Postherpetic neuralgia

Most frequent chronic complication of herpes zoster and the most common neuropathic pain from infection.

As an estimated prevalence of 9.6-43.5%.

After the initial infection, the chickenpox virus sits in the dorsal ganglion of the spinal nerves.

When the immune system fails, the virus escapes and runs down the nerves and causes burning and pain in the skin even before the classic rash emerges.

The blisters only appear when the virus has reached the skin.

The immunity to zoster decreases with age, and the risk of zoster increases.

Independent risk factors for its development include: age greater than 60 years, female gender, severe acute pain on presentation, and rash duration before the diagnosis is made.

Risk increased in immunosuppressed or immunocompromise diseases such as diabetes.

Risk increases significantly when two or more adverse risk are present.

The zoster vaccine at age 60 is useful to boost the immune system against the virus.

The zoster vaccine reduces the number of zoster attacks.

If a patient does get zoster after vaccination, the risk of post herpetic neuropathy is reduced dramatically.

The diagnosis is mainly made clinically, except in patients with atypical manifestations or certain complications, such as central nervous system involvement, in which laboratory virologic testing is required.

Can markedly impair physical, psychological, and social functioning.

Immunocompromised individuals have atypical and severe clinical findings and are at greater risk for complications and recurrence.

Treatment of HZ includes the use of antiviral agents, analgesics for control of acute zoster pain, good skin care for healing, and prevention of secondary bacterial infection.

Antiviral agents, preferably valacyclovir or famciclovir, should be started within 72 hours of onset to reduce the severity of the infection, and intensity of pain.

Most common complication is post-herpetic neuralgia (PHN) and it is the most debilitating.

Can substantially impaired physical, psychological, and social functioning.

Varicella-zoster virus vaccine and early treatment with either famciclovir or valacyclovir are the only measures proven to prevent post-herpetic neuralgia.

Options for treating PHN include topical agents, such as lidocaine patches, and systemic agents, such as the anticonvulsants gabapentin and pregabalin.

Measures for preventing Hz include routine hand hygiene and appropriate use of isolation precautions and personal protective equipment; immunoglobulins, such as the varicella-zoster virus immunoglobulin and vaccine; and antiviral agents.

The zoster vaccine has been shown to be effective in reducing the incidence of Hz and Post herpetic neuralgia.

The vaccine is recommended for all individuals aged ≥ 60 years who have no contraindications, including individuals who report a previous episode of Hz. Can put on singles site with editing

A complex neuropathic pain process in which the pain is a direct consequence of the response to peripheral nerve damage during a herpes zoster attack.

Result of a viral infection that usually presents as a childhood infection of varicella wiith human herpesvirus-3 (HHV-3), also known as the varicella zoster virus.

During the acute phase, the virus enters the sensory nervous system, where it is harbored in the geniculate, trigeminal, or dorsal root ganglia and remains dormant for many years

With advancing age or immunocompromised states, the virus reactivates and an eruption occurs and pain persists or recurs in the afected areas, and this process is known as postherpetic neuralgia.

Process predominately affects the elderly and may cause a change from independent living to patients with impaired quality of life, physical functioning, and psychological well being.

Approximately 20% of patients given antiviral drugs for herpes zoster will develop postherpetic neuralgia, while 40% of patients not treated will do so.

Both central and peripheral areas are involved in the production of pain.

Associated with pathologic damage to the nerve tissue from skin to spinal cord.

Defined as dermatomal pain persisting at least 90 days after the appearance of acute herpes zoster rash.

Clinically significant pain scores part of definition.jl M

Frequency of PHN: at 1 month after onset of shingles is 9-14.3% and at 3 months about 5% and at 1 year, 3% continue to have severe pain.

Family history as a risk factor for herpes zoster has been described.

Risk increases with age and is the most significant risk factor.

At age 60 years, approximately 60% of patients with shingles develop PHN, and at age 70 years, 75% develop this complication.

Pain that continues for 3 months or more, in the dermatomal site is defined as postherpetic neuralgia.

Pain is intense and may be described as burning, stabbing, or gnawing.

Rarely a diagnostic challenge. I’m Incidence and prevalence varies with definition.

Approximately one fifth of patients with herpes zoster have pain at three months after the onset of symptoms, and 15% report pain to be present at two years.

The proportion of patients with spontaneous resolution of pain decreases with increasing time since the onset of symptoms.

Risk factors for postherpetic neuralgia include older age, greatest severity of rash and pain during the acute phase of the illness.

Incidence increased among persons with chronic diseases such as COPD and diabetes, it may be increased among immunocompromised patients.

Using the a definition of only 30 days of age as HZ associated pain PHN incidence is as high as 30% for people younger than 40 and up to 74% and those older than 60 years (Klompas M et al).

Using a definition of HZ associated pain lasting more than 90 days Oxman et al. reported 6% of patients younger than 40 years and 12% 60 years or older have PHN.

In longitudinal studies. 50 to 75% of pain present at 30 days resolves by 90 days.

Risk of developing PHN is related to the site of infection: Lower risk – Jaw, neck, sacral, and lumbar, Moderate risk – Thoracic and Highest risk – Trigeminal (especially ophthalmic division), brachial plexus

About 70% will have pain reduction with lidocaine patches.

Pain associated occurs in three categories: spontaneous pain that is ongoing, paroxysmal shooting or electric shock like pains and evoked sensations that are pathological amplification of responses to light touch in other mild stimuli or to noxious stimuli.

Comparison of sensory function in the affected dermatomes frequently indicates a loss of sensory function in response to mechanical and thermal stimuli, and also.pathological sensory amplifications.

Treatment is based on symptom control.

The coincidental use of gabapentin before reactivation of herpes zoster significantly reduced likelihood of postherpetic neuralgia.

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