Electrophysiological assessment of the effect of intrathecal baclofen in dystonic children

Objective: To evaluate the effect of intrathecal baclofen in a group of dystonic children using electrophysiological procedures previously validated in spastic children. Methods: Seven children (aged 2–16 years) with dystonia of various aetiologies (dyskinetic cerebral palsy, pantothenate kinase-associated neurodegeneration and Aicardi-Goutières syndrome) underwent transcranial magnetic stimulation, H-reflex and flexor reflex studies before and after intrathecal injection of baclofen. The Barry-Albright Dystonia Scale (BADS) was used for clinical evaluation of dystonia. Results: Motor-evoked potentials, present in 2 of 5 patients before baclofen, were preserved after injection. Before baclofen, H reflex was present in 6 of 7 patients (mean Hmax/Mmax: 0.45±0.21). It was markedly reduced after the injection (mean Hmax/Mmax: 0.09±0.11) (P<0.001). Area of flexor reflex significantly decreased after baclofen (P=0.047), while threshold significantly increased (P=0.01). No significant clinical improvement of the BADS scores was observed (P=0.058). Conclusions: These electrophysiological procedures, previously demonstrated to quantify the action of intrathecal baclofen in spastic adults and children, also appear sensitive in dystonic children. The electrophysiological changes are consistent with primarily spinal sites of action of baclofen. They appear more sensitive than clinical evaluation.