Zeljko Kojadinovic, MD- Neurosurgeon and Pain Specialist
Postherpetic neuralgia (postshingles neuropathy, PHN) is a chronic neuropathic pain that lags behind a herpes zoster infection. This happens in 20% of cases, more often among older patients. The infection is caused by the varicella virus as a reinfection after chickenpox, which patients have usually had in childhood. This illness is more common among patients who are older or have an immunodeficiency. This disease is present around the world in different countries (USA, Nigeria, Kenya, Tanzania, Ghana, Germany, Japan, etc.).
Infection with a rash and subsequent pain extends along the nerves. The most commonly affected nerves are: intercostal nerve (nerve between ribs), facial sensitive nerves (postherpetic trigeminal neuralgia), neck nerves, limb nerves. Sometimes the infection is not recognized and subsequent pain is therefore not diagnosed and treated as postherpetic neuralgia. This occurs when there is either no skin rash (shingles) or it is very mild.
The pain is mostly a burning pain when the body is at rest (especially at night), and when moving. There is also numbness and an unpleasant sensitivity to weaker touches along the nerve (allodynia).
Intercostal and other neuralgias can also occur in the absence of herpes zoster (skin changes did not occur or there is no herpes varicella virus infection at all). They are harder to diagnose. The pain can be localized anywhere on the trunk (chest or abdomen). They can imitate pain in internal organs (heart, lungs, breast, stomach, gallbladder, abdomen, groin, etc.). The pain is often persistent, in spite of treatment.
Management of postherpetic neuralgia: To treat this neuralgia successfully it is important to determine three things: whether it is herpetic or another type of neuralgia, which nerve is involved (one or more of them) and which pathological processes actually occur in and around these nerves leading to their irritation. In everyday practice the last component is often missing and that is the reason for unsuccessful treatment. The most common mistake in diagnosis is excessive reliance on images of the spine, such as magnetic resonance imaging (MRI). Namely, in most cases of intercostal neuralgia, MR of the spine is normal or shows pathology that can lead to a wrong diagnosis. The correct diagnosis is actually arrived at through extensive conversation with the patient. The purpose of this conversation is to gather very detailed information about the pain and other symptoms. Great expertise is needed to get all the important details of a patient’s illness.
In most cases, neuropathic changes in the nerve after herpes zoster are not the only cause of intense pain in neuralgia. So medications for neuropathic pain are not sufficient on their own (Gabapentin, Neurontin, Pregabalin, Lyrica, Carbamazepine or Tegretol). All causes of this pain should be determined to prescribe an adequate combination of medication. This combination of medication is always individual and should be adjusted through regular contact with the patient over the first 6 weeks of treatment. At the beginning of this period the pain should be significantly reduced or completely resolved. This should continue throughout the 6 weeks in order to achieve long-lasting results. To ensure this, the doctor must be available to the patient at any time during this period so that he can easily contact him if the pain increases. With this approach, it is possible to achieve an excellent result even with long-term persistent pain in over 80% of cases. This is a new treatment strategy. Sometimes interventional diagnostic and therapeutic methods are indicated.
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In conclusion: When it is precisely determined what is irritating the nerve and causing the neuralgia, appropriate treatment can take place. In everyday practice this is not determined precisely enough, so treatment is often unsuccessful. Treatment failure is usually blamed on the patient’s age, obesity, poor posture, mental state, other chronic diseases, etc. However these conditions cannot serve as an excuse for not carrying out successful treatment.