The journal of pain : official journal of the American Pain Society
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Seventy-one percent of 122 patients with central post-stroke pain (CPSP) had allodynia that was tactile-, cold-, or movement-evoked. Site of thalamic (and some infratentorial) lesions as revealed by magnetic resonance imaging (MRI) was correlated in some cases with allodynia type and sensory perception threshold testing (QST). Notably, patients with cold allodynia tend to have more dorsally placed thalamic lesions than those without, and those with movement allodynia more anteriorly placed lesions. Suggestions are made for improved correlation. ⋯ Only about half of patients with CPSP have allodynia (pain caused by innocuous stimulation); such stimulation is usually tactile- or cold-evoked or due to activation of stretch receptors (movement). We have found that, in some of our cases, the type of allodynia may depend on lesion location within the thalamus.
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Different laboratory animal models of neuropathic pain that replicate pathophysiological changes in patients have been developed. In most animal models of neuropathic pain, both sensory and motor nerves are injured. Thus, animals usually show both abnormal sensory and motor responses. Assessment of the sensory system is likely to be affected by the motor defects, although motor functions have not been evaluated in previous neuropathic pain models. An ideal neuropathic pain model to assess behavioral nociceptive responses in animals is one without affecting motor function and without muscle injury. Here, we report a novel mouse model of neuropathic pain with normal motor functions. Ligation of the common peroneal nerve near the head of fibula was performed by a less invasive procedure. Long-lasting behavioral allodynia and thermal hyperalgesia was observed in mice after the ligation. Furthermore, behavioral allodynia is resistant to morphine treatment at 5 mg/kg body weight, as reported in some cases of neuropathic pain. Standard rotarod test analysis confirmed intact motor functions. Our results show that ligation of the common peroneal nerve can be used as an efficacious mouse model for assessing behavioral nociceptive responses in neuropathic pain. ⋯ Tests to assess behavioral responses in a neuropathic pain model depend on intact motor functions. Here we report a less invasive procedure to ligate common peroneal nerve of leg to induce neuropathic pain with least motor defects.
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In this study we investigated the involvement of cutaneous versus knee joint afferents in the antihyperalgesia produced by transcutaneous electrical nerve stimulation (TENS) by differentially blocking primary afferents with local anesthetics. Hyperalgesia was induced in rats by inflaming one knee joint with 3% kaolin-carrageenan and assessed by measuring paw withdrawal latency to heat before and 4 hours after injection. Skin surrounding the inflamed knee joint was anesthetized using an anesthetic cream (EMLA). Low (4 Hz) or high (100 Hz) frequency TENS was then applied to the anesthetized skin. In another group, 2% lidocaine gel was injected into the inflamed knee joint, and low or high frequency TENS was applied. Control experiments were done using vehicles. In control and EMLA groups, both low and high frequency TENS completely reversed hyperalgesia. However, injection of lidocaine into the knee joint prevented antihyperalgesia produced by both low and high frequency TENS. Recordings of cord dorsum potentials showed that both low and high frequency TENS at sensory intensity activates only large diameter afferent fibers. Increasing intensity to twice the motor threshold recruits Adelta afferent fibers. Furthermore, application of EMLA cream to the skin reduces the amplitude of the cord dorsum potential by 40% to 70% for both high and low frequency TENS, confirming a loss of large diameter primary afferent input after EMLA is applied to the skin. Thus, inactivation of joint afferents, but not cutaneous afferents, prevents the antihyperalgesia effects of TENS. We conclude that large diameter primary afferent fibers from deep tissue are required and that activation of cutaneous afferents is not sufficient for TENS-induced antihyperalgesia. ⋯ Transcutaneous electrical nerve stimulation (TENS) is an accepted clinical modality used for pain relief. It is generally believed that TENS analgesia is caused mainly by cutaneous afferent activation. In this study by differentially blocking cutaneous and deep tissue primary afferents, we show that the activation of large diameter primary afferents from deep somatic tissues, and not cutaneous afferents, are pivotal in causing TENS analgesia.
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Comparative Study
Differences in prescription opioid analgesic availability: comparing minority and white pharmacies across Michigan.
Little is known about physical barriers to adequate pain treatment for minorities. This investigation explored sociodemographic determinants of pain medication availability in Michigan pharmacies. A cross-sectional survey-based study with census data and data provided by Michigan community retail pharmacists was designed. Sufficient opioid analgesic supplies was defined as stocking at least one long-acting, short-acting, and combination opioid analgesic. Pharmacies located in minority (
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Multicenter Study
Pediatric surgeons and pediatric emergency physicians' attitudes towards analgesia and sedation for incarcerated inguinal hernia reduction.
Inguinal hernias become incarcerated in 10% to -15% of children and reduction of the hernia is an urgent painful procedure. No recommendations exist for analgesia during this procedure. We surveyed pediatric emergency physicians (PEP) and pediatric surgeons (PS) for their analgesia and sedation use during the reduction. The survey was mailed to 19 centers in North America. A total of 56% (185/331) surveys were completed by PEP and 56% (68/122) from PS. A total of 96.7% (245/253) of responders reported giving analgesia or sedation during reduction. PS were more likely to use intravenous drugs, try for a longer time, wait longer between trials, and conduct more trials compared to the PEP. Clinically related variables were more important for PEPs than PS for analgesia and sedation. System-related variables were more important by PS for admission. ⋯ This survey shows significant variability between specialties in the drugs, route, and number of attempts during reduction of a painful incarcerated hernia in children. Development of a sedation and analgesia protocol may be useful in order to unify management of pain and discomfort during hernia reduction.