Normal sensorimotor plasticity in complex regional pain syndrome with fixed posture of the hand

The afferent volley evoked by peripheral nerve stimulation has an inhibitory influence on transcranial magnetic stimulation induced motor evoked potentials. This phenomenon, known as afferent inhibition, occurs in two phases: short-latency afferent inhibition (SAI) and long-latency afferent inhibition (LAI). SAI exerts its inhibitory influence via cholinergic and GABAergic activity. The neurotransmitter receptors that mediate LAI remain unclear. The present study aimed to determine whether LAI is contributed by GABA and/or GABA receptor activity. In a double-blinded, placebo-controlled study, 2.5 mg of lorazepam (GABA agonist), 20 mg of baclofen (GABA agonist) and placebo were administered to 14 males (mean age 22.7 ± 1.9 years) in three separate sessions. SAI and LAI, evoked by stimulation of the median nerve and recorded from the first dorsal interosseous muscle, were quantified before and at the peak plasma concentration following drug ingestion. Results indicate that lorazepam reduced LAI by ∼40% and, in support of previous work, reduced SAI by ∼19%. However, neither SAI, nor LAI were altered by baclofen. In a follow-up double-blinded, placebo-controlled study, 10 returning participants received placebo or 40 mg of baclofen (double the dosage used in Experiment 1). The results obtained indicate that SAI and LAI were unchanged by baclofen. This is the first study to show that LAI is modulated by GABA receptor activity, similar to SAI, and that afferent inhibition does not appear to be a GABA mediated process.

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“…), complex regional pain syndrome (Morgante et al . ) and focal hand dystonia (Pirio Richardson et al . ).…”

Section: Discussionmentioning

confidence: 99%

“…) and complex regional pain syndrome (Morgante et al . ). Furthermore, the magnitude of SAI and LAI declines with age (Young‐Bernier et al.…”

Section: Introductionmentioning

confidence: 97%

Effects of lorazepam and baclofen on short‐ and long‐latency afferent inhibition

Turco

El-Sayes

Locke

et al. 2018

The Journal of Physiology

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Section: Discussionmentioning

confidence: 99%

“…Finally, chronic functional dystonia might be related to a reorganization of sensory areas, as has been demonstrated in complex pain regional syndrome type I, a condition that should be included into the functional symptoms spectrum based on clinical and neurophysiological evidence. 37 When dealing with pain, it is also fundamental to discuss the role of emotions and mood on pain processing. Indeed, decreased pain thresholds and pain tolerances in Parkinson's disease were correlated with severity of depressive symptoms, 5 and a similar association was found in patients with major depressive disorder.…”

Section: Discussionmentioning

confidence: 99%

Pain processing in functional and idiopathic dystonia: An exploratory study

et al. 2018

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“…There have been several studies aiming to explore at this question. A recent study looking at patients with a fixed hand posture and CRPS compared to healthy controls found sensorimotor abnormalities potentially compatible with a psychogenic dystonia and in contrast to findings found in isolated focal hand dystonia (125). Identifying similarities and contrasts between the underlying pathophysiology of these disorders will be helpful moving forward perhaps both in diagnosis and in treatment.…”

Section: Pathogenesismentioning

confidence: 94%

Research Priorities in Limb and Task-Specific Dystonias

et al. 2017

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Dystonia, which causes intermittent or sustained abnormal postures and movements, can present in a focal or a generalized manner. In the limbs, focal dystonia can occur in either the upper or lower limbs and may be task-specific causing abnormal motor performance for only a specific task, such as in writer’s cramp, runner’s dystonia, or musician’s dystonia. Focal limb dystonia can be non-task-specific and may, in some circumstances, be associated with parkinsonian disorders. The true prevalence of focal limb dystonia is not known and is likely currently underestimated, leaving a knowledge gap and an opportunity for future research. The pathophysiology of focal limb dystonia shares some commonalities with other dystonias with a loss of inhibition in the central nervous system and a loss of the normal regulation of plasticity, called homeostatic plasticity. Functional imaging studies revealed abnormalities in several anatomical networks that involve the cortex, basal ganglia, and cerebellum. Further studies should focus on distinguishing cause from effect in both physiology and imaging studies to permit focus on most relevant biological correlates of dystonia. There is no specific therapy for the treatment of limb dystonia given the variability in presentation, but off-label botulinum toxin therapy is often applied to focal limb and task-specific dystonia. Various rehabilitation techniques have been applied and rehabilitation interventions may improve outcomes, but small sample size and lack of direct comparisons between methods to evaluate comparative efficacy limit conclusions. Finally, non-invasive and invasive therapeutic modalities have been explored in small studies with design limitations that do not yet clearly provide direction for larger clinical trials that could support new clinical therapies. Given these gaps in our clinical, pathophysiologic, and therapeutic knowledge, we have identified priorities for future research including: the development of diagnostic criteria for limb dystonia, more precise phenotypic characterization and innovative clinical trial design that considers clinical heterogeneity, and limited available number of participants.

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Normal sensorimotor plasticity in complex regional pain syndrome with fixed posture of the hand

Cited by 26 publications

References 51 publications

Effects of lorazepam and baclofen on short‐ and long‐latency afferent inhibition

Effects of lorazepam and baclofen on short‐ and long‐latency afferent inhibition

Pain processing in functional and idiopathic dystonia: An exploratory study

Research Priorities in Limb and Task-Specific Dystonias

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