Effect of intrathecal baclofen in low back pain with root compression syndromes

Baclofen was injected intrathecally to seven patients suffering from continuous severe low back pain accompanied by contracted paraspinal muscles and neurological deficit. The intrathecal injection of baclofen 0.25 mg resulted in the disappearance of pain, tendon stretch reflexes, and H and T electrical reflexes within 2 1/2 h. The pain, albeit of lesser intensity, reappeared within 6 to 39 h in five patients, while in one it did not recur. The stretch and electrical reflexes reappeared unchanged after 16-39 h. Decreased sensation returned to normal in two out of five patients within the same time period. The decreased muscle strength returned to normal in four out of five patients, in two within 3 h and in two other patients after 2-6 days. Motor nerve conduction, pathologically slow in all the patients, was not affected in four and returned to normal in the three others within 4 h. Generalized hypotonia caused unstable standing and transient urinary retention. Nausea in one patient, and drowsiness and dizziness in two others subsided spontaneously within 12 h.