Differential sensitivity of thick and thin fibers to HIV and therapy-induced neuropathy

Paresthesia Predicts Increased Risk of Distal Neuropathic Pain in Older People with HIV-Associated Sensory Polyneuropathy

OBJECTIVE

Distal sensory polyneuropathy (DSP) is a disabling consequence of human immunodeficiency virus (HIV), leading to poor quality of life and more frequent falls in older age. Neuropathic pain and paresthesia are prevalent symptoms; however, there are currently no known curative treatments and the longitudinal course of pain in HIV-associated DSP is poorly characterized.

METHODS

This was a prospective longitudinal study of 265 people with HIV (PWH) enrolled in the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) study with baseline and 12-year follow-up evaluations. Since pain and paresthesia are highly correlated, statistical decomposition was used to separate the two symptoms at baseline. Multivariable logistic regression analyses of decomposed variables were used to determine the effects of neuropathy symptoms at baseline on presence and worsening of distal neuropathic pain at 12-year follow-up, adjusted for covariates.

RESULTS

Mean age was 56 ± 8 years, and 21% were female at follow-up. Nearly the entire cohort (96%) was on antiretroviral therapy (ART), and 82% had suppressed (≤50 copies/mL) plasma viral loads at follow-up. Of those with pain at follow-up (n = 100), 23% had paresthesia at the initial visit. Decomposed paresthesia at baseline increased the risk of pain at follow-up (odds ratio [OR] 1.56; 95% confidence interval [CI] 1.18, 2.07), and decomposed pain at baseline predicted a higher frequency of pain at follow-up (OR 1.96 [95% CI 1.51, 2.58]).

CONCLUSIONS

Paresthesias are a clinically significant predictor of incident pain at follow-up among aging PWH with DSP. Development of new therapies to encourage neuroregeneration might take advantage of this finding to choose individuals likely to benefit from treatment preventing incident pain.

Neuropathic pain in HIV patients receiving ART without stavudine in an Indonesia Referral Hospital

Lower limb neuropathic pain in HIV patients is a common manifestation of sensory neuropathy (HIV-SN), but can be seen in patients who do not meet standard definitions of HIV-SN. The drug stavudine is a risk factor for HIV-SN, but some patients treated without stavudine experience HIV-SN, and the prevalence and risk factors influencing neuropathic pain in this setting are unknown. A cross sectional study at Cipto Mangunkusumo Hospital Jakarta tested 197 HIV patients treated for >12 months without stavudine. HIV-SN was defined using the AIDS Clinical Trial Group Brief Peripheral Neuropathy Screening Test (ACTG-BPNST). A validated Indonesia translation of Douleur Neuropathique en 4 (DN4) questionnaire was used to assess lower limb neuropathic pain. Nerve conduction studies assessed large nerve fiber function and Stimulated Skin Wrinkle (SSW) tests were performed to assess small nerve fibers. The prevalence of neuropathic pain was 6.6%. BPNST⁺HIV-SN was diagnosed in 14.2% of the cohort and 38.5% of patients with pain. Use of protease inhibitors and ART duration <2 years associated with neuropathic pain in univariate (p = .036, p = .002, resp.) and multivariable analyses (model p < .001). SSW tests were abnormal in 53.8% of subjects with neuropathic pain and only 25.5% without pain (p = .05). Patients with pain without BPNST⁺HIV-SN had begun ART more recently than those with both diagnoses. Overall this preliminary study showed that neuropathic pain associated with protease inhibitors and a shorter duration of ART in Indonesian HIV patients, and may be an early symptom of small fiber neuropathy in this context.

Early detection of peripheral neuropathy using stimulated skin wrinkling test in human immunodeficiency virus infected patients: A cross-sectional study

Peripheral neuropathy is a common condition of human immunodeficiency virus (HIV)-infected patients, which often remains undetected. We assessed the performance of stimulated skin wrinkling-eutectic mixture of local anesthetic (SSW-EMLA) test compared with brief peripheral neuropathy screening (BPNS) to detect HIV neuropathy.This is a cross-sectional study conducted in HIV-positive patients. A modified skin wrinkling grading was used to assess SSW-EMLA effect. BPNS-detectable neuropathy was assessed by a combination of neuropathy severity scoring scale (subjective) and objective method of sensory and tendon reflex examination. The SSW-EMLA test accuracy with reference to BPNS was assessed using sensitivity and specificity and predictive values.In a total of 99 HIV patients, 61.6% were males and the majority age group were between 30 and 40 years (52%). The neuropathy detection was SSW-EMLA test 36.4% versus BPNS 15.2% (P = .04). The sensitivity of SSW-EMLA test was 60.0% [95% confidence interval (95% CI) 34.5-81.7], specificity 67% (95% CI 63.3-3-71.7), and overall accuracy of 66.7% (95% CI 58.9-73.2).The SSW-EMLA test detected many more peripheral neuropathy cases than BPNS in HIV patients and has potential as an alternative test for screening for HIV neuropathy in resource-constraint hospitals in Indonesia.

Quality of life and self-reported lower extremity function in adults with HIV-related distal sensory polyneuropathy

BACKGROUND

Distal sensory polyneuropathy (DSP) is a common complication of HIV disease. Its effects on quality of life (QOL) and function have not been well described.

OBJECTIVE

The study objectives were: (1) to compare QOL and lower extremity function in people with HIV-related DSP and people with HIV disease who do not have DSP, (2) to determine the extent to which function predicts QOL, (3) to evaluate the agreement of 2 function scales, and (4) to describe the use of pain management resources.

DESIGN

This was a cross-sectional survey study with predictive modeling and measurement tool concordant validation.

METHODS

A demographic questionnaire, the Medical Outcomes Study HIV Health Survey, the Lower Extremity Functional Scale (LEFS), the Lower Limb Functional Index (LLFI), and a review of medical records were used. General linear modeling was used to assess group differences in QOL and the relationship between function and QOL. Bland-Altman procedures were used to assess the agreement of the LEFS and the LLFI.

RESULTS

Usable data for analyses were available for 82 of the 94 participants enrolled. The 67% of participants who reported DSP symptoms tended to be older, had HIV disease longer, and were more likely to receive disability benefits. Participants without DSP had better LLFI, LEFS, and physical health summary scores. In multivariate models, lower limb function predicted physical and mental health summary scores. The LLFI identified participants with a lower level of function more often than the LEFS. Participants with DSP were more likely to use medical treatment, physical therapy, and complementary or alternative treatments.

LIMITATIONS

A sample of convenience was used; the sample size resulted in a low power for the mental health summary score of the Medical Outcomes Study HIV Health Survey.

CONCLUSIONS

Quality of life and function were more impaired in participants with HIV disease and DSP. The LLFI was more likely to capture limitations in function than the LEFS. Participants with DSP reported more frequent use of pain management resources.

Insulin-like growth factor-1 prevents dorsal root ganglion neuronal tyrosine kinase receptor expression alterations induced by dideoxycytidine in vitro

Dideoxycytidine (zalcitabine, ddC) produces neurotoxic effects. It is particularly important to understand the toxic effects of ddC on different subpopulations of dorsal root ganglion (DRG) neurons which express distinct tyrosine kinase receptor (Trk) and to find therapeutic factors for prevention and therapy for ddC-induced peripheral sensory neuropathy. Insulin-like growth factor-1 (IGF-1) has been shown to have neurotrophic effects on DRG sensory neurons. However, little is known about the effects of ddC on distinct Trk (TrkA, TrkB, and TrkC) expression in DRG neurons and the neuroprotective effects of IGF-1 on ddC-induced neurotoxicity. Here, we have tested the extent to which the expression of TrkA, TrkB, and TrkC receptors in primary cultured DRG neurons is affected by ddC in the presence or absence of IGF-1. In this experiment, we found that exposure of 5, 25, and 50 μmol/L ddC caused a dose-dependent decrease of the mRNA, protein, and the proportion of TrkA-, TrkB-, and TrkC-expressing neurons. IGF-1 (20 nmol/L) could partially reverse the decrease of TrkA and TrkB, but not TrkC, expression with ddC exposure. The phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 (10 μmol/L) blocked the effects of IGF-1. These results suggested that the subpopulations of DRG neurons which express distinct TrkA, TrkB, and TrkC receptors were affected by ddC exposure. IGF-1 might relieve the ddC-induced toxicity of TrkA- and TrkB-, but not TrkC-expressing DRG neurons. These data offer new clues for a better understanding of the association of ddC with distinct Trk receptor expression and provide new evidence of the potential therapeutic role of IGF-1 on ddC-induced neurotoxicity.

Frequency and risk factors for distal sensory polyneuropathy in HIV infection in a developing country

Distal sensory polyneuropathy is a source of morbidity in HIV infection. This study aims to determine the frequency and effect of demographic and clinical variables on distal sensory polyneuropathy, among HIV-positive participants in south-east Nigeria. The study involved highly active antiretroviral therapy (HAART)-naive, patients on HAART and HIV-negative matched controls conducted at the University of Nigeria Teaching Hospital, Enugu south-east Nigeria. Distal sensory polyneuropathy was diagnosed with clinical evaluation and the use of Bio Thesiometer, 10 g monofilament and ankle reflex. There were 100 participants in each of the groups, comprising 109 (36.3%) men and 191 (63.7%) women, with median age of 35 years. About 42.5% (85/200) of the HIV-positive participants (37 drug naive and 48 on HAART) had distal sensory polyneuropathy. None in the control group had distal sensory polyneuropathy. Age ( p = 0.02), height ( p = 0.002), low haemoglobin ( p = 0.03) and mean duration on HAART ( p = 0.006) were significantly associated with distal sensory polyneuropathy, while gender ( p = 0.497), body mass index ( p = 0.657) and CD4 count ( p = 0.482) did not affect distal sensory polyneuropathy. Low haemoglobin, height, and duration on HAART were independent risk factors for distal sensory polyneuropathy. Addressing correctable causes of anaemia, and alternatives to neurotoxic HAART may minimize the risk of distal sensory polyneuropathy.

Polyneuropathy induced by HIV disease and antiretroviral therapy

OBJECTIVE

To investigate the underlying mechanisms of polyneuropathy induced by HIV infection or antiretroviral drugs.

METHODS

We tested 100 HIV patients (59 with AIDS). Ninety-three patients received antiretroviral drugs. Forty-four were treated with neurotoxic compounds (ddI, ddC, d4T). Nerve conduction velocities and the sympathetic skin response (SSR) in palms and soles were measured in all patients. In skin biopsies (ankle and thigh), the intraepidermal nerve fiber density (IENFD) and the number of epidermal fibers without contact to the basal membrane (fragments) were quantified using PGP9.5 staining.

RESULTS

Severity of the disease (CD4 +count) correlated to conduction velocities of peroneal (p < 0.01, Spearmans rank correlation), sural (p < 0.01) and median nerves (p < 0.05/p < 0.001, sensory/motor). In contrast, the duration of neurotoxic treatment did not impair conduction velocities (p > 0.3) but correlated to reduced IENFD in the ankle (r = -0.24, p < 0.05). Despite their reduced IENFD, patients with long neurotoxic treatment had a high number of fragments irrespective of their CD4 +count.

CONCLUSIONS

Neurotoxic treatment appears to primarily impair thin fiber conduction, whereas HIV neuropathy is linked to large fiber impairment and reduction of fragments of nerve fibers.

SIGNIFICANCE

These findings emphasize the differential pattern of polyneuropathy in HIV patients caused by the infection or induced by antiretroviral treatment.

Lipodystrophy and adrenal insufficiency: potential mediators of peripheral neuropathy in HIV infection?

The mechanisms behind certain co-morbid conditions associated with chronic HIV disease still remain elusive. HIV-associated peripheral neuropathy is one among those rarely studied manifestations in HIV-1 infection. Numerous underlying factors associated with peripheral neuropathy have been described in HIV disease. Herein, we hypothesized certain heretofore undescribed potential mechanisms that lead to HIV associated neuropathy. Being a multifactoral manifestation, HIV-associated neuropathy is presumed to have an association with physiological factors namely, adrenal inadequacy/steroid resistance and lipodystrophy-induced cushion-effect loss in peripheral nerves. Therefore, management of the adrenals with steroids at the time-point of high inflammatory burden thereby preventing lipodystrophy by selecting the optimum treatment regimen could markedly alleviate the severity of HIV-associated neuropathic manifestations.

Electrically induced quantitative sudomotor axon reflex test in human volunteers

Chemically-induced quantitative sudomotor axon reflex test (QSART) and quantitative sensory testing (QST) are established clinical tools to assess thin fiber function in humans. We investigated stimulus-response functions to transcutaneous electrical stimuli of different current intensity (3.75 to 10mA) and pulse frequency (5 to 100Hz) comparing sweat output (ml/h/m(2)) and pain intensity (numeric rating scale [NRS], 0-10). Efferent sudomotor and afferent nociceptive responses were recorded after a 30s electrical stimulation period of distal (hand and foot) and proximal (forearm and thorax) body sites with 3 repetitive measures per body site. Sweat responses increased intensity dependently and peaked (~100ml/h/m(2)) at highest currents (10mA) that had been administered. Similarly, pain ratings increased with an escalating current intensity. At a constant stimulus intensity of 7.5mA, sudomotor activity was highest (~75ml/h/m(2)) at a stimulus frequency of 20Hz without further increase at 50 or 100Hz. In contrast, pain ratings increased frequency dependently and reached NRS 7 at 100Hz. Sudomotor activity, but not pain ratings, was significantly different between the body sites (p<0.05, ANOVA) with maximum sweat responses obtained at the ventral forearm. Varying response patterns for higher stimulation frequencies between sweating (peak maximum at 20Hz) and pain (maximum at 100Hz) might indicate differential axonal properties of sympathetic efferent and nociceptive afferent fibers. Electrically induced QSART could be a useful explorative and clinical method to indirectly study characteristics of frequency-dependent axonal excitability changes of sudomotor fibers.