Central control of visceral pain and urinary tract function

Silodosin Improves Pain and Urinary Frequency in Bladder Pain Syndrome/Interstitial Cystitis Patients

Purpose: Bladder Pain Syndrome/Interstitial Cystitis (BPS/IC) is a bladder-related chronic inflammatory disease. Data indicate that stress enhances the excitability of bladder nociceptors through the stimulation of alpha1A-adrenoceptors. Stress is known to play a crucial role in BPS/IC patients. We aimed to assess the efficacy and safety of daily silodosin in refractory BPS/IC female patients and its correlation with stress coping. Materials and Methods: An open-label trial was conducted with 20 refractory BPS/IC patients. Evaluations occurred at baseline and the 8th and 12th weeks. Primary endpoint was bladder pain evaluated by visual analogue scale (VAS). Secondary endpoints included daily frequency, nocturia and maximum voided volume obtained from a 3-day bladder diary, the O’Leary−Sant Symptom Score, and two questions accessing stress coping. Patients initiated daily doses of 8 mg silodosin, which could be titrated to 16 mg. Median values with percentiles 25 and 75 (25; 75) were used. Wilcoxon signed-rank test was used for comparisons. A minimally important difference of 3 points for pain was established to define clinically relevant improvement. Results: Median age was 56 years. Median pain score decreased from 8.00 (6.00; 8.00) at baseline to 4.00 (2.00; 5.50) (p < 0.001), meaning that the primary endpoint was reached. Total urinary frequency decreased from 14.00 (13.00; 21.00) to 9.00 (7.50; 11.00) (p < 0.05), and all the other secondary endpoints also showed a statistically significant improvement. Eleven patients improved by ≥3 pain points in VAS, meaning that 65% of patients that ended the study protocol achieved clinical significant improvement or, in the full analysis set, that 55% of the 20 initial patients improved significantly. Fourteen (82%) decreased by ≥2 micturitions/day. Overall, the cohort’s stress coping was low. Conclusions: Silodosin can be an effective and well-tolerated treatment for refractory BPS/IC female patients.

Pain after upper limb surgery under peripheral nerve block is associated with gut microbiome composition and diversity

Gut microbiota play a role in certain pain states. Hence, these microbiota also influence somatic pain. We aimed to determine if there was an association between gut microbiota (composition and diversity) and postoperative pain. Patients (n = 20) undergoing surgical fixation of distal radius fracture under axillary brachial plexus block were studied. Gut microbiota diversity and abundance were analysed for association with: (i) a verbal pain rating scale of < 4/10 throughout the first 24 h after surgery (ii) a level of pain deemed "acceptable" by the patient during the first 24 h following surgery (iii) a maximum self-reported pain score during the first 24 h postoperatively and (iv) analgesic consumption during the first postoperative week. Analgesic consumption was inversely correlated with the Shannon index of alpha diversity. There were also significant differences, at the genus level (including Lachnospira), with respect to pain being "not acceptable" at 24 h postoperatively. Porphyromonas was more abundant in the group reporting an acceptable pain level at 24 h. An inverse correlation was noted between abundance of Collinsella and maximum self-reported pain score with movement. We have demonstrated for the first time that postoperative pain is associated with gut microbiota composition and diversity. Further work on the relationship between the gut microbiome and somatic pain may offer new therapeutic targets.

Intracranial Mimics of Cauda Equina Syndrome: Heads or Tails?

BACKGROUND

To report cases of extraspinal mimics of cauda equina syndrome (CES) to enable prompt diagnosis and treatment in the future. CES results from compression of spinal nerve roots. Current practice mandates lumbosacral magnetic resonance imaging (MRI) scanning to diagnose CES. However, it may not reveal compression or provide an explanation for the presentation. We present 3 cases of suspected CES who went on to have intracranial pathology.

METHODS

Retrospective review of all patients presenting with CES-type features who were subsequently found to have causative intracranial pathology over a 6-month period.

RESULTS

Three cases were found, and these are hereby presented.

CASE PRESENTATION

Case 1: A 57-year-old lady presented with urinary retention and bilateral leg weakness. She underwent an MRI spine which showed no evidence of CES. She was diagnosed with haemorrhagic intracranial metastases. Case 2: A 52-year-old lady presented with lower back and right buttock pain, with right-sided leg numbness, saddle hypoesthesia, and bowel and bladder incontinence. MRI spine showed no cauda equina compression. MRI neuraxis revealed a subdural haematoma. Case 3: A 69-year-old lady presented with a 6-day history of urinary incontinence, right foot drop, and leg weakness. MRI spine was negative for CES. She was diagnosed with an intraparenchymal haematoma of posterior left frontal lobe.

CONCLUSIONS

Negative lumbosacral MRI will not exclude extraspinal mimics of CES and, although rare, these cases should be considered.

Hypothalamic paraventricular nucleus neurons activated by estrogen GPER1 receptors promote anti-inflammation effects in the early stage of colitis

The hypothalamus-pituitary-adrenal (HPA) axis is known to mediate gut-brain interaction, and the pathological inflammatory process in the intestine can induce HPA axis involved 'fight or flight' response to suppress or facilitate intestinal inflammation. Hypothalamic paraventricular nucleus (PVN) neurons are responsible for controlling the HPA axis activity, but their exact role in modulating intestinal inflammation remains unclear. In this study, we used the dextran sulfate sodium (DSS)-induced mice colitis model, gene editing, and RNA interference to determine the effects of PVN neurons on intestinal inflammation. We found that at the early stage (third day) after DSS treatment, there was a mild inflammation in the colorectal area and an increased neuron activation in the PVN but not in the adjacent area. At the same time, ~80% of activated PVN neurons also expressed novel estrogen GPER1 receptor. The colitis noticeably worsened in GPER1-knockout mice and local PVN GPER1-knockdown mice. These results indicated that PVN GPER1 positive neurons potentially have a protective function during the early stages of DSS-induced colitis, and this may be a mechanism by which the central nervous system attempts to suppress intestinal inflammation to achieve self-protection.

Would early removal of indwelling catheter effectively prevent urinary retention after hip fracture surgery in elderly patients?

BACKGROUND

This study aimed to investigate the incidence and risk factors of postoperative urinary retention (POUR) among elderly patients who underwent hip fracture surgery and to evaluate the effect of indwelling catheterization on the occurrence of POUR.

MATERIALS AND METHODS

From January 2012 to January 2015, consecutive patients aged over 70 years who underwent hip fracture surgery were enrolled in this study. All patients underwent indwelling catheterization due to voiding difficulty upon admission. Demographic data, perioperative variables, and postoperative duration of patient-controlled analgesia and indwelling catheterization, postoperative complications, and mortality were collected. The incidence of POUR was investigated, and the risk factors related to POUR were analyzed using a logistic regression analysis. The cutoff value for the timing of catheter removal was determined using receiver operating characteristic (ROC) curve analysis.

RESULTS

POUR developed in 68 patients (31.8%) of the 214 patients. Of these, 24 (35.3%) were male. The indwelling catheter was left in place for an average of 3.4 days (range, 0-7 days) postoperatively. A significant difference was noted in gender and duration of indwelling catheterization between patients with POUR and without. The cutoff value for the timing of catheter removal as determined by ROC curve analysis was 3.5 postoperative day with 51.4% sensitivity and 71.5% specificity. Multiple logistic regression revealed that the duration of the indwelling catheter [odds ratios (OR), 0.31; p = 0.016)] and male gender (OR, 2.22; p = 0.014) were independent risk factors related to the occurrence of POUR.

CONCLUSIONS

The significant risk factors of POUR among elderly patients undergoing hip fracture surgery were early indwelling catheter removal and male gender. Therefore, early removal of indwelling catheter in elderly patients following hip fracture surgery may increase the risk of POUR, especially in male patients.

Mechanisms Underlying Overactive Bladder and Interstitial Cystitis/Painful Bladder Syndrome

The bladder is innervated by extrinsic afferents that project into the dorsal horn of the spinal cord, providing sensory input to the micturition centers within the central nervous system. Under normal conditions, the continuous activation of these neurons during bladder distension goes mostly unnoticed. However, for patients with chronic urological disorders such as overactive bladder syndrome (OAB) and interstitial cystitis/painful bladder syndrome (IC/PBS), exaggerated bladder sensation and altered bladder function are common debilitating symptoms. Whilst considered to be separate pathological entities, there is now significant clinical and pre-clinical evidence that both OAB and IC/PBS are related to structural, synaptic, or intrinsic changes in the complex signaling pathways that mediate bladder sensation. This review discusses how urothelial dysfunction, bladder permeability, inflammation, and cross-organ sensitisation between visceral organs can regulate this neuroplasticity. Furthermore, we discuss how the emotional affective component of pain processing, involving dysregulation of the HPA axis and maladaptation to stress, anxiety and depression, can exacerbate aberrant bladder sensation and urological dysfunction. This review reveals the complex nature of urological disorders, highlighting numerous interconnected mechanisms in their pathogenesis. To find appropriate therapeutic treatments for these disorders, it is first essential to understand the mechanisms responsible, incorporating research from every level of the sensory pathway, from bladder to brain.

Neonatal bladder inflammation alters the role of the central amygdala in hypersensitivity produced by Acute Footshock stress in adult female rats

There is increasing evidence that chronic pain may be associated with events that occur during critical periods of development. Recent studies have identified behavioral, spinal neurophysiological and spinal/peripheral neurochemical differences in rats that have experienced neonatal bladder inflammation (NBI): a putative model of the chronically painful bladder disorder, interstitial cystitis. Stress has been shown to exacerbate symptoms of interstitial cystitis and produces bladder hypersensitivity in animal models. We recently reported that Acute Footshock-induced bladder hypersensitivity was eliminated in otherwise normal rats by prior bilateral lesions of the central nucleus of the amygdala. Since the spinal and peripheral nervous systems of NBI-treated rats are known to differ from normal rats, the present experiments sought to determine whether a supraspinal nervous system structure, the central amygdala, is still necessary for the induction of Acute Footshock-induced hypersensitivity. The effect of bilateral amygdala electrolytic lesions on Acute Footshock-induced bladder hypersensitivity in adult female rats was tested in Control rats which underwent a control protocol as neonates and in experimental rats which experienced NBI. Consistent with our previous report, in Control rats, Acute Footshock-induced bladder hypersensitivity was eliminated by bilateral Amygdala Lesions. In contrast, Acute Footshock-induced bladder hypersensitivity in NBI-treated rats was unaffected by bilateral Amygdala Lesions. These findings provide evidence that NBI results in the recruitment of substrates of bladder hypersensitivity that may differ from those of normal rats. This, in turn, suggests that unique therapeutics may be needed for painful bladder disorders like interstitial cystitis.

Potential of Endocannabinoids to Control Bladder Pain

Bladder-related pain is one of the most common forms of visceral pain, and visceral pain is among the most common complaints for which patients seek physician consultation. Despite extensive studies of visceral innervation and treatment of visceral pain, opioids remain a mainstay for management of bladder pain. Side effects associated with opioid therapy can profoundly diminish quality of life, and improved options for treatment of bladder pain remain a high priority. Endocannabinoids, primarily anandamide (AEA) and 2-arachidonoylglycerol (2-AG), are endogenously-produced fatty acid ethanolamides with that induce analgesia. Animal experiments have demonstrated that inhibition of enzymes that degrade AEA or 2-AG have the potential to prevent development of visceral and somatic pain. Although experimental results in animal models have been promising, clinical application of this approach has proven difficult. In addition to fatty acid amide hydrolase (FAAH; degrades AEA) and monacylglycerol lipase (MAGL; degrades 2-AG), cyclooxygenase (COX) acts to metabolize endocannabinoids. Another potential limitation of this strategy is that AEA activates pro-nociceptive transient receptor potential vanilloid 1 (TRPV1) channels. Dual inhibitors of FAAH and TRPV1 or FAAH and COX have been synthesized and are currently undergoing preclinical testing for efficacy in providing analgesia. Local inhibition of FAAH or MAGL within the bladder may be viable options to reduce pain associated with cystitis with fewer systemic side effects, but this has not been explored. Further investigation is required before manipulation of the endocannabinoid system can be proven as an efficacious alternative for management of bladder pain.

Lesions of the central amygdala and ventromedial medulla reduce bladder hypersensitivity produced by acute but not chronic foot shock

Both acute and chronic stress has been shown to exacerbate symptoms of chronic visceral pain conditions such as interstitial cystitis. Studies using animal models support these findings in that both acute and chronic exposure to foot shock-induced stress (FS) augment nociceptive reflex responses to urinary bladder distension (UBD). Only a few studies have examined the neural substrates mediating these phenomena and it is not clear whether acute and chronic stress engage the same or different substrates to produce bladder hypersensitivity. The present studies examined the role of two important central nervous system structures - the amygdala (AMG) and the ventromedial medulla (VMM) - in mediating/modulating hypersensitivity evoked by acute versus chronic FS using responses to graded UBD in adult, female Sprague-Dawley rats. Bladder hypersensitivity produced by acute FS was significantly reduced by either bilateral central AMG or VMM lesions using measures generated by graded UBD, but these lesions had no significant effects using the same measures on bladder hyperalgesia produced by chronic FS. Our findings provide evidence that neural substrates underlying bladder hypersensitivity produced by chronic stress differ from those produced by acute stress. These findings suggest that while the AMG and VMM participate in pain processing during periods of limited exposure to stress, prolonged stress may recruit a new set of neural substrates not initially activated by acute exposure to stress.

Urodynamic function during sleep-like brain states in urethane anesthetized rats

The aim was to investigate urodynamic parameters and functional excitability of the periaqueductal gray matter (PAG) during changes in sleep-like brain states in urethane anesthetized rats. Simultaneous recordings of detrusor pressure, external urethral sphincter (EUS) electromyogram (EMG), cortical electroencephalogram (EEG), and single-unit activity in the PAG were made during repeated voiding induced by continuous infusion of saline into the bladder. The EEG cycled between synchronized, high-amplitude slow wave activity (SWA) and desynchronized low-amplitude fast activity similar to slow wave and 'activated' sleep-like brain states. During (SWA, 0.5-1.5 Hz synchronized oscillation of the EEG waveform) voiding became more irregular than in the 'activated' brain state (2-5 Hz low-amplitude desynchronized EEG waveform) and detrusor void pressure threshold, void volume threshold and the duration of bursting activity in the external urethral sphincter EMG were raised. The spontaneous firing rate of 23/52 neurons recorded within the caudal PAG and adjacent tegmentum was linked to the EEG state, with the majority of responsive cells (92%) firing more slowly during SWA. Almost a quarter of the cells recorded (12/52) showed phasic changes in firing rate that were linked to the occurrence of voids. Inhibition (n=6), excitation (n=4) or excitation/inhibition (n=2) was seen. The spontaneous firing rate of 83% of the micturition-responsive cells was sensitive to changes in EEG state. In nine of the 12 responsive cells (75%) the responses were reduced during SWA. We propose that during different sleep-like brain states changes in urodynamic properties occur which may be linked to changing excitability of the micturition circuitry in the periaqueductal gray.