eMedicine Specialties > Neurology > Neurological Infections

Varicella Zoster

Author: Wayne E Anderson, DO, Assistant Professor of Internal Medicine/Neurology, Western University of Health Sciences; Assistant Professor of Family Medicine, Touro University College of Osteopathic Medicine; Consulting Staff in Pain Management, Department of Neurology, California Pacific Medical Center
Contributor Information and Disclosures

Updated: Aug 30, 2007

Introduction

Background

Herpes zoster presents in many ways. It should not be considered simply a self-limited dermatomal rash with pain. Varicella-zoster virus (VZV) infection is an acute neurologic disease that warrants immediate evaluation. A common misperception is that VZV always is a benign disorder.

Following initial infection, usually as chickenpox in childhood, VZV remains dormant in the dorsal spinal root ganglion neurons and the fifth cranial nerve ganglion neurons. Upon reactivation, a spectrum of signs and symptoms can occur, including a self-limited painful rash, pain without skin manifestations, keratitis, vertigo, and spinal cord disease with weakness. Once VZV infection resolves, many individuals continue to suffer pain, a condition known as postherpetic neuralgia (PHN).

Pathophysiology

VZV remains latent in the dorsal root ganglia after an initial infection (chickenpox). Host immunologic mechanisms suppress replication of the virus, but VZV reactivates when the host mechanisms fail to contain the virus. This occurs from a wide spectrum of issues, from stress to severe immunosuppression. Occasionally this follows direct trauma. VZV viremia occurs frequently with chickenpox but also may occur with herpes zoster, albeit with a lower viral load. The virus migrates from the sensory root and produces a dermatomal sensory loss and a characteristic painful rash.

Inflammatory involvement may include the leptomeninges. When the cervical and lumbar roots are involved, motor involvement (which often is overlooked) may be seen, depending on the virulence and/or extent of migration.

VZV is a DNA virus. The viral genome encodes approximately 70 proteins. Once activated at the spinal root or cranial nerve neurons, an inflammatory response occurs that also encompasses the leptomeninges. Both plasma cells and lymphocytes are noted. In at least one case of motor neuron involvement, lymphocytic infiltration and myelin breakdown were observed with preservation of axons.

Frequency

United States

Incidence is approximately 5 per 1000 per year. Immunosuppression increases risk. The incidence of PHN increases with age. Half of patients older than 60 years may have a temporary or prolonged pain syndrome. Although 50% or more of patients with PHN may have resolution of the pain within 1-2 years, the remainder may have a continuing pain syndrome. Fortunately newer treatments are available for PHN. 

Although the frequency of varicella zoster may decrease as the vaccinated children grow to adulthood, the present frequency of varicella zoster in adults may be increasing.

International

The international frequency is the same as for the United States.

Mortality/Morbidity

Ninety-five percent of patients with zoster experience severe pain. The acute pain and insomnia are most bothersome.

• Variant presentations of zoster (eg, keratitis, myelitis) may carry additional morbidity.
• Duration of symptoms, incidence of complications and duration of post-herpetic neuralgia if it should occur, are longer in immunocompromised patients.
• Complications may occur. For example, staphylococcal and streptococcal bacteria may superinfect the skin lesions and require treatment.

Race

Although the pathophysiology is uncertain, the vesicular eruption may be less frequent in African Americans. The reason is not clear.

Sex

• Prevalence in males and females is equal.
• Ertunc and colleagues suggested both that zoster frequency is higher in right-handed patients and that the rash appears more frequently on the left side in females.¹ The pathophysiology for these differences is uncertain.

Age

• Although zoster can occur at any age after primary infection, incidence increases with age. Also troublesome is the increasing incidence of PHN with advancing age.

Clinical

History

During the prodromal phase, paresthesias and pain may present a diagnostic dilemma; however, the dermatomal distribution helps clarify the diagnosis.

• Goh and Khoo studied 164 patients with zoster and recorded the frequency of prodromal symptoms: 41% had pain (more common in patients older than 50 years), 27% had itching, and 12% had paresthesias.²
• Once the typical rash erupts, the diagnosis is easier, but zoster has various presentations. Goh and Khoo reported the frequency of active disease symptoms: 90% had pain, 20% had feelings of helplessness and depression, and 12% had flu-like symptoms.²
• Zoster may have atypical presentations. Cases of unilateral headache, the appearance of an ocular chemical burn, and facial palsy have been reported in the literature.

Physical

• Shingles
  • Shingles refers to the painful rash associated with reactivated VZV infection; it typically affects a single dermatome, most commonly a thoracic dermatome. After a prodromal illness, erythematous macules and papules appear and progress to vesicles within 1 day. The lesions eventually crust and resolve. Patients may experience pain and sensory loss in the distribution of the rash. Motor weakness, especially in lumbar and cervical radicular distributions, is often present but not appreciated and represents viral activity beyond the sensory root. Because the weakness often is not diagnosed accurately, the incidence and prevalence are uncertain.
  • Note that zoster may present in multiple dermatomes and possibly bilaterally (ie, zoster multiplex). The frequency of multiple, disseminated, and visceral zoster is increased in the immunocompromised population. Occasionally, patients experience paresthesias and pain in a dermatomal distribution without a rash (ie, zoster sine herpete).
• Zoster multiplex
  • Zoster occurring in noncontiguous dermatomes is rare, even in immunocompromised individuals. Terminology depends on whether the condition is unilateral or bilateral and on the number of involved dermatomes.
  • For example, zoster duplex unilateralis refers to the involvement of 2 unilateral dermatomes. Vu and colleagues report one case of zoster multiplex involving 7 noncontiguous dermatomes.
• Myelitis and encephalitis
  • Be aware of possible VZV myelitis. Devinski and colleagues report spinal cord involvement in immunosuppressed persons.³ The condition emerges as the expected dermatomal rash.
  • Spinal cord involvement becomes apparent within 2-3 weeks from the initial rash with myelopathic findings on examination. Manifestations are usually bilateral. The disease may progress for 3 weeks, although a few cases of progression for as long as 6 months have been reported in patients with AIDS. Recurrent zoster myelitis is rare, although one case has been reported of a previously healthy young woman who developed recurrent myelopathy at the same spinal level. The condition resolved fully with intravenous (IV) acyclovir treatment.
  • Rarely, VZV may cause encephalitis. Westenend and Hoppenbrouwers reported fatal hemorrhagic encephalitis in an otherwise healthy woman.⁴
  • Myelitis and encephalitis may occur in previously healthy individuals.
• Ramsay-Hunt syndrome
  • If the geniculate ganglion is involved, this syndrome of peripheral facial palsy with pain and vesicles in the ear may occur.
  • The vesicles are noted in the external ear canal or on the tympanic membrane; additional auditory and vestibular symptoms may be present.
• Keratitis
  • Ocular involvement occurs when the ophthalmic division of the trigeminal nerve is involved in the viral reactivation (see Media file 1).
  • Complications range from corneal ulcers to conjunctivitis to blindness.
  • Occasionally, no vesicles are seen (ie, zoster sine herpete).
  • Svozilkova and colleagues report one case of varicella-caused retinal necrosis after ocular trauma.⁵
• Zoster sine herpete
  • VZV reactivation may occur without cutaneous vesicles. In such cases, patients may experience pain and weakness in a dermatomal distribution but have no visible signs of shingles.
  • Furuta and coworkers noted that VZV may be demonstrated in 8-25% of patients with acute peripheral facial palsy without cutaneous vesicles.⁶
  • This condition presents a diagnostic dilemma; however, VZV DNA may be detected by polymerase chain reaction (PCR) from oropharyngeal swabs in patients with zoster peripheral facial palsy. Because such studies are not routine, the true incidence and prevalence are unknown.
• Brachial plexus neuritis
  • Fabian and colleagues reported one patient who had a left upper arm monoplegia after a C4, C5, and C6 zoster multiplex.
  • The authors believed that the brachial plexus inflammation was an extension of a dorsal ganglionitis. They found that the motor neuropathy was an inflammatory demyelinating process.

Causes

Risk of typical shingles and atypical presentations (eg, myelitis, encephalitis, disseminated disease, visceral involvement) is increased in immunosuppressed patients.

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