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At least 775 records · Page 43Linked to original sources
PubMed2001

Sternomastoid paradox.

In the standard routine for testing cranial nerve function following a cerebrovascular accident (CVA) compromising the corticonuclear supply to the cranial nerves, sternomastoid muscle (SCM) function is checked by means of head rotation against resistance. SCM appears to be an exception to the generally contralateral motor weakness resulting from a CVA. The thrust of this article is that appearances can be deceptive: SCM is more likely to be a postural stabilizer than a prime mover in head rotation.

Cranial Nerves↗
PubMed1985

[Progressive supranuclear ophthalmoplegia--a clinical entity?].

The syndrome of progressive supranuclear ophthalmoplegia (Richardson-Steele-Olszewski-Syndrom) and its relation to other syndromes are discussed on the basis of a number of case histories and a survey of the pertinent literature. The validity of vertical ophthalmoplegia as a pathognomonic symptom is questioned. The main symptoms are as follows: the heightened tone of the neck muscles, as a rule combined with other indications of parkinsonism and an inclination to fall down. To varying degress there are also bulbar signs and subcortical dementia. Neuropathologically the syndrome can be classed with the "multiple system degeneration" group, on which little enough is known. It remains an open question whether the syndrom of Richardson-Steele-Olszewski is a syndrome of its own or whether it is just a variety of parkinsonism.

Aged↗
PubMed1997

Reflex jaw motions and jaw stiffness pertaining to whiplash injury of the neck.

Because a so-called mandibular whiplash injury requires the absence of short-latency jaw-closing reflexes in order to explain the postulated mechanism of injury (excessive jaw opening); the authors studied the presence and absence and more importantly, the kinematics (duration, displacement, velocity, acceleration) of monosynaptic and possibly, polysynaptic myotatic (stretch) reflexes in the jaw elevator muscles. In six healthy adults jaw jerk maneuvers were elicited through a brisk tap on the chin, and surface electromyography identified elevator reflexes while translational electrognathography identified the kinematics of the reflexes. The maneuvers were done while maintaining the rest position (3% MVC) and moderate clenching of the teeth (30% MVC). Electromyography was also used to identify phasic elevator excitations during a passive brisk neck extension maneuver. A sudden and unexpected elongation of the jaw elevators released autogenic reflex responses that, in conjunction with augmented tissue elasticity (stiffness), elevated the mandible into centric occlusion within approximately 150 milliseconds. In 86% of trials, the responses occurred regardless of the prevailing resting and clenching contractile activities. There was no evidence of a depressor force that consistently would and could anchor the mandible in a position of extreme or moderate depression, the theoretical linchpin of the mandibular whiplash injury. It was concluded that the mandibular locomotor system is very efficient in maintaining the rest and intercuspal positions of the mandible. This study found no evidence corroborating the mechanism claimed to release a so-called mandibular whiplash injury.

Acceleration↗
PubMed2005

Model-based detection of partially obstructed endotracheal tube.

OBJECTIVES: A five-element lumped pulmonary model was developed to estimate respiratory mechanics automatically and noninvasively. The model was applied to diagnose obstructed endotracheal tube. Events like bronchospasm and stiff chest wall were also tested to determine the specificity of the diagnosis. Cases with positive end-expiratory pressure were also included in the analysis to see the effects of positive end-expiratory pressure on the model. DESIGN: Randomized controlled animal study. SETTING: University department of anesthesiology. SUBJECTS: Ten anesthetized, paralyzed, and mechanically ventilated mongrel dogs (19-45 kg) of either gender. INTERVENTIONS: Two levels of upper airway obstruction were induced in ten dogs by partially constricting the endotracheal tube. Acute bronchial constriction was produced in five dogs by injecting methacholine through a central venous catheter. In the same five dogs, the chest wall was stiffened by wrapping a pressure cuff around the chest. Positive end-expiratory pressure was also applied as a separate event in these five animals. MEASUREMENTS AND MAIN RESULTS: Airway pressure and flow were continuously recorded at the mouth. Model parameters were iteratively identified until the root mean square error between respiratory impedance (obtained from airway pressure and flow) and model-predicted impedance (calculated using Ohm's law) was minimum. The peak inspiratory pressure increased and the peak expiratory flow rate decreased with increasing levels of partial obstruction. The value of the model parameters R(1) and C(2) increased and C(1) decreased with partial obstructed endotracheal tube, whereas R(1) increased and L and C(2) decreased with bronchospasm. With stiff chest wall, R(2) increased and C(2) decreased. With positive end-expiratory pressure, the L parameter decreased and no significant change in other model parameters was observed. Obstructed endotracheal tube is indicated if R(1) increased > or =30%, C(1) decreased > or =10%, and C(2) increased > or =10% from baseline. The test results using 45 events, including control, three complications, and positive end-expiratory pressure, show that when the model is used to diagnose obstructed endotracheal tube, the method has a sensitivity of 90% and specificity of 97%. CONCLUSIONS: During an obstructed endotracheal tube, model parameters change such that the event can be diagnosed noninvasively, automatically, and accurately. The model differentiates between upper airway obstruction and complications like bronchospasm and stiff chest wall.

Airway Resistance↗
PubMed1976

Measurements of stiffness of extraocular muscles of the rabbit.

1. The stiffness of the eye and the extraocular muscles of the conscious rabbit was measured and compared with similar measurements made on human subjects. 2. The extraocular muscles of the rabbit developed less than 0.5 g at optimal isometric length when the contralateral eye was in "primary position". Deviations of the eye of the rabbit from primary position were accomplished by an increase in force of the agonist muscle with only a nominal decrease in force in the antagonist. 3. With all muscles attached to the globe, the stiffness of the eye for displacements of up to 35 degrees from primary position was 0.11 +/- 0.03 g/deg. 4. The stiffness of the human eye to lateral rotations was 1.09 +/- 0.24 g/deg. Hence, identical disturbances in force would cause deviations in the position of the eye of the rabbit which are nearly an order of magnitude greater than those of man. 5. The stiffness of the extraocular muscles of the rabbit was sensitive to levels of muscle activation produced either by indirect electrical stimulation or by the vestibuloocular reflex. 6. The implications of these findings for the development of eye position control in animals with good binocular vision are discussed.

Animals↗
PubMed1997

[Studies on kinetic viscoelasticity of slow muscle fibers--1. Tension, fatigue resistance and stiffness in rabbit extraocular muscles].

To evaluate the mechanical properties of the slow fibers and fast fibers which make up the extraocular muscle, I studied the contractibility and viscoelasticity properties of the superior rectus muscle (SR) and the retractor bulbi muscle (RB) of rabbits. Eighteen to nineteen percent of whole muscle tension was produced by slow fibers in SR and 1 to 5% by those in RB. After long continuous contraction, fatigue-resistant fibers left residual tension in SR, but the tension was almost entirely absent in RB. The frequency response method was used to examine kinetic viscoelasticity. The muscle was stretched sinusoidally, with an amplitude of 1 mm at 20 Hz in Lmax. The tension amplitude to sine wave vibrations during tetanus (P) and resting (Po) were then examined. The dynamic stiffness ratio (P/Po) was higher in SR (3.1) than in RB (2.0). I suggest that the viscoelasticity of the activated cross bridge is greater in slow fibers than in fast fibers.

Animals↗
PubMed1977

[Gamma rigidity in parkinsonism].

The paper presents the results of the study on a muscle tension in patients with parkinsonism. The great role in the maintenance of the motor tonic activity in parkinsonism is played by an increased excitability (of a static type) of the receptors of the muscle length. The assumption is made that an increased sensitivity in these receptors is the result of the increased fusiomotor activity. The author discusses a possibility of changes in the structure of intrafusal fibres in spindles of the muscle due to which these receptors can preserve an excited state for a long time.

Humans↗