A 64-year-old lady suffering from rheumatoid arthritis on disease-modifying drugs complained of shooting pain in the left thigh and leg. Initially, she took NSAID which was not very helpful. A telephonic opinion from the doctor suggested possible sciatica. However, she was perturbed when she found few crops of rash over the thigh region. She thought it to be due to either allergy to one of the medications or an insect bite. The next day the rash started spreading and she consulted our medical team. Examination revealed vesicular rash over the left thigh which was excruciatingly painful. There was no neurological deficit and the straight leg raising test was normal.
DIAGNOSIS: Herpes zoster infection of the L3 L4 segment.
Herpes zoster infection is a common clinical condition encountered in clinical practice. Sometimes it is misdiagnosed as an allergic reaction. insect bite etc. by an inexperienced clinician leading to delay in commencing specific treatment.
Varicella zoster (VZT causes two distinct clinical entities — chickenpox and herpes zoster. Chickenpox is a common condition in childhood characterized by vesicular rash while herpes zoster usually presents in the middle or old age with painful vesicular rash unilaterally restricted to specific dermatomal distribution of VZV virus resulting in Herpes zoster in later years. The exact mechanism is unknown: however it is presumed that following chickenpox, the virus may remain latent in the dorsal root ganglion from where it may reactivate later on.
- Classically it is distributed over a particular dermatomal segment. However, dermatomal overlap, although uncommon, may occur.
- The lesions are vesicular initially with scab formation later on.
- In immune competent patients, it does not cross the midline. If the lesions are bilateral, one should consider immuno-compromised state like —
- Diabetes mellitus
- Underlying malignancy like leukaemia, lymphoma, chronic lymphatic leukaemia
- Long-term steroid therapy
- HIV infection
Any dermatome can be involved. Involvement of ophthalmic division of trigeminal nerve is a potentially serious condition as there is 50% chance of involvement of the eyes.
Herpes zoster should be considered in any painful unilaterally distributed vesicular lesion involving a particular dermatome.
differential diagnosis of vesicular rash:
- Herpes zoster — usually unilateral
- Chicken pox
- Disseminated Herpes simplex in atopic patients
- Coxsackievirus infection
- Echo virus infection
- Atypical measles
- Rickettsial pox — There is a herald spot at the site of mite bite.
Treatment instituted within 72 hours of vesicle formation may reduce the severity of pain and duration of the illness. Specific treatment beyond 72 hours may not be of much help unless there is the development of fresh crops of vesicles indicating ongoing infection. Timely intervention may also reduce postherpetic neuralgia.
The specific antiviral medication is acyclovir (800 mg 5 times a day for 7 days). Other antivirals that can be used are famciclovir (500 mg thrice daily X 7 days) or valacyclovir (1000 mg twice daily X 7 days). They are all equipotent but the newer drugs have better user-friendly dose schedules. There is no role of topical anti-viral agents in the treatment. Drugs must be used as soon as possible in Herpes zoster ophthalmicus as it reduces the chance of sight-threatening eye involvement from 50% to 20%. Similarly, all immune-compromised patients should be treated with antiviral as soon as possible.
Steroids can reduce the duration of pain and unwell being. It has no role in the reduction of postherpetic neuralgia. It should be used in conjunction with antivirals. It should be avoided on its own and in patients with the immune compromised state.
Pain relief may be needed with analgesics and tricyclic antidepressants (Amitriptyline). Antibiotics should be used to prevent secondary infection.
The vaccine is available for the prevention of VZV infection which is effective in the prevention of chickenpox and herpes zoster infection which is effective and safe.
In high-risk patients like immuno-compromised transplant recipients, varicella-zoster immunoglobulin may be considered within the first 3-4 days of exposure to an infected person.
Anti-viral prophylaxis (7 days course) may be considered in a high risk exposed person who is ineligible for vaccination.
It is difficult to treat and can be a chronic problem leading to severe depression. The principles of management are.
- Tricyclic antidepressants
- Gabapentin or carbamazepine
- Local application of — Lignocaine ointment, Capsaicin ointment
In a study of patients with intractable postherpetic neuralgia, intrathecal injection of methylprednisolone acetate once weekly for four weeks resulted in a significant reduction in pain. However, this is still investigational.
Patients should be referred to the pain clinic for further evaluation and consideration for nerve blockage.
This patient was promptly treated with acyclovir and steroid with the quick resolution of her symptoms. Till now she has not complained of any postherpetic neuralgia.
CASE: A 59 years old patient presented with features of Herpes zoster involving the right trigeminal nerve. There was significant involvement of the ophthalmic division. He was treated with valacyclovir, steroids and other supportive therapy. However, the anti-viral treatment was started late because of delayed presentation to the hospital. One week following discharge, the patient presented with drowsiness and weakness of the left side of the body. He was readmitted and MRI scan demonstrated a right-sided stroke on the right thalamic region.
DIAGNOSIS: Post Herpes zoster CVA.
Herpes zoster vasculopathy is increasingly described nowadays presenting with the cerebrovascular accident, myocardial infarction or giant cell arteritis. Both extracranial and intracranial arteries may be involved and the symptoms may appear after the disappearance of the rash. The exact mechanism is unknown. However, it is postulated that probably there is endothelial dysfunction and associated vasculopathy which leads to vascular damage. Involvement of the ophthalmic branch of the trigeminal nerve is the strongest association. Although not conclusively proved, early antiviral therapy may reduce the incidence of vasculopathy. Since herpes zoster is a common presentation in clinical practice, internists should be aware of this newly described association.
- In any unilateral painful vesicular rash, Herpes zoster should be considered.
- Bilateral or disseminated Herpes zoster can occur in the immunocompromised state.
- Antiviral drug should be started within 72 hrs of onset of rash.
- There is no role of topical antiviral drugs.
- Steroids used in conjunction with antiviral medication can reduce the duration of pain and swelling. It should be used with caution in immunocompromised patients.
- Except for appropriately timed used of antiviral, no other measures reduce the incidence and severity of postherpetic neuralgia.