair and the remaining two had poor results. No serious side effects were seen. The mechanism of pain relief by the internal capsule stimulation is discussed.     

Topical cryotherapy-use for relief of pain and spasticity

Cold applications are sometimes of pronounced symptomatic benefit in some rheumatic disorders such as acute myalgia; in the temporary relief of spasticity; in helping to release tight structures in poliomyelitis and allied diseases; and in temporary recovery of energy in multiple sclerosis.     

Safety of early pain relief for acute abdominal pain.

OBJECTIVES--(a) to determine the efficacy of papaveretum in treating pain when administered early to patients presenting with acute abdominal pain and (b) to assess its effect on subsequent diagnosis and management. DESIGN--Prospective, randomised, placebo controlled study. SETTING--Walsgrave Hospital, Coventry. SUBJECTS--100 consecutive patients with clinically significant abdominal pain who were admitted as emergencies to a surgical firm. INTERVENTIONS--Intramuscular injection of up to 20 mg papaveretum or an equivalent volume of saline. OUTCOME MEASURES--Pain and tenderness scores, assessment of patient comfort, accuracy of diagnosis, and management decisions. RESULTS--Median pain and tenderness scores were lower after papaveretum (pain score 8.3 in control group and 3.1 in treatment group, p < 0.0001; tenderness score 8.1 in control group and 5.1 in treatment group, p < 0.0001). Forty eight patients were deemed to be comfortable after papaveretum compared with nine after saline. Incorrect diagnoses and management decisions applied to two patients after papaveretum compared with nine patients after saline. CONCLUSION--Early administration of opiate analgesia to patients with acute abdominal pain can greatly reduce their pain. This does not interfere with diagnosis, which may even be facilitated despite a reduction in the severity of physical signs. These patients should not be denied effective treatment.     

Pain relief following stimulation of the pontomesencephalic parabrachial region in humans: brain sites for nonopiate-mediated pain control

It has been demonstrated that stimulation of the pontomesencephalic parabrachial region (PBR) by microinjection of cholinergic drugs or electricity in the cat produces potent pain suppression which is not antagonized by the opiate antagonist, naloxone. We report the application of electrical PBR stimulation in 2 patients whose pain was resistant to conventional methods of treatment including morphine administration. Intermittent use of low-frequency PBR stimulation was found to relieve pain in these patients. The present results appear to suggest that PBR stimulation, unlike periaqueductal gray stimulation, may be useful for the control of morphine-resistant pain in humans.     

Hypotheses of peripheral and central mechanisms underlying occupational muscle pain and injury

In an overview of the problem of occupational muscle pain the evidence indicates that injury is more common the greater the load and the worse the posture in which the work is performed. The commonest are backstrains or ligament or joint damage due to overuse. Fatigue is associated with alterations in energy metabolites in muscle while pain is often due to microscopical damage to the cellular architecture. The progress of pathological changes in muscle following occupational injury may be similar to those seen in primary fibromyalgia (fibrositis) because of a final common pathway involving calcium-induced secondary damage. Occupational muscle pain frequently occurs in the muscles supporting the upper limb girdle and head in workers engaged in repetitively performing skilled manipulations or activities requiring high or sustained mental concentration. It is suggested that both occupational myalgia of this kind may be due to an imbalance in the use of muscles for postural activity (holding or supporting fine movements) compared to phasic use in dynamic work. While there are undoubtedly muscular indications of damage these may be secondary to alterations in (unconscious) central motor control mechanisms.     

TRP channels: targets for the relief of pain

Patients with inflammatory or neuropathic pain experience hypersensitivity to mechanical, thermal and/or chemical stimuli. Given the diverse etiologies and molecular mechanisms of these pain syndromes, an approach to developing successful therapies may be to target ion channels that contribute to the detection of thermal, mechanical and chemical stimuli and promote the sensitization and activation of nociceptors. Transient Receptor Potential (TRP) channels have emerged as a family of evolutionarily conserved ligand-gated ion channels that contribute to the detection of physical stimuli. Six TRPs (TRPV1, TRPV2, TRPV3, TRPV4, TRPM8 and TRPA1) have been shown to be expressed in primary afferent nociceptors, pain sensing neurons, where they act as transducers for thermal, chemical and mechanical stimuli. This short review focuses on their contribution to pain hypersensitivity associated with peripheral inflammatory and neuropathic pain states.     

A method for studying the peripheral mediators of the dental pain induced by electrical stimulation.

A useful method is described in this paper for studying the mediators released from tooth pulp of the dog during the electrical stimulation of dentine. This method is based upon the perfusion of the pulp and superfusing the return continuously over the isolated, in cascade, cat jejunum and rat stomach fundus strip. The presented evidences in this study indicate the possibility of the release of bradykinin and prostaglandin - like materials from the tooth pulp during the electrical stimulation of dentine. Possible relationship of these mediators and tooth pain due to the electrical stimulation of dentine is discussed.     

Musculotendon parameters and musculoskeletal pathways within the human foot

In order to create a flexible model of the foot for dynamic musculoskeletal models, anthropometric data combined with geometric information describing the intrinsic musculature are needed. In this study, the left feet of two male and two female cadavers were dissected to expose the intrinsic musculotendon pathways. Three-dimensional coordinates of bony landmarks, tendon origins, insertions, and via points were digitized to submillimeter accuracy. Muscle architectural parameters were also measured, including volume, weight, and pennation angle and sarcomere, fascicle, and free tendon lengths. Optimal muscle fascicle lengths, pen-nation angles at optimal length, physiological cross-sectional areas (PCSA), and tendon slack lengths were calculated from the directly measured values. Fascicle length and pennation angle varied greatly within each subject. Average fascicle lengths normalized by optimal fascicle length varied between 0.73 and 1.25, with 75% of the formalin-preserved muscles being found in a shortened state. The muscle volume and PCSA also had a large variability within subjects but less variation between subjects. The ratio of tendon slack length to optimal fascicle length was found to vary between 1.05 and 9.56. Using this data, a deformable model of the foot can now be created. It is envisioned that deformable feet will significantly improve stability and realism in models of gait, posture, and sporting activities.