The effect of baclofen on the transmission in spinal pathways in spastic multiple sclerosis patients.

OBJECTIVES: To measure the effect of baclofen on the transmission in different spinal pathways to soleus motoneurones in spastic multiple sclerosis patients. METHODS: Baclofen was administered orally in 14 and intrathecally in 8 patients. H(max)/M(max), presynaptic inhibition by biceps femoris tendon tap of femoral nerve stimulation, depression of the soleus H-reflex following previous activation of the Ia afferents from the soleus muscle (i.e. postactivation depression), disynaptic reciprocal Ia inhibition of the soleus H-reflex and the number of backpropagating action potentials in primary afferents, which may be a sign of presynaptic inhibition, were examined. RESULTS: Baclofen depressed the soleus H(max)/M(max) ratio significantly following oral and intrathecal baclofen. None of the two tests of presynaptic inhibition, or the postactivation depression or the disynaptic reciprocal Ia inhibition of the soleus H-reflex were affected by baclofen administration. Also the action potentials of the primary afferents were unchanged during baclofen administration. CONCLUSIONS: The antispastic effect of baclofen is not caused by an effect on the transmitter release from Ia afferents or on disynaptic reciprocal Ia inhibition. One possible explanation of the depression of the H-reflex by baclofen is suggested to be a direct depression of motoneuronal excitability.

Effect of baclofen on gait in spastic MS patients.

OBJECTIVES: To measure gait and postural stability by objective methods in spastic MS patients and to evaluate the effect of baclofen on gait and postural stability. PATIENTS AND METHODS: Fourteen spastic MS patients were examined in a placebo controlled double-blind, cross-over trial of oral baclofen treatment. The gait was measured on a computerized treadmill and postural stability was measured on a computer assisted force-plate. RESULTS: Only insignificant improvements in the clinical measurements during baclofen treatment were found. At baseline gait was characterized by low speed, short steps and unsteadiness. Postural stability was severely impaired. During baclofen treatment only vertical unsteadiness of gait diminished significantly. DISCUSSION: We conclude that patients primarily with spasticity, concomitant with hampering or painful spasms and co-contractions should be offered treatment with baclofen. Only some will experience improvement of their gait disorders, when treated with baclofen.

Amplitude of the maximum motor response (Mmax) in human muscles typically decreases during the course of an experiment.

It was shown that the amplitude of the soleus Mmax and Hmax responses decreases in the course of long-lasting H-reflex studies. The peak-to-peak amplitudes of the Mmax and Hmax responses in the soleus muscle (and the Mmax in the tibialis anterior muscle and small hand muscles) were measured repeatedly for 1-3 h in 20 subjects. 3-5 Mmax responses and 5-10 Hmax responses were elicited about every 3 min while the subject was at rest. Decreases in the soleus Mmax response of up to 50.5% (mean 20.5% SEM 2.2) and of the soleus Hmax of up to 49.7% (mean 19.1% SEM 3.7) in relation to the amplitudes measured at the beginning of the experiment were seen in 17 subjects. In 3 subjects no Mmax amplitude decrease was seen. The maximum decrease was reached between 10 and 100 min (mean 44.2 min SEM 4.3). An Mmax amplitude decrease was also seen in the tibialis anterior muscle and in two small hand muscles. In some subjects the decrease of the Mmax response seemed to be initiated by the infrequent supramaximal stimulations. The possible causes for this amplitude reduction, as well as the methodological consequences of these findings for H-reflex studies and fatigue studies, are briefly discussed.

Evaluation of electronic equipment for quantitative registration of tremor.

OBJECTIVES: To test new electronic equipment, TREMOR, for quantitative registration of rest tremor and kinetic tremor of the extremities. PATIENTS AND METHODS: The tremor intensity of rest tremor and kinetic tremor was studied in 14 multiple sclerosis (MS) patients. Clonazepam was used in an open study in 11 MS patients to evaluate the sensitivity of TREMOR, compared to the clinical observations. RESULTS: We found no diurnal variations in tremor. Five patients discontinued the trial because of side effects due to clonazepam. Clonazepam significantly reduced clinically rest tremor in all 6 patients and clinically kinetic tremor in 5 patients. Tested by TREMOR all patients showed significant reduction in rest tremor and kinetic tremor. Correlation between electronic assessment of kinetic tremor, clinical score and Peg board test were good. CONCLUSION: TREMOR was found useful for assessment of the severity of tremor in patients with kinetic tremor and thereby avoid intra- and interobserver variation.