Effects of acyclovir on sensory axonal neuropathy, segmental motor paresis and postherpetic neuralgia in herpes zoster patients

An Ultrasonographic Evaluation for the Early Detection of Nerve Root Changes in Herpes Zoster-associated Motor Paresis

We herein report a case of herpes zoster complicated by right-arm paralysis, wherein cervical nerve root ultrasonography enabled the early diagnosis and a therapeutic efficacy evaluation. A 71-year-old man developed progressive weakness in the muscles innervated by the right C5-6 nerve root following the appearance of a painful rash. Cervical nerve root ultrasonography revealed C5-6 nerve root inflammatory swelling. Methylprednisolone pulse therapy and subsequent oral prednisolone therapy gradually improved the muscle weakness. At three weeks following admission, ultrasonography revealed C5-6 nerve root inflammatory swelling improvement. Ultrasonography may aid in the early detection of nerve root inflammatory swelling and help monitor treatment efficacy.

Pain Fluctuations of Women with Subacute Herpetic Neuralgia During Local Methylcobalamin in Combination with Lidocaine Treatment: A Single-Blinded Randomized Controlled Trial

Purpose

To evaluate the efficacy and pain fluctuations of methylcobalamin in combination with lidocaine local injection treatment for subacute herpetic neuralgia (SHN).

Methods

Seventy-nine women (60.4 ± 2.7 years) with thoracic SHN were enrolled and randomized to receive a combination of methylcobalamin and lidocaine local injection (MI, N=40), or a combination of lidocaine patch 5% and oral methylcobalamin (PO, N=39) for four weeks. Repeated-measures analyses of variance were used to evaluate the effect on pain levels. Generalized estimation equations were used to analyze the cause-effect relationship between pain fluctuations and influencing factors.

Results

At the treatment endpoint, the group, treatment time, and group interacted with treatment time effects of the pain scores and area were statistically significant (P<0.001), The pain scores were 2.9 ±0.9 (MI) and 4.3 ± 1.5 (PO). 80.00% (MI) or 28.21% (PO) of patients had pain scores ≤ 3, the odds ratio was 2.84 (95% CI: 1.68 to 4.79). The incidence of postherpetic neuralgia was 5.0% (2/40) at 3 months. Pain fluctuated repeatedly during treatment. The pain fluctuation increased from 8.75 log folds in the afternoon, to 79.85 log folds at night. With the ADLs level increasing from 1 to 3, the pain fluctuated from 4.28 to 17.70 log folds. Allodynia, itching, sleep quality, and ADLs were the significant influencing factors (P<0.05).

Conclusion

This study validated the efficacy of methylcobalamin combined with lidocaine for SHN, and confirmed that pain levels in patients with SHN had an obvious circadian rhythm. ADLs were an important cause of pain fluctuations.

Claw Hand Deformity: A Rare Complication of Herpes Zoster

Distal upper extremity weakness is a rare complication after herpes zoster, which can be easily misdiagnosed by other nerve entrapment syndromes. We present a 31-year-old immunocompromised woman who developed a claw-like deformity of her right hand after full medical treatment and resolution of herpes zoster. The electrodiagnostic finding was compatible with right multiple mononeuropathies of the median and ulnar nerves, ongoing axonal loss, unlike the nerve entrapment patterns. The early recognition and early electrodiagnosis of herpes zoster-induced distal motor weakness, especially in the upper extremity, is necessary to exclude the nerve entrapment syndrome and to be the baseline for functional motor recovery prediction. The prognosis of functional motor recovery is considered good but may take months to years to accomplish. Rehabilitation management plays an important role after full medical treatment.

Pharmacological and non-pharmacological strategies for preventing postherpetic neuralgia: a systematic review and network meta-analysis

Background

Postherpetic neuralgia (PHN) is a refractory complication of herpes zoster (HZ). To prevent PHN, various strategies have been aggressively adopted. However, the efficacy of these strategies remains controversial. Therefore, we aimed to estimate the relative efficacy of various strategies used in clinical practice for preventing PHN using a network meta-analysis (NMA).

Methods

We performed a systematic and comprehensive search to identify all randomized controlled trials. The primary outcome was the incidence of PHN at 3 months after acute HZ. We performed both frequentist and Bayesian NMA and used the surface under the cumulative ranking curve (SUCRA) values to rank the interventions evaluated.

Results

In total, 39 studies were included in the systematic review and NMA. According to the SUCRA value, the incidence of PHN was lower in the order of continuous epidural block with local anesthetics and steroids (EPI-LSE), antiviral agents with subcutaneous injection of local anesthetics and steroids (AV + sLS), antiviral agents with intracutaenous injection of local anesthetics and steroids (AV + iLS) at 3 months after acute HZ. EPI-LSE, AV + sLS and AV + iLS were also effective in preventing PHN at 1 month after acute HZ. And paravertebral block combined with antiviral and antiepileptic agents was effective in preventing PHN at 1, 3, and 6 months.

Conclusions

The continuous epidural block with local anesthetics and steroid, antiviral agents with intracutaneous or subcutaneous injection of local anesthetics and a steroid, and paravertebral block combined with antiviral and antiepileptic agents are effective in preventing PHN.

Zoster-associated limb paralysis mimicking acute stroke: a case report

Background

Varicella zoster virus is a Deoxyribonucleic acid (DNA) virus exclusively affecting humans. Reactivation of varicella zoster virus causes herpes zoster with vesicular eruptions in a restricted dermatomal distribution. Peripheral motor neuropathy is a very rare complication of varicella zoster virus.

Case presentation

A 57-year-old previously well Sri Lankan female presented with acute onset painful weakness of the left upper limb with a preceding history of a febrile illness. Subsequently she developed vesicular eruptions in the dermatomal distribution of cervical 5, 6, and 7. Electromyography was suggestive of acute denervation of cervical 5, 6, and 7 myotomes. Diagnosis of zoster-associated brachial plexopathy was made, and the patient was treated with acyclovir, steroids, and analgesics. She made a good recovery.

Conclusion

Brachial plexus neuritis due to varicella zoster infection should be considered in an acute monoparesis of a limb as it is a treatable and reversible condition

Complete recovery of herpes zoster radiculopathy based on electrodiagnostic study: A case report

BACKGROUND

Herpes zoster is a painful infectious disease caused by the varicella zoster virus. Herpes zoster radiculopathy, which is a type of segmental zoster paresis, can complicate the disease and cause motor weakness. This complication should be considered when a patient with a rash complains of acute-onset motor weakness, and the diagnosis can be verified via electrodiagnostic study.

CASE SUMMARY

A 64-year-old female with a history of asthma presented to the emergency department with stabbing pain, an itching sensation, and a rash on the right anterior shoulder that had begun 5 d prior. Physical examination revealed multiple erythematous grouped vesicles in the right C4-5 and T1 dermatome regions. Because herpes zoster was suspected, the patient immediately received intravenous acyclovir. On the third hospital day, she complained of motor weakness in the right upper extremity. Magnetic resonance imaging of the cervical spine revealed mild intervertebral disc herniation at C4-C5 without evidence of nerve root compression. On the 12^th hospital day, electrodiagnostic study revealed right cervical radiculopathy, mainly in the C5/6 roots. Six months later, monoparesis resolved, and follow-up electrodiagnostic study was normal.

CONCLUSION

This case emphasizes that clinicians should consider the possibility of post-herpetic paresis, such as herpes zoster radiculopathy, and that electrodiagnostic study is useful for diagnosis and follow-up.

Segmental zoster paresis of unilateral upper extremity: A case report and literature review

RATIONALE

Segmental zoster paresis (SZP) is a relatively rare neurologic complication of herpes zoster (HZ), and is characterized by focal asymmetric motor weakness in the myotome that corresponds to skin lesions of the dermatome. The upper extremities are the second most commonly involved regions after the face, and predominantly involve proximal muscles. The pathogenesis of SZP remains unclear; however, most of the reports indicate that it is the inflammation because of the spread of the herpes virus.

PATIENT CONCERNS

A 72-year-old man without trauma history of the left shoulder joint developed weakness of the left proximal upper extremity 10 days after vesicular eruption of HZ.

DIAGNOSES

His left shoulder girdle paresis was diagnosed with the upper truncus of the brachial plexus as a HZ complication according to a series of tests, including cervical magnetic resonance imaging (MRI), cerebral fluid analysis, sonography, and electrophysiological studies.

INTERVENTIONS

Acyclovir and prednisolone were administered during hospitalization to treat SZP. Meanwhile, analgesics and gabapentin were administered to control the patient's neuralgic pain. He also received inpatient (daily) and outpatient (3 times per week) physical therapy along with range of motion and strengthening exercises.

OUTCOMES

Partial improvement of the strength of the left shoulder girdle, and no improvement of the left deltoid muscle was observed 2 months after the interventions.

LESSONS

This case emphasizes that HZ infections may be complicated by segmental paresis and they should be considered in the differential diagnosis of acute paresis in the upper limb. Awareness of this disorder is important because it avoids unnecessary invasive investigations and interventions, leading to suitable treatments with favorable prognosis.

Antiviral treatment for preventing postherpetic neuralgia

BACKGROUND

Postherpetic neuralgia (PHN) is a painful and refractory complication of herpes zoster. Treatments are either partially or totally ineffective for many people with PHN. Antiviral agents, used at the time of the rash, have been proposed as an intervention to prevent the development of PHN. This is the first update since the first publication of the review in 2009.

OBJECTIVES

To assess the effectiveness of antiviral agents in preventing PHN.

SEARCH METHODS

On 26 April 2013, we updated the searches in the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, EMBASE, LILACS, and the Chinese Biomedical Retrieval System. We checked the references of published studies to identify additional trials, and contacted authors to obtain additional data. We searched other databases in The Cochrane Library for information for the Discussion and two clinical trials registries for ongoing trials.

SELECTION CRITERIA

We considered all randomised controlled trials (RCTs) of antiviral treatment given within 72 hours after the onset of herpes zoster for preventing PHN. There were no language restrictions.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials, evaluated the risk of bias in included trials, and extracted and analysed data.

MAIN RESULTS

Six RCTs with a total of 1211 participants were eligible; five trials evaluated oral aciclovir, and one, with 419 participants, evaluated oral famciclovir. We were able to conduct meta-analyses as there were sufficient similarities in the included studies, such as the reporting of the presence of PHN, duration of rash before treatment initiation and treatment regimen. For our primary outcome, based on three trials (609 participants) we found no significant difference between the aciclovir and control groups in the incidence of PHN four months after the onset of the acute herpetic rash (risk ratio (RR) 0.75, 95% confidence interval (CI) 0.51 to 1.11), nor was there a significant difference at six months (RR 1.05, 95% CI 0.87 to 1.27, two trials, 476 participants). In four of the trials (692 participants), there was some evidence for a reduction in the incidence of pain four weeks after the onset of rash. In the trial of famciclovir versus placebo, neither 500 mg nor 750 mg doses of famciclovir reduced the incidence of herpetic neuralgia significantly. The most commonly reported adverse events were nausea, vomiting, diarrhoea and headache for aciclovir, and headache and nausea for famciclovir. For neither treatment was the incidence of adverse events significantly different from placebo. None of the studies were at high risk of bias, although the risk of bias was unclear in at least one domain for all but one study. We found no new RCTs when we updated the searches in April 2013.

AUTHORS' CONCLUSIONS

There is high quality evidence that oral aciclovir does not reduce the incidence of PHN significantly. In addition, there is insufficient evidence to determine the effect of other antiviral treatments; therefore, further well-designed RCTs are needed to investigate famciclovir or other new antiviral agents in preventing PHN. Future trials should pay more attention to the severity of pain and quality of life of participants, and should be conducted among different subgroups of people, such as people who are immunocompromised.

Herpes zoster virus: an unusual but potentially treatable cause of sciatica and foot drop

The herpes zoster virus is a rare but potential cause of acute motor weakness. This article describes 2 patients with drop foot secondary to an infection of varicella zoster who were incorrectly referred to an orthopedic clinic from their general practitioners. The first patient was a 74-year-old man who presented with weakness in the right foot and a vesicular rash. The pattern of disease supported the clinical diagnosis of shingles affecting the L5 motor and sensory division. No investigation was required, and the patient was treated with a foot drop splint. The second patient was a 71-year-old man who presented with right leg and foot weakness and a vesicular rash affecting his right buttock and posterior right thigh. Lumbar magnetic resonance excluded a stenotic lesion; electrophysiological studies supported the diagnosis of a lower motor neuron lesion. The patient was treated with a 1-week course of acyclovir and a foot drop splint. The correct diagnosis will aid in correct referral and will prompt management, which will potentially provide a faster and better outcome for the patient.

Monoparesis secondary to herpes zoster

We describe a 90-year-old woman with right upper limb monoparesis secondary to varicella zoster virus infection as a result of extensive inflammatory involvement of the entire brachial plexus at root level. To our knowledge, this is the first report of entire brachial plexus involvement in a living patient of such advanced age. Despite a delay in presentation and thus initiation of treatment, a favourable clinical response was observed.

Antiviral treatment for preventing postherpetic neuralgia

BACKGROUND

Postherpetic neuralgia (PHN) is a painful and refractory complication of herpes zoster. Treatments are either partially or totally ineffective for many people with PHN. Antiviral agents, used at the time of the rash, are one of the best-established approaches that may prevent the development of PHN.

OBJECTIVES

To investigate the effectiveness of antiviral agents in preventing PHN.

SEARCH STRATEGY

We searched the Cochrane Neuromuscular Disease Group Trials Register (January 13 2009), the Cochrane Central Register of Controlled Trials (The Cochrane Library 2008, Issue 4), MEDLINE (January 1966 to November Week 3 2008), EMBASE (January 1980 to Week 02 2009), LILACS (January 1982 to 13 January 2009), and the Chinese Biomedical Retrieval System (January 1978 to 13 January 2009). We checked the references of published studies to identify additional trials.

SELECTION CRITERIA

All randomised and quasi-randomised controlled trials for antiviral treatment given within 72 hours after the onset of herpes zoster for preventing PHN irrespective of any language restrictions.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials and evaluated the methodological quality, then extracted and analysed data from the included trials.

MAIN RESULTS

Twenty trials were identified. Twelve trials were excluded and two trials are awaiting classification. Six randomised controlled trials, with a total of 1211 participants were eligible; five trials evaluated oral acyclovir, and one trial with 419 participants evaluated oral famciclovir. There was no significant difference between the oral acyclovir and control groups on the incidence of PHN four months (risk ratio (RR), 0.75; 95% CI 0.51 to 1.11; P = 0.15) or six months (RR 1.05, 95% CI 0.87 to 1.27; P = 0.62) after the onset of the acute herpetic rash. There was some evidence for a reduction in the incidence of pain four weeks after the onset of rash. In the trial of famciclovir versus placebo, neither 500 mg and 750 mg doses of famciclovir reduced the incidence of herpetic neuralgia significantly.

AUTHORS' CONCLUSIONS

Oral acyclovir did not reduce the incidence of PHN significantly. There is insufficient evidence from randomised controlled trials to determine whether other antiviral treatments prevent PHN. Additional well-designed, randomised controlled trials of famciclovir or other new antiviral agents, with a greater number of participants are needed. Future trials should pay more attention to the severity of pain and quality of life of participants, and should be conducted among different subgroups of people, such as people who are immunocompromised.

Segmental zoster paresis of limbs: report of three cases and review of literature

OBJECTIVES

Segmental zoster paresis is a relatively rare complication characterized by focal motor weakness, which may occur in limbs affected by herpes zoster. We demonstrate the clinical characteristics of segmental zoster paresis by reviewing the cases of 138 patients, including 3 of our patients.

CASE REPORT AND REVIEW SUMMARY

We report 3 patients with zoster paresis of the limbs. Patients 1 and 3 showed motor weakness in the left shoulder and arm after developing a herpetic rash in the left C5-C6 dermatomes. Patient 2 showed weakness in the right thigh and groin after a right L2-L3 herpetic eruption. The electromyograms of all 3 patients showed abnormal spontaneous activity in the affected muscles. Intravenous acyclovir and corticosteroid pulse therapy were added to oral antiviral drugs for patients 1 and 2. All 3 patients recovered favorably. Our review of the literature revealed that antiviral treatment may prevent the occurrence of zoster paresis; however, there is insufficient evidence to show what treatment hastens recovery from zoster paresis.

CONCLUSIONS

Segmental zoster paresis is still underrecognized by neurologists. Awareness of this disorder is important because it may eliminate unnecessary invasive investigations and lead to appropriate treatment. Further studies on the treatment are necessary.

Isolated double herpes zoster paresis involving the left facial nerve and the right peroneal nerve following disseminated herpes zoster

A 72-year-old Japanese male developed disseminated herpes zoster and could not easily walk due to right drop foot and pain. He soon developed numbness and pain on the left side of his face, and noticed difficulty closing his left eye. The left angle of his mouth dropped. The patient was diagnosed as having a double mononeuropathy (a left facial nerve paresis and a right peroneal nerve paresis) following disseminated herpes zoster. Given that the patient was elderly and had diabetes mellitus, the patient appeared to be an immunocompromised host. We also describe other rare complications of herpes zoster from the published work.

Segmental Zoster Paresis of the Upper Extremity: A Case Report

Segmental zoster paresis, a rare complication of herpes zoster, is characterized by focal, asymmetric motor weakness in the myotome that corresponds to the dermatome of the rash. The pathogenesis of segmental zoster paresis is inflammation caused by the spread of the herpes virus. Motor damage may affect the root, plexus, or peripheral nerve. A woman in her early seventies with right shoulder pain and shoulder girdle muscle weakness was diagnosed with involvement of the C5-7 motor roots and upper truncus of the brachial plexus as a complication of herpes zoster. Recognition of herpes zoster as a cause of acute motor weakness is important in avoiding unnecessary interventions as well as in determining the treatment and outcome of the patient. This case is presented to emphasize that herpes zoster infection may be complicated by segmental paresis, which should be considered in the differential diagnosis of acute painful motor weakness of the upper extremity.

Herpes zoster sciatica with paresis preceding the skin lesions. Three case-reports

We report three cases of herpes zoster sciatica with motor loss preceding the typical skin lesions. Serological tests and cerebrospinal fluid examination established the diagnosis. Two patients had residual motor loss after 1 and 3 months, respectively. Immunodepression and other risk factors should be looked for routinely. Early diagnosis and treatment may improve the prognosis. Tests for antibodies or viral DNA in cerebrospinal fluid can be helpful, although negative results do not rule out the diagnosis.

Pharmacological management of postherpetic neuralgia

Postherpetic neuralgia, which occurs most typically in older persons, is one of the most common and serious complications of herpes zoster (or shingles). It is a chronic neuropathic pain syndrome and remains one of the most difficult pain disorders to treat. Known beneficial agents include antidepressants, antiepileptic drugs, opioid analgesics, local anaesthetics, capsaicin and other, less applied, modalities. Although monotherapy is commonly applied, no single best treatment for postherpetic neuralgia has been identified; nevertheless, gabapentin (antiepileptic) and transdermal lidocaine (anaesthetic) are often used as the first-choice treatments. Recent research has shed light on possible pain mechanisms as well as new avenues of treatment, which are discussed in the article. For patients with pain that is not adequately controlled, individualised treatment plans must be pursued. It is critical to recognise that postherpetic neuralgia, while difficult to manage, can be a treatable neuropathic pain syndrome.

Factors influencing the features of postherpetic neuralgia and outcome when treated with tricyclics

This paper retrospectively reviews features of postherpetic neuralgia (PHN) in up to 279 personal patients in relation to treatment outcome when treated with tricyclic antidepressants (TCAs). Factors affecting characteristics of PHN: (i) Patients with allodynia (89%) and/or burning pain (56%) have a much higher visual analogue pain intensity score than those without; (ii) Acyclovir (ACV) given for acute shingles (HZ) does not reduce the incidence of subsequent PHN, but reduces the pain intensity in PHN patients with allodynia; (iii) ACV given for acute HZ reduces the incidence of burning pain in subsequent PHN, but not of allodynia; (iv) ACV given for acute HZ reduces the incidence of clinically detectable sensory deficit in subsequent PHN. Factors affecting outcome of TCA-treated PHN: (i) The point in time at which TCA treatment is commenced is by far the most critical factor: started between 3 and 12 months after acute HZ onset, more than two-thirds obtain pain relief (NNT=1.8); between 13 and 24 months, two-fifths (41%) (NNT=3.6); and more than two years, one-third (NNT=8.3). Background and paroxysmal pain disappear earlier and are more susceptible of relief than allodynia. (ii) Twice as many (86%) of PHN patients without allodynia obtain pain relief with TCA treatment than those with (42%); (iii) the use of ACV for acute HZ more than halves the time-to-relief of PHN patients by TCAs; (iv) PHN patients with burning pain are significantly less likely to obtain pain relief with TCAs than those without (p<0.0001).

Herpes zoster of the head and limbs: electroneuromyographic and clinical findings in 158 consecutive cases

OBJECTIVES

To quantify electromyographic and neurographic changes and to correlate them with the clinical data of outpatients with herpes zoster.

DESIGN

Prospective case series.

SETTING

Outpatient department.

PATIENTS

A consecutive, unselected series of 158 outpatient cases (88 women, 70 men; mean age, 64y) of herpes zoster of the head and limbs.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Blink reflex and electromyography and motor and sensory nerve conduction velocities of nerves and muscles corresponding to affected dermatomes.

RESULTS

Postherpetic neuralgia (PHN), segmental zoster paresis, and polyneuropathy were found in 31%, 19%, and 2.5% of cases, respectively. Absence or reduction of sensory action potential amplitudes, blink reflex areas, and compound muscle action potential amplitudes were found in 60%, 31%, and 18% of cases, respectively. Sensory and motor conduction velocities and motor and blink reflex latencies were nearly always normal or only slightly slowed. Electromyographic signs of abnormal spontaneous activity were found in 36% of the cases. Electrophysiologic alterations were correlated among themselves, with age, with presence of segmental zoster paresis, and with absence of antiviral therapy. The extent of the skin rash (number of dermatomes affected by herpes zoster) was the only variable predictive of disappearance or improvement of PHN.

CONCLUSIONS

Sensory axonal neuropathy, often associated with similar motor involvement, can be shown by classical electrophysiologic methods in herpes zoster. The severity of damage to motor fibers was related to damage to sensory fibers, but no relation was found between peripheral axon damage and PHN. The site of motor system damage may be the ventral roots, plexus, or peripheral nerve. The probability of complications and the severity of sensory and motor peripheral axonal damage were increased in older patients. Appropriate antiviral therapy seems to reduce the incidence of segmental zoster paresis and the severity of damage to the peripheral fibers. A reduced extent of herpetic rash was the only factor to correlate with a good outcome of PHN.

Current pharmacological approaches to the therapy of varicella zoster virus infections: a guide to treatment

Varicella zoster virus (VZV), a member of the herpesvirus family, is responsible for both primary (varicella, chickenpox) as well as reactivation (zoster, shingles) infections. In immunocompetent patients, the course of varicella is generally benign. For varicella zoster, post-herpetic neuralgia is the most common complication. In immunocompromised patients (particularly those with AIDS), transplant recipients and cancer patients, VZV infections can be life-threatening. For these patients and also for immunocompetent patients at risk such as pregnant women or premature infants, the current treatment of choice is based on either intravenous or oral aciclovir (acyclovir). The low oral bioavailability of aciclovir, as well as the emergence of drug-resistant virus strains, have stimulated efforts towards the development of new compounds for the treatment of individuals with VZV infections. Among these new compounds, penciclovir, its oral prodrug form famciclovir and the oral pro-drug form of aciclovir (valaciclovir), rank among the most promising. As with aciclovir itself, all of these drugs are dependent on the virus-encoded thymidine kinase (TK) for their intracellular activation (phosphorylation), and, upon conversion to their triphosphate form, they act as inhibitors/alternative substrate of the viral DNA polymerase. Therefore, cross-resistance to these drugs may be expected for those virus mutants that are TK-deficient and thus resistant to aciclovir. Other classes of nucleoside analogues dependent for their phosphorylation on the viral TK that have been pursued for the treatment of VZV infections include sorivudine, brivudine, fialuridine, fiacitabine and netivudine. Among oxetanocins, which are partially dependent on viral TK, lobucavir is now under clinical evaluation. Foscarnet, which does not require any previous metabolism to interact with the viral DNA polymerase, is used in the clinic when TK-deficient VZV mutants emerge during aciclovir treatment. TK-deficient mutants are also sensitive to the acyclic nucleoside phosphonates (i.e. [s]-1-[3-hydroxy-2-phosphonylmethoxypropyl]cytosine; HPMPC); these agents do not depend on the virus-encoded TK for their phosphorylation but depend on cellular enzymes for conversion to their diphosphoryl derivatives which then inhibit viral DNA synthesis. Vaccination for VZV has now come of age. It is recommended for healthy children, patients with leukaemia, and patients receiving immunosuppressive therapy or those with chronic diseases. The protection induced by the vaccine seems, to some extent, to include zoster and associated neuralgia. Passive immuniatin based on specific immunoglobulins does not effectively prevent VZV infection and is therefore restricted to high risk individuals (i.e. immunocompromised children and pregnant women).