Sensory function after cavernous haemangioma: a case report of thermal hypersensitivity at and below an incomplete spinal cord injury.

STUDY DESIGN: Case report of a 42-year-old woman with non-evoked pain diagnosed with a cavernous C7-Th6 spinal haemangioma. OBJECTIVES: To assess the effect of intramedullary haemorrhage (IH) on nociception and neuropathic pain (NP) at and below an incomplete spinal cord injury (SCI). SETTING: Sensorimotor Function Group, Hospital Nacional de Parapléjicos de Toledo (HNPT). METHODS: T2*-susceptibility weighted image (SWI) magnetic resonance imaging (MRI) of spinal haemosiderin and a complete pain history were performed 8 months following initial dysaesthesia complaint. Thermal pain thresholds were assessed with short 1 s stimuli, while evidence for central sensitization was obtained with psychophysical electronic Visual Analogue Scale rating of tonic 10 s 3 °C and 48 °C stimuli, applied at and below the IH. Control data were obtained from 10 healthy volunteers recruited from the HNPT. RESULTS: Non-evoked pain was present within the Th6 dermatome and lower legs. T2*-SWI MRI imaging detected extensive haemosiderin-rich IH (C7-Th5/6 spinal level). Cold allodynia was detected below the IH (left L5 dermatome) with short thermal stimuli. Tonic thermal stimuli applied to the Th6, Th10 and C7 dermatomes revealed widespread heat and cold allodynia. CONCLUSION: NP was diagnosed following IH, corroborated by an increase in below-level cold pain threshold with at- and below-level cold and heat allodynia. Psychophysical evidence for at- and below-level SCI central sensitization was obtained with tonic thermal stimuli. Early detection of IH could lead to better management of specific NP symptoms, an appreciation of the role of haemorrhage as an aggravating SCI physical factor, and the identification of specific spinal pathophysiological pain mechanisms.

Opioid modulation of reflex versus operant responses following stress in the rat.

In pre-clinical models intended to evaluate nociceptive processing, acute stress suppresses reflex responses to thermal stimulation, an effect previously described as stress-induced "analgesia." Suggestions that endogenous opioids mediate this effect are based on demonstrations that stress-induced hyporeflexia is enhanced by high dose morphine (>5 mg/kg) and is reversed by naloxone. However, reflexes and pain sensations can be modulated differentially. Therefore, in the present study direct comparisons were made of opioid agonist and antagonist actions, independently and in combination with acute restraint stress in Long Evans rats, on reflex lick-guard (L/G) and operant escape responses to nociceptive thermal stimulation (44.5 degrees C). A high dose of morphine (>8 mg/kg) was required to reduce reflex responding, but a moderate dose of morphine (1 mg/kg) significantly reduced escape responding. The same moderate dose (and also 5 mg/kg) of morphine significantly enhanced reflex responding. Naloxone (3 mg/kg) significantly enhanced escape responding but did not affect L/G responding. Restraint stress significantly suppressed L/G reflexes (hyporeflexia) but enhanced escape responses (hyperalgesia). Stress-induced hyperalgesia was significantly reduced by morphine and enhanced by naloxone. In contrast, stress-induced hyporeflexia was blocked by both naloxone and 1 mg/kg of morphine. Thus, stress-induced hyperalgesia was opposed by endogenous opioid release and by administration of morphine. Stress-induced hyporeflexia was dependent upon endogenous opioid release but was counteracted by a moderate dose of morphine. These data demonstrate a differential modulation of reflex and operant outcome measures by stress and by separate or combined opioid antagonism or administration of morphine.

Abnormal sensitization and temporal summation of second pain (wind-up) in patients with fibromyalgia syndrome.

Although individuals with fibromyalgia syndrome (FMS) consistently report wide-spread pain, clear evidence of structural abnormalities or other sources of chronic stimulation of pain afferents in the involved body areas is lacking. Without convincing evidence for peripheral tissue abnormalities in FMS patients, it seems likely that a central pathophysiological process is at least partly responsible for FMS, as is the case for many chronic pain conditions. Therefore, the present study sought to obtain psychophysical evidence for the possibility that input to central nociceptive pathways is abnormally processed in individuals with long standing FMS. In particular, temporal summation of pain (wind-up) was assessed, using series of repetitive thermal stimulation of the glabrous skin of the hands. Although wind-up was evoked both in control and FMS subjects, clear differences were observed. The perceived magnitude of the sensory response to the first stimulus within a series was greater for FMS subjects compared to controls, as was the amount of temporal summation within a series. Within series of stimuli, FMS subjects reported increases in sensory magnitude to painful levels for interstimulus intervals of 2-5 s, but pain was evoked infrequently at intervals greater than 2 s for control subjects. Following the last stimulus in a series, after-sensations were greater in magnitude, lasted longer and were more frequently painful in FMS subjects. These results have multiple implications for the general characterization of pain in FMS and for an understanding of the underlying pathophysiological basis.

The effect of maximal exercise on temporal summation of second pain (windup) in patients with fibromyalgia syndrome.

Exercise activates endogenous opioid and adrenergic systems, but attenuation of experimental pain by exercise has not been shown consistently. In this study, effects of exercise on temporal summation of late pain responses to stimulation of unmyelinated (C) nociceptors were assessed. When a preheated thermode was applied repetitively to glabrous skin of the hand in a series of brief contacts at rates of 0.2 to 0.5 Hz, the perceived intensity of late thermal sensations increased after successive contacts. This summation of pain sensations provides information regarding the status of central opioid and N-methyl-D-aspartate receptor systems. For normal subjects, temporal summation of late pain sensations was substantially attenuated when testing began 1.5 or 10 minutes after exercise. Individuals diagnosed with fibromyalgia syndrome (FMS) report generalized chronic pain that is increased after exercise. Therefore, we hypothesized that strenuous exercise would increase summation of late pain sensations in this cohort. Patients with FMS and control subjects exerted to similarly high metabolic rates, as shown by physiologic monitoring. Ratings of late pain sensations increased for patients with FMS after exercise, an effect opposite to a decrease in ratings for age/sex-matched control subjects. In contrast to this result for experimentally induced pain, clinical pain ratings were not substantially altered after strenuous exercise by patients with FMS.

An operant assay of thermal pain in conscious, unrestrained rats.

Methods are described which provide quantification of learned operant and innate reflex responses to a thermal stimulus (heat or cold) and provide matched motor controls. The apparati and procedures consist of (1) an 'Escapetest' which measures latencies and durations of escape from a compartment where the floor is heated or cooled to a platform at neutral temperature in an adjacent compartment; (2) a motor and motivational control for the Escapetest, the 'Darkboxtest', which measures escape latency from bright light in a shuttle box; and (3) assessment of latencies and durations of licking or guarding responses to thermal stimulation in the absence of the escape option. Avoidance responses in the Escapetest (retreating to the escape platform in the absence of an experience of pain) are discouraged by bright illumination of the compartment containing the escape platform (brightly lit areas are aversive to rodents). Stimulus-response functions for escape from heat and cold are compared to stimulus response functions for innate lick/guard responses to the same temperatures. Substantial differences in the relationships between learned or innate responses and temperature attest to a need for methods which evaluate operant responses to nociceptive stimulation.

The role of pharmacy in the management of patients with temporomandibular disorders and orofacial pain.

OBJECTIVE: To provide information regarding the current understanding of the etiology and treatment, both nonpharmacologic and pharmacologic, of orofacial pain conditions including temporomandibular disorders (TMDs). This review briefly discusses the etiology and pathophysiology underlying the development of TMDs, generally accepted nonpharmacologic methods of treatment, and the most common current pharmacologic management approaches. DATA SOURCES: Current medical literature and the authors' clinical experiences. DATA SYNTHESIS: TMDs encompass a number of diagnostic subgroups that involve the masticatory musculature, the temporomandibular joint(s), and associated structures. More than 10 million individuals in the United States are affected by TMDs. Most current pharmacologic management approaches in the treatment of orofacial pain conditions, including TMDs, involve the use of antidepressants, anticonvulsants, muscle relaxants, corticosteroids, and nonsteroidal anti-inflammatory drugs. CONCLUSION: Inclusion of pharmacists who are knowledgeable in the nonpharmacologic and pharmacologic treatment approaches on the TMD management team would improve therapeutic monitoring, follow-up, and outcomes in these patients.

Visual and profilometric wear measurements.

Wear of composites can be estimated by the degree of marginal discrepancy between the prepared cavity wall and the occlusal margins of composites. Such evaluations are done on casts by comparing and rating the marginal discrepancy with those on standard casts. We analyzed the reliability of this technique on metal and stone specimens. These specimens contained grooves of different width and depth. For the visual comparison we used stone casts of machined standards of known groove depth. We measured the depths of the metal specimens with a profilometer and made stone casts of these original specimens. Using the stone casts of the standards, five dentists estimated the unknown groove depths on the remaining stone casts. These estimates were done under standardized conditions and repeated by each dentist on five different occasions. The results showed that visual depth evaluations of die stone specimens underestimated the depths when compared with the values measured with a profilometer on the original metal models. One investigator gave significantly different (p less than 0.05) groove depth estimates at different occasions.

Facilitatory effect of lingual nerve stimulation on masseteric EMG Activities of the cat.

Unitary EMG activities in masseter muscle of decerebrate cats were recorded during repetitive stimulation (20-50 Hz) of the lingual nerve and during vibration. These two kinds of stimuli facilitated EMG activities, whereby their effects could summate. Masseteric EMG response was also obtained during jaw opening phase of the cyclic jaw movement. With the jaw cyclically moved at a widely opened position: motor units discharged even at the jaw closing phase during simultaneous lingual nerve stimulation or during vibration. Based on the results obtained, two possible pathways for lingually induced excitation of masseteric EMG can be speculated on: an excitatory pathway from the lingual nerve to the masseteric motoneurons, secondly a direct pathway to masseteric motoneurons. As facilitation of masseteric EMG was obtained with the threshold lower than that of jaw opening reflex, separate afferent fibers concerning these two reflexes should also be considered.