Can pain treatment of post herpetic neuralgia be prioritized?

Abstract

The incidence of herpes zoster (HZ) virus infection is 215 per 100 000 person-years. It is more common in the elderly at a rate of 1400 per 100 000 person-years. Approximately 8% of these patients are sufficiently symptomatic to require treatment within a month and this decreases to 3% at 12 months. Prevention is the best insurance against PHN, implying that early treatment with anti-viral regional anesthesia-sympathetic, or mixed central neural (epidural) blocks if available, and the concurrent use of tricyclics and anticonvulsants are all helpful. While PHN and diabetic neuropathy are two common neuropathic pain syndromes, PHN differs in having inflammatory changes that extend from the skin to the central nervous system which may spread to the contralateral and asymptomatic dermatomes. The most effective treatments at this time are tricyclic anti-depressants, anticonvulsants and antiarrhythmics. These agents should be combined with long acting opioids and recent results suggest that NMDA antagonists are additive. Topical lidocaine may be quite effective in the treatment of hyperalgesia and in reducing the incidence of spontaneous paresthesiae. In most cases while the foregoing methods may be only marginally successful if the area is circumscribed such as is the case in the trigeminal region, sequential circumferention subcutaneous infiltration of a local anesthetic and steroid may be effective. Neuromodulation using neurostimulation may be effective for intractable PHN of the trunk or lower extremity. It is less successful in managing symptoms in the cervical dermatomes or upper extremity. Zirconitide (SNX111) the n-calcium channel blocking agent has been effective in treating severe intractable PHN. Its application requires implantation of an intrathecal infusion system and the acceptance of some central nervous system side effects, which however, may be insignificant in comparison with the pain relief obtained. In summary: PHN treatment can be prioritized by use of those agents which have been found most effective and to which other treatment modalities may be added to achieve the best efficacy.