Biomedical subjects

Anthony K P Jones

Publications and source records attributed to Anthony K P Jones.

9 recordsLinked to original sources

PubMed2005

Paracetamol use in musculoskeletal pain: an audit of use and patient perceptions of paracetamol as an effective analgesic.

Musculoskeletal pain is a complex problem with often very detrimental consequences which affects a high proportion of the general population. Health care professionals, when prescribing for musculoskeletal pain, often overlook simple analgesia. Patient perceptions of analgesia may vary to those of health care professionals, and in part affect the use of simple analgesia for musculoskeletal pain. This paper describes an audit of paracetamol use and patient perceptions of paracetamol as an effective analgesic agent, in 113 patients attending a musculoskeletal pain outpatient clinic in a university teaching hospital. The audit has helped prompt the development of a multi-disciplinary strategy to achieve optimum management.

Journal Article↗

PubMed2004

Cerebral decreases in opioid receptor binding in patients with central neuropathic pain measured by [11C]diprenorphine binding and PET.

Central neuropathic pain (CNP) is pain resulting from damage to the central nervous system. Up till now, it has not been possible to identify a common lesion or pharmacological deficit in these patients. This preliminary study in a group of patients with CNP with predominantly post-stroke pain, demonstrates that there is significantly less opioid receptor binding in a number of cortical and sub-cortical structures that are mostly, but not exclusively, within the medial pain system in patients compared to age-matched pain-free controls. The reductions in opioid receptor binding within the medial system were observed mainly in the dorsolateral (Brodman area 10) and anterior cingulate (Brodman area 24 with some extension into area 23) and insula cortices and the thalamus. There were also reductions in the lateral pain system within the inferior parietal cortex (Brodman area 40). These changes in binding could not be accounted for by the cerebral lesions shown by CT or MRI, which were outside the areas of reduced binding and the human pain system. To our knowledge this is the first systematic demonstration of a reduction in opioid receptor-binding capacity in neurones within the human nociceptive system in patients with CNP. This may be a key common factor resulting in undamped nociceptor activity within some of the structures that are predominantly within the medial nociceptive system. If confirmed, these findings may explain why certain patients with CNP require high doses of synthetic opiates to achieve optimum analgesia. The findings also raise the possibility of new pharmacological approaches to treatment.

Aged↗

PubMed2004

Lateralisation of nociceptive processing in the human brain: a functional magnetic resonance imaging study.

Nociceptive processing within the human brain takes place within two distinct and parallel systems: the lateral and medial pain systems. Current knowledge indicates that the lateral system is involved in processing the sensory-discriminative aspects of pain, and that the medial system is involved in processing the affective-motivational aspects of pain. Hemispheric differences in brain activation (lateralisation) during nociceptive processing were studied to further clarify the division of function between the lateral and medial pain systems. Hemispheric lateralisation was studied by applying painful CO(2) laser stimuli of 3-s duration sequentially to the left and right medial lower calves of five normal right-handed human subjects. The resultant brain activity was measured using 3-T functional magnetic resonance imaging, by determining significant changes in blood oxygen level dependent (BOLD) signal and applying a general linear modelling approach. Volumes of interest were defined for the primary and secondary somatosensory cortices (SI and SII), the insular cortex, and the thalamus, on individual subjects' high-resolution structural scans. Hemispheric lateralisation was quantified by comparing the level of activation between brain hemispheres within each volume of interest. In SII, no significant hemispheric difference in activation was detected. In the insula, activation was significantly greater in the left hemisphere than the right. In both SI and the thalamus, activation in response to painful stimulation was significantly greater in the hemisphere contralateral to the stimulus, which is consistent with these areas being involved in processing the sensory-discriminative aspects of pain.

Adult↗

PubMed2003

Caudal cingulate cortex involvement in pain processing: an inter-individual laser evoked potential source localisation study using realistic head models.

Electrophysiological studies have revealed a source of laser pain evoked potentials (LEPs) in cingulate cortex. However, few studies have used realistically shaped head models in the source analysis, which account for individual differences in anatomy and allow detailed anatomical localisation of sources. The aim of the current study was to accurately localise the cingulate source of LEPs in a group of healthy volunteers, using realistic head models, and to assess the inter-individual variability in anatomical location. LEPs, elicited by painful CO(2) laser stimulation of the right forearm, were recorded from 62 electrodes in five healthy subjects. Dipole source localisation (CURRY 4.0) was performed on the most prominent (P2) peak of each LEP data set, using head models derived from each subject's structural magnetic resonance image (MRI).For all subjects, the P2 LEP peak was best explained by a dipole whose origin was in cingulate cortex (mean residual variance was 3.9+/-2.4 %). For four out of five subjects, it was located at the border of the caudal division of left anterior cingulate cortex (area 24/32') with left posterior cingulate cortex (area 23/31). For the fifth subject the dipole was centred in right posterior cingulate cortex (area 31). This study demonstrates that the location of the cingulate source of LEPs is highly consistent across subjects, when analysed in this way, and supports the involvement of caudal cingulate regions in pain processing.

Adult↗

PubMed2002

Selective attention to pain: a psychophysical investigation.

Laboratory research suggests that the processing of painful stimuli can be modulated by selective attention to a particular sensory modality. However, alternative accounts for previous findings remain possible in terms of task-switching and spatial attention effects. In the present study, we examined whether attention can be selectively directed to the pain modality in order to facilitate the processing of the sensory-discriminative aspects of painful laser heat stimuli when these alternatives were ruled out. Participants made speeded spatial discrimination responses to an unpredictable sequence of painful laser heat and visual stimuli presented on the left forearm. On each trial, a symbolic cue predicted the likely modality for the upcoming target on the majority of trials. Participants responded more rapidly when the target was presented in the expected as opposed to the unexpected modality, demonstrating that selective attention can modulate the processing of painful stimuli. These findings are discussed in relation to contemporary theories of crossmodal attention and multisensory information-processing.

Attention↗

PubMed2002

Functional imaging of pain perception.

The application of functional imaging techniques has revolutionized the field of human pain physiology and has elaborated the understanding of mechanisms involved in pain processing at the cortical and subcortical levels. With these insights, new therapeutic interventions are being developed in the treatment of acute and chronic pain conditions.

Acute Disease↗

PubMed2002

Poststroke shoulder pain: a prospective study of the association and risk factors in 152 patients from a consecutive cohort of 205 patients presenting with stroke.

BACKGROUND AND PURPOSE: Shoulder pain is known to retard rehabilitation after stroke. Its causes and prognosis are uncertain. This study describes the incidence of poststroke shoulder pain prospectively, in an unselected stroke population in the first 6 months after stroke and identifies risk factors for developing pain. METHODS: 297 patients with possible stroke were screened and stroke diagnosed in 205 cases. The 152 patients entered the study of which 123 patients were assessed up to 6 months. This cohort, with a mean age of 70.6 years, was examined at 2 weeks, 2, 4, and 6 months. A history of shoulder pain, Barthel score, anxiety and depression score were recorded. Full neurological and rheumatological examination was undertaken, using the contralateral side as a control. Pain outcome and stroke outcome was recorded at subsequent visits. RESULTS: 52 (40%) patients developed shoulder pain on the same side of their stroke. There was a strong association between pain and abnormal shoulder joint examination, ipsilateral sensory abnormalities and arm weakness. Shoulder pain had resolved or improved at 6 months in 41 (80%) of the patients with standard current treatment. CONCLUSIONS: Shoulder pain after stroke occurred in 40% of 123 patients surviving, consenting and not too unwell to participate. This included 52 patients of an original cohort of 205 patients presenting with stroke. Eighty percent of patients made a good recovery with standard treatment Patients with sensory and or motor deficits represent at risk sub-groups.

Adult↗

PubMed2002

Gender differences in patterns of cerebral activation during equal experience of painful laser stimulation.

A previous functional imaging study demonstrated greater female response in the anterior insula and thalamus and left prefrontal activation in men and right prefrontal activation in women during equal heat intensity but unequal pain experience. For the current study, subjective intensities of noxious heat delivered to the back of the right hand were equalized across subjects, and regional cerebral blood flow was recorded by using positron emission tomography. The female subjects required less laser energy before reporting pain, but the difference was not significant. Correlation of regional cerebral blood flow with subjective pain experience in the whole group showed significant bilateral responses in the parietal, lateral premotor, prefrontal, secondary somatosensory, anterior cingulate and insula cortices, as well as the thalamus. There was significantly greater activation in the left, contralateral, prefrontal, primary and secondary somatosensory, parietal, and insula cortices in the male subjects compared with the female subjects and greater response in the perigenual cingulate cortex in the female subjects. Our study is the first to associate consistent pain experience with gender differences in central response. These differences may relate to differential processing of acute pain with implications for clinical disorders that show a female dominance. The subtle behavioral differences and inconsistent findings across studies, however, suggest the need for caution and further experimentation before speculating further.

Journal Article↗

PubMed1997

Pain processing during three levels of noxious stimulation produces differential patterns of central activity.

Previous functional imaging studies have demonstrated a number of discrete brain structures that increase activity with noxious stimulation. Of the commonly identified central structures, only the anterior cingulate cortex shows a consistent response during the experience of pain. The insula and thalamus demonstrate reasonable consistency while all other regions, including the lentiform nucleus, somatosensory cortex and prefrontal cortex, are active in no more than half the current studies. The reason for such discrepancy is likely to be due in part to methodological variability and in part to individual variability. One aspect of the methodology which is likely to contribute is the stimulus intensity. Studies vary considerably regarding the intensity of the noxious and non-noxious stimuli delivered. This is likely to produce varying activation of central structures coding for the intensity, affective and cognitive components of pain. Using twelve healthy volunteers and positron emission tomography (PET), the regional cerebral blood flow (rCBF) responses to four intensities of stimulation were recorded. The stimulation was delivered by a CO2 laser and was described subjectively as either warm (not painful), pain threshold just painful), mildly painful or moderately painful. The following group subtractions were made to examine the changing cerebral responses as the stimulus intensity increased: (1) just painful - warm; (2) mild pain - warm; and (3) moderate pain - warm. In addition, rCBF changes were correlated with the subjective stimulus ratings. The results for comparison '1' indicated activity in the contralateral prefrontal (area 10/46/44), bilateral inferior parietal (area 40) and ipsilateral premotor cortices (area 6), possibly reflecting initial orientation and plans for movement. The latter comparisons and correlation analysis indicated a wide range of active regions including bilateral prefrontal, inferior parietal and premotor cortices and thalamic responses, contralateral hippocampus, insula and primary somatosensory cortex and ipsilateral perigenual cingulate cortex (area 24) and medial frontal cortex (area 32). Decreased rCBF was observed in the amygdala region. These responses were interpreted with respect to their contribution to the multidimensional aspects of pain including fear avoidance, affect, sensation and motivation or motor initiation. It is suggested that future studies examine the precise roles of each particular region during the central processing of pain.

Adult↗