A new approach to control central deafferentation pain: spinal intrathecal baclofen.

Baclofen, an agonist of the gamma-aminobutyric acid (GABA) receptor, has antinociceptive effects, and its intrathecal administration reduces allodynic responses in animal models of neurogenic central pain. Such experimental studies lead to the hypothesis that neurogenic pain may be induced in part by functional abnormalities in spinal GABAergic systems. However, whether a GABAergic system is actually involved in human central pain is unknown. The authors investigated the effect of an intrathecal bolus injection of baclofen in 14 patients with central pain due to a stroke or spinal cord injury. Nine reported substantial pain relief they had never experienced previously. The effect appeared 1-2 h after the injection and persisted for 10-24 h. Allodynia and hyperalgesia, if present, were relieved as well. Pinprick and light touch sensations did not change in nonaffected regions. The results indicate that dysfunction of spinal GABAergic systems plays a role in the clinical expression of central pain. In clinical situations, continuous intrathecal infusion of baclofen seems feasible for relief of central pain.