Baclofen, the most effective
drug for treating spasticity, is a specific agonist of
gamma-aminobutyric acid-B receptors, and is very abundant in the superficial layers of the spinal cord. Given orally,
baclofen does not easily penetrate the blood-brain barrier, and is distributed equally to the brain and spinal cord. Direct intrathecal administration was given in order to change the distribution of the
drug by preferentially perfusing the spinal cord. Eighteen patients presenting a severe
spastic syndrome were treated with chronic intrathecal infusion of
baclofen in the lumbar cerebrospinal fluid. After clinical preselection, 38 patients were implanted with a lumbar access port allowing long-term trials in order to determine the efficacy of
baclofen therapy and the effective 12-hour dose. The 18 patients selected for chronic administration were implanted with a programmable pump. The pathology in these cases was:
multiple sclerosis (6 cases), posttrauma
spastic syndrome (eight cases), and (one case each)
cerebral palsy, ischemic cerebral lesion, spinal
ischemia, and
transverse myelitis. The mean follow-up period was 18 months (range 4 to 43 months). The clinical results were evaluated according to muscular hypertony on Ashworth's scale (changed for occurrence of painful
spasms) and functional improvement. Results were better for
spastic syndrome secondary to traumatic medullary lesion than for
demyelinating disease. Hypertonia was improved in all cases as confirmed by the registration of the Hoffman (H) reflex. Painful
muscular spasms disappeared in 14 of the 16 affected patients. Significant functional improvement was noted in nine patients and was considerable in three. The risk of side effects secondary to overdose (such as excessive
hypotonia or central depression) and the absence of a specific
baclofen antagonist stresses the necessity for accurate determination of the efficient dose. After an initial titration period and adjustment of the therapeutic dose, the individual doses were from 21 to 500 micrograms/24 hrs (mean 160 micrograms/24 hrs). This new conservative method is very effective, perfectly reversible, and safe when administered in conditions favorable to its use.