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Multiple arm lipomatosis and posterior interosseus nerve palsy
No full textBACKGROUND:
Lipomas are common benign soft tissue tumours which tend to be indolent and risk free. Lipomas rarely spread in the deep soft tissue causing posterior interosseous nerve (PIN) neuropathy.
METHODS (CASE DESCRIPTION):
We present two patients with multiple lipomatosis of the arms and PIN paralysis, with a brief review of the cases reported in literature.
RESULTS AND CONCLUSION:
We emphasize the role of electromyographic study as unique methodical capable to reveal an early radial nerve damage, permitting an optimal post-surgical nerve function recoverin
Corticospinal drive during painful voluntary contractions at constant force output.
No full textIn the voluntary contractions, output force can be maintained constant although the inhibitory influences exerted by pain on muscle activity. We investigated changes in the spontaneous and evoked activity of the abductor digiti minimi muscle (ADM) and the biceps brachii muscle (BIC) in healthy volunteers during constant force noxious contraction, resulting from chemically activated nociceptive afferents. EMG-force relationship, motor-evoked response (MEP) to transcranial magnetic stimulation and determinism (DET) of surface EMG signals during constant force contraction was analyzed before, during and after chemically induced tonic activation of their nociceptive afferents. Under constant force contraction, amplitude of surface EMG signal decreased in BIC and increased in ADM during pain with respect to control condition. In both muscles, the size of motor-evoked potential (MEP) induced by transcranial magnetic stimulation (TMS) of the primary motor cortex was significantly higher during pain than in control. Level of determinism extracted from surface EMG signal by non-linear method was similarly and significantly increased in both muscles during pain stimulation. Finally, nociceptive stimulation caused a decline in steadiness of the force exerted by ADM and BIC. These results are interpreted in terms of increased corticospinal synchronizing inputs. The possibility that it may play a role in governing force production to counteract pain inhibitory influences on motor system is considered
Spinal reflex pattern to foot nociceptive stimulation in standing humans.
No full textIpsi- and contralateral patterns of lower limb nociceptive reflex responses were studied in 6 normal subjects in free standing position. Once the position was stabilized, only ankle extensor muscles showed consistent tonic activity while ankle flexors and knee extensors and flexors were virtually silent. Reflex responses, elicited by painful electrical stimuli to the skin of the plantar and dorsal aspect of the foot, were recorded from ipsi- and contralateral quadriceps (Q), biceps femoris (Bic), tibialis anterior (TA) and soleus (Sol) muscles. Plantar foot stimulation evoked a large excitatory response in the ipsilateral TA at about 80 ms and a smaller responses in Bic and Q at 70 ms and 110 ms, respectively. Ipsilateral excitatory effects after dorsal foot stimulation consisted of a Bic response at about 75 ms. In addition to excitatory effects, both plantar and dorsal foot stimulation evoked long-lasting suppression of ipsilateral Sol background activity starting at about 60 ms. Contralaterally, the only nociceptive effects after plantar or dorsal foot stimulation were a small excitatory response of Sol at about 85 ms. Evidence is provided that only excitatory responses were contingent upon nociceptive volley. The main mechanical effects seen after plantar stimulation were dorsiflexion of the foot without loss of heel contact with the floor; no withdrawal response of the foot followed nociceptive dorsal stimulation. Our main conclusion is that only reflex nociceptive responses serving to avoid the stimulus without conflicting with limb support function are expressed. The mechanisms reconciling nociceptive action and postural function of the lower limbs are discussed
Early somatosensory processing during tonic muscle pain in humans: relation to loss of proprioception and motor 'defensive' strategies
No full textOBJECTIVE:
It is known that tonic muscle pain induced by a Levo-Ascorbic (L-AS) solution injected in a foot muscle can transiently modify both regional proprioception and stimulus perception. These findings are paralleled by changes of middle-latency lower-limb somatosensory evoked potentials (SEPs). However, little is known on the behaviourally relevant aspect whether eventual SEP pain-induced changes could be partly due to a sort of 'motor strategy' of subjects in the frame of a self-protective reaction towards the noxious stimulus. Movement and imagery of movements are in fact known to reduce mainly pre-central SEP amplitude (i.e. gating effect).
METHODS:
Low-threshold afferents ulnar SEPs, psychophysical pain ratings and fingers' position sense were monitored in the time-course during L-AS injection in the right first dorsal interosseous muscle. Control experiments included SEPs (either following prevalent ulnar nerve low-threshold afferent stimulation or more conventional mixed nerve stimulation) during actual movements execution and imagery of movements of the right hand.
RESULTS:
Tonic pain induced a significant reduction of the post-central N(20)-P(25)-N(33) complex and a significant increase of the N(18) wave. These changes, that were paralleled by distortion of the finger position sense, were delayed 2-5 min with respect to the maximal subjective pain sensation. Conversely, movement imagery tasks lead to a significant, selective, reduction of the pre-central N(30) complex. This wave was even more reduced during actual movements, in combination with a reduction of those post-central components peaking after the first activation of the primary sensory cortex.
CONCLUSIONS:
Early sensory processing at cortical level is changed during tonic muscle pain, mainly for those components which may be theoretically involved in proprioceptive afferent elaboration. These changes are likely not due to subconscious or voluntary motor strategies of the subjects in the frame of a self-protective aversive reaction towards the noxious stimulus. © 2003 International Federation of Clinical Neurophysiology. Published by Elsevier Science Ireland Ltd. All rights reserved
Changes in coordination of postural control during dynamic stance in chronic low back pain patients
No full textThe human postural system operates on the basis of integrated information from three independent sources: vestibular, visual and somatosensory. It is conceivable that a derangement of any of these systems will influence the overall output of the postural system. The peripheral proprioceptive system or the central processing of proprioceptive information may be altered in chronic low back pain (CLBP). We therefore investigated whether patients with CLBP exhibited an altered postural control during quiet standing. Dynamic posturography was performed by 12 CLBP patients and 12 age-matched controls. Subject's task was to stand quietly on a computer-controlled movable platform under six sensory conditions that altered the available visual and proprioceptive information. While the control of balance was comparable between the two groups across stabilized support surface conditions (1-3), CLBP patients oscillated much more than controls in the anterior-posterior (AP) direction in platform sway-referenced conditions (4-6). Control experiments ruled out that increased sway was due to pain interference. In CLBP patients, postural stability under challenging conditions is maintained by an increased sway in AP direction. This change in postural strategy may underlie a dysfunction of the peripheral proprioceptive system or the central integration of proprioceptive informatio
Interactions between nociceptive and non-nociceptive afferent projections to cerebral cortex in humans.
No full textWe investigated the effect of a tonic discharge of muscle nociceptive afferents on somatosensory evoked potentials (SEPs) in humans in response to stimulation of non-nociceptive afferents arising from the same muscle. Conditioning nociceptive muscle stimulation was achieved by local injection of 50 mg levo-ascorbic acid (in a volume of 0.3 ml) in the body of the extensor digitorum brevis muscle (EDB). The test stimulus for SEPs was an electrical pulse applied to the EDB nerve at an intensity below the motor threshold. The main finding was that tonic muscle nociceptive stimulation strongly depressed the middle-latency P60-N75 complex without modifying the size of the early P40-N50 complex of SEPs. Depression of the P60-N75 complex was correlated with the pain-induced loss of proprioception of the foot, making it plausible that this cortical complex reflects neuronal processes leading to perception
Influences of chemically-induced muscle pain on power output of ballistic upper limb movements
No full textObjective: To analyse the conditioning effects of localised acute muscle pain on power output during ipsi- and contra-lateral ballistic arm extensions.
Methods: Eight male subjects performed right arm (ipsilateral) and left arm (contra-lateral) bench press movements. The power output (and force and velocity) of the concentric phase of movement was measured before and during muscle pain induced by a standardised intramuscular injection of levo-ascorbic acid in the right pectoralis major muscle (prime mover muscle) and in the lateral head of the right triceps brachii muscle (synergist).
Results: The power output of ipsi- and contra-lateral arm bench press movements was significantly decreased during pain of the right pectoralis major muscle, but not during pain of the right lateral triceps muscle. The velocity and force were both affected and contributed to the decrease in power output.
Conclusions: Acute muscle pain of a prime mover muscle reduces ipsi- and contra-lateral motor performance of ballistic upper limb
extension. This is not a generalised or non-specific inhibitory effect on the motor system, since pain failed to modify motor performance when applied to a synergist, non-prime mover, muscle. A basically bilateral executive cortical plan for ballistic upper limb extension could explain the conditioning effect of muscle pain on both ipsi- and contra-lateral arm.
Significance: The results presented here contributes to the understanding of the conditioning effects of muscle pain on movement
performance
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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