Intrathecal baclofen and the H-reflex.

Abstract

suMMARY Baclofen was given intrathecally to six patients with severe lower limb spasticity due to traumatic spinal cord injury. The effects of the drug on spasticity and the ratio between the maximum amplitude of the H reflex and the M response from the soleus (Hmax/Mmax ratio) were assessed. In each patient, spasticity was reduced following intrathecal baclofen and in four patients there was a reduction in the amplitude of the H reflex and Hmax/Mmax ratio. These results suggest that the Hmax/Mmax ratio may be helpful in establishing optimum drug dosage, particularly when the drug is used on a chronic basis.

Effect of intrathecal baclofen on the monosynaptic reflex in humans: evidence for a postsynaptic action.

“…Between these series, the Hmax/Mmax ratio was measured to assess the amount of MSR inhibition caused by baclofen. This experiment was performed in five patients (cases 8, 10,11,13,14) with doses ranging from 50 to 150 pug. In two other patients (cases 4 and 7), the experiment could not be performed because heteronymous facilitation was too small before baclofen injection.…”

Pharmacologic interventions for management of spasticity in cerebral palsy

“…In clinical trials, both reduced spasticity and improved clonus have been noted with IT baclofen. Decreases in response to joint movement, H-reflexes, ankle clonus, and defensive reactions are notably suppressed in patients with spinal cord injury on EMG after IT baclofen [Latash, 1989;Macdonell, 1989]. More recently, Dressnandt et al [1995] examined F-waves.…”

Clinical Pharmacology of Motor Neurons

“…These changes were interpreted as a modification of motor neuron excitability secondary to segmental and suprasegmental mechanisms, possibly by an action on interneurons (Delwaide and Schoenen 1985). Intrathecal baclofen suppresses tonic EMG activity in geneticalIy "spastic" rats and H and spinaI ftexor reftexes in normal rats (Klockgether et al 1989); in patients with severe spasticity it reduces both the amplitude of the H-reftex and the HmaxIM max (Latash et al 1989;MacDonnel et al 1989).…”