Risk Factor and Prevention of Postherpetic Neuralgia.

Herpes zoster (HZ) and postherpetic neuralgia (PHN) are common diseases in a pain clinic. In Korea, the rate of clinical visits due to the incidence of herpes zoster was 7.93-12.54/1000 annually [1]. PHN is a painful neuropathy and the most common complication of HZ. A complete recovery from PHN is difficult for doctors despite of proper HZ treatment. In spite of the treatment, some patients suffered from severe PHN for several years. Therefore, the most important aspects are the risk factor of PHN and the method of prevention of PHN.

In this issue of the Korean Journal of Pain (KJP), Jung et al. [2] reported the incidence of HZ in Cheonan, Korea. The results show that patients 50 years and older have a higher incidence of HZ, and the most common site of HZ was the thoracic nerve (47.9%), followed by the trigeminal nerve (21.4%). The incidence rate was similar to the affected site of PHN (thoracic area: 52.9%, trigeminal area: 15.6%) in Korea [3]. In patients who suffer from HZ, the risk factors of PHN are old age, presence of a painful prodrome, severe pain of HZ, severe rash, and immuno-compromised status [456]. In patients with HZ over 60 years, up to 25% progressed to PHN [7]. The proportion of PHN increases steadily from young ages up to 80-84 years [8]. Therefore, patients who are elderly and possess the risk factor with HZ must undergo more intensive treatment. The main treatment of HZ is medication and interventional therapy. Taking antiviral medication beginning within 72 hrs of rash onset is usually recommended [7910]. Two meta-analyses suggest that the antiviral medication can reduce the overall duration of pain and incidence of PHN [1112]. Epidural injection with a steroid within 2 months of HZ development is also recommended for the prevention of PHN [13].

In the previous survey of Korea, epidural injection was the most commonly performed interventional treatment in PHN patients [3]. Other interventions such as paravertebral block, peripheral block and sympathetic block are clinically effective for the treatment of HZ and PHN. For evidence-based medicine of interventional treatment of HZ and PHN, the investigations of randomized controlled trials regarding the interventions will be necessary.

In this issue, Jeon et al. [10] described the prevention and treatment of HZ and PHN. They mention that vaccination against varicella zoster virus (VZV) can be the first line for the prevention of HZ and PHN. A previous review article reported that vaccination of VZV reduced morbidity from HZ and PHN [14].

Vaccination of VZV reduced the occurrence of herpes zoster by approximately 70% in individuals aged 50-59 years old [15]. In persons 60 years or older, the vaccination reduced the burden of illness from HZ by 61.1% and the risk of PHN by 66.5% [16]. Therefore, the vaccination of patients over 50 years old can be effective for the prevention of HZ and PHN.

Although PHN is difficult to treat, early and intensive treatment of patients with HZ can reduce the occurrence of PHN. In healthy elderly people, a vaccination of VZV can also decrease the incidence of HZ and PHN.