Pain management of lumbosacral plexopathy with the new anticonvulsant gabapentin

Clinical manifestation of radiation-induced lumbosacral plexopathy (LSP) re main a rare event. Paintreatment is mainly supportive. Recovery with LSP is less satisfactory and occurs over months to years, but may be incomplete. A 59-year old man was referred for intermittent, neuralgic pain localized t o the right gluteal region and leg. He also developed slight neurologic sym ptoms such as numbness, paraesthesias and a slight weakness of the right le g. The symptoms had begun 6 months after radiation therapy after prostatect omy for prostate carcinoma. There were no antecendent back or hip injuries. There was a right Lasegue sign. On the visual analog scale pain ranks betw een 0 (rest) and 8-10 (attack) were recorded. Needle electromyography showe d denervation in gluteus medius and maximus, biceps femoris, quadriceps fem oris, tibialis ant. and peroneus longus. Normal laboratory studies included urin analysis, complete blood count, erythrocyte sedimention rate, serumgl ucose, electrolytes, rheumatoid factor, and protein electrophoresis. Pelvic computed tomography (CT) was normal. Lumbosacral MRI was not performed. Li ver- and renal enzymes were elevated. On admission the patient was treated with diclofenac (2 x 50 mg/d) and carbamazepine (3 x 200 mg). Gabapentin wa s chosen because it is well tolerated and it appears to have a favorable ef ficacy-to-toxicity ratio. He was then started on gabapentin, 100 mg given o rally three times daily. 60 minutes after the first dose of gabapentin, the patient had a significant pain relief that lasted 6 h. The gabapentin dose was increased to 300 mg three times daily. After 6 months he continued to report good pain relief with minimal sedating side effects on a regimen of 3 x 300 mg/d gabapentin. To our knowledge this is the first case report of LSP which was successfully treated with the novel anti-epileptic drug gabap entin.