Axonal Excitability Does Not Differ between Painful and Painless Diabetic or Chemotherapy-Induced Distal Symmetrical Polyneuropathy in a Multicenter Observational Study.

Objective: Axonal excitability reflects ion channel function, and it is proposed that this may be a biomarker in painful (vs painless) polyneuropathy. Our objective was to investigate the relationship between axonal excitability parameters and chronic neuropathic pain in deeply phenotyped cohorts with diabetic or chemotherapy-induced distal symmetrical polyneuropathy.

Methods: Two hundred thirty-nine participants with diabetic polyneuropathy were recruited from sites in the UK and Denmark, and 39 participants who developed chemotherapy-induced polyneuropathy were recruited from Denmark.

Pain thresholds and intensities of CRPS type I and neuropathic pain in respect to sex.

Background And Aims: Healthy women have generally been found to have increased experimental pain perception and chronic pain has a higher prevalence in female as compared to male patients. However, no study has investigated whether pain intensity and pain perception thresholds are distinct or similar between sexes within various chronic pain entities. We investigated whether average pain intensities and pain thresholds assessed using quantitative sensory testing (QST) differed between women and men suffering from three distinct chronic pain conditions: Complex Regional Pain Syndrome (CRPS type I), peripheral nerve injury (PNI) or polyneuropathy (PNP), as compared to paired healthy volunteers.

DOLORisk: study protocol for a multi-centre observational study to understand the risk factors and determinants of neuropathic pain.

Neuropathic pain is an increasingly prevalent condition and has a major impact on health and quality of life. However, the risk factors for the development and maintenance of neuropathic pain are poorly understood. Clinical, genetic and psychosocial factors all contribute to chronic pain, but their interactions have not been studied in large cohorts.

Patterns of Distribution of the Nerves Around the Axillary Artery Evaluated by Ultrasound and Assessed by Nerve Stimulation During Axillary Block.

Our objective was to define the positions of the nerves around the brachial artery and, secondarily, to assess the risk of intraneural injection during dual guided axillary block. Sixty ultrasound-guided axillary blocks were performed. The locations of the musculocutaneous, median, ulnar, and radial nerves relative to the brachial artery were determined.

Symptom profiles in the painDETECT Questionnaire in patients with peripheral neuropathic pain stratified according to sensory loss in quantitative sensory testing.

The painDETECT Questionnaire (PDQ) is commonly used as a screening tool to discriminate between neuropathic pain (NP) and nociceptive pain, based on the self-report of symptoms, including pain qualities, numbness, and pain to touch, cold, or heat. However, there are minimal data about whether the PDQ is differentially sensitive to different sensory phenotypes in NP. The aim of the study was to analyze whether the overall PDQ score or its items reflect phenotypes of sensory loss in NP as determined by quantitative sensory testing.

Effects of a T-type calcium channel blocker, ABT-639, on spontaneous activity in C-nociceptors in patients with painful diabetic neuropathy: a randomized controlled trial.

T-type calcium channels are a potential novel target for treatment of neuropathic pain such as painful diabetic neuropathy. ABT-639 is a peripherally acting highly selective T-type Ca(v)3.2 calcium channel blocker that has demonstrated analgesic efficacy in preclinical models and may have the potential to reduce spontaneous fiber activity.

Behavioral and electrophysiological abnormalities in two rat models of antiretroviral drug-induced neuropathy.

Painful peripheral neuropathy due to the antiretroviral therapy used to treat HIV is one of the most prevalent side effects occurring in at least 30% of patients living with this infection. We have evaluated the electrophysiological and behavioral effects of d4T and ddC on peripheral large and small nerve fibers in male rats treated with d4T (Sprague-Dawley, 50 mg/kg, twice within 1 week), ddC (Wistar, 50 mg/kg, 3 times per week for 3 weeks), or vehicle. The effect of the interventions was assessed using behavioral measures of mechanical sensitivity, conventional nerve conduction studies, and microneurographic single nerve C-fiber recordings.

Hyperexcitable C nociceptors in fibromyalgia.

Objective: To test the hypothesis that peripheral C nociceptor function may be abnormal in fibromyalgia and that C nociceptor dysfunction may contribute to the symptoms reported by these patients.

Methods: Microneurography was used to record C nociceptors of 30 female patients meeting criteria for fibromyalgia and compared with recordings from 17 female patients with small-fiber neuropathy and 9 female controls.

Results: We obtained stable recordings of 186 C nociceptors in the fibromyalgia group, 114 from small-fiber neuropathy patients, and 66 from controls.

Microneurographic identification of spontaneous activity in C-nociceptors in neuropathic pain states in humans and rats.

C-nociceptors do not normally fire action potentials unless challenged by adequate noxious stimuli. However, in pathological states nociceptors may become hyperexcitable and may generate spontaneous ectopic discharges. The aim of this study was to compare rat neuropathic pain models and to assess their suitability to model the spontaneous C-nociceptor activity found in neuropathic pain patients.

Double and triple spikes in C-nociceptors in neuropathic pain states: an additional peripheral mechanism of hyperalgesia.

It was previously reported that in 5 patients with small-fiber neuropathy, neuropathic pain, and hyperalgesia, application of a single, brief electrical stimulus to the skin could give rise to 2 afferent impulses in a C-nociceptor fiber. These double spikes, which are attributed to unidirectional conduction failure at branch points in the terminal arborisation, provide a possible mechanism for hyperalgesia. We here report that similar multiple spikes are regularly observed in 3 rat models of neuropathic pain: nerve crush, nerve suture, and chronic constriction injury.

C-nociceptors sensitized to cold in a patient with small-fiber neuropathy and cold allodynia.

Cold allodynia is a common sign of neuropathic pain patients but its underlying mechanisms are still largely unknown, partly because the populations of neurons responding to cold stimuli and their transduction mechanisms have not been fully determined. We report a patient with a small-fiber neuropathy of unknown origin, whose main complaint is cold allodynia. Microneurographic recordings showed ongoing spontaneous activity and abnormal responses to cold and menthol in identified subtypes of C-nociceptors.