Pain
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The aim of this study was to determine if the application of mustard oil (MO), a small-fiber excitant and inflammatory irritant, or other algesic chemicals (capsaicin, CAP, and bradykinin, BK) to the rat maxillary molar tooth pulp induces electromyographic (EMG) activity of the masseter and digastric muscles, and also to determine if endogenous opioid mechanisms may be involved in any documented EMG changes. Application of MO to the tooth pulp induced a significant increase in EMG activity of the ipsilateral masseter up to 30 min. The application of mineral oil to the pulp or MO application to the pulp-extirpated tooth did not induce any significant EMG increases. ⋯ These findings suggest that pulp afferent inputs to the central nervous system evoked by BK. CAP and especially MO may induce enhanced jaw muscle activity. In addition, the naloxone data suggest that an opioid suppresive mechanism may be induced by the pulpal afferent inputs evoked by MO, and may serve to limit the jaw muscle activity elicited by these inputs.
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Complex regional pain syndrome (CRPS) remains a poorly understood chronic pain disorder. Little data has been published assessing the epidemiology of CRPS (and reflex sympathetic dystrophy, RSD). This study assessed epidemiological variables in 134 CRPS patients evaluated at a tertiary chronic pain clinic in the US, including demographic, health care utilization and legal/workman's compensation measures. ⋯ The duration of CRPS symptoms and the involvement of the upper extremity was significantly associated with the presence of myofascial dysfunction. Thus, this study found that most CRPS patients are referred to a pain specialty clinic after several years of symptoms and many failed therapies. The data also suggest the lack of utility of a diagnostic bone scan and highlight the prominence of myofascial dysfunction in a majority of CRPS patients.
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We investigated behavioral symptoms of neuropathic pain, and associated changes in dorsal horn neurons, in a rat model involving loose ligation of lumbar dorsal roots. The L4-L6 dorsal roots were exposed unilaterally and loosely constricted central to the respective ganglia with one (1-ligation) or two (2-ligation) silk 7-O ligatures. In control groups the dorsal roots were exposed but not ligated (sham-operated), or sutures were placed lengthwise between the dorsal roots (suture control). ⋯ Enlarged cutaneous receptive fields of dorsal horn neurons may contribute to mechanical allodynia associated with dorsal root constriction. However, the slow (>5 week) development of receptive field enlargement does not match the rapid development of allodynia. The lack of effect of dorsal root constriction on thermal sensitivity of dorsal horn units ipsilaterally corresponds to the lack of marked thermal hyperalgesia observed behaviorally.
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Narrative accounts of their lived experiences were collected from twenty back pain patients who were seeking help from two pain clinics in the UK. Following analysis using a phenomenological approach, five themes emerged which tell a typical story of back pain. ⋯ These systems, designed to treat or support those who are ill or disabled, effectively rendered participants powerless, helpless and angry. It is suggested that these accounts may help clinicians and researchers to gain a better understanding of the origins and nature of the negative attitudes exhibited by many back pain patients who seek help from pain treatment centres.
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Clinical Trial
Electrophysiological testing of the trigeminofacial system: aid in the diagnosis of atypical facial pain.
The aim of this study was to evaluate the yield of objective electrophysiological testing of the trigeminofacial system in atypical facial pain (AFP). In addition to the clinical neurological examination, two brainstem reflexes covering both the peripheral parts and the central connections of the trigeminal and the facial nerves, the blink and jaw reflexes (BR and JR), were recorded in 17 AFP patients. The control group consisted of 18 healthy volunteers with no history of facial pain or chronic headache. ⋯ Additionally, one patient had abnormal BAEP and EEG recordings. On the group level, the AFP patients had significantly higher thresholds of the tactile R1 component of the BR than the control subjects. Electrophysiological testing may offer a valuable tool for both the clinical evaluation, and the scientific study of AFP.