Shingles and Postherpetic Neuralgia: The Importance of Early Aggressive Treatment
About 1 in 3 people develop shingles during their lifetime, with an estimated 1 million episodes in the United States annually. The primary infection with the varicella zoster virus (VZV) is known as chicken pox, and then the virus lies dormant in the dorsal root ganglia (DRG) until reactivation many decades later that can result in severe pain and skin lesions, i.e. shingles. The initial symptom of Herpes zoster (HZ or shingles) may be only neuropathic pain for a few days prior to the onset of skin lesions, and thus HZ may be misdiagnosed at this early stage.
Depending on the specific level of spinal DRG or sensory cranial nerve involvement, your doctor may initially mistake your HZ pain for glaucoma, dental pain, heart attack, pleurisy, gallstone, stomach ulcer, kidney stone, appendicitis, etc. However, after a few days, the neuropathic pain is usually accompanied by classic skin lesions along a typical distribution on one side of the body or face supplied by the peripheral nerve of the affected DRG, known as a dermatome. Shingles is typically localized to a single dermatome, but adjacent dermatomes are involved in 20% of cases.
HZ lesions progress through stages, starting out as red macules and papules that evolve into vesicles 7-10 days later and form pustules before drying up into crust formations, i.e. scabs. HZ (shingles) is less contagious than primary varicella (chicken pox), but HZ lesions contain high concentrations of VZV, which may spread by direct skin to skin contact or airborne. HZ is only contagious after the rash appears and until the lesions crust, but complete skin healing may take more than 4 weeks. The most common sites are the thoracic nerves (trunk) and the ophthalmic division of the fifth cranial (trigeminal) nerve.
After chicken pox subsides, VZV persists in the ganglia of cranial or spinal nerves without producing any symptoms until the immune system weakens due to disease, such as HIV, or aging (half of all cases occur in persons older than 60 years). The virus reactivates and travels along the sensory nerves to the skin, producing the symptoms of shingles, but injury to the sensory nerve may lead to neuropathic pain that persists more than 3 months after the rash has healed, termed postherpetic neuralgia (PHN) – one of the most common and debilitating result of shingles.
Many pain management specialists anecdotally believe aggressive treatment during the early stage of shingles can reduce the occurrence and the severity of PHN pain. The goal of treatment during the acute episode of HZ is to control symptoms and prevent complications, such as PHN. Antiviral therapy can reduce the duration of viral shedding, promote rash healing, diminish the severity and duration of acute pain, and decrease the risk of progression to PHN.
Your physician may not prescribe oral antiviral if it is past 3 days of rash onset based on clinical trials that used 72 hours as an arbitrarily selected time point for antiviral treatment. Although it may be controversial, the potential benefits of antiviral therapy may outweigh the potential risks, and you may want to consider starting antivirals (one week course of acyclovir, famciclovir, or valacyclovir) even if you are past 72 hours of rash onset, especially if you are over 50 years old, immunocompromised, experiencing severe pain, or have high-risk lesions (involving tip of nose/eye).
Corticosteroids are not a good option as a sole agent, but may have some benefits (modest reduction in the severity and duration of acute symptoms) in combination with antiviral therapy. A typical course is 60 mg of prednisone for 7 days, then taper over the next two weeks. However, it probably will not have significant effect on PHN and is associated with a considerable number of adverse effects. The antiviral drugs will reduce the acute pain, but many patients still require analgesics to control their pain. NSAIDs, such as ibuprofen, are often insufficient, and opioids may be required to take the edge off the pain.
PHN is defined by pain persisting at least 90 days past rash healing and is a debilitating complication of HZ that occurs more often with advancing age. About half the cases involve the thoracic region, and the pain frequently interferes with sleep and recreational activities. Also, since the pain persists for so long, PHN tends to be associated with clinical depression. PHN messes with many patients’ minds because there may be no external signs after rash healing, but they do not understand why they continue to experience severe pain.
Unfortunately, PHN pain is often difficult to manage, and thus many pain management specialists emphasize the importance of early diagnosis and aggressive treatment with antivirals during the early stage of shingles. Antiviral therapy during the PHN stage is notoriously not helpful. Effective therapy often requires a combination of other drugs. Some patients with PHN, experiencing prolonged and severe pain, seek a quick fix in a situation where immediate results are difficult to provide. Trials of neuropathic pain medications, such as antidepressants, anticonvulsants, opioids, and topical agents, may be frustrating because it requires time and patience for proper dosage titration and finding the right combination of effective drugs for the individual.
It is important to take on the tasks of medication trial and monitoring the results in a systematic fashion to maximize the chance of finding effective pain control. Only one drug should be started at a time because if 2 medications are initiated simultaneously and you experience an adverse reaction, both medications may be eliminated. Another important principle is to begin a medication at a very low dose with gradual dose titration to increase the likelihood of a beneficial effect before the onset of adverse effects. You should keep detailed records of medication trials, including the dosage, titration schedule, benefit, and adverse effects in case your doctor is not as diligent and you change doctors or are referred to a pain management specialist. Careful record keeping can help prevent unknowing repeat trials of the same failed medications.
When the mainstay of treatment – medications – fail to provide sufficient pain relief or the pain is so severe that you cannot wait for medication trial and error, interventional pain management specialists, such as myself, may have to resort to more aggressive options. Although evidence for interventional procedures in PHN is weak and mostly anecdotal, the desperation of some patients may warrant trials of interventional pain management procedures. The procedures performed to manage pain during the acute HZ phase may be considered options in PHN, including a series of daily or near-daily intercostal nerve blocks, which can be performed in the doctor’s office, and outpatient procedures, such as sympathetic blockade and epidural anesthetic blocks.
Up to one third of patients with PHN have severe pain for over a year. Surgical treatment is usually considered the last resort. For instance, laminectomy and lesioning of the affected dorsal root entry zone have been performed on patients with refractory pain, uncontrolled by any other means. Finally, the possibility of prevention through a relatively recent licensed HZ vaccine is an exciting area. The FDA approved Zostavax, a live, attenuated vaccine containing the same strain of virus as the varicella vaccines, to prevent HZ. In a double-blind, randomized, placebo-controlled trial involving 38,000 healthy adults over than 60 years, the vaccine diminished the incidence of HZ by over 50% and the risk of PHN by 66%.