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H M Meinck

Publications and source records attributed to H M Meinck.

At least 73 records · Page 4Linked to original sources
PubMed1992

[Jaw opening reflex: a new electrophysiologic method for objective assessment of trigeminal sensory disorders. I. Method and normal values].

Retrospective analysis of trigeminal nerve evoked potentials in 40 consecutive patients, most of them with traumatic nerve lesions, showed that in 12 cases no trigeminal nerve SEP were obtainable, and 11 of the remaining 28 patients had normal trigeminal nerve SEP. Therefore the jaw-opening reflex was investigated as a potential tool for electrophysiologic analysis of facial sensory disturbances. The jaw-opening reflex was investigated in 60 healthy subjects (31 female, 29 male) aged 23-82 years. It was elicited by electrical 0.1 ms square wave pulses delivered to the lower and upper lips and to the infraorbital region on either side at a rate below 1 per 5s. The EMG responses were recorded from the bilateral masseter and temporalis muscles at a moderate voluntary activation. Under these conditions, the jaw-opening reflex reveals itself as two inhibitory pauses of the ongoing EMG on both sides, the onset latency of the first EMG-suppression being 10-15 ms, and of the second 35-50 ms. Particular attention was paid to the stimulus strength at threshold (TR) to evoke the jaw-opening reflex. We found that the jaw-opening reflex was constantly evoked by weak stimuli applied to the 2nd and 3rd trigeminal branches. Bilateral reflex responses with unilateral stimulation were a regular finding. The reflex responses increase with increasing stimulus strength (Fig. 1). Moderate to forcible activation of the jaw closing muscles is a prerequisite for optimum recordings of the jaw-opening reflex (Fig. 2).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[Stiff-man syndrome: an immunopathy?].

The discovery of autoimmune processes in the stiff-man syndrome (SMS) not only raises questions concerning the syndrome itself, but may also lead to new insights into pathogenetic principles of neurological disorders. Autoantibodies against GAD, the GABA synthesising enzyme, may become a helpful (though not specific) diagnostic tool, and furthermore may serve as a plausible explanation for both the symptoms of the syndrome and the delayed development of type I diabetes mellitus. However, it remains unexplained why autoimmunity against such widespread inhibitory transmitter systems should induce a syndrome which by definition is confined to only a few symptoms, and for which the majority of neurological signs are regarded as exclusion criteria. It is therefore hypothesised that SMS is part of a broad spectrum of encephalomyelopathies with autoimmunity against GABAergic neurones in common, but with a heterotopic manifestation. Progressive encephalomyelitis with rigidity may be an extreme variant within this spectrum.

Autoantibodies↗
PubMed1990

Borrelia burgdorferi myelitis presenting as a partial stiff man syndrome.

Eight weeks after a tick bite, a 33-year-old male patient presented with stiffness of one leg together with spasmodic painful jerks resembling stiff man syndrome. Isolated myelitis of lumbosacral segments of the spinal cord, apparently confined to the grey matter, was diagnosed and its spirochaetal aetiology confirmed by serology and CSF findings. Oligoclonal IgG bands in CSF specific for Borrelia burgdorferi were found. Thus, there is evidence that B. burgdorferi ist able to cause a localized myelitis, probably of spinal interneurons, presenting as a partial stiff man syndrome.

Adult↗
PubMed1989

Effect of cannabinoids on spasticity and ataxia in multiple sclerosis.

The chronic motor handicaps of a 30-year-old multiple sclerosis patient acutely improved while he smoked a marihuana cigarette. This effect was quantitatively assessed by means of clinical rating, electromyographic investigation of the leg flexor reflexes and electromagnetic recording of the hand action tremor. It is concluded that cannabinoids may have powerful beneficial effects on both spasticity and ataxia that warrant further evaluation.

Adult↗
PubMed1987

[Cutaneo-muscular reflexes of the human hand. II. Neurophysiologic aspects of reflex organization and coordination].

The organization and coordination of cutaneo-muscular reflexes of human finger and arm muscles to electrical stimulation of the digital nerves were investigated in 14 healthy volunteers. Thumb and finger muscles, although antagonists, showed homonymous reflex effects whereas the wrist and elbow muscles exhibited an reciprocally alternating reflex pattern in pairs of antagonists (Fig. 1). The mechanographical correlate of the homonymous reflex activity in distal muscles was a short release (Fig. 6). The receptive field for evoking such reflex effects covered both the palmar and dorsal surfaces of the fingers (Fig. 2). However, with stimulation of the thumb, the muscles of the fingers and of the wrist showed reflex reversal (Figs 3, 5). If the stimulus was moved from the second to the fifth fingers, a successive attenuation of the transcortical reflex component was seen (Fig. 4). It is concluded that the reflexes investigated are complex flexor reflexes comprising both a distal release and a proximal flexion synergy. According to opposition of the thumb in grasping, the receptive field terminates between thumb and index finger. These reflexes are supposed to have no assisting function during corticalized manipulatory movements--in contrast to the long-loop reflexes evoked by epicritic sensibility. The transcortical servo is blocked if the eliciting stimulus is contaminated by nociceptive signals; its receptive field is confined to those fingers used in the precision grip.

Adult↗
PubMed1986

Neuropharmacological investigations in the stiff-man syndrome.

In a patient with the stiff-man syndrome, abnormal exteroceptive reflexes in hand and arm muscles were used as a tool for investigating the effects of various centrally acting adrenergic drugs by means of acute testing. Clonidine, tizanidine and methamphetamine induced reflex suppression whereas reserpine had a biphasic effect: transient reflex suppression and delayed reflex enhancement. The drug actions on the reflexes paralleled to some degree those on the muscle stiffness. It is concluded that alpha-adrenergic stimulation leads to reflex suppression and muscular relaxation, whereas alpha-adrenergic blockade has the opposite effect. Correspondingly, long-term oral treatment with the alpha-stimulator, tizanidine, proved successful. The hypothesis is put forward that a noradrenergic system which exerts a net inhibitory influence on muscle tone and on exteroceptive reflexes plays an important role in the pathogenesis of the stiff-man syndrome.

Adrenergic Fibers↗
PubMed1986

Delayed visual evoked potentials in chronic alcoholism.

Pattern reversal visual evoked potentials (VEPs) were studied in 80 chronic alcoholics and in 43 normal subjects. In the patient group, P2 latencies and inter-eye differences were found above the 98% confidence limit in 30%, and above the 99.9% confidence limit in 10%. An abnormal waveform was observed in 12.5% and 7.5% of the patients. VEP abnormalities showed some statistical correlation with the gamma-type of alcoholism of Jellinek, but almost no correlation was observed with a variety of clinical and laboratory data. This suggest that VEP abnormalities are unrelated to other toxic effects of alcohol on the peripheral and central nervous systems or on metabolism.

Adult↗
PubMed1986

[Cutaneo-muscular reflexes of the human hand. I. Methodologic principles].

Cutaneo-muscular reflexes of the human hand were investigated with special regard to methodological characteristics. The reflexes were elicited by electrical stimulation of either the volar side of the index finger or the median nerve at the wrist, they were in both cases recorded from the abductor pollicis brevis muscle. Independent from the stimulus site, the reflex pattern consisted of four inhibitory and excitatory components (I1-E1-I2-E2): an H reflex was recorded from exclusively with median nerve stimulation. With increasing stimulus efficiency (stimulus strength or duration), the components I1, I2, and E2 were enhanced whereas the presumably transcortically mediated E1 component was successively attenuated. Systematic variation of the stimulus interval, in contrast, induced attenuation of I2 and slight enhancement of I1 only at short intervals (750 ms). Comparison of the reflex responses on both sides revealed a distinct asymmetry particularly of the amplitudes and--less distinct--of the latencies. Asymmetries of the E1 component should therefore be interpreted as pathologic only cautiously.

Adult↗
PubMed1985

Rapid goal-directed elbow flexion movements: limitations of the speed control system due to neural constraints.

In rapid goal-directed elbow flexion movements the influence of both movement amplitude and inertial load on the three-burst pattern and the consequences on movement time were studied. Subjects performed visually guided, self-paced movements as rapidly and as accurately as possible. An increase of both the movement amplitude and the inertial load were found to be interacting factors for the modulation of the three-burst-pattern and movement time. The first biceps burst progressively increased in duration and amplitude for larger movements, resulting in prolonged movement times. Surplus inertial loads further prolonged the agonist burst for large, but not for small movement amplitudes. The activity of the antagonist burst, in contrast, was largest in small movements and successively decreased at increasing movement amplitudes. Its duration, however, remained fairly constant. As was similarly observed for the agonist burst, surplus inertial loads lead to a prolongation of antagonist burst duration and an small movement amplitudes. It is suggested that in elbow flexion movements the programming of fastest goal-directed movements must take into account neural constraints and biomechanical characteristics of the agonist muscle and the antagonist muscle. Due to neural constraints of the biceps muscle, in contrast to finger movements, the concept of movement time invariance does not hold for elbow movements. Furthermore, neural constraints of the antagonist muscle lead to a limited force production of the agonist muscle at small movement amplitudes in order to avoid an overload of the braking process.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

The flexor reflex--influence of stimulus parameters on the reflex response.

The flexor reflex evoked in the tibialis anterior muscle by stimulation of the medial plantar nerve was investigated in 54 normal subjects. Three main reflex components were identified (excitation--inhibition-- excitation), the early excitation being composed of two subcomponents. Occasionally, a fourth (excitatory) reflex component was seen breaking through EMG inhibition. The individual reflex components were differentially susceptible to facilitatory influences which suggested transmission via a central multichannel system. Methodological experiments showed that the amplitudes and to some degree also the latencies of the individual reflex components were modified by both the parameters of the stimulus as well as by the degree of pre-innervation. However, the patterning of the reflex response was basically independent from methodological permutations.

Adult↗
PubMed1984

Human ballistic finger flexion: uncoupling of the three-burst pattern.

In isotonic and isometric goal-directed index finger movements made as fast as possible, the "braking hypothesis" ascribed to the antagonist burst was tested. Under isotonic conditions, the extensor burst often failed to occur in small angle movements with low inertial load. It regularly occurred, however, in small angle movements with high inertial load and in wide angle movements with both low and high inertial loads. Such features suggest, indeed, the antagonist burst as being part of braking strategies. Under isometric conditions, the antagonist burst - if it occurred - exhibited characteristics which suggested a rapidly alternating movement rather than a braking strategy.

Electromyography↗
PubMed1984

The stiff-man syndrome: new pathophysiological aspects from abnormal exteroceptive reflexes and the response to clomipramine, clonidine, and tizanidine.

Neurophysiological investigations of a patient suffering from the stiff-man syndrome revealed that exteroceptive reflexes, in particular those elicited from the skin, were excessively enhanced. In contrast, no abnormalities were found within the monosynaptic reflex arc. Clomipramine injection severely aggravated the clinical symptoms whereas diazepam, clonidine, and tizanidine decreased both muscular stiffness and abnormal exteroceptive reflexes. The hypothesis is put forward that the stiff-man syndrome is a disorder of descending brain-stem systems which exert a net inhibitory control on axial and limb girdle muscle tone as well as on exteroceptive reflex transmission. Detection of abnormal exteroceptive reflex activity in conjunction with neuropharmacological testing might help in the diagnosis of this rare disease.

Adult↗
PubMed1984

Centronuclear myopathy with special consideration of the adult form.

We report clinical, electrophysiological, enzyme histochemical and ultrastructural findings in 4 patients afflicted with centronuclear myopathy of adulthood whose disorder emphasizes the broad spectrum of this congenital myopathy including clear ocular ptosis in only one and facio-scapulo-peroneal syndrome in another patient. The morphological criteria for classification are central nuclei and the enzyme histochemical findings in muscle biopsies which did not show any significant progression over many years, more severe involvement of distal muscles in 2 patients and conspicuous presence of intrafascicular fat cells. 1 patient had associated minicores in a familial setting. Although electromyographic data comprised a mixed myopathic-neurogenic pattern, the morphological features in muscle biopsies did not further prove a neurogenic origin of our patients' neuromuscular disorder.

Adult↗