High Prevalence of Neuropathic Pain Component in Patients with Low Back Pain : Evidence from Meta-Analysis

BACKGROUND: Low back pain (LBP) is a complex syndrome which includes a nociceptive (NcP) component, a neuropathic (NeP) component, or a mixture of components (mixed pain). The NeP component (NePC) in LBP is defined as the presence of NeP with or without an NcP. OBJECTIVE: This meta-analysis aimed at assessing the pooled prevalence of NePC in patients with LBP and at identifying the factors causing significant heterogeneity in reported prevalence. STUDY DESIGN: Meta-analysis. METHODS: A systematic literature search was carried out, with inclusion of all epidemiological studies describing the NeP prevalence levels in LBP patients while using standard diagnostic methods. The "pooled prevalence rate (PPR)" of NePC, either on its own or in combination with NcP, was calculated. A pre-specified subgroup analysis was carried out, considering LBP duration, presence of leg pain, diagnostic method(s), and questionnaire(s) used. RESULTS: The meta-analysis included 20 studies relating to a total of 14,269 LBP patients, of whom 7,969 patients (55.8%) were identified as presenting with NePC. The pooled PR (95% CI) of NePC in patients with LBP was 0.47 (0.40 - 0.54), while the pooled PR of NcP was 0.56 (0.48 - 0.63). Higher NePC pooled PR values were identified in LBP with leg pain as compared to uncomplicated LBP (respectively: 0.60; 0.47 - 0.73 vs 0.27; 0.23 - 0.31; Pinteraction < 0.01). LIMITATIONS: The quality of the included studies was assessed using ad-hoc criteria. Due to the limited number of available studies, one may need to be cautious in reaching conclusions about the impact of disease duration on NePC prevalence values. We pooled studies which used a range of different diagnostic methods, with putatively different sensitivity/specificity diagnosing levels. CONCLUSIONS: Overall, high NePC prevalence levels were here identified in LBP patients. As the pain is a subjective phenomenon and there is no gold standard for the diagnosis of NePC, there is the possibility that the pooled effect estimate may alter depending upon the diagnostic method used. KEY WORDS: Neuropathic pain, nociceptive pain, low back pain, symptom-based questionnaire, chronicity.Peer reviewedFinal Published versio

Measurement of self-shaped ellipsoidal bunches from a photoinjector with postacceleration

Recent work has shown the possibility of generating self-shaped ellipsoidal beams with properties commensurate with the requirements of future light sources such as free-electron lasers and inverse Compton sources. In this so-termed “blowout” regime, short laser bunches are transformed via photoemission into short electron bunches which then self-consistently evolve into nearly uniform-density ellipsoids under space-charge forces. We report here on the first blowout studies conducted in collaboration between the UCLA Particle Beam Physics Lab and the Photo Injector Test Facility, Zeuthen (PITZ). The measurements conducted at the PITZ photoinjector facility examine the evolution of 750 pC, 2.7 ps FWHM electron bunches born in an L-band photoinjector and subsequently accelerated through a nine-cell L-band booster for a resulting energy of 12 MeV. These measurements represent the first observations of self-shaped ellipsoid evolution under postinjector acceleration, a key step in demonstrating the utility of such self-shaped beams at higher energy, where the advantages in both transverse and longitudinal and transverse phase space may be exploited in creating very high brightness beams