ACUTE HERPES ZOSTER AND POSTHERPETIC NEURALGIA

Burden of herpes zoster: the direct and comorbidity costs of herpes zoster events in hospitalized patients over 50 years in France

Background

The objectives of this study were to describe hospital stays related to HZ and to evaluate the direct and indirect cost of hospitalizations due to HZ among patients aged over 50 years.

Methods

The hospitalizations of people aged over 50 years were selected from the French national hospital 2011 database (PMSI) using ICD-10 diagnosis codes for HZ.

Firstly, stays with HZ as principal or related diagnostic were described through the patient characteristics, type of hospitalization and the related costs. Secondly, a retrospective case–control analysis was performed on stays with HZ as comorbidity in 5 main hospitalizations causes (circulatory, respiratory, osteo-articular, digestive systems and diabetes) to assess the impact of HZ as co-morbidity on the length of stay, mortality rate and costs.

Results

In the first analysis, 2,571 hospital stays were collected (60 % of women, mean age: 76.3 years and mean LOS: 9.5 days). The total health assurance costs were 10,8 M€. Mean cost per hospital stay was 4,206€. In the second analysis, a significant difference in LOS and costs was shown when HZ was associated as comorbidity in other hospitalization’s causes.

Conclusions

HZ directly impacts on the hospital cost. When present as comorbidity for other medical reasons, HZ significantly increases the length of hospital stay with subsequent economic burden for the French Health System.

Treatment of postherpetic neuralgia: a review of therapeutic options

Postherpetic neuralgia (PHN) is a disabling consequence of the reactivation of the varicella zoster infection. The observation that patients with PHN experience various types of pain suggests that multiple pathophysiologic mechanisms are involved, which may include the peripheral and central nervous systems. A reasonable initial strategy would involve selecting from among multiple agents that have complementary mechanisms of action and that have been proven effective in controlled clinical trials, such as the lidocaine patch 5%, gabapentin, tricyclic antidepressants, and opioids. Based on initial assessment and ongoing reassessment, sequential trials should be undertaken until adequate pain relief is achieved. This may ultimately lead to therapy with more than one medication. Safety and tolerability are important considerations in choosing initial therapy, particularly in older patients. Physicians can either add another agent to the current regimen or switch to a new type of monotherapy if there is inadequate response to initial therapy. Alternative therapies, (i.e., ketamine, intrathecal corticosteroid injections) have not been adequately studied. Well-designed, multicenter, controlled clinical trials are needed to develop a treatment algorithm that provides an evidence-based, rational approach to treating PHN.

[Corticosteroid therapy of zoster-associated pain]

INTRODUCTION

Lack of exact clinical studies on effects of corticosteroids in therapy and prevention of herpes zoster-related pain, elicited many controversies in the past. The aim of our study was to estimate effects of prednisone on frequency, intensity and duration of postherpetic neuralgia.

MATERIAL AND METHODS

68 immunocompetent herpes zoster patients, 8-90 years of age (37 females and 31 males, mean age 55.7 years) were enrolled for study; 30 patients were treated with acyclovir (5 x 800 mg daily for a 7-day period) and prednisone (initial daily dose 60 mg, tapering over 14 days), and the control group of 38 patients with acyclovir only. Patients were clinically followed up for 3 months after complete resolution of skin lesions. Chi-square test was used in statistical data analysis.

RESULTS

The difference regarding incidence of postherpetic neuralgia in acyclovir/prednisone group and acyclovir group (although slightly less in the former one) was not significant. Duration of postherpetic neuralgia over 3 months was similar in both groups. Mild postherpetic pain was more common in the acyclovir/prednisone group (44.4%) than in the acyclovir group (28.6%); however, statistical validation requires more patients to be studied.

DISCUSSION

Results of our study didn't confirm efficiency of prednisone regarding occurrence and characteristics of postherpetic neuralgia. Failure of prednisone therapy may be partly contributed to advanced age of patients and delayed onset of therapy.

CONCLUSION

Use of corticosteroids in zoster patients gives neither reliable protection from appearance of postherpetic neuralgia, nor shortens its duration. Further investigations are necessary to estimate their effects on postherpetic pain.

Nociceptive response to innocuous mechanical stimulation is mediated via myelinated afferents and NK-1 receptor activation in a rat model of neuropathic pain

Peripheral nerve injury in humans can produce a persistent pain state characterized by spontaneous pain and painful responses to normally innocuous stimuli (allodynia). Here we attempt to identify some of the neurophysiological and neurochemical mechanisms underlying neuropathic pain using an animal model of peripheral neuropathy induced in male Sprague-Dawley rats by placing a 2-mm polyethylene cuff around the left sciatic nerve according to the method of Mosconi and Kruger. von Frey hair testing confirmed tactile allodynia in all cuff-implanted rats before electrophysiological testing. Rats were anesthetized and spinalized for extracellular recording from single spinal wide dynamic range neurons (L(3-4)). In neuropathic rats (days 11-14 and 42-52 after cuff implantation), ongoing discharge was greater and hind paw receptive field size was expanded compared to control rats. Activation of low-threshold sensory afferents by innocuous mechanical stimulation (0.2 N for 3 s) in the hind paw receptive field evoked the typical brief excitation in control rats. However, in neuropathic rats, innocuous stimulation also induced a nociceptive-like afterdischarge that persisted 2-3 min. This afterdischarge was never observed in control rats, and, in this model, is the distinguishing feature of the spinal neural correlate of tactile allodynia. Electrical stimulation of the sciatic nerve at 4 and at 20 Hz each produced an initial discharge that was identical in control and in neuropathic rats. This stimulation also produced an afterdischarge that was similar at the two frequencies in control rats. However, in neuropathic rats, the afterdischarge produced by 20-Hz stimulation was greater than that produced by 4-Hz stimulation. Given that acutely spinalized rats were studied, only peripheral and/or spinal mechanisms can account for the data obtained; as synaptic responses from C fibers begin to fail above approximately 5-Hz stimulation [Pain 46 (1991) 327], the afterdischarge in response to 20-Hz stimulation suggests a change mainly in myelinated afferents and a predominant role of these fibers in eliciting this afterdischarge. These data are consistent with the suggestion that peripheral neuropathy induces phenotypic changes predominantly in myelinated afferents, the sensory neurons that normally respond to mechanical stimulation. The NK-1 receptor antagonist, CP-99,994 (0.5 mg/kg, i.v.), depressed the innocuous pressure-evoked afterdischarge but not the brief initial discharge of wide dynamic range neurons, and decreased the elevated ongoing rate of discharge in neuropathic rats. These results support the concept that following peripheral neuropathy, myelinated afferents may now synthesize and release substance P. A result of this is that tonic release of substance P from the central terminals of these phenotypically altered neurons would lead to ongoing excitation of NK-1-expressing nociceptive spinal neurons. In addition, these spinal neurons would also exhibit exaggerated responses to innocuous pressure stimulation. The data in this study put forth a possible neurophysiological and neurochemical basis of neuropathic pain and identify substance P and the NK-1 receptor as potential neurochemical targets for its management.

[Clinical characteristics and prognostic significance of preherpetic neuralgia]

INTRODUCTION

Herpes zoster is a world-wide disease of older age commonly presenting with preherpetic pain. The aim of the study was to determine clinical characteristics of preherpetic neuralgia and its influence on occurrence of postherpetic neuralgia.

MATERIAL AND METHODS

A prospective, controlled trial included 88 patients with preherpetic neuralgia. 44 herpes zoster patients without preherpetic neuralgia were included in the control group. All of them were clinically followed-up for three months after complete healing of skin lesions.

RESULTS

Older age (> 60 years) was significantly predominant (59.1%) compared with other age groups (p < 0.01) as well as female sex (59.9%) compared with the male sex (p < 0.01). There was no significant predominance of any type of preherpetic neuralgia (stabbing, burning, itching, dull pain). More intense preherpetic pain (reported as "severe" and "moderate") was established more often than mild pain. The mean duration of preherpetic pain was 4.4 days (ranged between 1-20 days). Postherpetic neuralgia developed in 36/88 patients with preherpetic neuralgia (affecting predominantly older than 50 years of age--31/36), but there was no significant difference in proportion of postherpetic neuralgia (PHN) according to those without preherpetic neuralgia.

DISCUSSION AND CONCLUSION

People older than 60 years are the most common age group among herpes zoster patients suffering from preherpetic neuralgia. Sex distribution of patients with preherpetic pain reveals highly significant predominance of female sex. Opposite to some other authors' reports, preherpetic neuralgia and its severity have not been proven as risk factors for postherpetic neuralgia in patients involved in our trial.

The role of sympathetic nerve blocks in herpes zoster and postherpetic neuralgia

The most common complication of herpes zoster in immunocompetent patients is postherpetic neuralgia (PHN). Sympathetic blocks have been traditionally used for patients with herpes zoster and PHN with three different therapeutic goals: pain relief during acute herpes zoster, pain relief during PHN, and prevention of PHN by treating patients with acute zoster. The role of sympathetic blocks in herpes zoster and PHN remains controversial due to methodologic shortcomings in published studies and the limited current understanding of the role of the sympathetic nervous system in mediating pain. Current theories of the pathophysiology of PHN, the role of the sympathetic nervous system in herpes zoster and PHN, and published studies investigating use of sympathetic nerve blocks in herpes zoster and PHN are reviewed.