Chapter 34 Classification of neuropathic pain syndromes based on symptoms and signs

Real-Time Object Tracking via Adaptive Correlation Filters

Although correlation filter-based trackers (CFTs) have made great achievements on both robustness and accuracy, the performance of trackers can still be improved, because most of the existing trackers use either a sole filter template or fixed features fusion weight to represent a target. Herein, a real-time dual-template CFT for various challenge scenarios is proposed in this work. First, the color histograms, histogram of oriented gradient (HOG), and color naming (CN) features are extracted from the target image patch. Then, the dual-template is utilized based on the target response confidence. Meanwhile, in order to solve the various appearance variations in complicated challenge scenarios, the schemes of discriminative appearance model, multi-peaks target re-detection, and scale adaptive are integrated into the proposed tracker. Furthermore, the problem that the filter model may drift or even corrupt is solved by using high confidence template updating technique. In the experiment, 27 existing competitors, including 16 handcrafted features-based trackers (HFTs) and 11 deep features-based trackers (DFTs), are introduced for the comprehensive contrastive analysis on four benchmark databases. The experimental results demonstrate that the proposed tracker performs favorably against state-of-the-art HFTs and is comparable with the DFTs.

Chronic Pain following Chest Trauma: Prevalence, Associated Factors, and Psychosocial Impact

Background

Chronic pain (CP) is a real public health concern. It is a common cause of poor quality of life and workplace absenteeism. It is well studied in many medical and surgical fields. However, only few data are available as regards to its occurrence in trauma patients.

Purpose

To assess the prevalence, associated factors, and psychosocial impact of CP following chest trauma.

Methods

This is an observational, descriptive, and analytic cross-sectional study performed in a Tunisian department of anesthesia and intensive care over a two-month period. Adult patients admitted one year ago for isolated chest trauma were enrolled. Data were collected by a phone interview. Studied variables were sociodemographic characteristics, traumatic injuries and their management, the occurrence of CP, and its psychosocial impact. CP was diagnosed by the Brief Pain Inventory (BPI) considering an evolution period of at least 3 months. Its impact was assessed by the BPI and the Posttraumatic stress disorder Checklist Scale (PCLS).

Results

Fifty-four patients were included in the study. The prevalence of CP was 79.6%. The average CP intensity was 3.18 ± 1.4. It was neuropathic in 90.7%. Its main associated factors were pleural effusion (p=0.016), time to ICU admission (p=0.016), time to ICU admission (p=0.016), time to ICU admission (p=0.016), time to ICU admission (.

Conclusion

CP following chest trauma is frequent and severe requiring preventive measures such as high risk patients screening, better management of acute pain, and a multidisciplinary approach for patients with diagnosed CP.

Allodynia and hyperalgesia in neuropathic pain: clinical manifestations and mechanisms

Allodynia (pain due to a stimulus that does not usually provoke pain) and hyperalgesia (increased pain from a stimulus that usually provokes pain) are prominent symptoms in patients with neuropathic pain. Both are seen in various peripheral neuropathies and central pain disorders, and affect 15-50% of patients with neuropathic pain. Allodynia and hyperalgesia are classified according to the sensory modality (touch, pressure, pinprick, cold, and heat) that is used to elicit the sensation. Peripheral sensitisation and maladaptive central changes contribute to the generation and maintenance of these reactions, with separate mechanisms in different subtypes of allodynia and hyperalgesia. Pain intensity and relief are important measures in clinical pain studies, but might be insufficient to capture the complexity of the pain experience. Better understanding of allodynia and hyperalgesia might provide clues to the underlying pathophysiology of neuropathic pain and, as such, they represent new or additional endpoints in pain trials.

Quantitative sensory testing of neuropathic pain patients: potential mechanistic and therapeutic implications

Quantitative sensory testing (QST) is a widely accepted tool to investigate somatosensory changes in pain patients. Many different protocols have been developed in clinical pain research within recent years. In this review, we provide an overview of QST and tested neuroanatomical pathways, including peripheral and central structures. Based on research studies using animal and human surrogate models of neuropathic pain, possible underlying mechanisms of chronic pain are discussed. Clinically, QST may be useful for 1) the identification of subgroups of patients with different underlying pain mechanisms; 2) prediction of therapeutic outcomes; and 3) quantification of therapeutic interventions in pain therapy. Combined with sensory mapping, QST may provide useful information on the site of neural damage and on mechanisms of positive and negative somatosensory abnormalities. The use of QST in individual patients for diagnostic purposes leading to individualized therapy is an interesting concept, but needs further validation.

Differential pain modulation in patients with peripheral neuropathic pain and fibromyalgia

Background

The definition of neuropathic pain has recently been changed by the International Association for the Study of Pain. This means that conditions such as fibromyalgia cannot, as sometimes discussed, be included in the neuropathic pain conditions. However, fibromyalgia and peripheral neuropathic pain share common clinical features such as spontaneous pain and hypersensitivity to external stimuli. Therefore, it is of interest to directly compare the conditions.

Material and methods

In this study we directly compared the pain modulation in neuropathic pain versus fibromyalgia by recording responses to a cold pressor test in 30 patients with peripheral neuropathic pain, 28 patients with fibromyalgia, and 26 pain-free age-and gender-matched healthy controls. Patients were asked to rate their spontaneous pain on a visual analog scale (VAS (0–100 mm) immediately before and immediately after the cold pressor test. Furthermore the duration (s) of extremity immersion in cold water was used as a measure of the pain tolerance threshold, and the perceived pain intensity at pain tolerance on the VAS was recorded on the extremity in the water after the cold pressor test. In addition, thermal (thermo tester) and mechanical stimuli (pressure algometer) were used to determine sensory detection, pain detection, and pain tolerance thresholds in different body parts. All sensory tests were done by the same examiner, in the same room, and with each subject in a supine position. The sequence of examinations was the following: (1) reaction time, (2) pressure thresholds, (3) thermal thresholds, and (4) cold pressor test. Reaction time was measured to ensure that psychomotoric inhibitions did not influence pain thresholds.

Results

Pain modulation induced by a cold pressor test reduced spontaneous pain by 40% on average in neuropathic pain patients, but increased spontaneous pain by 2.6% in fibromyalgia patients. This difference between fibromyalgia and neuropathic pain patients was significant (P < 0.002). Fibromyalgia patients withdrew their extremity from the cold water significantly earlier than neuropathic pain patients and healthy controls; however, they had a higher perceived pain intensity on the VAS than neuropathic pain patients and control subjects. Furthermore, neuropathic pain patients had a localized hypersensitivity to mechanical and thermal stimuli in the affected area of the body. In contrast, fibromyalgia patients displayed a general hypersensitivity to mechanical and thermal stimuli when the stimuli were rated by the VAS, and hypersensitivity to some of the sensory stimuli.

Conclusions

These findings are the first to suggest that a conditioning stimulus evoked by a cold pressor test reduced spontaneous ongoing pain in patients with peripheral neuropathic pain, but not in fibromyalgia patients when directly compared. The current study supports the notion that fibromyalgia and neuropathic pain are distinct pain conditions with separate sensory patterns and dysfunctions in pain-modulating networks. Fibromyalgia should therefore not, as sometimes discussed, be included in NP conditions.

Implications

On the basis of the findings, it is of interest to speculate on the underlying mechanisms. The results are consistent with the idea that peripheral neuropathic pain is primarily driven from damaged nerve endings in the periphery, while chronic fibromyalgia pain may be a central disorder with increased activity in pain-facilitating systems.

Maldynia: pathophysiology and management of neuropathic and maladaptive pain--a report of the AMA Council on Science and Public Health

BACKGROUND

Because of disparate taxonomic arrays for classification, the American Academy of Pain Medicine has proposed categorizing pain on a neurobiologic basis as eudynia (nociceptive pain), Greek for "good pain," or maldynia (maladaptive pain), Greek for "bad pain." The latter has been viewed as maladaptive because it may occur in the absence of ongoing noxious stimuli and does not promote healing and repair.

OBJECTIVE

To address recent findings on the pathogenesis of pain following neural injury and consider whether the development of maladaptive pain justifies its classification as a disease and to briefly discuss the scope of pharmacologic and non-pharmacologic approaches employed in patients with such pain.

METHODS

English language reports on studies using human subjects were selected from a PubMed search of the literature from 1995 to August 2010 and from the Cochrane Library. Further information was obtained from Internet sites of medical specialty and other societies devoted to pain management.

RESULTS

Neural damage to either the peripheral or central nervous system provokes multiple processes including peripheral and central sensitization, ectopic activity, neuronal cell death, disinhibition, altered gene expression, and abnormal sprouting and cellular connectivity. A series of neuro-immune interactions underlie many of these mechanisms. Imaging studies have shown that such damage is characterized by functional, structural, and chemical changes in the brain. Such pain is maladaptive in the sense that it occurs in the absence of ongoing noxious stimuli and does not promote healing and repair.

CONCLUSION

As defined, maldynia is a multidimensional process that may warrant consideration as a chronic disease not only affecting sensory and emotional processing but also producing an altered brain state based on both functional imaging and macroscopic measurements. However, the absolute clinical value of this definition is not established.

Heterogeneous sensory processing in persistent postherniotomy pain

Previous studies on sensory function in persistent postherniotomy pain (PPP) have only identified pressure pain threshold to be significantly different from pain-free patients despite several patients reporting cutaneous pain and wind-up phenomena. However the limited number of patients studied hinders evaluation of potential subgroups for further investigation and/or treatment allocation. Thus we used a standardized QST protocol to evaluate sensory functions in PPP and pain-free control patients, to allow individual sensory characterization of pain patients from calculated Z-values. Seventy PPP patients with pain related impairment of everyday activities were compared with normative data from 40 pain-free postherniotomy patients operated>1 year previously. Z-values showed a large variation in sensory disturbances ranging from pronounced detection hypoesthesia (Z=6, cold) to pain hyperalgesia (Z=-8, pressure). Hyperalgesia for various modalities were found in 80% of patients, with pressure hyperalgesia in approximately 65%, and cutaneous (mechanical or thermal) hyperalgesia in approximately 35% of patients. The paradoxical combination of tactile hypoesthesia and hyperalgesia was seen in approximately 25% of patients. Increased pain from repetitive tactile and/or brush stimulation was found in 51%, suggesting a role of altered central nociceptive function in this subpopulation. A high incidence (26%) of pressure hyperalgesia was found in the contralateral groin, with a significant correlation (rho=0.58, p=0.002) to the hyperalgesic level on the painful side, again suggesting central nervous mechanisms in PPP. In conclusion, this study shows that a standardized trauma results in heterogeneous combinations of hypo- and hyperalgesia. Z-score evaluation of sensory function identifies subpopulations in PPP, which may be used in selecting surgical and/or pharmacological treatment strategies.