Influence of antipsychotic medication on pain perception in schizophrenia

Risks of complicated acute appendicitis in patients with psychiatric disorders

BACKGROUND

Acute appendicitis often presents with vague abdominal pain, which fosters diagnostic challenges to clinicians regarding early detection and proper intervention. This is even more problematic with individuals with severe psychiatric disorders who have reduced sensitivity to pain due to long-term or excessive medication use or disturbed bodily sensation perceptions. This study aimed to determine whether psychiatric disorder, psychotropic prescription, and treatment compliance increase the risks of complicated acute appendicitis.

METHODS

The diagnosis records of acute appendicitis from four university hospitals in Korea were investigated from 2002 to 2020. A total of 47,500 acute appendicitis-affected participants were divided into groups with complicated and uncomplicated appendicitis to determine whether any of the groups had more cases of psychiatric disorder diagnoses. Further, the ratio of complicated compared to uncomplicated appendicitis in the mentally ill group was calculated regarding psychotropic dose, prescription duration, and treatment compliance.

RESULTS

After adjusting for age and sex, presence of psychotic disorder (odds ratio [OR]: 1.951; 95% confidence interval [CI]: 1.218-3.125), and bipolar disorder (OR: 2.323; 95% CI: 1.194-4.520) was associated with a higher risk of having complicated appendicitis compared with absence of psychiatric disorders. Patients who are taking high-daily-dose antipsychotics, regardless of prescription duration, show high complicated appendicitis risks; High-dose antipsychotics for < 1 year (OR: 1.896, 95% CI: 1.077-3.338), high-dose antipsychotics for 1-5 years (OR: 1.930, 95% CI: 1.144-3.256). Poor psychiatric outpatient compliance was associated with a high risk of complicated appendicitis (OR: 1.664, 95% CI: 1.014-2.732).

CONCLUSIONS

This study revealed a close relationship in the possibility of complicated appendicitis in patients with severe psychiatric disorders, including psychotic and bipolar disorders. The effect on complicated appendicitis was more remarkable by the psychiatric disease entity itself than by psychotropic prescription patterns. Good treatment compliance and regular visit may reduce the morbidity of complicated appendicitis in patients with psychiatric disorders.

Altered physical pain processing in different psychiatric conditions

Several reports indicate either increased or decreased pain sensitivity associated with psychiatric disorders. Chronic pain is highly prevalent in many of these conditions. We reviewed the literature regarding experimental pain sensitivity in patients with major depression, bipolar disorder, posttraumatic stress disorder (PTSD), generalized anxiety disorder, panic disorder, obsessive-compulsive disorder and schizophrenia. Electronic searches were performed to identify studies comparing experimental pain in patients with these conditions and controls. Across 31 depression studies, reduced pain threshold was noted except for ischemic stimuli, where increased pain tolerance and elevated sensitivity to ischemic pain was observed. A more pervasive pattern of low pain sensitivity was found across 20 schizophrenia studies. The majority of PTSD studies (n = 20) showed no significant differences compared with controls. The limited number of bipolar disorder (n = 4) and anxiety (n = 9) studies precluded identification of clear trends. Wide data variability was observed. Awareness of psychiatric patients' pain perception abnormalities is needed for active screening and addressing physical comorbidities, in order to enhance quality of life, life expectancy and mental health.

Dissecting pain processing in adolescents with Non-Suicidal Self Injury: Could suicide risk lurk among the electrodes?

Background

Although non‐suicidal self‐injury (NSSI) disorder is highly prevalent in adolescents, its relationship with pain system function and suicidality is still controversial. The present study was designed to assess the function of the nociceptive afferent pathways and the endogenous pain modulation in adolescent patients with NSSI and to longitudinally register any suicide attempt, describe its frequency and find a possible association between suicide, neurophysiological measures and psychological measures.

Methods

We enrolled 30 adolescents suffering from NSSI and 20 age‐ and gender‐matched healthy controls. Patients underwent a comprehensive psychological evaluation. Each participant underwent thermal pain thresholds of the quantitative sensory testing, laser‐evoked potential recording to study the ascending nociceptive pathway and the conditioned pain modulation testing to test the endogenous pain modulation.

Results

We found that patients with NSSI had a reduced amplitude of the N2 component of laser‐evoked potentials and an abnormal conditioned pain modulation. The amplitude of the N2 was associated with suicidal risk.

Conclusions

The deficit of the endogenous pain modulation likely depends on a saturation due to continuous pain solicitation. The strong association of a reduced amplitude of the N2 component with suicide suggests that it may serve as a possible biomarker in self‐harming adolescents.

Significance

The present study identifies the N2 component of laser‐evoked potentials as a possible neurophysiological biomarker of suicidal risk in patients with non‐suicidal self‐injury, therefore, raising the possibility for a non‐invasive test to identify subjects at higher risk of suicide among self‐harming patients.

Reduced pain perception in patients with schizophrenia; A missed case of hand fracture

Altered pain perception among patients with schizophrenia is often underrecognized in the medical community. The cause is not known, and medical professionals are not sure whether these patients experience less pain or are simply unable to express it. There are documented cases of patients with schizophrenia presenting to hospital settings with serious injuries without obvious (expected) pain. Research into the underlying cause(s) is underway; meanwhile, ensuring awareness of this issue among medical providers is of upmost importance. We report a case of a patient with schizophrenia who presented voluntarily to the emergency department (ED) with a hand fracture that went unrecognized in the ED and further discuss the implications of reduced pain perception. Additionally, we summarize existing hypotheses regarding the source of this reduced pain perception in this population.

The Opioid Interactions of the Antipsychotic Medications Risperidone and Amisulpride in Mice and Their Potential Use in the Treatment of Other Non-Psychotic Medical Conditions

Pain is defined as an unpleasant sensory and emotional experience associated with actual or potential tissue damage. The opioid epidemic in the USA has highlighted the need for alternative treatments for pain. Following reports on the opioid interactions of various antipsychotic medications, we speculated that the involvement of the opioid system in some of the antipsychotics' mechanism of action may suggest their potential use in the treatment of pain. Risperidone is a neuroleptic with a potent dopamine D2 and serotonin 5-HT2 receptor-blocking activity as well as a high affinity for adrenergic and histamine H1 receptors. Amisulpride is a neuroleptic which selectively blocks dopamine D2 and D3 receptors. Both had a potent antinociceptive effect on ICR mice tested with a tail flick assay. That effect on both medications was antagonized by naloxone, indicating that at least some of the antinociceptive effects were mediated by an opioid mechanism of action. Further investigation found that β-Funaltrexamine hydrochloride (β-FNA), naloxonazine, and nor-Binaltorphimine dihydrochloride (nor-BNI) reversed the antinociceptive effect of both risperidone and amisulpride. Naltrindole at a dose that blocked [D-Pen2,D-Pen5]enkephalin (DPDPE, δ analgesia) blocked notably amisplride effect and only partially reversed that of risperidone. Risperidone induced an antinociceptive effect, implying involvement of μ and κ-opioid and δ-opioid mechanisms. Amisulpride-induced antinociception was mediated through selective involvement of all three opioid receptor subtypes. These findings emphasize the need for clinical trials to assess the possibility of extending the spectrum of medications available for the treatment of pain.

Differences in the Opioid Consumption of Terminally Ill Schizophrenic and Nonschizophrenic Cancer Patients: Analysis of Secondary National Population Data

CONTEXT

It is uncertain whether terminally ill schizophrenic cancer patients are hypoalgesic or have disparities in pain management.

OBJECTIVES

The objective of this study was to analyze the dosage of opioids used in terminally ill cancer patients with and without schizophrenia.

METHODS

This is a population-based retrospective cohort study based on data derived from the Taiwan National Health Insurance Research Database. Patients aged >20 years and newly diagnosed between 2000 and 2012 with at least one of the six most common cancers were included. After 1:4 matching, 1001 schizophrenic cancer patients comprised the schizophrenia cohort, while 4004 cancer patients without schizophrenia comprised the nonschizophrenia cohort. The percentage of opioid use, accumulated dose, and average daily dose near the end of life were analyzed for each cohort using multiple logistic and linear regression models.

RESULTS

The percentage of opioid use was lower in the schizophrenic cohort than the nonschizophrenic cohort during the last month before death (69.6% vs. 84.8%, odds ratio = 0.40, 95% CI = 0.34-0.48). The accumulated dose of opioid consumption was also lower in the schizophrenic cohort (2407 mg vs. 3694 mg, P value < 0.05).

CONCLUSION

Near the end of life, cancer patients with schizophrenia use less opioid than their nonschizophrenic counterparts. Cognitive impairment may be a cause in the disparity in end-of-life care for terminally ill schizophrenic cancer patients. Thus, we should formulate a more accurate pain scale system and pay attention to their need for pain treatment.

A modality-specific dysfunction of pain processing in schizophrenia

Clinical observations showed that schizophrenia (SCZ) patients reported little or no pain under various conditions that are commonly associated with intense painful sensations, leading to a higher risk of morbidity and mortality. However, this phenomenon has received little attention and its underlying neural mechanisms remain unclear. Here, we conducted two experiments combining psychophysics, electroencephalography (EEG), and functional magnetic resonance imaging (fMRI) techniques to investigate neural mechanisms of pain insensitivity in SCZ patients. Specifically, we adopted a stimulus–response paradigm with brief stimuli of different sensory modalities (i.e., nociceptive, non‐nociceptive somatosensory, and auditory) to test whether pain insensitivity in SCZ patients is supra‐modal or modality‐specific, and used EEG and fMRI techniques to clarify its neural mechanisms. We observed that perceived intensities to nociceptive stimuli were significantly smaller in SCZ patients than healthy controls, whereas perceived intensities to non‐nociceptive somatosensory and auditory stimuli were not significantly different. The behavioral results were confirmed by stimulus‐evoked brain responses sampled by EEG and fMRI techniques, thus verifying the modality‐specific nature of the modulation of nociceptive information processing in SCZ patients. Additionally, significant group differences were observed in the spectral power of alpha oscillations in prestimulus EEG and the seed‐based functional connectivity in resting‐state fMRI (seeds: the thalamus and periaqueductal gray that are key nodes in ascending and descending pain pathways respectively), suggesting a possible contribution of cortical–subcortical dysfunction to the phenomenon. Overall, our study provides insight into the neural mechanisms of pain insensitivity in SCZ and highlights a need for systematic assessments of their pain‐related diseases.

Pain Processing in Psychiatric Conditions: A Systematic Review

Pain is a universal, multidimensional experience with sensory, emotional, cognitive, and social components, which is fundamental to our environmental learning when functioning typically. Understanding pain processing in psychiatric conditions could provide unique insight into the underlying pathophysiology or psychiatric disease, especially given the psychobiological overlap with pain processing pathways. Studying pain in psychiatric conditions is likely to provide important insights, yet, there is a limited understanding beyond the work in depression and anxiety. This is a missed opportunity to describe psychiatric conditions in terms of neurobiological alterations. To examine the research into the pain experiences of these groups and the extent to which a-typicality is present, a systematic review was conducted. An electronic search strategy was developed and conducted in several databases. The current systematic review included 46 studies covering five Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM-5) disorders: autism, attention-deficit hyperactivity disorder (ADHD), schizophrenia, personality disorder, and eating disorders, confirming tentative evidence of altered pain and touch processing. Specifically, hyposensitivity is reported in schizophrenia, personality disorder and eating disorder, hypersensitivity in ADHD, and mixed results for autism. Review of the research highlights a degree of methodological inconsistency in the utilization of comprehensive protocols, the lack of which fails to allow us to understand whether a-typicality is systemic or modality specific.

Internalizing Symptoms Mediate the Relation Between Acute Pain and Autism in Adults

Research on pain in autism spectrum disorder (ASD) is in its infancy, with almost nothing known about how individual differences may predicting pain response in ASD. In the present study, 45 adults (28 male, age 22-48 years) with diagnoses of autism and intellectual delay were observed during vaccination or dental cleaning and their pain behaviours coded and measures of autism symptom severity, anxiety, depression and obsessivity taken. Our findings showed that greater autism severity predicted greater pain response which was partially mediated by anxiety and depression. These data suggest that mental health symptoms are important when considering pain response in autism. Mood must therefore be considered in future research on pain in ASD as well as clinical pain management.

Pain-processing abnormalities in bipolar I disorder, bipolar II disorder, and schizophrenia: A novel trait marker for psychosis proneness and functional outcome?

OBJECTIVES

Overlapping neural system dysfunctions, mainly involving the secondary somatosensory cortex (S2), the anterior cingulate cortex (ACC) and the anterior insular cortex (AIC), seem to be related to both pain-perception abnormalities and psychotic symptoms in schizophrenia (SCZ) and bipolar disorder (BD). Laser-evoked potentials (LEPs) were used to investigate pain-perception and central pain-processing abnormalities in SCZ, bipolar I disorder (BD-I), and bipolar II disorder (BD-II), and to evaluate their relationship with history of psychosis, and social-cognitive and functional impairments.

METHODS

Twenty patients with SCZ, 17 patients with BD-I, and 21 patients with BD-II who were all under similar pharmacological treatment underwent clinical, functional, and neuro-psychological assessment. LEPs were analyzed in patients and 19 healthy subjects (HS). LEPs elicit responses reflecting the activity of the S2 (N1 wave) and the ACC/AIC cortices (N2/P2 complex). A four-group ANOVA was conducted between patients and HS to compare pain-perceptive thresholds (PThs), N1, and N2/P2-LEP components.

RESULTS

Compared to HS: (i) patients with SCZ showed pain-processing and pain-perception abnormalities, as revealed by significantly higher PTh (P<.01), and lower N1 (P<.01) and N2/P2 (P<.01) amplitudes, (ii) patients with BD-I showed only pain-processing abnormalities, as revealed by significantly lower N1 (P<.05) and N2 (P<.01) amplitudes; and patients with BD-II did not differ for any of the LEP variables investigated. N1 and N2 amplitudes negatively correlated to history of psychosis (P<.01), social-cognition (P<.05), and real-world functioning (P<.01) measures in the whole group of patients.

CONCLUSIONS

To the best of our knowledge, this is the first study comparing central pain processing in patients with SCZ, BD-I, and BD-II. Our results suggest that pain-processing abnormalities may represent a novel locus of interest for research investigating trait markers of the psychosis spectrum.

Neurophysiological responses to unpleasant stimuli (acute electrical stimulations and emotional pictures) are increased in patients with schizophrenia

Patients with schizophrenia have often been described as insensitive to nociceptive signals, but objective evidence is sparse. We address this question by combining subjective behavioral and objective neurochemical and neurophysiological measures. The present study involved 21 stabilized and mildly symptomatic patients with schizophrenia and 21 control subjects. We applied electrical stimulations below the pain threshold and assessed sensations of pain and unpleasantness with rating scales, and Somatosensory Evoked Potentials (SEPs/EEG). We also measured attention, two neurochemical stress indices (ACTH/cortisol), and subjective VEPs/EEG responses to visual emotional stimuli. Our results revealed that, subjectively, patients’ evaluations do not differ from controls. However, the amplitude of EEG evoked potentials was greater in patients than controls as early as 50 ms after electrical stimulations and beyond one second after visual processing of emotional pictures. Such responses could not be linked to the stress induced by the stimulations, since stress hormone levels were stable. Nor was there a difference between patients and controls in respect of attention performance and tactile sensitivity. Taken together, all indices measured in patients in our study were either heightened or equivalent relative to healthy volunteers.

Schizophrenia and Suicide Attempts: Findings from a Representative Community-Based Canadian Sample

This study examined factors associated with suicide attempts among those with schizophrenia (n = 101) versus those without (n = 21,643) in a representative sample of noninstitutionalized Canadians. The lifetime prevalence of suicide attempts among persons with schizophrenia was 39.2% versus 2.8% of nonafflicted individuals. After adjusting for sociodemographics, childhood adversities, substance abuse/dependence, depression/anxiety, and chronic pain, those with schizophrenia had 6 times the odds (OR = 6.47) of attempting suicide. Among persons with schizophrenia, suicide attempts were associated with female gender (OR = 4.59), substance abuse/dependence (OR = 6.31), depression (OR = 4.93), and childhood physical abuse (OR = 5.75). Community-dwelling persons with schizophrenia appear to be at high risk for suicide attempts.

Pain perception in schizophrenia: influence of neuropeptides, cognitive disorders, and negative symptoms

OBJECTIVES

The causes and nature of insensitivity to pain in schizophrenia remain unknown. The role of endorphins and the association of cognitive dysfunction and negative symptoms are postulated.

METHODS

In this study, 43 patients with schizophrenia, five first-degree relatives, and 34 healthy controls were examined. Participants' plasma concentrations of substance P, β-endorphin, and calcitonin gene-related peptide (CGRP) were assessed. In patients, the Trail-Making Test, the Color Reading Interference Test (Stroop test), and the Positive and Negative Syndrome Scale Negative Syndrome subscale (PANSS N) test were performed. We also evaluated pain threshold using nociceptive reflex (RTIII) testing.

RESULTS

The mean β-endorphin concentration was about 20% higher in patients than in healthy controls (P<0.05). CGRP concentrations were significantly higher in patients than in controls (5.34 ng/mL versus 4.16 ng/mL; P<0.01). Subjects treated with antipsychotic polytherapy had higher concentrations of CGRP than did patients treated with second-generation antipsychotic monotherapy (5.92 ng/mL versus 5.02 ng/mL; P<0.05). There were no correlations between any biochemical parameters and Trail-Making Test, Stroop test, and PANSS N scores. There were no differences in RTIII among study groups. Strong negative correlation (P<0.001) was found between PANSS N scores and subjective pain threshold on the right lower limb.

CONCLUSION

The insensitivity to pain in schizophrenia is a complex phenomenon that is probably not related to changes in nociceptive pathways. Increase in β-endorphin level may be related to this issue, but it is uncertain if such concentration ensures analgesic effect. It is unknown if patients with schizophrenia in fact experience less pain. Cognitive impairment and excess negative symptoms may strongly influence the patient's expression of pain.

Effects of neonatal treatment with the TRPV1 agonist, capsaicin, on adult rat brain and behaviour

Treatment of neonatal rats with the transient receptor potential vanilloid 1 (TRPV1) channel agonist, capsaicin, produces life-long loss of sensory neurons expressing TRPV1 channels. Previously it was shown that rats treated on day 2 of life with capsaicin had behavioural hyperactivity in a novel environment at 5-7 weeks of age and brain changes reminiscent of those found in subjects with schizophrenia. The objective of the present study was to investigate brain and behavioural responses of adult rats treated as neonates with capsaicin. It was found that the brain changes found at 5-7 weeks in rats treated as neonates with capsaicin persisted into adulthood (12 weeks) but were less in older rats (16-18 weeks). Increased prepulse inhibition (PPI) of acoustic startle was found in these rats at 8 and 12 weeks of age rather than the deficit commonly found in animal models of schizophrenia. Subjects with schizophrenia also have reduced flare responses to niacin and methylnicotinate proposed to be mediated by prostaglandin D2 (PGD2). Flare responses are accompanied by cutaneous plasma extravasation. It was found that the cutaneous plasma extravasation responses to methylnicotinate and PGD2 were reduced in capsaicin-treated rats. In conclusion, several neuroanatomical changes observed in capsaicin-treated rats, as well as the reduced cutaneous plasma extravasation responses, indicate that the role of TRPV1 channels in schizophrenia is worthy of investigation.

Temporomandibular disorders in patients with schizophrenia using antipsychotic agents: a discussion paper

Patients with psychiatric problems show a tendency to develop temporomandibular disorders (TMD). Particularly, patients with schizophrenia are quite likely to have signs and symptoms of TMD due to the impairment of their oral health, the use of antipsychotic drugs, and other general health problems. In nonschizophrenic populations, TMD have been considered as the main cause of nondental pain in the orofacial region, involving mechanisms associated with changes in masticatory activity at the cortical and neuromuscular levels. Individuals with schizophrenia do not usually complain of pain, and TMD is misdiagnosed in this population. In this paper, we aimed to review the clinical aspects of TMD in people with schizophrenia on antipsychotic drug therapy.

Clinical pain in schizophrenia: a systematic review

Studies about clinical pain in schizophrenia are rare. Conclusions on pain sensitivity in people with schizophrenia are primarily based on experimental pain studies. This review attempts to assess clinical pain, that is, everyday pain without experimental manipulation, in people with schizophrenia. PubMed, PsycINFO, Embase.com, and Cochrane were searched with terms related to schizophrenia and pain. Methodological quality was assessed with the Mixed Methods Appraisal Tool. Fourteen studies were included. Persons with schizophrenia appear to have a diminished prevalence of pain, as well as a lower intensity of pain when compared to persons with other psychiatric diseases. When compared to healthy controls, both prevalence and intensity of pain appear to be diminished for persons with schizophrenia. However, it was found that this effect only applies to pain with an apparent medical cause, such as headache after lumbar puncture. For less severe situations, prevalence and intensity of pain appears to be comparable between people with schizophrenia and controls. Possible underlying mechanisms are discussed. Knowledge about pain in schizophrenia is important for adequate pain treatment in clinical practice.

PERSPECTIVE

This review presents a valuable insight into clinical pain in people with schizophrenia.

Isolation rearing reduces mechanical allodynia in a mouse model of chronic inflammatory pain

Social isolation rearing in mice after weaning reduces pain sensitivity to acute pain, and this hypoalgesia is mediated by the descending serotonergic pain inhibitory system in which the spinal serotonin (5-HT)1A receptor is involved. However, it is not known whether isolation rearing affects pain sensitivity to neuropathic or inflammatory chronic pain. In this study, we examined the effects of isolation rearing on chronic pain induced by Freund's complete adjuvant (FCA) and partial sciatic nerve ligation using the von Frey test (to assess mechanical allodynia) and the plantar test (to assess thermal hyperalgesia). In the FCA model, isolation rearing reduced mechanical allodynia, but not thermal hyperalgesia. In contrast, isolation rearing had no effect on allodynia or hyperalgesia in the sciatic nerve ligation model. The isolation rearing-induced inhibition of allodynia was alleviated by intrathecal injection of WAY100635, a selective 5-HT1A receptor antagonist. FCA increased 5-HT turnover and decreased 5-HT1A receptor expression in the spinal cord of group-reared mice, while it did not have these effects in isolation-reared mice. These results suggest that FCA suppresses the serotonergic pain inhibitory system selectively in group-reared mice. Moreover, systemic administration of osemozotan, a selective 5-HT1A receptor agonist, inhibited FCA-induced mechanical allodynia in group-reared mice, and this effect of the drug was suppressed by intrathecal injection of WAY100635. Collectively, these findings suggest that isolation rearing selectively reduces FCA-induced mechanical allodynia in mice and that this effect is mediated by the activation of spinal 5-HT1A receptors.

Insular dysfunction and descending pain inhibition in anorexia nervosa

OBJECTIVE

Reduced perception of pain is a well-established phenomenon in patients with anorexia nervosa (AN). We tested the hypothesis that altered processing of pain within the insula might account for reduced perception of pain.

METHOD

Heat pain thresholds were obtained in nineteen patients with AN and matched controls. Thereafter, a thermode was used to deliver thermal painful stimuli to the right arm during functional magnetic resonance imaging (fMRI) measurements. Stimuli were initiated for 10 s from a baseline resting temperature (32°C) to three different levels (37, 42, 45°C).

RESULTS

Significantly increased heat pain thresholds were observed in patients. A stronger activation during heat pain perception was found in the left posterior insula in controls. In contrast, higher levels of activity were shown in the ipsilateral pons in patients when compared to controls. In patients, we found a significant interrelation between the depression score (Beck depression inventory) and heat pain activations.

CONCLUSION

We suggest that reduced activity in the left posterior insula might contribute to increased pain thresholds in patients, while increased activations in the right anterior insula and pons mirror augmented sympathetic modulation putatively related to amplification of adrenergic descending pain inhibition. In addition, pain thresholds and brain activations were influenced by disease-inherent depressed mood.

Alteration of pain recognition in schizophrenia

BACKGROUND

Schizophrenia patients display impaired recognition of their own emotions and those of others and deficits in several domains of empathy. The first-person experience of pain and observing others in pain normally trigger strong emotional mechanisms. We therefore hypothesized that schizophrenia patients would display impaired recognition and categorization of both their own pain and the pain of others.

METHODS

We studied 29 patients (18 men/11 women; 36 ± 13 years old) with paranoid schizophrenia-spectrum disorder and 27 healthy volunteers (20 men/7 women; 31 ± 9 years old) matched for age, gender, IQ and socio-cultural level. We assessed symptom severity and theory of mind. The participants' ability to detect and categorize pain in others was assessed with the sensitivity to expressions of pain (STEP) test, which is based on facial expressions, and another dynamic test involving a series of video sequences showing various pain-inducing events. The ability of patients to evaluate their own pain was assessed with the situational pain questionnaire (SPQ), which includes a series of questions assessing how one would expect to feel in different imaginary situations. Empathic tendencies were assessed with the interpersonal reactivity index.

RESULTS

Patients and controls differed significantly in STEP, pain video and SPQ scores. By contrast with control subjects, the patients' pain judgements were not correlated with their affective or cognitive empathic capacities.

CONCLUSIONS

Schizophrenic patients have a deficit of the identification and categorization of pain both in themselves and in others.

[The processing of pain in psychiatric diseases]

The perception and processing of pain is disturbed in many psychiatric diseases. Some diseases are known to show decreased perception of pain (e.g. borderline personality disorder), while others are associated with augmented pain perception (e.g. alcohol and drug dependence). The close relationship between psychiatric diseases and pain is most probably caused by aberrant processing of pain in brain structures, known to be involved in psychiatric disorders as well. Aberrant perception and processing of pain in patients with anorexia nervosa (AN) will be used to demonstrate this close relationship. Dysfunction within the insula has been suggested to account for many features of AN and might contribute to reduced pain perception. Moreover, it might lead to increased adrenergic descending inhibition associated with increased sympathetic modulation. Thus, pain research might be able to alter our view on autonomic regulation, which is putatively associated with increased cardiac mortality of the disease.

Increased cold and heat pain thresholds influence the thermal grill illusion in schizophrenia

BACKGROUND

Patients with schizophrenia show decreased sensitivity towards clinical and experimental painful conditions. To date, the exact underlying mechanisms are not completely understood. One method to examine central integrative processes of pain perception is the thermal grill illusion (TGI), in which interlacing cold and warm bars create the illusion of a painful sensation.

METHODS

In 18 unmedicated patients with acute paranoid schizophrenia, cold and heat pain thresholds (CPT/HPT) as well as the perception of the TGI were examined and compared to 18 matched controls. In addition, symptom scales were obtained in order to relate pain perception to psychopathology.

RESULTS

CPT and HPT were significantly increased in patients compared to controls. In the range of TGI stimuli that were perceived painful by controls, patients did not indicate painful sensations, instead the stimulus response curve of TGI pain perception was shifted towards higher stimulus intensities, i.e., greater temperature differentials between cold and warm bars. This increase was comparable to that seen in CPT and HPT. There was no association with psychopathology for any pain parameter.

CONCLUSIONS

CPT and HPT, as well as temperature differentials for the perception of the TGI were increased in patients with schizophrenia as compared to controls. Similar to visual illusions, in which reduced contrast sensitivity has been shown to alter the perception of illusions, the discriminatory somatosensory deficit, which is reflected in higher CPT and HPT as well as the previously reported increased warmth perception thresholds, might account for the attenuation of TGI in patients.

Pain, affective symptoms, and cognitive deficits in patients with cerebral dopamine dysfunction

Converging preclinical, and human epidemiological, neuroimaging, and genetic evidence suggests a central role for dopamine neurotransmission in modulating pain perception and analgesia. Dysregulation in dopamine signaling may modulate the experience of pain both directly, by enhancing or diminishing the propagation of nociceptive signals, and indirectly, by influencing affective and cognitive processes, which affect the expectation, experience, and interpretation of nociceptive signals. Hypersensitivity to pain and high rates of comorbid chronic pain are common in disorders linked with deficits in dopamine system function, including disorders of mood and affect, substance abuse, and Parkinson disease. Hyposensitivity to pain, however, is common in patients with schizophrenia, which has been linked with excessive dopamine neurotransmission. Although patients are typically affected most by the primary symptoms of their disorders, alterations in pain perception may further increase the burden of their illness, compromising their quality of life. The present review focuses on this relationship, and discusses clinical and potential therapeutic implications for both patients with dopamine-related disorders and those with chronic pain syndromes.

Experimental pain hypersensitivity in schizophrenic patients

OBJECTIVE

Whether schizophrenic patients are hypoalgesic or feel pain in the same manner as unaffected individuals can affect the primary care of schizophrenic patients, which often involves an assessment of pain severity made by a medical provider. This study was developed to explore the pain sensitivity of schizophrenics under conditions similar to those of a medical examination that included investigating for sites of pain.

METHODS

We developed 2 experimental models of pain induction using either pressure or ischemia and used them with 35 schizophrenic patients and 35 controls to record: (1) the stimulus intensity required to induce moderate pain; and (2) the pain intensity induced by a predetermined level of pressure. Clinical data were also collected for the schizophrenic group.

RESULTS

Schizophrenic patients needed less pressure (P=0.006) and a shorter duration of ischemia (P<0.001) than controls to record moderate pain, and they felt more pain from a fixed pressure stimulus (P<0.001). Pain histories for the previous 6 months and the heart rate variations that occurred during the tests did not differ between the groups. Pain responses were unrelated to the clinical characteristics of the schizophrenic patients, although hallucination production correlated with the pain felt during the fixed pressure test.

DISCUSSION

Under these conditions, schizophrenic patients were hypersensitive to pain induction compared with normal individuals. The hypoalgesia typically associated with schizophrenic patients may correspond to fewer than normal reports of pain, rather than to impaired sensations of pain. This should be taken into account during routine medical practice.

Neural response to experimental heat pain in stable patients with schizophrenia

Diminished pain sensitivity in schizophrenia has been reported in clinical studies. While the role of antipsychotic medications as a cause of the decrease in pain perception has been questioned, little is known about neural pain processing in treated schizophrenia patients. The aim of this pilot study was to examine the blood oxygen level-dependent (BOLD) changes induced by an experimental pain tolerance (endure) hot stimuli vs. non-painful stimuli in clinically stable patients with schizophrenia and in healthy controls. Twelve patients with schizophrenia, treated with risperidone and considered clinically stable, and 13 gender- and age-matched healthy controls were studied using painful and non-painful thermal stimuli in a periodic block design. BOLD changes were assessed using high field, 3 T functional Magnetic Resonance Imaging (fMRI). Pain tolerance in stable patients was not statistically different than healthy controls. Interestingly, patients showed higher activation in the primary somatosensory cortex (S1) and superior prefrontal cortex, and less activation in the posterior cingulate cortex and brainstem than controls. Our pilot study indicates that pain tolerance is similar in clinically stable patients and controls, although the neural processing of pain is not normalized with antipsychotic treatment.

Pseudohypoalgesia on the skin: a novel view on the paradox of pain perception in depression

Previous studies reported increased heat pain thresholds and decreased ischemic pain thresholds in patients experiencing depression. The increased sensitivity to ischemic muscle pain was assumed to represent a model for the investigation of physical symptoms in the disease. Here, we explored how the serotonin and noradrenaline reuptake inhibitor duloxetine influences experimental pain thresholds and tolerances in depressed patients during treatment. Twenty-two patients experiencing unipolar depression were included. Pain assessments were conducted unmedicated at baseline, after 1 week, and after 6 weeks of duloxetine treatment. We observed the expected clinical response of patients indicated by a significant reduction in the Montgomery Depression Rating Scale after 6 weeks. At baseline, we found increased heat pain thresholds in patients in comparison to controls while patients simultaneously rated augmented pain perception on the visual analog scale. In contrast, patients were significantly more perceptive to ischemic muscle pain at baseline. During treatment, the examined pain thresholds showed differential changes: Increased heat pain thresholds of patients normalized during treatment, whereas no significant change was observed for ischemic pain thresholds. Thus, our results might change the view on the paradox of pain perception in major depression because increased heat pain thresholds are associated with augmented pain perception in the disease.

Gastric dysmotility in healthy first-degree relatives of patients with schizophrenia

Gastric dysmotility has been reported in patients suffering from major depression or schizophrenia. An increased sympathetic activity modulating the gastric pacemaker located in the antrum of the stomach has been suggested as the underlying pathology. Similar to patients suffering from schizophrenia, their first-degree relatives showed alterations in cardiac autonomic modulation. Here we aimed to investigate gastric myoelectrical activity in healthy relatives of patients suffering from paranoid schizophrenia. Electrogastrography (EGG) was performed before and after test meal ingestion in 20 patients with paranoid schizophrenia, 20 of their first-degree relatives and 20 healthy matched controls. Autonomic and abdominal symptoms were assessed by the autonomic symptom score as previously reported. Autonomic parameters were correlated with the positive and negative syndrome scale (PANSS). Only minimal differences were observed before test meal ingestion between relatives and controls. In contrast, after test meal ingestion we observed a significantly increased tachygastria within the signal of the gastric pacemaker in relatives compared to controls, whereas normogastria was reduced. Significant difference between relatives and controls were also found for postprandial ICDF (instability coefficient of dominant frequency) and slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in relatives. Between relatives and patients just a difference for ICDP (instability coefficient of dominant power) was observed. After stimulation of the enteric nervous system we have observed an increased sympathetic modulation in first-degree relatives of patients suffering from schizophrenia. This result adds evidence to an ongoing debate on the genetic influence of autonomic dysfunction in the disease.

Functional magnetic resonance imaging response to experimental pain in drug-free patients with schizophrenia

Clinical evidence suggests that there is decreased pain sensitivity in schizophrenia; however, the neurobiological mechanism of this decrease remains unknown. Using functional magnetic resonance imaging, we examined the blood oxygen level-dependent (BOLD) changes induced by experimental pain-tolerance (endure) hot stimuli vs. non-painful stimuli during an acute psychotic episode in 12 drug-free patients with schizophrenia and in 13 gender- and age-matched healthy controls. The analyses revealed that patients showed a greater BOLD response at S1 compared with controls but a reduced BOLD response in the posterior cingulate cortex (PCC), insula, and brainstem during pain-tolerance stimuli. Pain-tolerance temperature was higher in patients than in healthy controls. BOLD response in the insula positively correlated with unpleasantness and temperature in controls, but this effect was not observed in patients. S1 BOLD response positively correlated with unpleasantness in patients but not in controls. These initial results confirm that unmedicated patients with schizophrenia have a higher pain tolerance than controls, decreased activation in pain affective-cognitive processing regions (insula, PCC, brainstem), and an over-activation of the primary sensory-discriminative pain processing region (S1). These pilot results are the first to explore the mechanism driving altered pain sensitivity in schizophrenia.

Spontaneous rupture of urinary bladder associated with massive fecal impaction (fecaloma)

We report a case of sudden death due to a catastrophic spontaneous rupture of a urinary bladder associated with megacolon due to a fecal impaction (fecaloma). The massively distended rectum and sigmoid colon filled the pelvic cavity and pressed up against the posterior aspects of the uterus, vagina, and urinary bladder. This produced bladder outlet obstruction, followed by massive dilatation and rupture of the urinary bladder, bilateral hydronephrosis, and a 3.5 liter collection of urinary fluid within the abdominal cavity. Complications of chronic constipation, fecalomas, and rupture of the urinary bladder are reviewed.

Neurological disorders in schizophrenia

Schizophrenia (SZ) is a complex, heterogeneous, and disabling psychiatric disorder that impairs multiple aspects of human cognitive, perceptual, emotional, and behavioral functioning. SZ is relatively frequent (prevalence around 1%), with onset usually during adolescence or early adulthood, and has a deteriorating course. The rapidly growing area of neuroimaging research has has found clear evidence of many cortical and subcortical abnormalities in individuals with SZ. In this article the most recent findings from multiple studies on neurological disorders in SZ are reviewed, and the authors make a strong argument for a neurological basis of the schizophrenic process.

Linear and non-linear measures indicate gastric dysmotility in patients suffering from acute schizophrenia

Cardiac autonomic dysfunction has been reported in patients suffering from schizophrenia. The aim of the present study was to evaluate gastric electrical activity in unmedicated patients suffering from acute schizophrenia in relation to their symptoms. Electrogastrography was performed before and after test meal ingestion in 26 patients suffering from schizophrenia and 26 matched controls. The non-linear measure approximate entropy (ApEn) was calculated for the first time from the obtained signal in addition to standardized measures. Results were correlated with the scales for the assessment of positive symptoms and negative symptoms. In addition, autonomic and abdominal symptoms were assessed by the autonomic symptom score. We found a significantly increased amount of tachygastria and arrhythmia within the signal of the activity of the gastric pacemaker before and after test meal digestion in patients compared to controls, indicating increased sympathetic modulation within the enteric nervous system. A significant difference was observed for slow wave, which represents the dominant frequency of gastric pacemaker activity, indicating gastric dysmotility in our patients. The elevated ApEn measure points to increased complexity and dysregulation. In addition, we have observed a correlation between delusions and tachygastria. Sympathetic function seems to be altered in the enteric nervous system of patients suffering from schizophrenia. Future studies need to explore the influence of the disease on different branches of the autonomic nervous system and clinical consequences of enteric dysfunction. Our findings point to a possible systemic autonomic imbalance that needs to be studied in respect to the neurobiology of schizophrenia.

Haloperidol and risperidone have specific effects on altered pain sensitivity in the ketamine model of schizophrenia

RATIONALE

The ketamine (ket) model reflects features of schizophrenia as well as secondary symptoms such as altered pain sensitivity.

OBJECTIVES

In the present study, we investigated the effect of subchronic oral treatment with haloperidol (hal, 0.075 mg/kg) and risperidone (ris, 0.2 mg/kg) on altered pain perception and locomotor activity in this model.

RESULTS

In reaction to 5 mg/kg morphine, ket pretreated animals showed a diminished analgesic response. Hal had no analgesic effect per se, but the compound normalised the analgesic reaction to morphine in the ket pretreated animals. The effect of ris was complex. First, there was no analgesic effect per se, and control animals showed a dose-dependent increase in the analgesic index after morphine injection. In the ket group treated with ris, the analgesic response to 5 mg/kg morphine was attenuated and in response to 10 mg/kg analgesia was comparable with that measured in controls. The reduced analgesic effect was not due to pharmacokinetic differences in morphine metabolism. After administration via drinking water in saline-injected control animals, the hal blood serum concentration was 2.6 +/- 0.45 ng/ml. In ket-injected animals, the mean serum concentration of hal amounted to 1.2 +/- 0.44 ng/ml. In the experiment using ris, animals in the control group had higher ris serum concentrations compared with ket-injected animals. In control animals, morphine dose dependently decreased locomotor activity. This effect was significantly stronger in the ket pretreated groups.

CONCLUSIONS

Hal and ris had different effects on altered pain sensitivity. It was hypothesised that these results are connected with alterations in dopamine D2 and mu opioid receptor binding.

Pain perception in schizophrenia: no changes in diffuse noxious inhibitory controls (DNIC) but a lack of pain sensitization

BACKGROUND

Pain is a dynamic phenomenon resulting from the activity of both excitatory (e.g. sensitization) and inhibitory endogenous modulation systems. Preliminary experimental studies have shown diminished pain sensitivity in schizophrenia patients. The objective of the study was to investigate the role of excitatory and inhibitory systems on pain perception in schizophrenia.

METHODS

Participants were 23 patients with a schizophrenia-spectrum disorder (DSM-IV criteria) and 29 healthy volunteers, who did not differ in age, sex or ethnicity. Excitatory and inhibitory systems were elicited using a temporal summation test (Peltier thermode) administered before and after activation of the diffuse noxious inhibitory control (DNIC) by means of a cold-pressor test.

RESULTS

Time was a significant predictor of pain scores in controls, but not in patients. That is, pain ratings increased during the tonic thermal stimulation among controls but not in schizophrenia patients. When correlation coefficients (between time and pain ratings) for patients and controls were compared, the correlation coefficient emerged as significantly weaker in the schizophrenia group (Z=12.04; p=0.0001), suggesting a lack of sensitization in schizophrenia. DNIC was similar in magnitude in both patients and controls.

CONCLUSIONS

Diminished pain sensitivity in schizophrenia may be related to abnormal excitatory mechanisms, but not to DNIC. More studies are needed to better characterize the neurophysiological and neurochemical mechanisms involved in the lack of sensitization in schizophrenia.

Lack of pain in schizophrenia: a patient whose arm was burned and amputated

Diminished pain sensitivity or loss of pain sensation in schizophrenic patients has previously been reported. We report an interesting case of a schizophrenia patient who had the disease for 20 years and who had his forearm amputated below the elbow level due to severe burn injury to his muscles, tendons, nerve fibers and bone tissue, caused by direct exposure to flames from a liquefied petroleum gas cylinder, in an attempt to make himself warm during a medicine-free period with active symptoms and without pain sensation.