Definition

Postherpetic neuralgia is a complication of a herpes zoster infection (shingles). Herpes zoster is caused by the reactivation of the varicella-zoster virus, the same virus responsible for chickenpox. Chickenpox is a common viral infection, particularly in childhood, known as varicella. Herpes zoster manifests as a rash with small, blister-like lesions accompanied by pain. This rash typically occurs on one side of the body, forming a circular pattern. Even after the rash subsides, the pain may persist; this lingering pain is called postherpetic neuralgia. Approximately one in five patients with herpes zoster develop postherpetic neuralgia. The risk increases with age (over 60) and a weakened immune system. While no definitive treatment exists for postherpetic neuralgia, therapy focuses on prevention in high-risk populations and symptom management.

Cause

Postherpetic neuralgia results from nerve fibre damage during a herpes zoster infection. Herpes zoster is caused by the varicella-zoster virus, which also causes chickenpox. After recovering from chickenpox, the virus remains dormant within the body for years. When reactivated, it triggers herpes zoster (shingles). The nerve fibers in the affected area of the skin may become damaged, disrupting the transmission of signals to the brain. This nerve damage can lead to severe, long-lasting pain that may persist for months or even years. Postherpetic neuralgia, therefore, refers to nerve pain following a herpes zoster infection.

Risk factor

The development of postherpetic neuralgia is closely linked to the immune system and a history of herpes zoster. In addition to advancing age, other factors that heighten the risk include:

• Age over 50
• Severe herpes zoster, especially when it occurs on the face or chest
• Underlying conditions that weaken the immune system, such as diabetes mellitus
• Delayed treatment for herpes zoster (beyond 72 hours after symptoms begin)
• A history of intense pain

The location of the herpes zoster infection also correlates with the likelihood of postherpetic neuralgia:

• Low risk: Jaw, neck, lower back
• Moderate risk: Chest
• High risk: Trigeminal nerve (forehead, cheek, and lower jaw, especially if the eye nerve is involved), brachial plexus (shoulder, elbow, wrist, and fingers)

Symptoms
Pain is the most common symptom reported by patients. If you have postherpetic neuralgia, the pain will be localized in the same area as the original herpes zoster outbreak. This pain can present with several characteristics:

• A burning sensation or sharp, stabbing pain
• Pain that comes and goes without external stimuli
• Sensations that are typically non-painful, such as touch, may be experienced as pain or burning
• Pain that worsens at night or with exposure to heat or cold

The pain can persist for over three months, with a burning or stabbing nature. In addition to pain, other nerve-related symptoms may include reduced sensitivity to external stimuli, numbness, and itching.

Symptoms

Pain is one of the symptoms complained by patients. If you experience postherpetic neuralgia, the location of the pain is in the same place as the appearance of Herpes Zoster. The pain that arises can have several characteristics, namely:

1. Pain like a burning sensation or sharp pain.
2. Pain that comes and goes without any external stimulation.
3. Stimuli that do not cause pain, but are felt as pain (for example: touch is felt as pain or burning).
4. The pain that is felt gets worse at night, hot or cold temperatures.

The pain can last for more than three months with characteristics of burning or stabbing pain. In addition to pain, other nerve disorders are a decreased response to external stimuli or numbness and itching.

Diagnosis

To diagnose postherpetic neuralgia, your doctor will ask about your medical history, including a history of herpes zoster. This is crucial since postherpetic neuralgia is caused by the reactivation of the varicella zoster virus. A physical examination will follow to identify other potential causes of the pain. The affected area may be tested for sensitivity to stimuli, using cotton or a toothpick. Some questions your doctor might ask include:

1. Are the symptoms continuous or intermittent?
2. How severe is the pain (on a scale of 1 to 10)?
3. Have you had chickenpox before? When did you have it?
4. Have you received the herpes zoster vaccine?
5. What factors alleviate or exacerbate the symptoms?
6. Do you have a history of immune disorders or cancer treatments?

Management

The goal of treating postherpetic neuralgia is to manage pain and alleviate symptoms. Currently, no specific cure exists, but several medications have proven effective in reducing pain. Over-the-counter pain relievers like paracetamol and ibuprofen are not effective for postherpetic neuralgia. A doctor may prescribe one of the following medications to help with the pain:

• Gabapentin and pregabalin
• Antidepressants such as amitriptyline, nortriptyline, or desipramine
• Narcotic medications in patch form, like lidocaine patches or creams. Second-line treatments include oxycodone, morphine, and tramadol

Other therapeutic options include:

• Glucocorticoid injections for patients who do not respond to oral medications
• Transcutaneous Electrical Nerve Stimulation (TENS) to reduce pain intensity by applying small electric currents to the affected area
• Cold compresses on the painful areas
• Wearing comfortable clothing made of cotton or silk

Complications

Complications arising from postherpetic neuralgia depend on the duration of the illness and the level of pain. These complications can include:

• Depression
• Fatigue
• Difficulty sleeping
• Loss of appetite
• Trouble concentrating

Prevention

Preventing postherpetic neuralgia begins with managing herpes zoster. Proper treatment can help prevent the condition. Medications such as acyclovir, famciclovir, and valacyclovir, which require a prescription, should be administered within two days of the appearance of herpes zoster symptoms. The herpes zoster vaccine is also effective in preventing both shingles and postherpetic neuralgia. The vaccine is recommended for individuals over 50, administered in two doses, two to six months apart. Eligibility for the vaccine requires a healthy immune system.

You should not receive the herpes zoster vaccine if:

• You have life-threatening allergies to gelatin, neomycin, or any vaccine components
• You have a weakened immune system
• You are undergoing steroid treatments, radiotherapy, chemotherapy, or both
• You have bone marrow cancer or lymphatic system cancers
• You have untreated active tuberculosis

When to see a doctor?

Consult your doctor if you experience early symptoms of herpes zoster. Often, pain precedes the appearance of the skin rash. Receiving antiviral treatment within 72 hours of the rash onset can reduce your risk of developing postherpetic neuralgia.

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