Pathophysiological mechanisms of neuropathic pain

Questionnaire-based somatosensory profiling in breast cancer survivors: are we there yet? Associations between questionnaires and quantitative sensory testing

PURPOSE

Pain and sensory disturbances are common side effects of breast cancer treatment. Differential somatosensory functioning may reflect distinct pathophysiological backgrounds and therapeutic needs. Aim was to examine whether questionnaires evaluating signs and symptoms related to somatosensory functioning correlate sufficiently with quantitative sensory testing (QST) in breast cancer survivors to warrant consideration for somatosensory profiling in clinical practice.

METHODS

One year after breast cancer surgery, 147 women underwent QST and completed following questionnaires: Douleur Neuropathique en 4 questions (DN4), Central Sensitization Inventory, Margolis Pain Diagram and Visual Analog Scales (VAS). Associations between the questionnaires and QST were evaluated using Spearman correlation coefficients (rs).

RESULTS

Significant but weak (rs < 0.30) correlations were found between total DN4 score and QST results at the inner upper arm for detection of sharp stimuli (rs = 0.227), cold stimuli (rs = -0.186), and painful heat stimuli (rs = 0.179), as well as between QST evaluating conditioned pain modulation and the Margolis Pain Diagram on one hand (rs = 0.176) and minimum-maximum pain intensity differences (VAS) on the other (rs = -0.170).

CONCLUSION

Questionnaires evaluating signs and symptoms related to somatosensory functioning are insufficient for somatosensory profiling. Although somatosensory profiling may be valuable in a mechanism-based management, more research on the most appropriate clinical tools is needed.IMPLICATIONS FOR REHABILITATIONClinicians should be able to recognize that patients with persistent pain or sensory disturbances following breast cancer surgery may have a component of altered somatosensory processing as a significant contributor to their complaint in order to address it appropriately.Somatosensory profiling has yet to be implemented into clinical practice.No evidence-based recommendations can be made on the use of self-reported questionnaires to assess somatosensory processing in a breast cancer population based on the findings of this study.It is suggested to combine information on how individuals process and experience somatosensory stimulation with information from the patient interview or questionnaires to consider which biological, psychological and/or social factors may drive or sustain these neurophysiological processes.

Outpatient Oral Neuropathic Pain Management with Photobiomodulation Therapy: A Prospective Analgesic Pharmacotherapy-Paralleled Feasibility Trial

Neuropathic pain (NP) can be challenging to treat effectively as analgesic pharmacotherapy (MED) can reduce pain, but the majority of patients do not experience complete pain relief. Our pilot approach is to assess the feasibility and efficacy of an evidence-based photobiomodulation (PBM) intervention protocol. This would be as an alternative to paralleled standard analgesic MED for modulating NP intensity-related physical function and quality of life (QoL) prospectively in a mixed neurological primary burning mouth syndrome and oral iatrogenic neuropathy study population (n = 28). The study group assignments and outcome evaluation strategy/location depended on the individual patient preferences and convenience rather than on randomisation. Our prospective parallel study aimed to evaluate the possible pre/post-benefit of PBM and to allow for a first qualitative comparison with MED, various patient-reported outcome measures (PROMs) based on Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT-II) were used for up to a nine-month follow-up period in both intervention groups (PBM and MED). The PBM protocol applied to the PBM group was as follows: λ810 nm, 200 mW, 0.088 cm2, 30 s/point, 9 trigger and affected points, twice a week for five consecutive weeks, whereas the MED protocol followed the National Institute of Clinical Excellence (NICE) guidelines. Our results showed that despite the severe and persistent nature of the symptoms of 57.50 ± 47.93 months at baseline in the PBM group, a notably rapid reduction in PISmax on VAS from 7.6 at baseline (T0) to 3.9 at one-month post-treatment (T3) could be achieved. On the other hand, mean PISmax was only reduced from 8.2 at baseline to 6.8 at T3 in the MED group. Our positive PBM findings furthermore support more patients' benefits in improving QoL and functional activities, which were considerably impaired by NP such as: eating, drinking and tasting, whereas the analgesic medication regimens did not. No adverse events were observed in both groups. To the best knowledge of the authors, our study is the first to investigate PBM efficacy as a monotherapy compared to the gold standard analgesic pharmacotherapy. Our positive data proves statistically significant improvements in patient self-reported NP, functionality, psychological profile and QoL at mid- and end-treatment, as well as throughout the follow-up time points (one, three, six and nine months) and sustained up to nine months in the PBM group, compared to the MED group. Our study, for the first time, proves the efficacy and safety of PBM as a potent analgesic in oral NP and as a valid alternative to the gold standard pharmacotherapy approach. Furthermore, we observed long-term pain relief and functional benefits that indicate that PBM modulates NP pathology in a pro-regenerative manner, presumably via antioxidant mechanisms.

Acupuncture for the Treatment of Taxane-Induced Peripheral Neuropathy in Breast Cancer Patients: A Pilot Trial

Objectives

Some chemotherapy drugs can damage the nerves and cause peripheral neuropathy which is accompanied by severe neuropathic pain or gait impairment. The purpose of this study was to assess the feasibility and the safety of acupuncture for the treatment of peripheral neuropathy following chemotherapy in Korean breast cancer patients.

Design

This study was a prospective single-arm observational study using before and after measurements in breast cancer patients presenting with taxane-induced peripheral neuropathy.

Settings/Location

This study was performed at East-West Medical Center at Daegu Catholic University Hospital, Daegu, South Korea.

Interventions

Acupuncture was administered 3 times a week for 4 consecutive weeks, for 25 ± 5 minutes at each session.

Outcome Measures

The primary outcome measure was severity of CIPN using the Neuropathic Pain Symptom Inventory (NPSI) assessed by a self-administered questionnaire and Nerve Conduction Study (NCS) of extremities. The secondary outcome measure was quality of life (QoL) assessed by a self-administered questionnaire using the 36-Item Short From Health Survey (SF-36).

Results

Acupuncture significantly reduced the severity of CIPN assessed by NPSI score. Four weeks after the last treatment, the symptoms were not aggravated. According to NCS, 42.9% of participants showed improvement of sensory neuropathy. At the end of the treatment, SF-36 scores were significantly increased for variables including physical functioning, role limitations due to physical health problems, social functioning, and general health perceptions compared to those of baseline measurement.

Conclusions

Acupuncture improved symptoms of CIPN and QoL in Korean women suffering from peripheral neuropathy after chemotherapy using taxane for breast cancer. The effects of acupuncture lasted for at least 1 month after the treatment.

An Evaluation of Efficacy and Safety of Commonly Prescribed Drugs and Effect of These Drugs on Quality of Sleep in Patients Suffering From Zoster-Associated Pain

This observational, prospective, single-center study was conducted to evaluate the efficacy and safety of commonly prescribed drugs for zoster-associated pain and their impact on quality of sleep at a tertiary care hospital in western India. Patients ≥18 years of age, newly diagnosed with zoster-associated pain were evaluated on days 0, 7, 14, 30, 60, 90, 120, 150, and 180 or until resolution of pain, whichever was earlier, using the Wong Baker FACES Pain Rating Scale, Neuropathic Pain Scale, and Insomnia Severity Index for intensity of pain, quality of pain, and quality of sleep, respectively. A total of 78 patients (46.0 [16.3] years) completed the study. They received nonsteroidal anti-inflammatory drugs (65), gabapentin (30), amitriptyline (27), and amitriptyline + gabapentin (21) for mean durations of 7.7 (3.0), 89.2 (7.2), 107.6 (46.3), and 104.5 (46) days, respectively. Improvement in the Wong Baker FACES Pain Rating Scale and Neuropathic Pain Scale score was similar among treatment groups except for a greater fall in Wong Baker FACES Pain Rating Scale score at days 7 and 120 and that in deep pain score at day 7 in combination treatment group vs the amitriptyline group. Clinically significant insomnia was detected in 35 patients at baseline and demonstrated progressive and similar improvement among groups. Treatment modification was required in 20 patients. Zoster-associated pain resolved in 69 patients. Nine adverse drug reactions, mostly mild, nonserious, and nonpreventable, were reported. To conclude, drugs commonly used for zoster-associated pain are effective and well tolerated. These have a similar effect on pain and quality of sleep, except for a possible greater effect of combination treatment in the early phase of intense and deep pain.

How diagnostic tests help to disentangle the mechanisms underlying neuropathic pain symptoms in painful neuropathies

Neuropathic pain, ie, pain arising directly from a lesion or disease affecting the somatosensory afferent pathway, manifests with various symptoms, the commonest being ongoing burning pain, electrical shock-like sensations, and dynamic mechanical allodynia. Reliable insights into the mechanisms underlying neuropathic pain symptoms come from diagnostic tests documenting and quantifying somatosensory afferent pathway damage in patients with painful neuropathies. Neurophysiological investigation and skin biopsy studies suggest that ongoing burning pain primarily reflects spontaneous activity in nociceptive-fiber pathways. Electrical shock-like sensations presumably arise from high-frequency ectopic bursts generated in demyelinated, nonnociceptive, Aβ fibers. Although the mechanisms underlying dynamic mechanical allodynia remain debatable, normally innocuous stimuli might cause pain by activating spared and sensitized nociceptive afferents. Extending the mechanistic approach to neuropathic pain symptoms might advance targeted therapy for the individual patient and improve testing for new drugs.

The Lived Experience of Peripheral Neuropathy after Solid Organ Transplant

Background

The immunosuppressants required after transplant cause peripheral neuropathy with an incidence of 10% to 60%. Peripheral neuropathy adversely affects health-related quality of life in other populations.

Objective

To describe the lived experience of peripheral neuropathy after solid organ transplant.

Design

A qualitative phenomenological study with semistructured interviews. A purposive sample of 7 solid organ transplant recipients with peripheral neuropathy was recruited from 2 transplant clinics at a large Midwest tertiary care center. Interviews were audio taped and transcribed verbatim. Data were analyzed line-byline and coded by using HyperResearch 2.0.

Results

Although participants' experiences were similar to those reported by others with peripheral neuropathy, there were also unique differences. Unique to this population was unexpected onset, rapid escalation of symptoms, lack of provider monitoring, and poor provider response to reported symptoms. Their experience demonstrated that peripheral neuropathy diminished health-related quality of life. Four themes emerged from the data: (1) nothing is supposed to happen after transplant; (2) neuropathy causes me more problems than my heart; (3) maybe there is something that could help; and (4) I've learned to live with certain limitations.

Conclusion

Development of or worsening of peripheral neuropathy after solid organ transplant may decrease health-related quality of life. Follow-up care should include vigilant monitoring for signs of peripheral neuropathy. Providers need to provide early treatment, education, support, empathy, and understanding.