Neuropathic pain has been recognized as an intractable pain which is difficult to treat. The author described the management of neuropathic pain in the pain clinic practice in Japan. The management includes pharmacological therapy, nerve blocks, neuromodulation therapy, electric convulsion therapy, surgical therapy, gamma knife therapy, low output laser therapy, rehabilitation andmirror box therapy. The author also described the mechanisms of neuropathic pain which shoud be considered when pain clinicians treat this pain. Importance of pharmacological tests for analyzing the mechanisms of neuropathic pain on the clinical aspect also was described.

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  Objective. To study the effect of ketamine on post-stroke pain, a drug challenge test was performed and the effects of a low-dose drip infusion of ketamine were examined in post-stroke pain patients.
  Methods. In the drug challenge test, 5 mg of ketamine hydrochloride (i.v.) was given every 5 min up to a total of 25 mg in 120 post-stroke pain patients, and the pain reduction rate was assessed using a visual analogue scale (VAS). On the basis of the results of the drug challenge test, the effects of a low-dose ketamine drip infusion (LDKDI) were examined in 55 ketamine-sensitive post-stroke pain patients. For the LDKDI, 20 mg of ketamine hydrochloride added to 100 ml of saline was administered intravenously by 1-hour drip infusion.
  Results. Fifty-five (45.8%) of 120 patients were evaluated as ketamine-sensitive with regard to their spontaneous pain. All of the 55 ketamine-sensitive patients treated with LDKDI could clearly experience pain reduction. The duration in which patients experienced pain reduction caused by LDKDI ranged from 1 to 6 hours in 27 patients (49%) and experienced in 38 patients (69.0%) up to 24 hours. In contrast, 17 (31%) of 55 patients experienced pain reduction lasting over 24 hours, and 4 (7.2%) of the 55 patients experienced pain reduction lasting about 1 week. In addition, 52 (94.5%) of the 55 patients were satisfied and expressed a desire to continue the LDKDI.
  Conclusions. About half of the post-stroke pain patients were ketamine-sensitive, and LDKDI is useful for the treatment of post-stroke pain if candidates are selected on the basis of the results of a drug challenge test of ketamine.

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