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Biomedical subjects

M Panizza

Publications and source records attributed to M Panizza.

30 records · Page 2Linked to original sources
PubMed1989

H-reflex in nonhomonymous muscles in the human forearm.

In 6 healthy volunteers, stimulation of the median nerve at the elbow elicited H-reflexes in muscles innervated by the ulnar nerve (flexor digitorum profundus of the 4th and 5th digits of the hand) as well as the median nerve (flexor carpi radialis). This finding offers direct physiologic evidence in humans of monosynaptic excitation from group Ia afferents to nonhomonymous muscles, a phenomenon for which only limited indirect evidence existed previously.

Adult↗
PubMed1989

Effect of passive transfer of myasthenic serum on mechanical, electrical and neuromuscular transmission properties of mouse skeletal muscle.

Neuromuscular transmission, muscle electrical activity and muscle mechanical properties have been studied in mice after the intraperitoneal transference of sera from myasthenic patients. Measurements of mepp's amplitude appear to be a suitable method for myasthenia gravis diagnosis since a high percentage of the sera from these patients caused a decrease in mepp's amplitude. The increase of the premenstrum weakness in myasthenic patients did not appear to be associated with greater fall of mepp's amplitude, since serum obtained in the premenstruum and far from it produced similar results. Myasthenic serum did not modify the electrical properties of innervated muscle sarcolemma. The resting membrane potential and the action potential parameters remained unchanged. However, tetrodotoxin resistant-action potentials of denervated muscles was reduced by myasthenic serum, possibly in association with receptor endocytosis process induced by the immunoglobulin. Muscle mechanical properties did not show alterations, even in the presence of positive titer of anti-striated muscle antibody.

Action Potentials↗
PubMed1988

[Electrophysiological study of neuromuscular function in a population poisoned by lead].

A comprehensive electrophysiological examination of the peripheral nervous system was carried out in 12 patients who proved to be toxicated with lead (high lead blood levels, and diminished activity of the delta-aminolevulinate dehydratase, ALA D, in erythrocytes). Maximal motor nerve conduction velocities and terminal latencies were investigated in the median, radial and deep peroneal nerves. Also the amplitude of the evoked muscle response (M wave) was measured in thenar, extensor longus and extensor digitorium brevis muscles. Sensory conduction velocity and amplitude of the nerve compound action potential were measured at the median nerve. Tibialis anterior muscle responses to deep peroneal nerve repetitive stimulation were also explored. Conventional needle electromyogram was performed in the deltoid and tibialis anterior muscles. Slight diminished motor and sensory conduction velocities were found as well as a reduction of the amplitude of the evoked muscle response of the compound sensory action potential. Four out of the 12 patients tested showed either decremental or incremental amplitude of the muscle response with nerve repetitive stimulation. A electromyographical diminished interference pattern was found in all patients tested. Most of the remaining motor unit potentials were fragmented or polyphasic. Just one patient disclosed potentials of enhanced duration and amplitude. No relationship was found between blood lead levels or ALA D erythrocytes concentration and the different electrophysiological tests performed, except between reduced ALA D concentration and diminished amplitudes of the M wave and of the sensory compound action potential, and also between ALA D and diminished radial motor conduction velocity.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMedDate not supplied

Transcranial magnetic stimulation and silent period in spasmodic torticollis.

OBJECTIVE: Our objective was to study the corticobulbar projections to neck muscles in cervical dystonia. DESIGN: We compared both the motor evoked potentials and the electromyographic silent period after transcranial magnetic stimulation from sternocleidomastoid and trapezius muscles in a group of 13 patients with spasmodic torticollis with those of 20 healthy volunteers. RESULTS: With the target muscle at rest, no changes of motor threshold, motor evoked potentials latency, and amplitude were observed in dystonic patients. With facilitation, the mean amplitude of the motor evoked potentials was increased in patients compared with controls, the significant difference being for the trapezius muscle, whereas the latency did not differ between groups. The cortical silent period was significantly shorter in dystonic patients than in healthy subjects in both muscles. The duration of the cortical silent period recorded from the sternocleidomastoid muscle showed a positive correlation with the degree of neurologic disability assessed by Tsui's scale. No abnormalities of both nerve conduction velocity and peripheral silent period by stimulation of accessory nerve were found. CONCLUSIONS: These results indicate an impairment of the mechanisms of inhibitory motor control in patients with spasmodic torticollis, which could be the result of a decrease of the basal ganglia inhibitory output over the motor cortex.

Adult↗
PubMedDate not supplied

Functional and clinical changes in upper limb spastic patients treated with botulinum toxin (BTX).

Spasticity is a motor disorder characterized by a velocity-dependent increase in tonic stretch reflexes (muscle tone) with exaggerated tendon jerks. In order to study the usefulness of botulinum toxin type A (BTX) as a therapy for spasticity, we studied 15 patients affected by spasticity secondary to stroke. Tests included: clinical evaluation of tone (Ashworth scale); active angles of extension and flexion at elbow and wrist; Hmax/Mmax ratio from flexor carpi radialis (FCR); Hreflex presynaptic inhibition from FCR during vibration; Task score; and video recording. Patients were injected with BTX into one or more muscles with total doses not exceeding 200 International Units (IU). The tests were performed immediately prior to injection and repeated 2 weeks afterwards. Furthermore, in eight patients, testing was also performed one month after BTX injection. Between two weeks and one month after BTX there were no statistically significant differences. A statistically significant difference in the Task and Ashworth scores before and after treatment emerged (p < 0.0014), but only 6 patients showed a clear improvement in motor performance. Overall, we observed an improvement in the angle of active extension and flexion at the wrist and elbow. There were no significant changes in the Hmax/Mmax ratio and the Hreflex presynaptic inhibition during vibration. All the patients reported a subjective improvement. The results suggest that subjective benefits can be gained from the use of BTX in patients affected by spasticity, and that the degree of motor improvement seems to depend on the motor recovery obtained before treatment.

Adult↗
PubMedDate not supplied

Masked myoclonus in corticobasal degeneration: neurophysiological study of a case.

A single case study of a 58 year-old male with right asymmetric apraxia and akinetic-rigid syndrome is described. Brainimaging scans (MRI, SPECT) indicated asymmetric cortical atrophy compatible with the diagnosis of Corticobasal Degeneration. Reflex myoclonus was absent and myoclonic discharges only appeared in response to pharmacological treatment of limb dystonia and rigidity. Electromyographic evidence of jerky movements was recorded only in the affected right hand and forearm after muscle relaxation, and myoclonus was not preceded by an EEG paroxysm. The cortical components of the correspondent SEPs were not increased in amplitude while LLRs recordings showed a late response over the muscles of the affected side. Furthermore, the duration of post MEP silent period was bilaterally reduced. This single case study report points out that sometimes myoclonus in Corticobasal Degeneration can be masked by the presence of increased muscle tone.

Apraxias↗
PubMedDate not supplied

EMGLAB: objective outcome measures in neurophysiological testing.

The aim of this work was to objectively measure and quantify the results of various neurophysiological tests and indirectly provide objective outcome measures for neurological therapy and rehabilitation. We have studied the silence of Electromyographic (EMG) activity after evoking motor potentials with magnetic cortical stimulation. Since different criteria were previously used to determine the level where the silence of muscle activity ends, an objective computer aided method was developed. This analysis was further developed to include objective testing of surface EMG, long latency reflexes, reciprocal inhibition of the H-reflex, H-reflex recovery curve and decrement testing. Responses were recorded at different sampling frequencies, depending on the application, time window, filter settings, etc. The developed software proved to be a fast and objective tool, able to standardize the determination of different neurophysiological tests, and as such a valuable tool facilitating multi-center studies and diminishing human bias. The software reduced the study time with each patient. Until date we have used the software with the Medtronic, Medelec and BTS EMG instruments.

Diagnosis, Computer-Assisted↗
PubMedDate not supplied

H-reflex recovery curve and reciprocal inhibition of H-reflex of the upper limbs in patients with spasticity secondary to stroke.

The H-reflex recovery curve of the lower limb is considered a useful test for the diagnosis of spasticity, and recently the reciprocal inhibition of the H-reflex has proven to be abnormal in patients affected with spasticity. We studied the H-reflex recovery curve and the reciprocal inhibition of the H-reflex in the upper limb of a group of 33 patients with different degrees of spasticity secondary to stroke. Results were compared with those of 25 controls. The aim of this study was to investigate if the two tests showed any direct correlation with the degree of spasticity and, furthermore, with other clinical measures that are present in patients with spasticity as part of an upper motoneuron syndrome (i.e., changes in muscle tone, reflexes, force, etc.). The results showed an abnormality of both tests in most patients (decrease of the three phases of inhibition in the reciprocal inhibition test and increase of the late facilitation part of the H-reflex recovery curve), and these abnormalities seem mostly to be related to muscle tone, most important being the degree of correlation between tone and changes in abnormality of the H-reflex recovery curve (P < 0.03).

Adult↗