Motor cortex excitability during unilateral muscle activity.

The effect of unilateral tonic muscle activity with and without co-activation of the antagonists on motor cortex excitability has been studied. Motor evoked potentials (MEPs) were recorded from the first dorsal interosseus muscles of both hands in response to transcranial magnetic stimulation (TMS) during relax, isometric index finger abduction and antagonistic co-activation. The intracortical inhibition (ICI) and intracortical facilitation (ICF) were investigated by paired-pulse TMS with interstimulus intervals of 3 and 13 ms. The unilateral tonic activation of the right hand facilitated contralateral and ipsilateral responses (cMEP and iMEP) recorded from both hands with an exception of iMEPs recorded from the left hand. During paired-pulse TMS ICI for cMEPs was not influenced by the unilateral tonic activity in both hands, while ICF was suppressed when MEPs were recorded from the active right hand. The effect of unilateral tonic activity on iMEP in response to paired-pulse TMS was essentially different: generally, ICI was greater for iMEPs and ICF was completely abolished with an exception of iMEPs recorded from the left hand during right finger isometric abduction when a strong ICF was evident. The decreased ICF and/or increased ICI are assumed to reflect mechanisms underlying the co-activation of antagonists.

The electrophysiological profile of hereditary motor and sensory neuropathy-Lom.

OBJECTIVE: To make electrophysiological observations on a large kindred with hereditary motor and sensory neuropathy-Lom (HMSN-L) containing 27 affected individuals. CLINICAL FINDINGS: Onset was in early childhood with gait difficulty related to progressive lower limb weakness. Upper limb weakness developed later. Bulbar involvement was present in one third of the patients, and deafness appeared during the second or third decades. ELECTROPHYSIOLOGICAL FINDINGS: Electromyographic evidence of denervation was progressive, more severe distally, and greater in the legs, being total in distal lower limb muscles in most patients. Sensory action potentials were absent and motor nerve conduction was severely slowed. This included proximal upper limb (musculocutaneous and axillary), hypoglossal, and facial nerves. The severity of slowing increased during childhood. M waves, often multiple, were recorded in all affected individuals. The blink reflex showed an unusual three component response. The latencies of all three components were prolonged. CONCLUSIONS: HMSN-L is shown to be a demyelinating neuropathy involving severe and early axonal loss. The progressive slowing of nerve conduction during childhood differs from the static reduction seen in type I HMSN.

A-waves in patients with novel hereditary motor and sensory neuropathy Lom.

OBJECTIVES: To determine A-waves of a family with autosomal recessive form of demyelinatig hereditary motor and sensory neuropathy Lom (HMSNL). METHODS: A-waves were investigated during conventional F-wave study of family members with HMSNL which had genetic testing. RESULTS: During routine F-wave studies A-waves were observed in all tested nerves. They appeared between M-responses and F-wave. The A-waves were with low amplitude, shorter duration and constant shape and latency than F-waves. They appeared independently of F-waves. A-waves were more often recorded as multiple waves in lower and upper extremities. More than three A-waves per nerve were found mostly in ulnar and facial nerves. In 16 cases A-waves were found in the absence of F-waves. CONCLUSION: It is assumed that the A-waves could be seen as additional signs of pathology because they were not observed in unaffected members of the family and in healthy subjects.

Comparative analyse of single motor unit pattern in healthy subjects and patients with neuromuscular disorders.

OBJECTIVE: The motor unit (MU) spike trains in human muscle contractions are an object to new mathematical processing. The aim is to identify the interspike interval relations characterizing normal and changed physiological states (neuro-muscular disorders). METHODS: MU activities in healthy subjects and patients with Schwartz-Jampel syndrome, neuromiotonia and Parkinson disease were investigated. Motor unit action potentials (MUAPs) were recorded by surface multielectrode with small leading-off area without provoking a burst of activity, as usually was observed during the needle electromyography study in patients with Schwartz-Jampel syndrome and neuromiotonia. RESULTS: Different single motor unit activity in healthy subjects and patients was observed. Discharge pattern of patients was basically changed. Disturbance of different parts of the motor system leads to the changes of temporal order of interspike interval. This permit us to suppose that the pattern of repetative neuronal discharges suggests an influence at a higher level than the muscle in all investigated patients but the reason of multiple discharges with an interimpulse interval of 2 to 10 ms probably originated in the muscle membrane. CONCLUSIONS: The comparative analysis of MU patterns in healthy subjects and patients with neuro-muscular disorders can help us to disclose inapparent connections between cortical and spinal level of motor control.

Peripheral late waves in patients with hereditary motor sensory neuropathy.

Patents with different forms of hereditary motor sensory neuropathy (HMSN) were investigated. Peripheral late waves (PLWs) were recorded when determining F wave at supramaximal stimulation. We registered them most frequently in patients with demyelinating neuropathies (HMSN1--58% and HMSN3--100%) and in patients with HMSN2--24% and HMN--13%. In patients with HMSN1 and HMSN3 the peripheral late waves sometimes were more than one--two or three. They had a consistent appearance above a maximal threshold of stimulation, an invariable latency, amplitude and wave-form. Their latency times were in parallel with the M-response latency. These PLWs can be explained by collateral regeneration in case of axonal neuropathy. The ephaptic transmission might be taken in consideration when interpreting data from patients with demyelinating processes.

Comparative analysis between Duchenne and Becker types muscular dystrophy.

Duchenne and Becker types of muscular dystrophy are usually differentiated according to age of onset and rate of progression criteria which are not sufficient. The aim of this paper was to re-establish the clues for distinguishing Duchenne from Becker types of muscular dystrophy. According to the onset and progression of the disease, one hundred and eleven patients were subdivided into two groups. First group--Becker muscular dystrophy--consisted of 40 patients and second one of 71 patients with Duchenne type of muscular dystrophy. Clinical data confirm some well known differences between Duchenne and Becker muscular dystrophy concerning the age of onset, severity of disease and rate of progression. Electromyographic signs of myopathic changes and spontaneous activity were found in both diseases. Spontaneous activity--bizarre and fibrillation potentials, as well as sharp waves are more common for Duchenne type. The differences between the Becker from Duchenne type of muscular dystrophy can be described on the basis of complex investigations (clinical, electromyographical, histological and biochemical).

Comparison between normal and parkinsonian pattern of motor unit firing.

There are many approaches to the study of the activity of separate motor units (MU) in man. In humans alpha motoneuron activity consists in generating spike trains that innervate groups of muscle fibers thus building MU. In the present study we used a new evolution of the joint interval density analysis in patients with Parkinson disease.