A correlative anatomical and clinical study of pain suppression by deep brain stimulation

The clinical results of electrical stimulation in medial thalamic regions for cancer pain have been correlated with the exact location of the stimulation sites. Five brains were examined by post-mortem histology. Chronic implantation of enamel coated platinum-iridium electrodes for up to 17 months caused relatively mild glial and neuronal reactions and no significant haemorrhage or infarction. The anatomical verifications showed that the electrodes were close to, but not exactly in, the regions defined by the stereotactic coordinates. From the clinico-anatomical correlations it appears that good pain relief can be obtained by electrical stimulation in the periventricular gray region of the posterior thalamus.     

Treatment of acute cervical pain — A comparative group study

Thirty patients with acute cervical pain were randomized into 3 groups and treated with neck collar, transcutaneous nerve stimulation, or manual therapy. The improvement was rapid in all groups, but the restoration of the cervical mobility was significantly more rapid in the transcutaneous nerve stimulation group. Some of the patients with manual therapy treatment had remarkably quick symptom reduction, although this was not significantly better than the collar alone. It is concluded that transcutaneous nerve stimulation is a valuable pain reducer and gives a more rapid restoration of cervical mobility in acute cervical pain.     

Extrasegmental transcutaneous electrical nerve stimulation and mechanical vibratory stimulation as compared to placebo for the relief of acute oro-facial pain

The present paper describes the pain reducing effect of high and low frequency transcutaneous electrical nerve stimulation (TENS) and 100 Hz mechanical vibratory stimulation as compared to placebo stimulation of the HoKu point in 50 patients suffering acute oro-facial pain. Ten of the 30 patients receiving actual stimulation reported pain reduction during treatment. In the placebo group of 20 patients, 4 of the subjects experienced pain relief during the trial. The findings in the present study showed that extrasegmental superficial stimulation of the HoKu point alters pain intensity in the patients studied to only a minor degree. The number of patients reporting pain alleviation and the magnitude of pain reduction in the groups receiving actual stimulation was comparable to that observed in earlier studies using intrasegmental placebo stimulation.     

Endorphins in chronic pain. I. Differences in CSF endorphin levels between organic and psychogenic pain syndromes

A series of 37 patients with chronic pain was investigated with regard to neurologic and psychiatric variables. Twenty of the patients were classified as having mainly organic (= somatogenic) pain syndromes while 17 patients were rather suffering from psychogenic pain syndromes. Samples of lumbar cerebrospinal fluid (CSF) were obtained from the patients and analyzed for the presence of opiate receptor-active material, here called endorphins. Patients classified as having mainly organic pain syndromes were found to have significantly lower endorphin levels than patients with predominantly psychogenic pain syndromes. In the total group of patients as well as in the two subgroups, there was a significant correlation between CSF endorphin levels and the depth of depressive symptomatology as reported by the patients. On the other hand, there was no correlation between CSF endorphin levels and extent of anxiety or motor retardation. It is concluded that CSF endorphins reflect central processes involved in chronic pain syndromes.     

Relation between intradental nerve activity and estimated pain in man--a mathematical model

Intradental nerve activity (INA) induced by cold stimulation of human teeth is regularly accompanied by pain perception. In this study a mathematical model was developed in order to quantify the relationship between INA and pain. In 5 patients (45 experiments) INA was recorded using electrodes implanted in lower incisor teeth. Brief cold stimulations induced bursts of INA. The intensity of the resulting pain was simultaneously evaluated by means of an intermodal matching technique, finger span. The relationship between perceived pain and the integrated INA was analyzed using various mathematical operations (inter alia Fourier analysis) by means of a computer. A transfer function which describes the pain response following INA was found. This preliminary mathematical model, which is characterized by 5 parameters, consists of 2 parts, one which responds to fast changes in the afferent nerve signal, and another which reacts with a delay. The validity of the model has been tested, and it was found that the model consists of an adequate number of parameters and their cross-interaction is low. The analysis indicates that the parameters which determine the pain response following INA can be quantified and that they might be used as a measure of the efficacy of various pain relieving procedures.     

Representation of the thoracic outlet syndrome as a problem in chronic pain and psychiatric management

The diagnosis of thoracic outlet syndrome depends upon subjective complaints and sometimes rather limited physical findings. There is a tendency to favour other non-specific diagnoses, like ‘soft tissue damage’ or to suspect neurosis, particularly in patients who have had motor vehicle or other injuries for which they claim compensation. We report here 3 patients in whom the diagnosis of thoracic outlet syndrome was overlooked and who responded to surgical treatment with good or excellent results.     

Long term results of peripheral conditioning stimulation as an analgesic measure in chronic pain.

In the present study 123 patients with chronic pain, consecutively referred for symptomatic pain treatment, were given peripheral conditioning stimulation as an analgesic measure and were followed for 2 years or till they terminated the treatment. The stimulation was either conventional transcutaneous nerve stimulation (TNS) [35] of mainly cutaneous afferents with high frequency (10-100 Hz) or acupuncture-like TNS [11] where muscle nerves are activated at a low repetition rate (1-4 Hz) with small trains of stimuli. The follow-up showed that 55, 41 and 31% of the patients continued the treatment after 3, 12 and 24 months, respectively. About 30% of the patients had to use acupuncture-like TNS to get useful analgesia, defined as a desire of the patient to continue stimulation treatment. Three-quarters of the successfully relieved patients reported more than 50% pain relief as measured from visual analogue scales and half of these reported an increased social activity and a decrease of analgesic drug intake by more than 50%. Psychogenic and visceral pains were less suitable for TNS treatment. It is concluded that peripheral conditioning stimulation is a valuable therapy in cases of chronic pain and that both conventional and acupuncture-like TNS should be tried before considering implantable devices or destructive surgery.     

Comparison of lipid and protein content of serum very low density lipoproteins isolated by ultrascentrifugation in uniform density and in density gradient.

Very low density lipoproteins (VLDL) were isolated from 21 fasting sera with serum triglyceride concentrations ranging from about 1 to 60 mmol/1 (90–5300 mg/dl) by two different preparative ultracentrifugation procedures. One was centrifugation in a density gradient under conditions calculated to float all VLDL. The other was in a fixed angle rotor at a density of 1.006 g/cm³ (routine centrifugation). Lipids were extracted with chloroform/methanol for the gradient fractions and with isopropanol for the routine fractions.The triglyceride content was the same for VLDL obtained by the two methods while the gradient method yielded VLDL with a higher cholesterol content. The ratio of cholesterol to triglycerides was higher for gradient than for routine VLDL. This difference could only in part be due to the differences in techniques for lip id extractions. A strong linear correlation (r = 0.99) existed between the amount of lipids found in VLDL prepared by the two methods.The amounts of total protein as well as of protein soluble in tetramethylurea and in isopropanol were more than 30% higher in VLDL prepared by the routine preparation than with the gradient method. Isopropanol extracted about 20% more protein from both VLDL preparations than tetramethylurea.The calculated values for insoluble protein, assumed to represent apolipo-protein B, showed a very good agreement between VLDL obtained by gradient and routine centrifugations except for two sera with very high levels of insoluble protein.     

The validation of visual analogue scales as ratio scale measures for chronic and experimental pain

Visual analogue scales (VAS) of sensory intensity and affective magnitude were validated as ratio scale measures for both chronic and experimental pain. Chronic pain patients and healthy volunteers made VAS sensory and affective responses to 6 noxious thermal stimuli (43, 45, 47, 48, 49 and 51 degrees C) applied for 5 sec to the forearm by a contact thermode. Sensory VAS and affective VAS responses to these temperatures yielded power functions with exponents 2.1 and 3.8, respectively; these functions were similar for pain patients and for volunteers. The power functions were predictive of estimated ratios of sensation or affect produced by pairs of standard temperatures (e.g. 47 and 49 degrees C), thereby providing direct evidence for ratio scaling properties of VAS. Vas sensory intensity responses to experimental pain, VAS sensory intensity responses to different levels of chronic pain, and direct temperature (experimental pain) matches to 3 levels of chronic pain were all internally consistent, thereby demonstrating the valid use of VAS for the measurement of and comparison between chronic pain and experimental heat pain.     

Relevant and irrelevant anxiety in the reaction to pain

Despite its importance in pain perception, there is a paucity of research investigating the influence of anxiety. This study tested the proposition that anxiety can lead to the exacerbation of pain perception when the source of anxiety is related to the pain experience. When the source is related to something else, anxiety may even reduce the reaction to pain. Sources of anxiety were manipulated in the laboratory — anxiety related to pain and anxiety related to successful learning or the combination of anxiety related to both pain and learning. Verbal, physiological and behavioral differences were obtained showing that focus upon both the pain and the learning task yielded the strongest pain reactions, while focus upon the learning alone yielded the lowest pain reaction, but the largest learning errors. Focus upon pain was in-between. The theoretical implications of these data were discussed.     

Subject versus experimenter control in the reaction to pain

Although perceived control has been used as a means of reducing the reaction to pain, conceptually, much is still unclear. The purpose of this study was to clarify the effects of control as a mediating variable in the reaction to pain as a function of the predispositional variables of perceived self-efficacy and trait anxiety. Self-efficacy refers to the subject's premeasured, perceived ability to control his pain. The type of control provided either to the subject or the experimenter was varied over 5 independent groups. Predictability of occurrence of the pain stimulation was varied on a within-subject basis. Results mirrored the complexity of the problem. Overall, when subjects were given decisional control alone the largest reactions to pain were obtained. Subjects given decisional plus behavioral control yielded the lowest reactions to pain. Both self-efficacy and trait anxiety significantly were predictive of outcomes. Unexpectedly, experimenter control reduced the reaction to pain among those with high self-efficacy, but increased the reaction among those with low self-efficacy. Results of trait anxiety appear to indicate the need to keep anxiety within bounds. Adding responsibility such as control to an individual who is already anxious may increase the reaction to pain. In general, it appears that control that is perceived as inadequate may be worse than not having any control. The theoretical and methodological implications of these results were discussed.     

Studies on alkaline phosphatase isoenzymes. Relation to gamma-glutamyltransferase and lactate dehydrogenase isoenzymes.

Gamma-Glutamyltransferase (GT) and isoenzymes of alkaline phosphatase (ALP) and lactate dehydrogenase (LDH) have been studied in 282 cases with increased S-ALP and in 18 chronic alcoholics with normal routine liver tests. There was a high degree of correlation between S-GT and the bile (alpha 1) and liver (alpha 2) fractions of S-ALP. Fractionation of alkaline phosphatases sometimes yielded clinical information, which could not be obtained by determinations of S-ALP and S-GT only. The presence of alpha 1-ALP and increased S-GT appeared to be more sensitive indicators of ethanol-induced liver involvement than other liver tests, including LDH-5/LDH-4 ratios.     

Problems with the use of oxycodone compound in patients with chronic pain

In a pain management program (200 patients), a group of daily users of oxycodone compound (29 patients) and a subgroup who were taking a “high dose” of oxycodone compound (13 patients) were compared with a group of 171 non-users of oxycodone compound. A significantly lower treatment success rate was observed in the users (P = 0.04) and high-dose users (P = 0.03). A similar trend was seen in preliminary data available in a larger sample (514 patients). Continued study of these findings is necessary. Meanwhile, in patients with chronic pain, there should be cautious use of this compound.     

Reliability and validity of the visual analogue scale for disability in patients with chronic musculoskeletal pain

To determine the reliability and concurrent validity of a visual analogue scale (VAS) for disability as a single-item instrument measuring disability in chronic pain patients was the objective of the study. For the reliability study a test-retest design and for the validity study a cross-sectional design was used. A general rehabilitation centre and a university rehabilitation centre was the setting for the study. The study population consisted of patients over 18 years of age, suffering from chronic musculoskeletal pain; 52 patients in the reliability study, 344 patients in the validity study. Main outcome measures were as follows. Reliability study: Spearman's correlation coefficients (rho values) of the test and retest data of the VAS for disability; validity study: rho values of the VAS disability scores with the scores on four domains of the Short-Form Health Survey (SF-36) and VAS pain scores, and with Roland-Morris Disability Questionnaire scores in chronic low back pain patients. Results were as follows: in the reliability study rho values varied from 0.60 to 0.77; and in the validity study rho values of VAS disability scores with SF-36 domain scores varied from 0.16 to 0.51, with Roland-Morris Disability Questionnaire scores from 0.38 to 0.43 and with VAS pain scores from 0.76 to 0.84.The conclusion of the study was that the reliability of the VAS for disability is moderate to good. Because of a weak correlation with other disability instruments and a strong correlation with the VAS for pain, however, its validity is questionable.     

Continuous epidural morphine treatment for intractable pain in terminal cancer patients

In patients with intractable cancer pain who failed to respond to conservative and neurosurgical procedures for pain relief, repeated injections of epidural morphine were found to be beneficial.A small dose of morphine (2–4 mg per injection) relieved pain for 6–24 h. A permanent subcutaneous epidural catheter led to successful ambulatory treatment without complications. The implantation of the epidural catheter is a minor surgical procedure, done under local anesthesia and is considered safe even in terminal cancer patients.     

Adjuvant-induced arthritis in rats: A possible animal model of chronic pain

Adjuvant-induced arthritic rats were observed clinically and behaviourally. The clinical disease has a duration of greater than 1 month and can be divided into a pre-clinical (1–10 days), an acute (15–30 days), postacute (30–50 days) and a late phase (> 50 days). Adjuvant arthritis induces significantly quantitative changes in the rats' behaviour. Two types of behavioural change merit special attention: freezing (arresting) and scratching. Freezing is significantly increased in the acute and postacute phases; it is increased by morphine, this effect being blocked by naloxone.Scratching is significantly increased in the acute, postacute and late phases; it is decreased by morphine, this effect being blocked by naloxone. The chronic presence of scratching, and the effects of morphine and naloxone on it, allow us to consider it as a possible pain-related behaviour and therefore as a possible parameter for the study of chronic pain in animals.