Postherpetic Neuralgia

Shingles is a painful disease. It is caused by the herpes zoster virus. This is the same virus which also causes chickenpox. It can affect the torso, limbs, or the face. For most people, shingles is a condition of rather sudden onset. Pain usually lasts about 1 month.

In older patients, or patients with poor immune systems, a painful, long-standing (chronic) condition called postherpetic neuralgia can develop. This condition rarely happens before age 50. But at least 50% of people over 50 become affected following an attack of shingles. There is a natural tendency for this condition to improve over time with no treatment. Less than 5% of patients have pain that lasts for more than 1 year.

DIAGNOSIS

Herpes is usually easily diagnosed on physical exam. Pain sometimes follows when the skin sores (lesions) have disappeared. It is called postherpetic neuralgia. That name simply means the pain that follows herpes.

TREATMENT

  • Treating this condition may be difficult. Usually one of the tricyclic antidepressants, often amitriptyline, is the first line of treatment. There is evidence that the sooner these medications are given, the more likely they are to reduce pain.

  • Conventional analgesics, regional nerve blocks, and anticonvulsants have little benefit in most cases when used alone. Other tricyclic anti-depressants are used as a second option if the first antidepressant is unsuccessful.

  • Anticonvulsants, including carbamazepine, have been found to provide some added benefit when used with a tricyclic anti-depressant. This is especially for the stabbing type of pain similar to that of trigeminal neuralgia.

  • Chronic opioid therapy. This is a strong narcotic pain medication. It is used to treat pain that is resistant to other measures. The issues of dependency and tolerance can be reduced with closely managed care.

  • Some cream treatments are applied locally to the affected area. They can help when used with other treatments. Their use may be difficult in the case of postherpetic trigeminal neuralgia. This is involved with the face. So the substances can irritate the eye and the skin around the eye. Examples of creams used include Capsaicin and lidocaine creams.

  • For shingles, antiviral therapies along with analgesics are recommended. Studies of the effect of anti-viral agents such as acyclovir on shingles have been done. They show improved rates of healing and decreased severity of sudden (acute) pain. Some observations suggest that nerve blocks during shingles infection will:

  • Reduce pain.

  • Shorten the acute episode.

  • Prevent the emergence of postherpetic neuralgia.

Viral medications used include Acyclovir (Zovirax), Valacyclovir, Famciclovir and a lysine diet.