Noninvasive Brain Stimulation, Maladaptive Plasticity, and Bayesian Analysis in Phantom Limb Pain

Abstract

Phantom limb pain (PLP) is a common and poorly understood pathology of difficult medical control that progressively takes place after amputation occurs. This article discusses the multifactorial bases of PLP. These bases involve local changes at the stump level, spinal modifications of excitability, deafferentation, and central sensitization, leading to the development of maladaptive plasticity, and consequentially, defective processing of sensory information by associative neural networks. These changes can be traced by neurophysiology and imaging topographical studies, indicating a degree of cortical reorganization that perpetuates pain and discomfort. Noninvasive brain stimulation can be an alternative way to manage PLP. This article discusses two techniques-transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS)-that have shown promising results for controlling PLP. The modulation that both techniques rely on is based on synaptic mechanisms linked to long-term potentiation and long-term depression phenomena. By applying tDCS or rTMS, clinicians can target processes associated with central sensitization and maladaptive plasticity, while promoting adequate sensory information processing by integrative cognitive behavioral techniques in a comprehensive rehabilitation program. Understanding PLP from a dynamic neurocomputational perspective will help to develop better treatments. Furthermore, Bayesian analysis of sensory information can help guide and monitor therapeutic interventions directed toward PLP resolution.

Characterisation of Phantom Limb Pain in Traumatic Lower-Limb Amputees

“…is involves a new pattern of visual, sensory, and motor afferences and afferents. is study confirms that the level of amputation is not associated with PLP in terms of quantity, intensity, or frequency; that is, the amount of afference lost by amputation may not be related to the whole neurogenic process that involves the appearance of PLP [13][14][15][16][17].…”

“…e patients needed a median of 13 (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) different pain descriptors to show what they felt, and 30% needed more than 10. Besides not being a single painful symptom, five descriptors were continuous, seven times a week: burning, tingling, cooling, pulsations, and shocks.…”

“…PLP is a new experience for patients who previously do not have any similar experience to aid in its identification [ 15 ]. Consequently, many patients do not recognise the unpleasant sensations they feel in the amputated part as pain, even though it is considered as PAIN by the IASP definition [ 5 ].…”

“…More years of schooling enable a wider range of vocabulary, which further allows a more detailed expression of what one feels [ 22 , 23 ]. The association of PLP with above-knee amputation can be explained by the larger area of the lost leg and consequently a larger orphan brain area, determining greater maladaptive neuroplasticity with a more chance of PLP [ 15 , 18 ].…”

“…ere is great variability of the prevalence of PLP in amputees, with reports indicating a prevalence from 2% to 98% [2,[7][8][9][10]. Biological mechanisms are insufficient to explain this disparity, with cultural variations leading to different interpretations of the definition [11][12][13][14][15]. e anamnesis method used to investigate PLP may also lead to variations in interpretation.…”