Pruritus after intrathecal baclofen withdrawal: A retrospective study

Abstract

Ben Smail D, Hugeron C, Denys P, Bussel B. Pruritus after intrathecal baclofen withdrawal: a retrospective study. ObjectivesTo determine the frequency of pruritus after intrathecal baclofen (ITB) withdrawal and to study the pathophysiology of this symptom. DesignRetrospective cohort study. SettingRehabilitation department of a general hospital. ParticipantsPatients (N=102) implanted with an ITB pump who had been followed up since 1988. InterventionsNot applicable. Main outcome measuresIncidence of pruritus after withdrawal. We studied the relation between pruritus and daily dose, concentration and mode of infusion of baclofen, and cause of the central nervous system lesion inducing spasticity. ResultsPruritus was observed in 10 of 23 cases of ITB withdrawal. It never occurred during the first 3 months after pump implantation. It seems likely that the segmental spinal action of baclofen is responsible for pruritus. There was no statistically significant difference between patients with ITB deprivation who did and did not experience pruritus in their daily infused dosage or in concentration and mode of infusion. Surprisingly, no pruritus was observed in patients with multiple sclerosis. ConclusionsPruritus is a frequent symptom after ITB withdrawal. Its occurrence is probably subsequent to chronic blocking of the liberation of substance P by baclofen at the spinal level. This symptom is a good clinical predictor of baclofen withdrawal, in contrast to an isolated increase of spasticity that may be due to drug tolerance or irritant factors. Pruritus requires investigation of a possible dysfunction of the infusion system.