Paradoxical effects of interferon on reactivation of oral infection with herpes simplex virus after microvascular decompression for trigeminal neuralgia.

Fifty-five patients undergoing microvascular decompression for trigeminal neuralgia were divided into three groups in a two-stage placebo-controlled study. All groups received two injections a day for five days beginning the day before surgery. Twenty-one patients received 10 placebo injections, 11 in the presurgical treatment group received three injections of 3.5 X 10(4) units of leukocyte interferon/kg before surgery, and 23 in the postsurgical treatment group received seven injections after surgery. The remaining injections in the two treatment groups were placebos. In the first stage, with 30 patients, 91% of the presurgical treatment group had reactivated oral herpesvirus infections (manifested by herpetic lesions and/or oral viral shedding) significantly more often than did concurrent controls (P less than .05). In the second stage, only the postsurgical treatment and placebo groups were studied, with no difference in reactivation of herpesvirus infection between the postsurgical treatment and placebo groups. Thus presurgical treatment with interferon alone may actually precipitate and accentuate herpesvirus infection.