Showing papers in "Pain in 1977"

The formalin test : a quantitative study of the analgesic effects of morphine, meperidine, and brain stem stimulation in rats and cats

Abstract: SUMMARYA method for assessing pain and analgesia in rats and cats is described. The procedure involves subcutaneous injection of dilute formalin into the forepaw, after which the animal's responses are rated according to objective behavioral criteria. The formalin test is a statistically valid techn

Narcotic analgetics: CNS sites and mechanisms of action as revealed by intracerebral injection techniques

Abstract: Narcotics reduce the behavioral response to injury, while leaving unaffected the response to other stimuli. This effect could be due to a reduction of the central transmission of injury signals (modulation of sensory throughput) or to an effect on higher inte~ative levels concerned with stimulus recognition or stimulus interpretation ** . Since much of the functional capacity of the central nervous system and nearly every level of the neuraxis is involved in signal processing, observations limited to the effect of systemically administered narcotics on behavior will provide little information regarding the specific sites and mechanisms of action of narcotic analgetics. Investigators interested in these aspects of narcotic activity have therefore resorted to experimental approaches which permit a detailed study of the interaction between narcotic analgetics and particular regions and/or functional systems within the central nervous system. Recording of local electrical activity following systemic application of a narcotic does not specify where the narcotic is acting. Similarly local lesions or electrical stimulation can only indicate through which systems narcotics may act and do not reveal the causal chain between injury and pain. As a consequence of the inadequacies of these approaches, investigators have turned with increasing frequency to methods which permit the application of drugs directly to single neurons or circumscribed neuronal pools. The mi~roiontophoretic technic has provided much of our limited information concerning the direct effects of narcotic analgetics on neuronal activity. ~n~o~unately, the microiontophoretic stimulation of a single neuron usually is incapable of eliciting a detectable behavioral response. Therefore, even though many neurons can be tested for their individual sensitivities to suspected neurotransmitter or other agents, it cannot be determined by ionto-

Peripheral suppression of first pain and central summation of second pain evoked by noxious heat pulses

Abstract: Psychophysical experiments were carried out on 6 huma subjects to determine how first and second pain are influenced by peripheral receptor mechanisms and by central nervous system inhibitory and facilitatory mechanisms. For these experiments, brief natural painful stimuli delivered to the hand were a train of 4-8 constant waveform heat pulses generated by a contact thermode (peak temp. = 51-5% C). The magnitude of first and second pain sensations was estimated using cross-modality matching procedures and reaction times were determined. The latter confirmed the relationship between first and second pain and impulse conduction in Adelta and C noxious heat afferents, respectively. The intensity of first pain decreased with each successive heat pulse when the interpulse interval was 80 sec or less. This decrease was most likely the result of heat induced suppression of Adelta heat nociceptors since it did not occur if the probe location changed between successive heat pulses. In contrast, second pain increased in intensity with each successive heat pulse if the interval was 3 sec or less. This summation was most likely due to central nervous system summation mechanisms since it also occurred after blockage of first pain by ulnar nerve compression and when the location of the thermode changed between heat pulses. These observations and their interpretations are supported by our recording of responses of singlt Adelta heat nociceptive afferents, C polymodal nociceptive afferents, and "warm" afferents of rhsus monkeys to similar trains of noxious heat pulses. Their responses to these heat pulses show a progressive suppression. Furthermore, previous studies have shown that wide dynamic range dorsal horn neurons show summated responses to repeated volleys in C fibers (greater than 1/3 sec). These spinal cord summation mechanisms could account for the summation of second pain.

Comparative study of perceived pain and nociceptive flexion reflex in man

Abstract: The purpose of this study was to compare the amplitude of the flexion reflex of the biceps femoris muscle (BF) with the intensity of the painful sensation elicited by a nociceptive stimulation resulting from application of constant-current either on the sural nerve or on the skin in its distal receptive field. Experiments were carried out on 15 normal volunteers. It was observed that: (1) Stimulation of the sural nerve (either on or through the skin) elicits two different reflex responses in the BF: the first (RII) is of short latency, low threshold and corresponds to a tactile reflex. The second (RIII) is of longer latency and higher threshold, and corresponds to a nociceptive reflex. The threshold of RIII was found to be the threshold of a pain sensation. (2) Stimulation of the skin elicits only a late nociceptive (RIII) response in the BF. The threshold of this response was also found to be that of pain. (3) The threshold of both pain and RIII were found to be higher for sural nerve stimulation (10 mA) than for cutaneous stimulation (5 mA). It was suggested that the large diameter cutaneous fibers could have an inhibitory effect of both pain and the nociceptive reflex. This was supported by the results obtained during a selective ischemic block of the largest diameter fibers in the sural nerve, when a 10 mA stimulation was applied to the nerve. In this case, a decrease of the RII reflex was observed in BF, together with an increase of both RIII and pain sensation. Functional implications of these results are discussed.

Trigger points and acupuncture points for pain: Correlations and implications

Abstract: Trigger points associated with myofascial and visceral pains often lie within the areas of referred pain but many are located at a distance from them. Furthermore, brief, intense stimulation of trigger points frequently produces prolonged relief of pain. These properties of trigger points--their widespread distribution and the pain relief produced by stimulating them--resemble those of acupuncture points for the relief of pain. The purpose of this study was to determine the correlation between trigger points and acupuncture points for pain on the basis of two criteria: spatial distribution and the associated pain pattern. A remarkably high degree (71%) of correspondence was found. This close correlation suggests that trigger points and acupuncture points for pain, though discovered independently and labeled differently, represent the same phenomenon and can be explained in terms of the same underlying neural mechanisms. The mechanisms that play a role in the genesis of trigger points and possible underlying neural processes are discussed.

Mechanosensitivity of dorsal root ganglia and chronically injured axons: a physiological basis for the radicular pain of nerve root compression.

Abstract: The radicular pain of sciatica was ascribed by Mixter and Barr to compression of the spinal root by a herniated intervertebral disc. It was assumed that root compression produced prolonged firing in the injured sensory fibers and led to pain perceived in the peripheral distribution of those fibers. This concept has been challenged on the basis that acute peripheral nerve compression neuropathies are usually painless. Furthermore, animal experiments have rarely shown more than several seconds of repetitive firing in acutely compressed nerves or nerve roots. It has been suggested that “radicular pain” is actually pain referred to the extremity through activation of deep spinal and paraspinal nociceptors. Our experiments on cat lumbar dorsal roots and rabbit sural nerves have confirmed that acute compression of the root or nerve does not produce more than several seconds of repetitive firing. However, long periods of repetitive firing (5–25 min) follow minimal acute compression of the normal dorsal root ganglion. Chronic injury of dorsal roots or sural nerve produces a marked increase in mechanical sensitivity; several minutes of repetitive firing may follow acute compression of such chronically injured sites. Such prolonged responses could be evoked repeatedly in a population of both rapidly and slowly conducting fibers. Since mechanical compression of either the dorsal root ganglion or of chronically injured roots can induce prolonged repetitive firing in sensory axons, we conclude that radicular pain is due to activity in the fibers appropriate to the area of perceived pain.

Serotonin-containing neurons: their possible role in pain and analgesia.

Abstract: Experimental evidence is reviewed showing that brain and spinal cord serotonergic neurons are involved in nociceptive responses, as well as in the analgesic effects of opiate narcotics. This evidence, based on studies employing pharmacological, surgical, electrophysiological and dietary manipulations of central nervous system serotonergic neurotransmission, suggests that increases in the activity of brain and spinal cord serotonin neurons are associated with analgesia and enhanced antinociceptive drug potency, whereas decreases in the activities of these neurons correlate with hyperalgesia and diminished analgesic drug potency.

Phantom body pain in paraplegics: Evidence for a central “pattern generating mechanism” for pain

Abstract: Phantom body pain in paraplegic patients is the most mysterious of all pain phenomena. It has been traditionally assumed [45] that the essential cause of pain in any part of the body is activity in the receptor-fiber units that innervate it. In this paper, however, we shall describe paraplegic patients who had undergone removal of an entire section of the spinal cord (segmental cordectomy) in the attempt to alleviate phantom body pain, yet they still suffered severe pain in the denervated areas of the body. There is no reason to believe that the pain was due to depression or neurosis. Furthermore, the possibility that the pain was produced by nociceptive signals transmitted along the sympathetic chain is ruled out because the pain was not relieved by bilateral sympathetic blocks. The perception of severe, chronic pain in the absence of any input from those parts of the body in which pain is felt has profound implications for theories of pain. The purpose of this paper is to examine the properties of phantom body pains in paraplegics and to propose a theoretical concept to explain them.

Reversal of morphine and stimulus-produced analgesia by subtotal spinal cord lesions.

Abstract: This study examined the hypothesis that descending inhibitory pathways from brain stem to spinal cord mediate the analgesic effect of both electrical brain stimulation and morphine. In the first set of experiments, the effect of subtotal midthoracic spinal cord lesions on the analgesic effect of electrical stimulation in the periaqueductal gray matter of the rat was examined. In the second, the effect of similar cord lesions on the analgesic effect of intraperitoneal morphine was studied. In both cases, a lesion of the dorsal part of the lateral funiculus (DLF) reduced or abolished the analgesia of the hindlimbs. Analgesia of the forelimbs was unaffected. Lesions of the dorsal columns, which include the corticospinal tract, or lesions of the ventral part of the lateral funiculus had no effect on analgesia. It is concluded that an inhibitory pathway, which descends in the dorsal part of the lateral funiculus and which probably originates in the nucleus raphe magnus of the medulla, mediates the descending control found in both morphine and stimulus-produced analgesia.

Observations on the algogenic actions of adenosine compounds on the human blister base preparation.

Abstract: The action of the adenyl compounds adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP) and adenosine was studied on the human blister base preparation. All 4 adenyl compounds produced pain which was slow in onset and not maintained. The threshold concentration for pain was of the order of 1–3 μM. The slopes of log concentration:pain intensity plots were relatively shallow and for moderate to severe pain a 100-fold increase of the threshold concentration was required. The adenyl compounds resembled 5-hydroxytryptamine and bradykinin with respect to onset and duration of action but were less potent. On the other hand, for threshold effects they were more potent than acetylcholine or potassium. Evidence was found for an interaction of adenyl compounds with 5-hydroxytryptamine but not with potassium, acetylcholine or bradykinin. Cyclic adenosine 3′,5′-monophosphate or the chelation of extracellular calcium or magnesium were shown not to be involved in the algogenic action of adenyl compounds and the action of adenyl compounds on the rabbit isolated jejunum too was found to be unrelated to their algogenic action on the human blister base preparation.

Pain, depression, and illness behavior in a Pain Clinic population

Abstract: The relationship between depression, illness behavior and persistent pain was studied in 100 patients referred to the University of Washington Hospital Pain Clinic. The instruments used were the Illness Behavior Questionnaire (IBQ) and the Levine-Pilowsky Depression Questionnaire (LPD). To delineate those aspects of illness behavior characteristic of the Pain Clinic group, their scores were compared to those attained on the IBQ by a Family Medicine Clinic sample. The Pain Clinic group showed greater conviction of disease and somatic preoccupation than the comparison group. Further, they were reluctant to consider their health problems in psychologic terms, and denied current life problems. The Pain Clinic group's performance on the LPD indicated a low degree of depressive affect overall and few patients manifesting a depressive syndrome. The association between IBQ and depression scores suggests that the predominant clinical pattern presented by pain clinic patients is best characterized as a form of "abnormal illness behavior".

Signal detection theory measurement of pain: a review and critique.

Abstract: Pain is a subjective experience. Therefore, attempts to measure its extent face the same difficulties which have long plagued experimenters hoping to scale other human sensations, but they are compounded further by complex emotional reactions and cognitive interpretations [ 411. Nonetheless, the need for improved methods of pain control mandates continued research on pain and its possible modulation by chemical, surgical, physiologic(al, or psychological procedures. Laboratory studies with normal rather than clinical subjecks allow parametric variations in the level of an experimentally induced pain, rather than reliance upon some unknown endogenous one. It is possible, as well, that some of the emotional variability associated with a pain of internti origin is thus eliminated, leading to more stable estimates of the magnitude of the pain sensation itself. The ability to vary the level of a potentially nociceptive stimulus has raised the hope that psychophysical procedures 1393, well-developed for studies of vision, audition, and the other senses, might also increase our understanding of human suffering. Although some notable advances have been made in the scaling of intense discomfort [1,26,34,51], many pain investigations have concentrated on the traditional “‘threshold” as the dependent variable, sometimes attempting to distinguish sep te thresholds for sensation, mild pain, strong pain, and maximal tolerance. The threshold appears, at first, to be easy to measure an easy to in”%3 pret. Its value can be obtained by noting the level of some uncomfor stimulus such as radiant heat or electric shock ntecessary to elicit a report of pain. In those instances where no manipulation is involved, thresholds hw been compared across groups (e.g. the variables of age, sex, race, or &l-ok group). In other instances, where the nature of a adecluate control is still

Localization of substance P-like immunoreactivity in nerves in the tooth pulp.

Abstract: The occurrence of substance P (SP)-like immunoreactivity was studied in dental pulps of the cat. In untreated animals SP-positive fibres were found in all areas of the pulp. Most fibres were seen in central parts of the pulp but they were also observed in relation to the odontoblasts. Single, possibly unmyelinated, or fine caliber fibres or small bundles of them were seen running close to large non-fluorescent myelinated nerves, to blood vessels or without any obvious association with either of these structures. Fourteen days after transection of the inferior alveolar nerve no SP-positive fibres were observed in pulps on the denervated side. Transection of the cervical sympathetic ganglion did not change the occurrence of SP-positive fibres. The results indicate the existence of at least two types of afferent fibres in the dental pulp of the cat. Since the tooth pulp has been demonstrated to give rise only to pain sensation when stimulated, the results give morphological support for a role of SP neurones in pain transmission.

Concurrent mapping of brain sites for sensitivity to the direct application of morphine and focal electrical stimulation in the production of antinociception in the rat

Abstract: The effect of morphine microinjection (5 microgram/0.5 microliter) and focal electrical stimulation on the animal's response to radiant heat and noxious pinch was studied concurrently at 117 brain loci extending from the medial thalamus caudally to the periaqueductal gray area (PAG). Three populations of brain sites were discernible based on their responsiveness to focal electrical stimulation and morphine microinjection in the production of antinociception: (a) sites which support stimulation-produced analgesia (SPA, n = 24), (b) sites which were sensitive to the direct application of morphine (n = 8), (c) sites responsive to both manipulations (n = 8). With a few exceptions, all morphine sensitive sites were located within the anatomical boundaries of the PAG while sites supporting SPA were located not only within the PAG but also in the brain regions peripheral to this structure. Sites responsive to both manipulations were generally distributed throughout thf lateral aspect of the posteroventral PAG. Stimulation strength-effect curves for sites subserving SPA were also obtained. No differences were discovered between curves obtained from morphine-sensitive and -insensitive brain loci.

Noxious thermal input from the rat tail: Modulation by descending inhibitory influences

Abstract: In anaesthetized rats, single fibres have been dissected from the tail nerves. Fibres were found which became excited when the temperature of water surrounding the tail was raised above 40 degrees C. Firing rate increased with stepwise increases in temperature, showing first a transient outburst followed by adaptation to a static level. Corresponding neurones were also found in the dorsal horn at the entry zone of the roots coming from the tail. The cord neurones had a higher threshold temperature of 42.5--45 degrees C. When the spinal cord was reversibly blocked by cooling in the thoracic region, then the threshold of the dorsal horn neurones was reduced to that of the afferent fibres. In addition, at suprathreshold temperatures dorsal horn activity was greater during cord blockade. We conclude that dorsal horn neurones responding to noxious heating are subject to a tonic descending inhibitory control.

A neurophysiological theory for the pain mechanism of tic douloureux.

Abstract: In attempting to understand the mechanism of pain production in tic douloureux, one must account for the myelination pathology seen in the primary afferent fibers, the cases where the trigger is in a different division than the pain, the frequent lack of a fixed neurologic deficit, the effective trigger stimuli corresponding to large caliber axons which would not seem to involve the small axons usually associated with pain production, and similar puzzling features of the disease. We present a theory which satisfactorily predicts, or is consistent with, most known features of tic; it is based upon two mechanistic assumptions, both of which have strong experimental foundations in the literature. The first is the trigeminal dorsal root reflex, and the second is the creation of extra action potentials at sites of altered myelination.

Affective and sensory dimensions of back pain.

Abstract: Pain words used to communicate suffering were analyzed to identify specific dimensions of back pain. The words were obtained from a group of 131 patients suffering from back pain who described their discomfort on a standardized 87-item pain questionnaire. The results indicate that words descriptive of back pain are not associated in completely random ways. When patients complain of back pain, their report falls into 7 distinguishable patterns. The major pattern accounts for 38% of the variance and refers almost entirely to emotional discomfort. The second pattern accounts for 9% of the variance and is a mixed emotional and sensory factor. The remaining 5 patterns account for 29% of the variance and constitute an entirely sensory class of factors.

Sensory decision theory methods in pain research: A reply to Rollman☆

Abstract: Positive reviews of the developing literature on Sensory Decision Theory (SDT) pain research have been provided by Lloyd and Appel [21] and Hall [17]. In contrast, Rollman [24] has criticized the application of SDT methodology to the study of pain, arguing that it is “an error in logic to utilize SDT parameters to reach definitive conclusions about mechanisms altered during pain modulation”, and he has attacked the procedures employed by decision theory researchers in data collection and analysis. This paper is a response to Rollman written from the perspective of a single group of SDT pain researchers. I will first bring to issue certain fundamental statements that appear recurrently throughout Rollman's paper, and I will argue that many of his criticisms lack substance because these assertions are inappropriate. In addition, I will deal briefly with some of Rollman's specific methodologic criticisms, limiting my comments to those points that are salient to the multidisciplinary audience of this journal, and I will briefly describe the pain model that has been implicit in the work of our laboratory group.

Choice of strong analgesic in terminal cancer: Diamorphine or morphine?

Abstract: A controlled trial of diamorphine (diacetylmorphine, heroin) and morphine is reported in which the two drugs were administered regularly by mouth in individually determined effective analgesic doses. Elixirs contained cocaine hydrochloride 10 mg/dose; other drugs were prescribed when indicated clinically. 699 patients entered the trial and, of these, 146 crossed from diamorphine to morphine, or vice versa, after about two weeks using an oral potency ratio of 1.5/1 determined in a pilot trial. Additional medication and survival were closely similar in both treatment groups. In the female crossover patients, no difference was noted in relation either to pain or the other symptoms evaluated. On the other hand, male crossover patients experienced more pain, and were more depressed, while receiving diamorphine. In these, the potency ratio of diamorphine to morphine appeared to be less than 1.5/1. If this is allowed for, then the difference in mood is probably not significant. Compared with male patients, fewer females required a dose of 10 mg or more, but more were prescribed an anxiolytic. The ability to do without a 2 a.m. dose appeared to be related more to the size of the dose than to gender or treatment. It is concluded that, provided allowance is made for the difference in potency, morphine is a satisfactory substitute for orally administered diamorphine. However, when injections are necessary, the greater solubility of its hydrochloride gives diamorphine an important practical advantage over morphine, especially when large doses are required.

Pain relief during delivery by transcutaneous electrical nerve stimulation

Abstract: The degree of pain alleviation achieved by transcutaneous electrical nerve stimulation (TNS) during delivery has been evaluated. The usual technique of TNS was modified to suit the requirements of pain relief during delivery. Two pairs of electrodes were taped on the parturient's back at levels TH10--L1 and S2--S4. These segments correspond to the pathway of pain afferents into the spinal cord during the first and second stages, respectively. Stimulation was delivered by a two-channel generator producing biphasic pulses which were variable in frequency and amplitude. A low-intensity stimulation was given continuously and a high-intensity stimulation could be initiated by the parturient herself whenever pain increased. Stimulation was provided via the thoracic electrodes throughout the delivery, whereas sacral stimulation was added from the later part of the first stage. No complications with respect to mother or child have occurred. One hundred and forty-seven women have been treated, 65 (44%) of whom considered the pain relief by TNS to be good to very good, 65 (44%) experienced moderate effect, while 17 (12%) women considered that TNS was without effect. In view of the relatively good results and since no complications have occurred, we consider the method recommendable as a primary pain relieving measure to which conventional methods can be added according to need.

Effects of pain-attenuating brain stimulation and morphine on electrical activity in the raphe nuclei of the awake rat.

Abstract: Evoked potential and multiple unit responses to noxious shock and pinch as well as to innocuous air puffs were recorded in the dorsal raphe, median raphe and raphe magnus nuclei of awake rats. Concurrent measurements of various behavioral responses to noxious stimuli were also made. Electrical stimulation of midbrain central gray and of medial thalamus, as well as systemic administration of morphine, greatly diminished all behavioral and electrophysiological responses to noxious stimuli without reliably affecting responses to air puffs. At the same time that brain stimulation and morphine attenuated nociceptive responses, a significant elevation was seen in the spontaneous multiple unit activity of these brain areas, particularly nucleus raphe magnus. In another group of animals, a comparison was made of the analgesic effectiveness of stimulation sites in the bulbar raphe (including raphe magnus) and sites dorsal or lateral to this region. More consistently potent effects were obtained from the raphe placements. These findings point to the importance of the bulbar raphe in mechanisms of analgesia. It is suggested that brain stem stimulation and morphine administration activate descending controls of raphe origin which selectively inhibit nociceptive elements in the spinal cord.

Effects of intrasegmental electrical acupuncture on dental pain: evaluation by threshold estimation and sensory decision theory.

Abstract: The effect of 80 min of low frequency (2 Hz) electric acupuncture stimulation at facial sites on the perception of induced dental pain was evaluated using both pain threshold and sensory decision theory (SDT) procedures. The demonstration of a 187% increase in threshold over a 20 min period of acupunctural stimulation replicated earlier work by Swedish investigators. SDT analyses indicated that the threshold increase reflected a relatively pure sensory change with no significant modification of response bias. However, subjects were able to perceive some of the stimuli presented below threshold level following acupuncture, thus indicating that the threshold concept has been an inadequate description of the phenomenon. This study demonstrated that intrasegmental analgesic stimulation is more efficacious than the extrasegmental meridian point stimulation used in our earlier studies. Possible mechanisms for the observed effect were discussed.

Evaluation of the efficacy and neural mechanism of a hypnotic analgesia procedure in experimental and clinical dental pain.

Abstract: Previous research implicates an endogenous central pain inhibitory mechanism in opiate analgesia, analgesia produced by focal electrical stimulation of the brain and acupuncture analgesia. This investigation evaluates the possibility that analgesia produced by hypnosis is also mediated by such a mechanism. Results suggest that hypnotic analgesia is unlikely to involve this central pain inhibitory mechanism since hypnotic analgesia is not altered by naloxone hydrochloride, a specific narcotic antagonist. Results further demonstrate that the hypnotic procedure used produces an unusually effective and reliable increase in pain threshold. This finding generalizes to the control of clinical dental pain and suggests that hypnotic pain control is a more widespread phenomenon in the population than has been thought.

Multidisciplinary treatment of chronic pain: long-term follow-up of low-back pain patients.

Abstract: Thirty-six p tients with low-back pain who had been treated in our multidisciplinary pain center returned for 80-week follow-up evaluations by the staff psychologist, physiatrist and physical therapist. Statistically significant gains were maintained in the reduction of prescription analgesics and on 4 measures of physical functioning 1. (a) long-sitting-to-toe 2. (b) straight-legraise 3. (c) knee-to-chest 4. (d) overall exercise performance. Despite verbal reports of continuing pain, most patients claimed they were coping much better with it, and they displayed a marked reduction in their utilization of medical resources for further pain treatment. These long-term results suggest that a multidisciplinary approach can offer an effective means of treating chronic low-back pain.

Pain-signalling systems in the dorsal and ventral spinal cord.

Abstract: A review of the literature on pain-signalling systems in the spinal cord provides convincing evidence that nociceptive information is transmitted by multiple ascending systems. These systems include: 1. (1) the postsynaptic fibers of the dorsal columns which relay in the rostral dorsal column nuclei; 2. (2) the spinocervical tract which relays in the lateral cervical nucleus; 3. (3) the neo-spinothalamic tract which ascends directly from cord to thalamus; 4. (4) the paleo-spinothalamic tract which projects to the midline-intralaminar thalamic regions; and 5. (5) the spinoreticular system which sends fibers throughout the brain stem reticular formation. In addition, the diffuse, polysynaptic, propriospinal systems may also carry pain-related information. The data indicate that the first 3 systems, which comprise the “lateral” group, are generally similar to each other on at least 4 dimensions: modalities represented, conduction velocities, loci of origin, and areas of termination. However, despite their overall similarities, there are clear differences, particularly in the precise modes of termination and routes of ascension. Moreover, they appear to be controlled differently by the inhibitory systems descending from the brain. The other 3 systems, which constitute the “medial” group, appear to have the same modality spectrum. However, they differ from the lateral group on other dimensions — they conduct more slowly; their cell bodies tend to be located more deeply in the spinal grey matter; and, most importantly, their patterns of termination are grossly different from those of the lateral group. Several speculative proposals are presented to explain the functions and possible interactions among the various systems. These proposals emphasize two main factors: 1. (1) the possible influence of on-going behavioral sequences on the relative activity among the systems; and 2. (2) the possible effects of existing tissue damage on the mediation of subsequent noxious stimuli. Although these proposals are speculative, they are amenable to experimental investigation. Implications for the treatment of pain are discussed.

Factors of the language of pain in patient and volunteer groups

Abstract: An empirical determination of the nature and minimum number of dimension necessary to describe responses to the McGill Pain Questionnaire, and a comparison of groups, experiencing clinical or experimentally induced pain, on the dimensions were carried out. Eighty-five patients referred to a low back pain diagnostic clinic and groups of 129 volunteer students exposed to electric shock to pain threshold and pain tolerance levels described their pain using the McGill Pain Questionnaire's descriptive words. An incomplete principle component factor analysis of subjects' ratings suggested that 5 factors should be retained. These factors were judged to reflect: (I) immediated anxiety, (II) perception of harm, (III) somesthetic pressure, (IV) cutaneous sensitivity, and (V) sensory information. Canonical Analysis of Variance and univariate comparisons of back pain, threshold, and tolerance groups on these dimensions were conducted and implications for clinical and laboratory research discussed.

Facet "denervation" in the treatment of low back syndrome.

Abstract: Long-term pain relief occurred in 21% of patients with low back and leg pain who underwent injection or radiofrequency rhizotomy. When pain was accompanied by unequivocal limitation of straight leg raising, neither injection nor rhizotomy produced long-term relief. Leg pain improved more than low back pain. Improvement was limited to pain relief as reported to the physician and reduction of medication. There was no improvement in work or activity status. Despite the low success rate, facet "denervation" is uncommonly safe and seems to be of some usefulness in the treatment of patients with low back pain and sciatica.

Significance of pain in psychiatric hospital patients

Abstract: In a consecutive series of 227 psychiatric hospital admissions, data were recorded in respect of the complaint of pain. Eighty-six (38%) had pain. Fourty-four (19%) mentioned it spontaneously and 49 (22%) had no relevant physical cause. Women were affected more often than men (P < 0.01) and tended to complain more often of severe pain (P < 0.01). Severe pain was more often reported spontaneously (P < 0.02). Also, the longer pain lasted the more likely the patient was to report it spontaneously (P < 0.02). Men more often had a relevant physical diagnosis (P < 0.05) and the low back was the commonest site of pain in them. Pain was relatively often associated with diagnoses of anxiety and personality disorder and relatively infrequently with schizophrenia, organic brain syndromes and transient situational disturbances. It is concluded that whilst there is a strong association between pain and psychiatric illness, this is less prominent, paradoxically, in some of the more severe psychiatric disturbances.