Shingles & Postherpetic Neuralgia
by: Nyla Azam
Most of us have had chicken pox as children, a painful and intensely irritating experience we are glad to have over. Unfortunately for some of us, though, it’s only the beginning. Chicken pox is caused by the varicella zoster virus. Once the associated rash has resolved, varicella zoster continues to live on inside our bodies– hiding out in the Central Nervous System for the rest of our lives. It stays dormant for decades, waiting for the right time to reactivate or awaken. When the virus “wakes up,” it will spread along and within the closest major nerve to its sleeping place causing a painful condition we call shingles.
Shingles usually begins with fever and headache, accompanied by itchiness and oversensitivity in a distinct and limited area of your skin. This resolves into a characteristic stripe, or belt like rash in which small blisters form. The pain can be intense and even last for years after the rash disappears, a condition referred to as postherpetic neuralgia (PHN). PHN is notoriously difficult to treat, so choosing the right pain management doctor is crucial.
At the Ainsworth Institute of Pain Management, we are uniquely trained and specialized in treating shingles and PHN. Our board certified pain management specialists can offer a combination of treatment options, many not available anywhere else.
What causes the varicella zoster virus to reactivate is not fully understood. It is known, however, that shingles are likely to appear when someone’s immune system is impaired, either by age, disease or psychological stress.
What are Shingles?
As mentioned above, shingles are the reactivation of the varicella zoster virus. After an episode of chicken pox, the virus lies dormant in the spine or central nervous system. Once reactivated, the virus spreads along the dermatome of the sensory dorsal root or cranial nerve ganglion. The virus is confined to spreading within a specific nerve, this is what gives shingles their pattern or strip-like appearance. The area of the body to develop the shingles rash, and subsequently PHN, is dependent on the region of the spine or central nervous system the virus chooses to hide and stay dormant after chicken pox.
In a manner of speaking, since varicella zoster picks its hiding place after the initial bout of chicken pox, the area of a shingles outbreak is predetermined long before the start of the rash. Most commonly, the virus will choose to hibernate in a region of the spine known as the dorsal root ganglion (DRG). Each DRG is responsible for collecting sensation of very specific, well-defined regions of the body known as dermatomes. There are DRG’s up and down both sides of the spine in the cervical, thoracic, lumbar and sacral spine. The most commonly affected dermatomes are in the thoracic region (50% of cases) – this is because the virus most commonly chooses to hide within the DRG of the thoracic spine. Cervical and lumbar dermatomes each make up 10% to 20% of cases. Sacral dermatomes are the least frequently affected, making up 2% to 8% of cases. Less commonly, the zoster virus will find its way to ganglion of the trigeminal nerve in the brain. In these cases, the rash will involve the eye and face.
Shingles has the highest incidence of all neurological illnesses, occurring in about 1 million people in the U.S. every year. It will affect about 20% to 30% of the U.S. population at some point in their lifetime, and up to 50% of people that live to the age of 85.,, The incidence of herpes zoster is markedly increased with age and people with impaired immune systems, e.g., those with HIV/AIDS, certain cancers, or those on immunosuppressive medications. Recurrent herpes zoster, on the other hand, is rare, occurring in less than 5% of the population.
Postherpetic neuralgia refers to the pain syndrome following an episode of shingles, after the rash has resolved. It will occur in approximately 20% of patients over the age of 50. PHN is thought to be the result of nerve damage caused by the spread of the herpes zoster virus during the reactivation phase. The damage causes the nerve(s) in a specific dermatome (an area of skin that is mainly supplied by a single spinal nerve) to send abnormal signals to the brain. These signals can cause intermittent electrical shock-like sensations in the region. Over time, normal sensations like light touch or temperature may be confused with sharp, excruciating pain by the brain. This will make it difficult for one to wear clothing or take a shower as the sensation of something like a bra strap or warm water to feel like a severe, unbearable pain.
What are the Symptoms of Shingles?
Most cases of shingles are preceded by a period of pain along a dermatome (an area of skin connected to a single spinal nerve). This period is called the prodrome; it precedes the development of the characteristic, unilateral shingles rash in the same area.
The prodrome usually lasts few days (1-2), but there are case reports that describe the prodrome to last anywhere from 7 to 100 days. If there is no pain during the prodrome phase, it will typically occur at the onset of the rash or shortly after. Symptoms during this “initial phase” include:
Burning pain accompanied with itching and oversensitivity in a distinct and limited area
Pins and needles (paresthesias), tingling, numbness in a distinct and limited area
Painful numbness (dysesthesias)
The Shingles Rash
Following the prodrome is the classic shingles rash – a large number of small, fluid-filled blisters called vesicles form over the area of pain and in a well defined region with visible boundaries. The vesicles will crust over after a few days and then lose the scabs over the next 2 to 4 weeks. In some cases, patients will skip the painful prodrome and will instead develop pain at the onset of the rash, or immediately after it resolves. There are rare cases where the rash is skipped (prodrome pain but no rash) – this is known as zoster sine herpete.
Characteristics of the Shingles Rash:
Most commonly occurs on the torso, but can also appear on the face, eyes and other parts of the body.
Typically affects only one side of the body, not both at the same time, and will not cross the midline.
Starts off looking like hives but confined to a specific, well-defined region with distinct borders.
Causes skin changes in a particular dermatome, resulting in a stripe or belt-like pattern. As the rash progresses, small blisters called vesicles will form.
In most patients the pain associated with shingles will gradually resolve before or shortly after the healing of the rash. Shingles pain has three categories or phases:
Acute pain (acute herpetic neuralgia) – This is pain that lasts for the duration of the rash, and resolves with the rash or up to 1 month after.
Subacute herpetic neuralgia – Pain lasting from 1 month to 4 months after the onset of the rash.
Postherpetic neuralgia (PHN) – Pain that persists in the affected region or dermatome previous afflicted with the shingles rash at least 4 months following the onset of the rash.
What are the Symptoms of Postherpetic Neuralgia (PHN)?
PHN will occur in approximately 20% of patients over the age of 50, even if anti-viral treatment is provided within the first 72 hours of the onset of the rash. PHN is characterized by a constant, severe burning, lancinating pain in the distribution of the affected nerve in the region of the rash. As PHN progresses, patients will describe allodynia – extreme pain to typically non-painful stimuli. Even the slightest pressure from clothing, bed sheets, or a light breeze can inflict paralyzing pain. Pain in PHN can have periods of remission during which the patient will describe intervals of no pain at all.
Chicken pox is a contagious airborne disease that is easily spread through coughs, sneezes and contact with the blisters of an infected person. If you had the chicken pox, the varicella zoster virus which caused it can remain with you for the rest of your life. As mentioned above, it is not fully understood what causes the virus to reactivate after a period of dormancy, though age, stress and poor immune function seem to have a lot to do with it. So basically if you’ve had chicken pox, you are a candidate for developing shingles.
The risk factors for PHN all indicate a greater severity of infection by the zoster virus. As the zoster virus resides in neural tissue, greater severity of infection is an indicator of a greater degree of nerve damage. The mechanism by which nerve damage is caused and how it causes PHN is still unknown. Postmortem studies carried out on patients with postherpetic neuralgia examining neural tissue of both affected and unaffected sides found changes in the sensory ganglion and decreased fiber density of sensory nerves on the affected side.
Risk Factors for Post-Herpetic Neuralgia
Elderly age – PHN is relatively uncommon in those under the age of 40. The older one is when the shingles virus strikes, the higher the likelihood of developing PHN.
Severity of pain early on – the greater the pain in the acute herpetic neuralgia-phase, the higher the likelihood of developing PHN.
The greater the severity and duration of the shingles rash, the higher the likelihood of developing PHN.
The best way to treat shingles and PHN is to prevent them altogether. Currently, there is a live attenuated zoster vaccine that has been shown to significantly increase the immune response to the zoster virus in older adults. Given that cellular immunity to the zoster virus decreases with age, the importance of developing a vaccine to boost immunity when it counts the most was imperative. The Shingles Prevention Study was a double blind, randomized, placebo controlled trial on 38,546 individuals 60 years of age and older. The study showed a statistically significant decrease not only in overall incidence of PHN by 66.5% and a reduced incidence of shingles. Even more importantly, those that did account episodes of shingles reported decreased burden of illness (a pain severity by duration measure).
The main goals for shingles is to relieve acute pain and prevent postherpetic neuralgia. To this aim, there are a number of medication options:
Antiviral medications: this class includes drugs like acyclovir, famciclovir, and valacyclovir. These medications inhibit viral replication, reduce the duration of viral shedding, hasten rash healing, and decrease the severity and duration of acute pain.
Corticosteroids: have been shown to decrease the acute pain caused by shingles but offer no additional benefits over antivirals
Opioids: these are recommended for patients with moderate to severe pain despite treatment with antivirals and corticosteroids
Gabapentin: in a study comparing opioids, gabapentin and placebo on postherpetic neuralgia, gabapentin showed greater pain relief compared to placebo
Tricyclic antidepressants: a trial comparing amitriptyline to placebo, started within 48 hours of onset of rash and continued for three months, showed decrease in prevalence of postherpetic neuralgia at 6 months. Amitriptyline can have a number of side effects in older patients however.
Nerve blockade: a single epidural injection of steroid and local anesthetic has been shown to decrease the acute pain associated with a shingles episode, compared to antiviral treatment alone. They have not shown to decrease incidence of postherpetic neuralgia. Studies of multiple epidural injections, continuous epidural infusion, and multiple paravertebral injections during shingles decreased the duration of postherpetic neuralgia.
Treating Postherpetic Neuralgia (PHN)
Treating PHN can be extremely difficult, so every effort should be made early on to prevent it. Even with the treatments currently available, it is rare for one to make a complete recovery from PHN and become totally pain free. The most effective treatment algorithms are those which employ a comprehensive and multidisciplinary approach. The application of select medications combined with interventional pain management treatments offers the best chances for those afflicted with PHN to regain their lives and most effectively treat their pain.
Medications for PHN
Gabapentin (Neurontin) & Pregabalin (Lyrica): These medications belong to a drug class known as “anticonvulsants.” They are thought to work to decrease the pain of PHN by stabilizing overactive nerves transmitting pain.
High concentration capsaicin patch: The active ingredient is the active component in chili peppers. These patches are thought to treat PHN by causing the nerves transmitting pain to exhaust their supply of neurotransmitters.
Lidocaine patches (Lidoderm): Lidocaine is a commonly used local anesthetic which serves to “numb” the painful nerves implicated in transmitting the pain from PHN.
Tramadol: A combination pain medication that acts not only as an opioid but on the same pathways as select antidepressants to increase levels of serotonin and norepinephrine.
Tricyclic antidepressants: Also known as TCA’s, these medications are powerful neuropathic pain agents used to treat a variety of neuropathies.
Combination therapy is commonly used as it can lead to even better pain relief than treatment with a single agent. The limiting factor with combination therapy can be side effects, which can increase with the number of medications.
Interventional Pain Management Treatments for PHN
Intercostal Nerve Block – This procedure is not only effective in managing the symptoms of PHN, but also in establishing a diagnosis of which spinal segment is involved. An intercostal nerve lies under the rib and is the extension of the spinal nerve at the same level. Typically performed under ultrasound guidance, your physician will insert a small needle along the course of the intercostal nerve in the path of the shingles rash. By injecting a small amount of local anesthetic (sometimes with the addition of cortisone), one can obtain profound pain relief.
Sympathetic nerve block – These can provide short-acting pain relief. Depending on the area of the body affected by PHN, different sympathetic blockades can be employed – stellate ganglion block, lumbar sympathetic block or sphenopalatine block. Studies have shown these procedures to be more effective when performed within 2 months of the onset of pain.
Trigeminal Nerve Block – In rare cases, shingles (and subsequently PHN) can occur on the face due to the spread of the virus along the Trigeminal Nerve. This procedure involves injecting a small amount of local anesthetic onto the affected branch of the Trigeminal Nerve to interrupt the chronic pain cycle. When performed correctly, the pain relief will be immediate and profound.
Neurolysis & Ablation – In cases where an injection provides only temporary relief, neurolysis or neuroablation can be utilized to increase the duration. There are several different methods that can be used:
- Radiofrequency Ablation (RFA) – Radio waves are applied to a nerve or plexus, preventing the transmission of pain.
- Cryoablation – Similar to RFA, however cold temperatures are applied to the area instead of radio waves.
- Chemodenervation – The premise is the same as cryoablation and RFA in that the goal is to prevent a nerve or plexus from transmitting pain; rather than applying mechanical stress to the nerve through radiowaves or cold temperatures, small amounts of either alcohol or phenol are injected to block the nerve’s ability to transmit a signal.
IV Infusion Therapy – An increasingly popular procedure for treating a variety pain syndromes, as well as depression and anxiety. Patients are hooked up to an IV and special medications are administered intravenously. The infusions can take as little as 30 minutes to complete.
Spinal Cord Stimulation (SCS) – This is a commonly performed procedure for a variety of pain syndromes. SCS utilizes technology similar to that of cardiac pacemakers whereby small electrodes are placed into the epidural space near the spinal cord. These electrodes will produce a small electrical current over the spinal cord that interfere with pain signals. In the case of PHN, SCS has been shown to improve pain and functioning in 82% of patients.
DRG Stimulation – DRG Stimulation (aka Dorsal Root Ganglion Stimulation) is THE most cutting-edge treatment for pain available in the United States. The clinical trial (ACCURATE Study) recorded unprecedented improvements in pain and overall successes that have never before been seen. The procedure is almost identical to traditional Spinal Cord Stimulation, except a special system called Axium™ (available exclusively through St. Jude Medical™) provides isolated stimulation to only the DRG. Even if you have failed traditional Spinal Cord Stimulation in the past, statistics suggest DRG Stimulation will still work! 
Peripheral Nerve Stimulation – The premise is similar to SCS but rather the leads are placed on the affected nerve – in the case of PN, the lead is placed on the pudendal nerve.
Intrathecal Pump – A small catheter is placed in the subarachnoid space (just below the epidural space) and extremely small amounts of medication are slowly delivered directly over the spinal cord. This enables your physician to provide the same medications you might take orally to manage the pain but at a fraction of the dose – thus decreasing the side effects.
The Ainsworth Institute is Here to Help
Choosing the right pain management doctor is crucial to have the best chance of success in beating shingles and PHN. The board certified physicians at the Ainsworth Institute are recognized leaders in the field – schedule a consultation today with one of our experts and take the first step toward taking your life back.
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