Clinical use of polysynaptic flexion reflexes in the management of spasticity with intrathecal baclofen.

The aim of this study was to evaluate the clinical usefulness of lower limb flexion reflexes (FR) in the assessment of spinal excitability responsible for spontaneous or induced spasms. FR were recorded on the short head of biceps femoris, after electrical stimulation of the ipsilateral sural nerve at the ankle, in 17 spastic patients selected for chronic intrathecal administration of baclofen. The results obtained before and after treatment were compared with clinical scores commonly used to assess spasticity (Ashworth and spasm scores). Before intrathecal baclofen 15/17 patients (88%) had pathologically enhanced flexor reflexes in the lower limbs, which were associated to clinical spasms. Reflex enhancement was accompanied in 47% of cases by abnormal decrease of reflex threshold. No significant correlation appeared between the magnitude or threshold of FR in control conditions and either the hypertonia (Ashworth scale) or the number of clinical spasms per unit of time. Intrathecal baclofen attenuated flexor reflex amplitude and increased reflex threshold in all patients. Our results suggest that FR investigate the intrinsic features of the spasms (threshold, intensity and duration) not assessed clinically, and that therefore the information gathered from FR recordings is not redundant with, and adds significantly to, that obtained by clinical scales. In our experience, FR recordings appeared to be a useful tool for quantifying the benefit of antispastic treatment and might be used as an ancillary indicator to determine the minimal effective dose of intrathecal baclofen.