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Phantom limb pain (PLP) is a complicated condition with diverse clinical challenges. It consists of pain perception of a previously amputated limb. The exact pain mechanism is disputed and includes mechanisms involving cerebral, peripheral, and spinal origins. Such controversy limits researchers' and clinicians' ability to develop consistent therapeutics or management. Neuroimaging is an essential tool that can address this problem. This review explores diffusion tensor imaging, functional magnetic resonance imaging, electroencephalography, and magnetoencephalography in the context of PLP. These imaging modalities have distinct mechanisms, implications, applications, and limitations. Diffusion tensor imaging can outline structural changes and has surgical applications. Functional magnetic resonance imaging captures functional changes with spatial resolution and has therapeutic applications. Electroencephalography and magnetoencephalography can identify functional changes with a strong temporal resolution. Each imaging technique provides a unique perspective and they can be used in concert to reveal the true nature of PLP. Furthermore, researchers can utilize the respective strengths of each neuroimaging technique to support the development of innovative therapies. PLP exemplifies how neuroimaging and clinical management are intricately connected. This review can assist clinicians and researchers seeking a foundation for applications and understanding the limitations of neuroimaging techniques in the context of PLP., (© 2022 The Authors. Brain and Behavior published by Wiley Periodicals LLC.)

Silicon particles have garnered attention as promising biomedical probes for hyperpolarized 29 Si magnetic resonance imaging and spectroscopy. However, due to the limited levels of hyperpolarization for nanosized silicon particles, microscale silicon particles have primarily been the focus of dynamic nuclear polarization (DNP) applications, including in vivo magnetic resonance imaging (MRI). To address these current challenges, we developed a facile synthetic method for partially 29 Si-enriched porous silicon nanoparticles (NPs) (160 nm) and examined their usability in hyperpolarized 29 Si MRI agents with enhanced signals in spectroscopy and imaging. Hyperpolarization characteristics, such as the build-up constant, the depolarization time ( T 1 ), and the overall enhancement of the 29 Si-enriched silicon NPs (10 and 15%), were thoroughly investigated and compared with those of a naturally abundant NP (4.7%). During optimal DNP conditions, the 15% enriched silicon NPs showed more than 16-fold higher enhancements─far beyond the enrichment ratio─than the naturally abundant sample, further improving the signal-to-noise ratio in in vivo 29 Si MRI. The 29 Si-enriched porous silicon NPs used in this work are potentially capable to serve as drug-delivery vehicles in addition to hyperpolarized 29 Si in vivo , further enabling their potential future applicability as a theragnostic platform.

Abstract: A 36-yr-old man with a history of industrial accident causing traumatic left hip disarticulation, pubic symphysis, and right sacroiliac joint fractures presented with a 3-yr history of left-sided lower back pain radiating down the amputated limb. Computed tomography lumbar spine showed osteophytes surrounding the sacroiliac joint bilaterally with reduced left L4-L5 foraminal space. A fluoroscopically guided left sacroiliac steroid injection led to mild improvement in low back pain. Magnetic resonance imaging of the lumbar spine without contrast showed transitional type L5 vertebral body with left-sided flowing osteophytes abutting the extraforaminal L4 and L5 nerves. Ultimately, multilevel left fluoroscopically guided transforaminal epidural steroid injection at L4-L5 and L5-S1 significantly improved symptoms. Although phantom radiculopathy is a rare entity, clinical suspicion of degenerative spine disease or other pathology contributing to nerve impingement in patients with amputations should remain; this unique case discusses bony osteophyte complex as the cause for phantom radiculopathy instead of previously described disc herniation. Magnetic resonance imaging remains a key tool in delineating causes of low back pain among patients with lower limb amputations., Competing Interests: Financial disclosure statements have been obtained, and no conflicts of interest have been reported by the authors or by any individuals in control of the content of this article., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Objectives: Functional neuroimaging studies have shown that amputees have altered cortical reorganization and functional connectivity (FC). This study aimed to investigate whether patients with phantom limb pain (PLP) and PLP-free lower limb amputees exhibit changes in corresponding primary cortical motor area/somatosensory cortex (M1/S1) cortical reorganization and supplementary motor area (SMA) network FC. The association between functional magnetic resonance imaging (fMRI) changes and clinical parameters is also explored., Methods: A total of 10 PLP patients were matched with 10 PLP-free amputees and 10 healthy controls (HCs). Before undergoing fMRI, all participants completed questionnaires evaluating pain, anxiety, depression, and health-related quality of life. Task-related activation and regions of interest (ROI)-wise connectivity analysis were applied to differentiate the brain regions of amputees from those of HCs. Linear correlation analysis was used to evaluate the correlation between altered FC and clinical manifestations., Results: As compared with HCs, PLP patients showed increased cortical activation in M1/S1 when moving the intact foot, imagining phantom big toe movement, or having the corresponding thumb stimulated. The increased FC in the SMA network included the SMA-caudate nucleus, SMA-bilateral insula, and SMA-anterior cingulate cortex. Furthermore, results of the linear correlation analysis demonstrated that this increased FC was positively correlated with VAS scores, negatively correlated with Medical Outcomes Study 36-item Short-Form (SF-36) scores, and not correlated with anxiety or depression scores., Conclusions: Phantom limb pain in lower limb amputees is associated with M1/S1 cortical reorganization and altered SMA network FC in different areas of the brain, which could help to support our understanding of the central mechanism of PLP., (© 2020 World Institute of Pain.)

The neural mechanism of phantom limb pain (PLP) is related to the intense brain reorganization process implicating plasticity after deafferentation mostly in sensorimotor system. There is a limited understanding of the association between the sensorimotor system and PLP. We used a novel task-based functional magnetic resonance imaging (fMRI) approach to (1) assess neural activation within a-priori selected regions-of-interested (motor cortex [M1], somatosensory cortex [S1], and visual cortex [V1]), (2) quantify the cortical representation shift in the affected M1, and (3) correlate these changes with baseline clinical characteristics. In a sample of 18 participants, we found a significantly increased activity in M1 and S1 as well as a shift in motor cortex representation that was not related to PLP intensity. In an exploratory analyses (not corrected for multiple comparisons), they were directly correlated with time since amputation; and there was an association between increased activity in M1 with a lack of itching sensation and V1 activation was negatively correlated with PLP. Longer periods of amputation lead to compensatory changes in sensory-motor areas; and itching seems to be a protective marker for less signal changes. We confirmed that PLP intensity is not associated with signal changes in M1 and S1 but in V1., Competing Interests: Declaration of Competing Interest The authors report no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Objective: The role of motor cortex reorganization in the development and maintenance of phantom limb pain (PLP) is still unclear. This study aims to evaluate neurophysiological and structural motor cortex asymmetry in patients with PLP and its relationship with pain intensity., Methods: Cross-sectional analysis of an ongoing randomized-controlled trial. We evaluated the motor cortex asymmetry through two techniques: i) changes in cortical excitability indexed by transcranial magnetic stimulation (motor evoked potential, paired-pulse paradigms and cortical mapping), and ii) voxel-wise grey matter asymmetry analysis by brain magnetic resonance imaging., Results: We included 62 unilateral traumatic lower limb amputees with a mean PLP of 5.9 (SD = 1.79). We found, in the affected hemisphere, an anterior shift of the hand area center of gravity (23 mm, 95% CI 6 to 38, p = 0.005) and a disorganized and widespread representation. Regarding voxel-wise grey matter asymmetry analysis, data from 21 participants show a loss of grey matter volume in the motor area of the affected hemisphere. This asymmetry seems negatively associated with time since amputation. For TMS data, only the ICF ratio is negatively correlated with PLP intensity (r = -0.25, p = 0.04)., Conclusion: There is an asymmetrical reorganization of the motor cortex in patients with PLP, characterized by a disorganized, widespread, and shifted hand cortical representation and a loss in grey matter volume in the affected hemisphere. This reorganization seems to reduce across time since amputation. However, it is not associated with pain intensity., Significance: These findings are significant to understand the role of the motor cortex reorganization in patients with PLP, showing that the pain intensity may be related with other neurophysiological factors, not just cortical reorganization., Competing Interests: Declaration of interest The authors report no conflict of interest., (Copyright © 2020 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.)

Following arm amputation the region that represented the missing hand in primary somatosensory cortex (S1) becomes deprived of its primary input, resulting in changed boundaries of the S1 body map. This remapping process has been termed 'reorganisation' and has been attributed to multiple mechanisms, including increased expression of previously masked inputs. In a maladaptive plasticity model, such reorganisation has been associated with phantom limb pain (PLP). Brain activity associated with phantom hand movements is also correlated with PLP, suggesting that preserved limb functional representation may serve as a complementary process. Here we review some of the most recent evidence for the potential drivers and consequences of brain (re)organisation following amputation, based on human neuroimaging. We emphasise other perceptual and behavioural factors consequential to arm amputation, such as non-painful phantom sensations, perceived limb ownership, intact hand compensatory behaviour or prosthesis use, which have also been related to both cortical changes and PLP. We also discuss new findings based on interventions designed to alter the brain representation of the phantom limb, including augmented/virtual reality applications and brain computer interfaces. These studies point to a close interaction of sensory changes and alterations in brain regions involved in body representation, pain processing and motor control. Finally, we review recent evidence based on methodological advances such as high field neuroimaging and multivariate techniques that provide new opportunities to interrogate somatosensory representations in the missing hand cortical territory. Collectively, this research highlights the need to consider potential contributions of additional brain mechanisms, beyond S1 remapping, and the dynamic interplay of contextual factors with brain changes for understanding and alleviating PLP., (Copyright © 2020 The Author(s). Published by Elsevier Inc. All rights reserved.)

Phantom limb pain (PLP) has been associated with reorganization in primary somatosensory cortex (S1) and preserved S1 function. Here we examined if methodological differences in the assessment of cortical representations might explain these findings. We used functional magnetic resonance imaging during a virtual reality movement task, analogous to the classical mirror box task, in twenty amputees with and without PLP and twenty matched healthy controls. We assessed the relationship between task-related activation maxima and PLP intensity in S1 and motor cortex (M1) in individually-defined or group-conjoint regions of interest (ROI) (overlap of task-related activation between the groups). We also measured cortical distances between both locations and correlated them with PLP intensity. Amputees compared to controls showed significantly increased activation in M1, S1 and S1M1 unrelated to PLP. Neural activity in M1 was positively related to PLP intensity in amputees with PLP when a group-conjoint ROI was chosen. The location of activation maxima differed between groups in S1 and M1. Cortical distance measures were unrelated to PLP. These findings suggest that sensory and motor maps differentially relate to PLP and that methodological differences might explain discrepant findings in the literature.

Limb amputations are carried out for a number of reasons, which include trauma, vascular disorders, infection, oncology and congenital abnormalities. These patients can develop multiple complications postoperatively with phantom limb pain being a well-recognised issue. That being said, phantom radiculopathy is far less encountered and can therefore be easily overlooked. There are limited cases described in literature and as a result pathophysiology is poorly understood. In this report, we present a patient who had developed phantom radiculopathy decades after his left above knee amputation surgery, which was performed after a road traffic accident. However, we were successfully able to treat the patient with foraminal epidural corticosteroid injection., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2020. No commercial re-use. See rights and permissions. Published by BMJ.)

Previous studies have indicated that amputation induces reorganization of functional brain network. However, the influence of amputation on structural brain network remains unclear. In this study, using diffusion tensor imaging (DTI), we aimed to investigate the alterations in fractional anisotropy (FA) network after unilateral upper-limb amputation. We acquired DTI from twenty-two upper-limb amputees (15 dominant-side and 7 nondominant-side amputees) as well as fifteen healthy controls. Using DTI tractography and graph theoretical approaches, we examined the topological changes in FA network of amputees. Compared with healthy controls, dominant-side amputees showed reduced global mean strength, increased characteristic path length, and decreased nodal strength in the contralateral sensorimotor system and visual areas. In particular, the nodal strength of the contralateral postcentral gyrus was negatively correlated with residual limb usage, representing a use-dependent reorganization. In addition, the nodal strength of the contralateral middle temporal gyrus was positively correlated with the magnitude of phantom limb sensation. Our results suggested a degeneration of FA network after dominant-side upper-limb amputation.

Mirror therapy (MT) has been proposed as an effective rehabilitative strategy to alleviate pain symptoms in amputees with phantom limb pain (PLP). However, establishing the neural correlates associated with MT therapy have been challenging given that it is difficult to administer the therapy effectively within a magnetic resonance imaging (MRI) scanner environment. To characterize the functional organization of cortical regions associated with this rehabilitative strategy, we have developed a combined behavioral and functional neuroimaging protocol that can be applied in participants with a leg amputation. This novel approach allows participants to undergo MT within the MRI scanner environment by viewing real-time video images captured by a camera. The images are viewed by the participant through a system of mirrors and a monitor that the participant views while lying on the scanner bed. In this manner, functional changes in cortical areas of interest (e.g., sensorimotor cortex) can be characterized in response to the direct application of MT.

Amputation in adults is associated with an extensive remapping of cortical topography in primary and secondary sensorimotor areas. Here, we used tactile residual limb stimulation and 3T functional magnetic resonance imaging in humans to investigate functional connectivity changes in the sensorimotor network of patients with long-term lower limb traumatic amputations with phantom sensation, but without pain. We found a pronounced reduction of inter-hemispheric functional connectivity between homologous sensorimotor cortical regions in amputees, including the primary (S1) and secondary (S2) somatosensory areas, and primary (M1) and secondary (M2) motor areas. We additionally observed an intra-hemispheric increased functional connectivity between primary and secondary somatosensory regions, and between the primary and premotor areas, contralateral to amputation. These functional connectivity changes in specialized small-scale sensory-motor networks improve our understanding of the functional impact of lower limb amputation in the brain. Our findings in a selective group of patients with phantom limb sensations, but without pain suggest that disinhibition of neural inputs following traumatic limb amputation disrupts sensorimotor topology, unbalancing functional brain network organization. These findings step up the description of brain plasticity related with phantom sensations by showing that pain is not critical for sensorimotor network changes after peripheral injury.

Objective: Phantom limb pain (PLP) is notoriously difficult to treat, partly due to an incomplete understanding of PLP-related disease mechanisms. Noninvasive brain stimulation (NIBS) is used to modulate plasticity in various neuropathological diseases, including chronic pain. Although NIBS can alleviate neuropathic pain (including PLP), both disease and treatment mechanisms remain tenuous. Insight into the mechanisms underlying both PLP and NIBS-induced PLP relief is needed for future implementation of such treatment and generalization to related conditions., Methods: We used a within-participants, double-blind, and sham-controlled design to alleviate PLP via task-concurrent NIBS over the primary sensorimotor missing hand cortex (S1/M1). To specifically influence missing hand signal processing, amputees performed phantom hand movements during anodal transcranial direct current stimulation. Brain activity was monitored using neuroimaging during and after NIBS. PLP ratings were obtained throughout the week after stimulation., Results: A single session of intervention NIBS significantly relieved PLP, with effects lasting at least 1 week. PLP relief associated with reduced activity in the S1/M1 missing hand cortex after stimulation. Critically, PLP relief and reduced S1/M1 activity correlated with preceding activity changes during stimulation in the mid- and posterior insula and secondary somatosensory cortex (S2)., Interpretation: The observed correlation between PLP relief and decreased S1/M1 activity confirms our previous findings linking PLP with increased S1/M1 activity. Our results further highlight the driving role of the mid- and posterior insula, as well as S2, in modulating PLP. Lastly, our novel PLP intervention using task-concurrent NIBS opens new avenues for developing treatment for PLP and related pain conditions. ANN NEUROL 2019;85:59-73., (© 2018 The Authors. Annals of Neurology published by Wiley Periodicals, Inc. on behalf of American Neurological Association.)

Phantom limb pain is a restricting condition for a substantial number of amputees with quite different characteristics of pain. Here, we report on a forearm amputee with constant phantom pain in the hand, in whom we could regularly elicit the rare phenomenon of referred cramping phantom pain by touching the face. To clarify the underlying mechanisms, we followed the cramp during the course of an axillary blockade of the brachial plexus. During the blockade, both phantom pain and the referred cramp were abolished, while a referred sensation of "being touched at the phantom" persisted. Furthermore, to identify the cortical substrate, we elicited the cramp during functional magnetic imaging. Imaging revealed that referred cramping phantom limb pain was associated with brain activation of the hand representation in the primary sensorimotor cortex. The results support the hypothesis that referred cramping phantom limb pain in this case is associated with a substantial brain activation in the hand area of the deafferented sensorimotor cortex. However, this alone is not sufficient to elicit referred cramping phantom limb pain. Peripheral inputs, both, from the arm nerves affected by the amputation and from the skin in the face at which the referred cramp is evoked, are a precondition for referred cramping phantom limb pain to occur, at least in this case.

Objectives Repetitive transcranial magnetic stimulation (rTMS) is a promising tool for treatment of chronic pain. We describe the use of navigated rTMS to treat a patient affected by phantom limb pain (PLP) and to modulate brain functional connectivity. We reviewed the literature on the use of rTMS as a tool for relieving central pain by promoting brain plasticity. Methods A 69-year-old patient came to our observation blaming severe pain (Visual Analog scale, VAS, score 9) to a phantom right lower limb. We mapped left primary motor area (PMA) by navigated TMS and assessed connectivity with resting-state functional MR (rsfMR). The patient underwent 30-days navigated rTMS treatment. We applied low-frequency stimulation (1 Hz) over the primary somatosensory area (PSA) and high-frequency stimulation (10 Hz) over PMA and dorsolateral prefrontal cortex (DLPFC) of the left hemisphere. Results This strategy allowed a pain relief with a reduction of 5 points of the VAS score after 1 month. Post-treatment rsfMR showed increased connectivity, mainly in the sensory-motor network and the unaffected hemisphere (P < 0.05). Discussion This report represents a proof-of-concept that navigated rTMS can be effectively used to stimulate selected brain areas in PLP patients in order to promote brain connectivity, and that rsfMR is a useful tool able to analyze functional results. In the literature, we found data supporting the assumption that, in patients affected by PLP, a reduced connectivity in interhemispherical and sensory-motor network plays a role in generating pain and that rTMS has the potential to restore impaired connectivity.

We report the case of a patient who had an important experience with painful events, allowing the investigation of brain concomitants to painful (P) memories in fMRI. The patient had to recall P events that were contrasted with non-painful (NP) memories. Painful memories of the right lower limb activated the left paracentral lobule,fronto-insular operculum and superior parietal cortex. Additionally, whilst the recall of non-painful events activated the hippocampus, the recall of painful events did not enhance the hippocampal signal to significant levels. These suggest that brain activations differ for the autobiographical recall of painful and non-painful memories.

Objective: The current study was designed to document clinical and ultrasound (US) findings of patients with residual limb pain (RLP) after amputation and to investigate the relationship between these findings., Materials and Methods: A chart review was performed to identify demographic and clinical data including the age (current and at the time of injury), time since amputation, gender, reason for amputation, affected limb number, side and level of limb loss, and ultrasonographic findings of young and traumatic amputees with RLP., Results: The study included a total of 147 patients. Inflammation and neuroma were the leading pathologies in 20-29 years and 30-39 years age groups, respectively. Inflammation/edema were detected significantly more in patients with <1 year since amputation (P = 0.001). Neuroma was found at a significantly high rate in patients at 1-5 years (P = 0.029) and infection/abscess was more common in patients at >5 years since amputation (P = 0.051). The percentage of neuromas in below-the-knee amputees was significantly higher than in non-below-the-knee amputees (45.8% vs. 28.6%). Neuroma formation was detected in 50% of the patients with land mine-related amputation and at 27% in patients with amputation secondary to other traumatic reasons. Regression analysis showed below-the-knee-level amputation to be an associated factor for US abnormality., Conclusion: The leading US findings were inflammation/edema, neuroma, and infection/abscess in traumatic amputees with RLP. The US findings might be different in patients according to the time since amputation. Patient with land mine-related amputations may have different US findings.

Purpose: To prospectively evaluate percutaneous image-guided nerve cryoablation for treatment of refractory phantom limb pain (PLP) in a pilot cohort for purposes of deriving parameters to design a larger, randomized, parallel-armed, controlled trial., Materials and Methods: From January 2015 to January 2016, 21 patients with refractory PLP underwent image-guided percutaneous cryoneurolysis procedures. Visual analog scale scores were documented at baseline and 7, 45, and 180 days after the procedure. Responses to a modified Roland Morris Disability Questionnaire were documented at baseline and 7 and 45 days after the procedure., Results: Technical success rate of the procedures was 100%. There were 6 (29%) minor procedure-related complications. Disability scores decreased from a baseline mean of 11.3 to 3.3 at 45-day follow-up (95% confidence interval 5.8, 10.3; P < .0001). Pain intensity scores decreased from a baseline mean of 6.2 to 2.0 at long-term follow-up (95% confidence interval 2.8, 5.6; P < .0001)., Conclusions: Image-guided percutaneous nerve cryoablation is feasible and safe and may represent a new efficacious therapeutic option for patients with phantom pains related to limb loss., (Copyright © 2017 SIR. Published by Elsevier Inc. All rights reserved.)

Researchers are interested in understanding phantom limb pain (PLP) and residual limb pain (RLP) in amputees and the neural mechanisms leading to it. fMRI can provide information on the intensity and the location of activated centers in the brain that control PLP and RLP. MR safe algometers are important to this work. This paper described the new pneumatically actuated algometer and the evaluation methods for MR safety. Our results indicate that the custom device is an improved MR safe algometer capable of autonomously producing reproducible pressure profiles.

Objective: Phantom limb pain and stump pain frequently occur after limb amputation, and stump neuromas play an important role in generation of the pain. The purpose of this study was to evaluate the effects of a previously described optimized procedure for sclerosis of painful stump neuromas under real-time high-resolution sonographic guidance., Subjects and Methods: In this prospective study, neurosclerosis was performed on 82 patients by means of high-resolution sonographically guided injection of up to 0.8 mL of 80% phenol solution according to a standardized protocol., Results: During treatment all patients had marked improvement in terms of reduction of pain measured with a visual analog scale. Twelve (15%) of the subjects were pain free after one to three treatments, nine of the 12 achieving relief with the initial instillation. At 6-month follow-up evaluation, 52 patients assessed their present pain quantity with a simplified three-step score. Twenty (38%) of the 52 patients reported almost unnoticeable pain, and 33 (64%) reported pain equal to the minimum reached during therapy. In 18 (35%) of the 52 patients, the incidence of painful periods had markedly decreased. The neurosclerosis procedure had a low complication rate (5% rate of minor complications, 1.3% rate of major complications)., Conclusion: The high-resolution sonographically guided neurosclerosis procedure had a significantly better outcome than other documented treatments. Sonographically guided neurosclerosis should be included in the management of chronic phantom limb and stump pain.

A 42-year-old man with a remote history of right transtibial amputation but no history of phantom pain developed severe phantom pain 10 years after amputation. A literature review suggested that his presentation was contrary to the natural history of phantom pain, which is usually most prominent in the early stages after amputation. Diagnostic workup revealed a popliteal artery aneurysm, which was successfully treated with coil embolization. The patient had complete resolution of his phantom pain after treatment of the aneurysm, suggesting it was the source of the pain. As a result of successful diagnosis and treatment, the amputation level did not need to be revised and the patient was able to continue his previously high level of function., (Copyright 2002 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation)

We report on a 29-year-old motorcyclist, who had suffered a traumatic right side arm plexus lesion. The myelo-CT image showed a avulsion of the cervical roots C7/C8. Five days after the accident the patient complained of phantom pain in the right plegic arm and was presented to our acute pain service (APS). The patient complained of lancinating attacks of severe phantom pain in the right arm (visual analogue scale intensity of 80-100 pts.). The initial pain treatment was performed with PCA (piritramide), and because of the lancinating pain character carbamazepine treatment was introduced. The pain intensity increased under carbamazepine (VAS = 100 pts.), and after treatment with five cycles of salmon-calcitonin infusion the pain intensity decreased (VAS = 10 pts). After withdrawal of the infusion therapy with salmon calcitonin the pain intensity increased up to VAS = 70 pts. TENS therapy five times per day showed no analgetic effect. We repeated the calcitonin-infusion therapy and after five i.v. cycles we continued with 200 I.U. salmon calcitonin intranasal per day. The initial phantompain intensity decreased (VAS = 40 pts.), but showed no long term analgesia. The additional psychological treatment with relaxation techniques (Jacobson/Bensen) showed the desired phantom pain relief. An interdisciplinary and multimodal cooperation between anesthesiologists, trauma surgeons, neurosurgeons and psychologists is needed for successful phantom pain treatment after traumatic brachial plexus lesion. Intravenous salmon calcitonin showed only short-term analgetic effect.

Pain and other phantom limb (PL) sensations have been proposed to be generated in the brain and to be reflected in activation of specific neural circuits. To test this hypothesis, hypnosis was used as a cognitive tool to alternate between the sensation of PL movement and pain in 8 amputees. Brain activity was measured using positron emission tomography. PL movement and pain were represented by a propagation of neuronal activity within the corresponding sensorimotor and pain-processing networks. The sensation of movement was significantly (corrected for multiple comparisons) related to activity in the supplementary motor area and the primary sensorimotor cortex. The sensation of a painful PL posture activated the same brain areas but was weaker and less extended in the supplementary motor area. In contrast to the sensation of movement, pain was significantly related to activity in the thalamus, anterior cingulate, and lateral prefrontal cortex. Subjectively rated PL pain sensation correlated positively to activations in the anterior and posterior cingulate. These findings provide evidence that PL sensations are produced by the same central nervous processes that underlie the experience of the body when it is intact and that the corporeal awareness of PL pain is encoded in a thalamocortical network.

To explore the possible mechanisms of phantom limb discomfort after amputation, three amputees with phantom limb pain were studied. This study examined the change of regional cerebral blood flow using technetium-99m hexamethylpropyleneamine oxime-single photon emission computerized tomography, which was arranged at the time of severe phantom limb discomfort and after the discomfort subsided or was completely relieved. Nine representative transverse slices parallel to the orbitomeatal line were selected for quantification. The cortical ribbon (2-cm thickness) was equally subdivided into 12 symmetrical pairs of sector regions of interest in each slice. The irregularly shaped regions of interest were drawn manually around the right thalamus and basal ganglion and then mirrored to the left thalamus and basal ganglion. The contralateral to ipsilateral ratio of regional cerebral blood flow for each area was calculated. The intensity of phantom limb pain was evaluated on a 0 to 10 visual analog scale. In Cases 1 and 2, the contralateral to ipsilateral regional cerebral blood flow ratios of multiple areas of the frontal, temporal, or parietal lobes were increased at the time of more severe phantom limb pain, and the ratios were normalized or even decreased when the phantom limb pain subsided. In Case 3, increased contralateral to ipsilateral regional cerebral blood flow ratios were also found over the frontal, temporal, and parietal lobe. However, most of the increased regional cerebral blood flow ratios of regions of interest in the first study persisted in the follow-up study. Also, the regional cerebral blood flow ratios of greater number of regions of interest of the same gyrus and new gyrus were increased. There was no significant right-left difference of regional cerebral blood flow over bilateral thalami and basal ganglia in all three cases. The results suggested that phantom limb pain might be associated with cortical activation involving the frontal, temporal, or parietal cortex, and it may imply the possibility of the existence of an ascending polysynaptic pathway that conveys the uncomfortable phantom limb sensation to the cerebral cortex. These findings may also indicate that reorganization of the cortical blood flow occurs in amputees. However, it is still difficult to conclude that the changes in regional cerebral blood flow were attributable directly to pain. With no comparison group of amputees and because of the small number of cases, it is hard to generalize about cerebrocortical involvement in phantom pain, and it is possible that the findings represent a normal phenomenon seen after 'amputation. Another possibility is that the findings represent increased arousal caused by pain rather than an intrinsic pain pathway. Further study is worthwhile.

1. Two complimentary techniques were used to study cortical function in six human upper limb amputees: positron emission tomographic (PET) measurements of regional cerebral blood flow (rCBF) were made in subjects during limb movements to study activation of the primary motor (M1), primary somatosensory (S1), and association cortices; and electromyographic responses to transcranial magnetic stimulation (TMS) were measured in proximal upper limb muscles to assess the excitability of corticospinal neurons in subjects at rest. 2. To explore possible cortical mechanisms governing the phantom limb phenomenon, PET and TMS findings were compared between subjects with acquired, traumatic upper limb amputations (n = 3), in whom phantom limb symptoms were prominent, and congenital upper limb amputees (n = 3) without phantom limbs. 3. Paced shoulder movements were associated with significant blood flow increases in the contralateral M1/S1 cortex of both groups of amputees. In traumatic amputees, these increases were present over a wider area and were of significantly greater magnitude in the partially deafferented cortex contralateral to the amputation. In congenital amputees blood flow increases were also present over a wider area in the partially deafferented M1/S1 cortex, but their magnitude was not significantly different from that in the normally afferented M1/S1 cortex. 4. Abnormal blood flow increases also were present in the partially deafferented M1/S1 cortex of traumatic amputees during movement of the ipsilateral, intact arm. Abnormal ipsilateral M1/S1 responses were not present during movement of the intact arm in the congenital group. 5. TMS studies showed that the abnormal blood flow increases in the partially deafferented M1 cortex of traumatic amputees were associated with increased corticospinal excitability.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between image noise and radiation dose was investigated in computed tomography (CT) images of a pediatric abdomen phantom. A protocol which provided a minimum absorbed dose consistent with acceptable image noise criteria was determined for a fourth generation CT scanner. It was found that pediatric abdominal CT scans could maintain diagnostic quality with at least a 50% reduction in dose from the manufacturers' suggested protocol.