Difficult differentiation of a somatic symptom disorder from anterior cutaneous nerve entrapment syndrome (ACNES): a case report.

BACKGROUND: Somatization is regarded as psychological or emotional distress in the form of physical symptoms that are otherwise medically unexplained. CASE PRESENTATION: We report a case of a patient with a somatic symptom disorder (SSD) and depression who was later diagnosed with anterior cutaneous nerve entrapment syndrome (ACNES) when Carnett's test was positive and block anesthesia using trigger point injections dramatically improved the symptom of abdominal pain. CONCLUSION: We concluded that the differentiation of SSDs, such as psychogenic pain, from ACNES is very difficult. Psychiatrists should be aware of this syndrome.

Treatment response and central pain processing in Anterior Cutaneous Nerve Entrapment Syndrome: An explorative study.

BACKGROUND: 10-30% of chronic abdominal pain originates in the abdominal wall. A common cause for chronic abdominal wall pain is the Anterior Cutaneous Nerve Entrapment Syndrome (ACNES), in which an intercostal nerve branch is entrapped in the abdominal rectus sheath. Treatment consists of local anaesthetics and neurectomy, and is ineffective in 25% of cases for yet unknown reasons. In some conditions, chronic pain is the result of altered pain processing. This so-called sensitization can manifest as segmental or even generalized hyperalgesia, and is generally difficult to treat. OBJECTIVE: The aim of this study was to assess pain processing in ACNES patients responsive and refractory to treatment by using Quantitative Sensory Testing, in order to explore whether signs of altered central pain processing are present in ACNES and are a possible explanation for poor treatment outcomes. METHODS: 50 patients treated for ACNES with locally orientated treatment were included. They were allocated to a responsive or refractory group based on their response to treatment. Patients showing an improvement of the Visual Analogue Scale (VAS) pain score combined with a current absolute VAS of <40mm were scored as responsive. Sensation and pain thresholds to pressure and electric skin stimulation were determined in the paravertebral bilateral ACNES dermatomes and at four control areas on the non-dominant side of the body, i.e. the musculus trapezius pars medialis, musculus rectus femoris, musculus abductor hallucis and the thenar. The ACNES dermatomes were chosen to signal segmental hyperalgesia and the sum of the control areas together as a reflection of generalized hyperalgesia. Lower thresholds were interpreted as signs of sensitized pain processing. To test for alterations in endogenous pain inhibition, a conditioned pain modulation (CPM) response to a cold pressor task was determined. Also, patients filled in three pain-related questionnaires, to evaluate possible influence of psychological characteristics on the experienced pain. RESULTS: Patients refractory to treatment showed significantly lower pressure pain thresholds in the ACNES dermatomes and for the sum of as well as in two individual control areas. No differences were found between groups for electric thresholds or CPM response. Duration of complaints before diagnosis and treatment was significantly longer in the refractory compared to the responsive group, and refractory patients scored higher on the pain-related psychological surveys. CONCLUSION AND IMPLICATIONS: In this hypothesis-generating exploratory study, ACNES patients refractory to treatment showed more signs of sensitized segmental and central pain processing. A longer duration of complaints before diagnosis and treatment may be related to these alterations in pain processing, and both findings could be associated with less effective locally orientated treatment. In order to validate these hypotheses further research is needed. REGISTRATION NUMBER: NCT01920880 (Clinical Trials Register; http://www.clinicaltrials.gov).

Evaluation of pain behavior and calcitonin gene-related peptide immunoreactive sensory nerve fibers in the spinal dorsal horn after sciatic nerve compression and application of nucleus pulposus in rats.

STUDY DESIGN: Animal study. OBJECTIVE: To evaluate pain behavior and neuropeptide changes in the spinal dorsal horn after sciatic nerve compression and application of nucleus pulposus (NP) in rats. SUMMARY OF BACKGROUND DATA: The pathomechanisms of lumbar disc herniation pain have not been fully elucidated. Pain-associated neuropeptides, including substance P and calcitonin gene-related peptide (CGRP), are produced in dorsal root ganglion neurons and transported to spinal dorsal horn nerve terminals where they function in pain transmission. However, changes in CGRP-immunoreactive (IR) sensory nerve terminals have not been reported in models of disc herniation. This study evaluated pain-related behavior and changes in CGRP-IR terminals in the spinal dorsal horn after combined sciatic nerve compression and NP application. METHODS: Five groups of rats underwent either sciatic nerve compression with NP (n = 20), application of NP only (n = 20), nerve compression only (n = 20), and sham operation with neither compression nor NP (n = 20) or no operation (controls, n = 20). Mechanical hyperalgesia was measured every second day for 3 weeks. CGRP-IR terminals in each spinal dorsal horn lamina were examined 7 and 14 days postsurgery. Pain behavior and CGRP immunoreactivity were compared among the 5 groups. RESULTS: Mechanical hyperalgesia was found in the NP only, nerve compression only, and the NP with nerve compression groups (P ≤ 0.05). CGRP-IR nerve terminals in the superficial laminae (I and II) and the deep laminae (III-VI) significantly increased in the NP only, nerve compression only, and NP with nerve compression groups compared with control and sham groups (P ≤ 0.05). Significant mechanical hyperalgesia and increased CGRP-IR nerve terminals were found in the NP with nerve compression group compared with the NP only and nerve compression only groups (P ≤ 0.05). CONCLUSION: Our results indicate that nerve compression plus NP application produces the most pain-related behavior. CGRP-IR nerve terminals increased in laminae I and II that transmit pain and in laminae III to VI that transmit proprioception. Findings suggest that nerve compression plus NP application induces changes in CGRP expression in the superficial and deep laminae, and these changes are partly responsible for disc herniation pain.

Fear of movement/(re)injury and activity avoidance in persons with neurogenic versus vascular claudication.

BACKGROUND CONTEXT: Activity avoidance and fear of movement/(re)injury are increasingly being recognized as important factors in the rehabilitation of persons suffering from chronic low back pain, yet these factors have not been thoroughly explored in persons suffering from neurogenic claudication resulting from lumbar spinal stenosis. PURPOSE: To determine, compare, and explain differences in the degree of fear of movement/(re)injury and activity avoidance in persons with neurogenic claudication, vascular claudication, and asymptomatic volunteers. STUDY DESIGN: Prospective controlled cohort study at an academic medical center. PATIENT SAMPLE: Eighty-two adults aged between 55 and 90 years with neurogenic claudication, vascular claudication, or no back and leg symptoms. METHODS: Subjects completed a visual analog scale for pain, the Center for Epidemiological Studies Depression Scale, the Quebec Back Pain Disability Scale, Short Form 36 (SF-36), and the 13-item version of the Tampa Scale for Kinesiophobia (Tampa). They were also asked to estimate their maximum walking distance. OUTCOME MEASURES: The difference in the level of fear of movement/(re)injury and activity avoidance in the two symptomatic populations, as well as the predictive validity of self-reported measures such as pain level, functional impairment, and depression in determining fear avoidance. RESULTS: The total Tampa score was significantly higher in individuals with neurogenic claudication (M=31.68; standard deviation [SD]=7.56; N=39) than vascular claudication (M=24.07; SD=6.57; N=15) (p=.002), whereas both symptomatic groups were significantly different from controls (M=18.71; SD=6.3; N=28) (p<.001 vs. neurogenic; p<.05 vs. vascular). Tampa scores were strongly correlated to the Center for Epidemiological Studies Depression Scale score (r=0.515; p<.001), SF-36 Physical Functioning score (r=-0.632; p<.001), and the visual analog scale average level of pain in a week (r=0.461; p<.001). Using a standard multiple regression model (R²=0.406; F(3,62)=13.47; p<.001), the amount of functional impairment, that is, the SF-36 Physical Functioning score, was the strongest contributor to the variance in the Tampa total score (ß=-0.371; p=.014). The average level of pain did not make a significant or unique contribution in predicting the Tampa total score. Functional impairment as measured by the SF-36 Physical Functioning was strongly correlated with both pain (r=-0.740; p<.001) and depression (r=-0.488; p<.001). CONCLUSIONS: Persons with neurogenic claudication have important elevations in fear and avoidance, higher than those with claudication from another source (vascular insufficiency). The impact of fear and avoidance along with other factors such as depression on pain, disability, and quality of life for persons with claudication and spinal stenosis need to be explored.

Coexistence of pain and depression predicts poor 2-year surgery outcome among lumbar spinal stenosis patients.

BACKGROUND: Lumbar spinal stenosis is a common cause of back and leg pain with the most severe cases treated surgically. Regarding the surgery outcome, the importance of early postoperative depression and pain is unknown. AIMS: To examine whether the coexistence of pain and depressive symptoms on 3-month follow-up predicts the 2-year surgery outcome. METHODS: 93 patients (mean age 62 years) with symptomatic lumbar spinal stenosis underwent decompressive surgery. They completed the same set of questionnaires, 3 months, 1 year and 2 years postoperatively. Depression was assessed with the 21-item Beck Depression Inventory (BDI). Physical functioning and pain were assessed with the Oswestry Disability Index, the Stucki Questionnaire, self-reported walking ability, the visual analogue scale (VAS) and pain drawing. Comparisons were made between groups according to the "misery" (i.e. the coexistence of elevated pain and depression on 3-month follow-up) status. Logistic regression analysis was used to examine the factors independently associated with a poor surgery outcome on 2-year follow-up. RESULTS: The patients in the misery group (n=24) showed greater symptom severity and greater disability than the patients in the non-misery group (n=69) at all follow-up stages. No clinical improvement was seen in the misery group during the follow-up. An independent association was observed between belonging to the misery group and 2-year disability, symptom severity and poor walking capacity. CONCLUSIONS: Even moderately increased VAS and BDI scores, when presenting simultaneously on an individual patient level during the early postoperative period, imply a strong clinical burden and a risk factor for poor recovery. The assessment of pain and depressive symptoms is encouraged.

Thiamine suppresses thermal hyperalgesia, inhibits hyperexcitability, and lessens alterations of sodium currents in injured, dorsal root ganglion neurons in rats.

BACKGROUND: B vitamins can effectively attenuate inflammatory and neuropathic pain in experimental animals, while their efficacy in treating clinical pain syndromes remains unclear. To understand possible mechanisms underlying B vitamin-induced analgesia and provide further evidence that may support the clinical utility of B vitamins in chronic pain treatment, this study investigated effects of thiamine (B1) on the excitability and Na currents of dorsal root ganglion (DRG) neurons that have been altered by nerve injury. METHODS: Nerve injury was mimicked by chronic compression of DRG in rats. Neuropathic pain was evidenced by the presence of thermal hyperalgesia. Intracellular and patch-clamp recordings were made in vitro from intact and dissociated DRG neurons, respectively. RESULTS: (1) In vivo intraperitoneal administration of B1 (66 mg/kg/day, 10-14 doses) significantly inhibited DRG compression-induced neural hyperexcitability, in addition to suppressing thermal hyperalgesia. (2) In vitro perfusion of B1 (0.1, 1 and 10 mM) resulted in a dose-dependent inhibition of DRG neuron hyperexcitability. In addition, the DRG neurons exhibited size-dependent sensitivity to B1 treatment, i.e., the small and the medium-sized neurons, compared to the large neurons, were significantly more sensitive. (3) Both in vitro (1 mM) and in vivo application of B1 significantly reversed DRG compression-induced down-regulation of tetrodotoxin-resistant but not tetrodotoxin-sensitive Na current density in the small neurons. B1 at 1 mM also reversed the compression-induced hyperpolarizing shift of the inactivation curve of the tetrodotoxin-resistant currents and the upregulated ramp currents in small DRG neurons. CONCLUSION: Thiamine can reduce hyperexcitability and lessen alterations of Na currents in injured DRG neurons, in addition to suppressing thermal hyperalgesia.

Abdominal cutaneous nerve entrapment syndrome (ACNES) in a patient with a pain syndrome previously assumed to be of psychiatric origin.

A 21-year-old female patient with chronic abdominal pain was referred to a psychiatric outpatient clinic after gastroenterological and gynaecological pathogeneses had been excluded and a treatment with an antidepressant had had no beneficial effects. The mental state examination, however, revealed no psychopathology whatsoever. The patient was injected with a local anaesthetic loco dolenti which resulted in immediate pain relief. She was diagnosed with abdominal cutaneous nerve entrapment syndrome (ACNES); no psychiatric diagnosis was given.

[Significance of unresolved financial compensation for the course of cervical root compression]. / Betydningen af uafklaret økonomisk kompensation for forløbet af nerverodstryk i nakken.

The aim of this study was to examine the influence of claims for financial compensation on the results of physiotherapeutic McKenzie treatment for cervical nerve root compression. This study was based on prospectively collected data for quality assurance purpose with baseline classification and included a follow-up postal questionnaire to measure the outcomes: Neck and arm pain, disability, use of analgesics and the perceived effect of the treatment registered by the patient. At baseline, patients with or without compensation issues were identical in regard to their neurological and clinical signs. The study showed that 6-12 months later there was no improvement in six out of seven patients with claims for compensation involvement, in contrast to the 21 patients without claims for financial compensation who all showed significant improvement. The results applied to all five outcome measures. In conclusion, compensation involvement seems to act as a negative factor on treatment results for patients with cervical nerve root compression who were treated conservatively.

Bilateral behavioral and regional cerebral blood flow changes during painful peripheral mononeuropathy in the rat.

A unilateral chronic constriction injury (CCI) of the sciatic nerve produced bilateral effects in both pain related behaviors and in the pattern of forebrain activation. All CCI animals exhibited spontaneous pain-related behaviors as well as bilateral hyperalgesia and allodynia after CCI. Further, we identified changes in baseline (unstimulated) forebrain activation patterns 2 weeks following CCI by measuring regional cerebral blood flow (rCBF). Compared to controls, CCI consistently produced detectable, well-localized and typically bilateral increases in rCBF within multiple forebrain structures in unstimulated animals. For example, the hindlimb region of somatosensory cortex was significantly activated (22%) as well as multiple thalamc nuclei, including the ventral medial (8%), ventral posterior lateral (10%) and the posterior (9%) nuclear groups. In addition, several forebrain regions considered to be part of the limbic system showed pain-induced changes in rCBF, including the anterior dorsal nucleus of the thalamus (23%), cingulate cortex (18%), retrosplenial cortex (30%), habenular complex (53%), interpeduncular nucleus (45%) and the paraventricular nucleus of the hypothalamus (30%). Our results suggest that bilateral somatosensory and limbic forebrain structures participate in the neural mechanisms of prolonged persistent pain produced by a unilateral injury.

Endogenous interleukin-6 contributes to hypersensitivity to cutaneous stimuli and changes in neuropeptides associated with chronic nerve constriction in mice.

Partial nerve injury is a potential cause of distressing chronic pain for which conventional analgesic treatment with opiates or anti-inflammatory agents is not very effective. Constriction nerve injury, widely used to study neuropathic pain, was shown here to induce interleukin-6 (IL-6) mRNA in a subset of rat primary sensory neurons. When we inflicted chronic nerve constriction on mice with null mutation of the IL-6 gene, the hypersensitivity to cutaneous heat and pressure that is induced in wild-type mice was not evident, the loss of substance P in sensory neurons was excessive and the induction of galanin in central sensory projections was reduced. In additional experiments, intrathecal infusion of IL-6 in rats was shown to stimulate synthesis of galanin in approximately one-third of lumbar dorsal root ganglion neurons. The results of these experiments indicate that endogenous IL-6 mediates some of the hypersensitive responses that characterize peripheral neuropathic pain, and influences two neuropeptides that have been implicated in pain transmission.

Psychometric assessment of patients with chronic upper extremity pain attributed to workplace exposure.

Upper extremity pain attributed to workplace exposure is a growing concern in medicine today. This study was undertaken to investigate the psychological findings in patients with chronic upper extremity pain attributed to workplace exposure. Sixty-three consecutive patients were evaluated. All patients underwent a history and physical examination by a hand surgeon and a psychological evaluation by a licensed psychologist, including a Minnesota Multiphasic Personality Inventory-2 (MMPI-2). Physical and psychological findings were then compared. Forty-one patients (65%) showed abnormalities on MMPI-2 examination (t score > 70 = 97% confidence). This result is far above what generally would be expected in medical patients. When physical findings were grouped with psychological findings, 5 distinct groups were identified: 1 patient had normal physical and psychological results, 6 patients had normal physical findings but abnormal psychological assessments, 21 patients had abnormal physical findings but normal psychological assessments, 28 patients had both abnormal physical and psychological findings, and 7 patients had abnormal physical results but invalid MMPI-2 evaluations due to purposeful attempts to deny psychological symptoms. Identification of these groups may have diagnostic, prognostic, and treatment value. In addition, identification of these groups may help clarify several aspects of the debate over the role of psychosocial factors in the development and maintenance of chronic upper extremity pain that patients attribute to workplace exposure.

Pain responses in patients with upper-extremity disorders.

The purpose of this study was to evaluate the relationship between pain response factors and upper-extremity disorders associated with work-related compensable disorders. In this retrospective study, the charts of 113 patients were examined. Compensation was not found to have any statistically significant association with pain levels. The degree of functional overlay in these patients, indicated by pain questionnaire scores, differed only slightly between compensated and noncompensated patients and indicated no significant difference between the 2 groups, except that the compensated group used a higher number of descriptors to describe their pain (p = .0143). These results indicate that compensation affects the verbalization of pain but does not affect the degree of pain experienced. Working status was found to be significantly correlated with a better ability to cope with stress at home, suggesting that employment status may be a more important factor than compensation status in the presentation of these patients.

Dissociation of microglial activation and neuropathic pain behaviors following peripheral nerve injury in the rat.

Peripheral nerve injury commonly leads to neuropathic pain states fostered, in part, by neuroimmunologic events. We used two models of neuropathic pain (L5 spinal nerve cryoneurolysis (SPCN) and chronic constriction injury (CCI)) to assess the role of spinal glial activation responses in producing pain behaviors. Scoring of glial responses subjectively encompassed changes in cell morphology, cell density and intensity of immunoreactivity with specific activation markers (OX-42 and anti-glial fibrillary acidic protein (GFAP) for microglia and astrocytes, respectively). Glial responses were compared with tactile sensitivity (mechanical allodynia) at 1, 3 or 10 days following SPCN and with thermal hyperalgesia at 10 days in the CCI group. Neuropathic pain behaviors preceded and did not closely correlate with microglial responses in either model. Perineural application of bupivacaine prior to SPCN prevented spinal microglial responses but not pain behaviors. Spinal astrocytic responses to SPCN were early, robust and not altered by bupivacaine. The current findings support the use of bupivacaine as a tool to suppress microglial activation and challenge the putative role of microglia in initiating or potentiating pain behaviors which result from nerve injury.

Response to psychological stressors in hand-arm vibration syndrome patients.

We investigated urinary catecholamines' response to acute psychological stress test in hand-arm vibration syndrome patients. Thirteen patients with vibration-induced white finger (VWF) in higher frequency of attack, 7 patients with VWF in lower frequency, 6 patients without VWF and 17 healthy subjects were examined. All subjects were male and their average age (SD) was 59.2 (6.4), 56.3 (2.9), 58.2 (4.7) and 56.8 (4.9), respectively. After an initial rest for 1 hour, acute psychological stress test with stressors--mirror drawing, watching horror video and arithmetic under intermittent noise was performed for 1 hour. Subjective complaints to the stress test were greater in patients with hand-arm vibration syndrome than in the healthy controls. The patient group with VWF in higher frequency indicated significant increases of urinary catecholamines (p < 0.05); average values (SD) at rest period and at stress test were 2.42 (1.17) and 3.71 (1.82) micrograms/h for norepinephrine, and 1.47 (0.73) and 2.66 (1.79) micrograms/h for epinephrine, respectively. Increasing tendency of urinary catecholamines was observed in other three groups, however, they were not statistically significant. The sympathoadrenal medullary response to psychological stressors increased especially in hand-arm vibration syndrome patients with VWF in higher frequency.

[Behavioral signs of neuropathic pain in cats due to compression of the infraorbital nerve]. / Povedencheskie priznaki neiropaticheskoi boli u koshek vsledstvie kompressii infraorbital'nogo nerva.

The changes in behavioral reactions were studied in cats after incomplete compression of the infraorbital nerve by means of two ligatures as a model of trigeminal neuropathy. It was found that there appeared a behaviour protective the damaged side of the face, sudden standstills of the animals which threw their head back and raised their anterior paws to the face, as well as inhibition of motor activity. Decreases in the nociceptive threshold and the threshold of emotionally affective responses to lip electrostimulation as the sensory threshold increased. These behavioral changes are regarded as signs of spontaneous pain and hyperalgesia in animals with nerve compression, and the used model is considered to be adequate for studying the mechanisms of neuropathic pain.

Pain, disability, and psychological functioning in chronic low back pain subgroups: myofascial versus herniated disc syndrome.

A series of patients with chronic low back pain evaluated at a tertiary referral center were the subjects for this study. Of 250 consecutive patients, 94 were diagnosed as having myofascial pain and 57 as having herniated disc syndrome. Before evaluation and diagnosis, all patients completed the McGill Pain Questionnaire, ratings of pain and disability, and the Symptom Checklist 90-R. Patients were also grouped on the basis of previous surgical history and workers' compensation benefits. Patients suffering from myofascial pain were significantly less likely to report periods of pain relief than patients with herniated disc syndrome. Those receiving workers' compensation benefits reported significantly greater levels of pain, disability, and psychological distress than those not receiving benefits, irrespective of diagnosis. Patients who underwent previous surgery did not differ significantly from those who never underwent surgery. All patients had elevated scores on the Somatization subscale of the Symptom Checklist 90-R. Patients with myofascial pain and workers' compensation benefits demonstrated the highest levels of somatization and phobia. These findings suggest that the effects of low back pain of myofascial origin have comparable, if not worse, consequences than disc herniation. These findings also reaffirm the importance of workers' compensation in understanding the differences in patients with chronic low back pain.

Life events in neurological patients with headache and low back pain (in relation to diagnosis and persistence of pain).

The series comprised 253 hospitalized patients with 3 groups of patients with low back pain differing in respect to the presence of nerve root compression, and 2 headache groups, i.e., migraine and other non-organic headache. Comparison of the frequency of single life events within the previous 12 months revealed no statistically significant differences among the diagnostic groups. Nor were there any statistically significant differences among the means of the total number of life events, the number of life events with transient distress and the number of life events with enduring distress. Self-rated treatment outcome on pain 6 months after discharge showed for headache patients a statistically significant negative association between persistence of pain and the number of life events with transient distress. In conclusion the findings attach more weight to vulnerability factors or coping abilities compared to social stress.

Learning and interocular transfer of visual discriminations by goldfish with retinotectal compression.

Visual function mediated by a compressed retinotectal projection was examined by training goldfish with unilateral retinotectal compression to perform red/green and horizontal/vertical discriminations. Fish were trained monocularly via the compressed or the normal visual field using an aversive classical conditioning model. Interocular transfer was then examined to determine if the mechanisms mediating this transfer functioned normally after retinotectal compression and to compare interpretation of visual information via normal and compressed visual fields. Both visual discriminations were learned successfully using the normal or the compressed visual field. Learning deficits (relative to controls) were, however, observed in fish trained with the color discrimination using the compressed visual field, or the horizontal/vertical discrimination using the compressed or the normal visual field. Interocular transfer of the color discrimination from the compressed to the normal visual field or in the reverse direction was demonstrated to occur at approximately normal values. Interocular transfer of the horizontal/vertical discrimination was successful from the compressed to the normal visual field, but was reduced or absent in the opposite direction. The results indicate that analysis of the colors red and green is essentially normal after retinotectal compression, and that the pathways mediating interocular transfer of this color discrimination remain functional. There were, however, abnormalities in the mechanism mediating interocular transfer of pattern discriminations after retinotectal compression.