Postherpetic neuralgia: characteristic symptoms, treatment regimens

Author: Druzhinkina V.Yu., neurologist.
April, 2021.

Synonyms: PHN, post-zoster neuralgia.
ICD-10 code: G53.0

Postherpetic neuralgia is a complication of herpes, manifested by severe pain that occurs at the site of the rash. It can bother the patient from several weeks to many months. Therapy drugs - anticonvulsants, antidepressants, local forms of anesthetics, antivirals, hormones. In women and elderly patients, a severe course with severe pain syndrome is more often observed.

According to most experts, postherpetic neuralgia should be called pain that occurs after herpetic eruptions - vesicles - dry out. They are small bubbles with transparent or slightly cloudy contents, their appearance is often accompanied by itching and scratching.

Photo: fresh herpes rash and dried rash after scratching

Another part of doctors uses the term PHN to refer to pain that occurs in any period of herpes manifestations, including during or even before the appearance of bubbles.

But nevertheless, postherpetic neuralgia ("fasting" means after) is more logical to call the pathology that manifested itself after the exacerbation of herpes, and not before that.

The pathology is characterized by a pronounced and prolonged pain syndrome, which worsens the quality of life of patients. It is diagnosed quite quickly, since it has a characteristic connection with the manifestations of herpes. Often requires the appointment of anticonvulsants and antidepressants to relieve pain.

Statistics

The number of cases is up to 3 diseases per 1000 people per year. According to statistics, elderly people are more susceptible to pathology - in people 80 years and older, the detection rate is already 10 cases per 1000.

If we consider the percentage distribution of pathology within age groups, then it can be noted that half of all cases are 60–75 years old, 76 years and older - already three quarters.

Age 60+ is at risk of developing persistent pain for a long time - about 10% of patients note that the discomfort persisted for up to six months.

In 6% of people who have undergone postherpetic neuralgia, relapses are observed, and from the first to the next case, 10 years or more may pass.

Causes and risk factors

The etiological factor leading to the development of postherpetic neuralgia is the herpes virus - varicellazoster. The mechanism of the onset of pain is not fully understood. One of the theories is the emergence of an immune-mediated reaction, as a result of which the body reacts aggressively to the cells of its own body, perceiving them as foreign agents.

As a result, irritation, swelling of nerve fibers occurs, and the work of pain receptors changes. All this gives the characteristic attacks of neuropathic pain - they can easily be described with a capacious, sonorous word, for example, "burning", "stitching". This is characteristic of nerve damage.

A well-established risk factor for the development of postherpetic neuralgia is old age. In such patients, the pain syndrome is observed even before the appearance of the rash, is so pronounced that the doctor has to exclude a heart attack, renal colic, an attack of gallstone disease.

Also increase the risk of postherpetic neuralgia, immunodeficiency, diabetes mellitus, cancer, a large area of ​​herpetic eruptions, female sex.

Views

In medical practice, it is important to subdivide the disease depending on the type of pain and the area of ​​the rash.

According to the duration of the pain syndrome, the following types of neuralgia are distinguished:

• Sharp. Manifestations are observed no more than a month from the moment the vesicles appear.
• Subacute. This name is appropriate when the pain persists for one to four months.
• Chronic. The pain syndrome can be for years, then subsiding, then manifesting again.

Localization of the rash can be in the chest (from a fifth to half of all cases), head (about 12-20%), neck (up to 11%), much less often - the lower back, extremities.

Symptoms

The main manifestation of postherpetic neuralgia is pain syndrome. It is characterized as burning, pronounced, sharp, shooting, stabbing, and may be accompanied by unpleasant itching. Symptoms develop quickly - pains in postherpetic neuralgia appear immediately, their intensity increases in 2-5 days.

The first signs of the disease are soreness in the area of ​​the rash, aggravated by touching (including clothing), with any exposure. Types of pain syndrome:

• Constant. A feeling of dull pain coming from the depths, often with stabbing, burning shades.
• Periodic. Shoots, pricks, burns. Attacks occur abruptly, comparable to an electric shock.
• Allodynic. Based on a change in perception, when any impact is perceived by nerve fibers as causing pain.

The manifestations of the disease differ in the strength of the pain syndrome. Symptoms of certain types of PHN:

• Postherpetic intercostal neuralgia is a common variant of the disease that occurs after the symptoms subside shingles. Pain syndrome is noted along the ribs, i.e. where the intercostal nerves go.

Photo: one of the common options for localizing a rash with herpes zoster

• Postherpetic trigeminal neuralgia or trigeminal neuralgia is quite rare. It is characterized by the occurrence of severe pain on the face - in the area of ​​the eyes, nose, cheeks, lips.
• Postherpetic neuralgia of the sciatic nerve - unpleasant sensations spread along the course of the nerve of the same name, i.e. from the back of the thigh to the heel.
• Postherpetic neuralgia in the oral cavity is very rare, associated with rashes after chickenpox.

What can be confused with

In situations where pain occurs before the appearance of vesicles, or the disease proceeds without a rash, postherpetic neuralgia can be mistaken for manifestations of other diseases.

Differential diagnosis:

• Attack renal colic - in the case of postherpetic neuralgia, there are no changes in the general blood test and during ultrasound of the kidneys.
• Cholelithiasis - it is not possible to see stones or sand in the gallbladder, liver, its ducts on ultrasound.
• Myocardial infarction - there are no signs of ischemia on the ECG. Difficulties with this point may arise in age-related patients who already have chronic myocardial ischemia, or with the development of hypoxia (lack of oxygen) in the heart muscle against the background of severe pain. In such cases, an electrocardiogram is required in dynamics - after 20-40 minutes from the first examination with subsequent comparison.
• Intercostal neuralgia - it is difficult to find a difference here, especially at the beginning of the development of the disease, but with intercostal neuralgia there is a clear increase in pain on inspiration, when coughing, sneezing, and sudden movements of the body. With PHN, pain is usually not distinguished by a pronounced increase in such actions.

Survey

If you suspect postherpetic neuralgia, it is advisable to consult a neurologist.

The diagnosis is straightforward in cases where pain occurs after the appearance or extinction of vesicles. The difficulty is presented by patients whose pain has developed to the cutaneous manifestations of herpes. Upon examination, a neurologist (in his absence, a therapist) notes the following deviations in the patient:

• hyperalgesia - excessive soreness with little exposure - pressure, collection of the skin in a fold;
• allodynia - the appearance of pain from contact with stimuli that normally do not cause it (touching clothes, patting with a palm);
• hypesthesia - a decrease in all types of sensitivity along the nerve fiber.

Laboratory and instrumental studies are rarely prescribed. In order to confirm GWP, 2 main studies are carried out:

• Tzank's test - scraping from a vesicle, placing the contents on a glass slide, followed by staining. This reveals multinucleated giant cells.
• Blood test for antibodies to the pathogen - HerpesZoster.

A general blood test, indicating the viral nature of the disease, and biochemical research, which determines an increase in acute phase proteins of inflammation, are less informative.

Herpesvirus infection does not always manifest itself as a rash. In such cases, in order to exclude other neurological pathologies, the patient may be referred for ENMG - a study that allows you to identify a violation of conduction along nerve fibers, a change in response when exposed irritant.

Treatment

Postherpetic neuralgia is treated by a neurologist, in his absence - by a therapist. Treatment recommendations were adopted at the 9th EFNS (European Federation of Neurological Societies) Congress postherpetic, neuropathic peripheral and diabetic pain, then Russian protocols were developed treatment of herpes and PHN.

Basic drugs:

• Anticonvulsants are first line drugs because they have the ability to reduce neuropathic pain. The best option is gabapentin. Also used are lamotrigine, valproate. The previously prescribed carbamazepine has not been confirmed to be effective in clinical trials; moreover, it has a set of side effects.
• Local impact. For analgesic and distracting purposes, ointments, gels are used, including with anesthesin, lidocaine, capsaicin.
• Antidepressants. These are fluoxetine, paroxetine, amitriptyline. They are prescribed strictly by the attending physician, and are dispensed with a prescription.
• NMDA receptor blockers. For the relief of acute pain, the drug of choice is amantadine sulfate.
• Glucocorticosteroids (for example, prednisolone) - are prescribed to inhibit the inflammatory process, reduce swelling around the nerve.
• GABAergic receptor agonists. Baclofen is used. It blocks the transmission of pain impulses at the level of the spinal cord, thereby relieving or reducing discomfort.
• Antiviral - they act on the herpes virus circulating in the blood, but do not reach pathogens sleeping in the nerve ganglia of the spinal cord. They are prescribed in the acute period or during exacerbation. Valciclovir (a relatively new agent in the treatment of postherpetic neuralgia), penciclovir, acyclovir, famciclovir, ganciclovir are used.
• As an alternative therapy for severe pain, opiates, tramadol, and less often anti-inflammatory drugs are prescribed.

Postherpetic neuralgia can be treated, especially with early treatment. But in some situations, even against the background of therapy, the pathology becomes chronic.

Duration of treatment:

• anticonvulsants, antidepressants - the timing is determined by the duration of the pain syndrome;
• immunostimulants - depending on the scheme, which is individual for each agent, the timing ranges from 5 days to 2 months;
• antiviral drugs - up to 3 weeks, also depends on the specific medication.

Over time, postherpetic neuralgia can go away on its own, but it is difficult to endure the pain syndrome in most cases, so patients seek medical help.

The approximate terms of treatment are determined by the duration of the pain syndrome, ranging from a month or more. Recovery and rehabilitation takes up to six months; in elderly patients, these periods are often prolonged, which is associated with a decrease in the general capabilities of the body.

Physiotherapy for postherpetic neuralgia, together with the main therapy, helps relieve pain. An exposure to a magnetic field with an intensity of 1.6 T and a frequency of 1 Hz is prescribed, the healed elements are irradiated with a laser.

They were not included in the recommendations for treatment, but additional acupuncture, vibration massage, blockade with glucocorticosteroids, and the introduction of botulinum toxin may be prescribed.

Forecast

With timely treatment, the prognosis is favorable - the vast majority of cases end with recovery. When predicting the outcome, it is important to take into account risk factors, the more there are, the higher the likelihood of becoming chronic.

The transition to a chronic form can be considered a complication, since intense pain significantly affects the patient's lifestyle and quality of life.

Other possible complications include a change in the sensitivity of the skin at the site of the rash, the addition of a secondary infection, mycosis,

Prophylaxis

There is no specific prevention of the development of postherpetic neuralgia, but there are measures to help prevent the onset of manifestations of herpes or to get sick in a mild form without complications. These include vaccinations against chickenpox and HerpesZoster.

The first is introduced according to the national vaccination calendar:

• from one to 13 years old - once 0.5 ml;
• over 13 years old - twice 1 ml with an interval of 6-10 weeks.

Adults from the risk group, if they have not been ill earlier (in doubtful cases, blood is donated for antibodies to the herpes simplex virus):

• suffering from diabetes mellitus;
• chronic diseases of the respiratory, digestive, cardiovascular systems;
• with acute leukemia;
• with diagnosed malignant neoplasms;
• patients undergoing radiation therapy;
• preparing for organ transplantation;
• when planning a pregnancy.

The second vaccination is carried out for people over 50 years old, in some cases over 40 years old. 2 injections are given 8 days apart.

Postherpetic neuralgia is a complication of herpes infection, accompanied by severe pain at the site of already dried out rashes. Treatment is aimed at relieving discomfort and suppressing the activity of the herpes virus.