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At least 523 records · Page 29Linked to original sources
PubMed1993

Cervical spine subluxation associated with congenital muscular torticollis and craniofacial asymmetry.

The relationship between craniofacial asymmetry, congenital muscular torticollis, and cervical spine subluxation was examined in a study of 30 children who presented to our Craniofacial Program from 1987 through 1990. Twenty-six of the 30 patients had craniofacial asymmetry and muscular torticollis without true suture synostosis documented by head and neck CT scans. These 26 patients had positional skull molding with consistent flattening of the contralateral occipitoparietal region and the ipsilateral fronto-orbital region relative to the side of the torticollis. Thirteen of the 26 patients also were found to have a C1-C2 subluxation. C1 was rotated forward of C2 on the side contralateral to the muscular torticollis in 12 of 13 patients. None of the patients with subluxation had neurologic deficits or required spinal stabilization. Ophthalmologic evaluations demonstrated amblyopia (4 patients) and horizontal strabismus (1 patient), both thought to be coincidental, with no evidence of nystagmus in any case. Seven of the 26 patients required surgical therapy for their neck muscle tightness, while the remainder responded to physiotherapy. Only 2 of the 26 patients underwent cranio-orbital reshaping for correction of their upper face asymmetry. Recognition of cervical subluxation in patients with congenital muscular torticollis may help to explain residual head-neck posturing problems even after successful neck muscle therapy.

Birth Injuries↗
PubMed2002

Effects of predictive mechanisms on head stability during forward trunk perturbation.

While much is known about reflex and mechanical contributions to the control of head stability, little is known about predictive control. The goal of this experiment was to determine the contribution of predictive mechanisms to head stability in space, in the pitch plane, during forward trunk perturbations. Eleven standing healthy subjects had their trunk pulled forward by a load-pulley apparatus. The perturbation was either self-triggered or imposed (triggered by the experimenter). Subjects were exposed to two loads: 2% and 4% of their body weight. The contributions of torques acting on the head-neck system were inferred from head and trunk kinematics, neck muscle EMG, and the torques acting on the head, which were computed using inverse dynamics. The results showed that both the head and trunk moved less during the self-triggered than imposed condition during both loads for most of the participants. There was no evidence of predictive neck countertorque or increased neck muscle co-contraction during the self-triggered condition. These findings suggest that most of the subjects improved head stability in the self-triggered condition by reducing trunk motion and the associated interactive torque that perturbed the head.

Adaptation, Physiological↗
PubMedDate not supplied

Immunization of rabbits with secific components of postsynaptic membrane. Acetylcholinesterase and cholinergic receptor.

Rabbits were immunized versus either an acetylcholinesterase- or a cholinergic receptor-rich fraction isolated from the electric organ of Torpedo marmorata. In both groups of animals we obtained a production of specific antibodies detected by immunodiffusion without cross reaction for the two antigens. Only rabbits immunized with the receptor-rich fraction developed a progressive flaccid paralysis, which affected first the leg muscles, progressively the neck muscles and eventually the respiratory muscles. The paralysis lasted in several animals up to 20 days. Eserine reversed the paralysis only in the first days but was ineffective in the "chronic" stage of the disease. In these animals high frequency stimulation of sciatic nerve induced a rapid failure of the responses of the anterior tibialis muscle while the muscle responded normally to a direct stimulation. A period of rest allowed a complete recovery of the muscle from fatigue. Tetani did not evoke the post-tetanic potentiation. Abnormalities, such as lymphocytic infiltration, fibers atrophy and necrosis, smearing and widening of Z line were sometimes present in muscles of Cho-R-immunized rabbits. In ACh-E immunized animals the neuromuscular transmission and the muscle morphology were similar to that of normal animals. Glycogen, ATP, cytochrome C oxidase, phosphorylases and acetylcholinesterase did not change significantly in the muscles of the immunized animals, while a large increase of cholineacetyltransferase activity was present. Red blood cell acetylcholinesterase showed a particularly high activity in ACh-E-immunized animals. The autoimmune paralysis induced in Cho-R-immunized rabbits may be a useful experimental model for further studies on human myasthenia gravis.

Acetylcholinesterase↗
PubMed2000

Multifunctional neuron CC6 in Aplysia exerts actions opposite to those of multifunctional neuron CC5.

The controls of somatic and autonomic functions often appear to be organized into antagonistic systems. This issue was explored in the bilaterally paired C cluster neuron, CC6, which was found to have properties that suggested that it might function antagonistically to the previously identified multiaction neuron, CC5. Similar to CC5, CC6 is an interganglionic neuron that sends its sole axon to the ipsilateral and contralateral pedal and pleural ganglia. Synaptic inputs to CC6 were opposite to those of CC5. For example, CC6 receives inhibitory inputs from mechanical touch to the lips and tentacles and is excited by firing of C-PR, a neuron involved in the control of a head extension response. Also during rhythmic buccal mass movements CC6 receives synaptic inputs that are out of phase with those received by CC5. CC6 is inhibited during a fictive locomotor program, whereas CC5 is excited, but unlike CC5, the inputs to CC6 are not rhythmic. CC6 has extensive mono- and polysynaptic outputs to many identified and unidentified neurons located in various central ganglia. Firing of CC6 evoked ipsilateral contraction of the transverse muscles of the neck, whereas CC5 contracts longitudinal neck muscles. CC6 monosynaptically inhibits the pedal artery shortener neuron, whereas CC5 monosynaptically excites the pedal artery shortener neuron. Specific motor neurons in the pedal ganglion receive synaptic inputs of opposite sign from CC5 and CC6. Although the inputs and most of the effects of CC6 were opposite to those of CC5, both cells were found to produce polysynaptic excitation of the abdominal ganglion neuron RBhe, a cell whose activity excites the heart. CC5 and CC6 appear to be multifunctional neurons that form an antagonist pair.

Action Potentials↗
PubMed1976

Diagnostic value of tomography in unilateral vocal cord paralysis.

Tomographic studies were made on 56 patients with unilateral paralysis of the vocal cord. The findings were examined in relation to etiology, course, and laryngoscopic findings. In 74.1 percent of the cases, marked enlargement of the ventricle was noticed on the side of the paralysis, especially during inhalation. The paralyzed vocal cord was higher than the intact cord during phonation in 46.4 percent of the cases. The rest of the cases (53.6 percent) demonstrated no level difference between the vocal cords. The position of the paralyzed vocal cord, unilateral involvement of the cricothyroid muscle and other neck muscles were suggested as possible contributors to the findings.

Adolescent↗
PubMed1999

Muscle fatigue caused by repeated aerial combat maneuvering exercises.

BACKGROUND: Little is known about the development of in-flight muscular fatigue during repeated flights. HYPOTHESIS: This study was conducted to evaluate muscular fatigue in different upper body and neck muscles during repeated aerial combat maneuvering exercises. METHODS: Six pilots volunteered as test subjects. They performed one-to-one dog fight exercise three times (1 pilot, four times) in one day. During the flights, the pilots' electromyographic activity (EMG) was measured from the abdomen, back, neck and lateral neck. The mean muscular strain for each muscle was calculated. Before the first flight and after each flight, the maximal isometric strength of each muscle was measured. RESULTS: The results showed that maximal isometric strength between the first and last measurement decreased in the back, neck (p < 0.05) and lateral neck muscles. While the G-stress remained the same, the muscular strain during exercises increased in every muscle, but was significant only in neck and lateral neck (p < 0.05-0.01). Due to these changes, the fatigue index in the neck and lateral neck muscles was 2.0-2.1, and 1.3-1.4 (1.0 = no fatigue) in the abdomen and back muscles. CONCLUSIONS: Repeated aerial combat maneuvering exercises caused fatigue in every muscle studied. The fatigue was greater in the neck area, which may increase the risk for neck injuries, and may reduce mission effectiveness. The fighter pilots' muscular strength and endurance in the neck area are subjected to very high demands, especially if exercises are repeated several times. The recovery of the neck muscles from fatigue after repetitive exercises should receive special attention.

Abdominal Muscles↗
PubMed2002

The perception of body orientation after neck-proprioceptive stimulation. Effects of time and of visual cueing.

Different sensory systems (e.g. proprioception and vision) have a combined influence on the perception of body orientation, but the timescale over which they can be integrated remains unknown. Here we examined how visual information and neck proprioception interact in perception of the "subjective straight ahead" (SSA), as a function of time since initial stimulation. In complete darkness, healthy subjects directed a laser spot to the point felt subjectively to be exactly straight ahead of the trunk. As previously observed, left neck muscle vibration led to a disparity between subjective perception and objective position of the body midline, with SSA misplaced to the left. We found that this displacement was sustained throughout 28 min of continuous proprioceptive stimulation, provided there was no visual input. Moreover, prolonged vibration of neck muscles leads to a continuing disparity between subjective and objective body orientation even after offset of the vibration; the longer the preceding vibration, the more persistent the illusory deviation of body orientation. To examine the role of vision, one group of subjects fixated a central visual target at the start of each block of continuous neck vibration, with SSA then measured at successive intervals in darkness. The illusory deviation of SSA was eliminated whenever visual input was provided, but returned as a linear function of time when visual information was eliminated. These results reveal: the persistent effects of neck proprioception on the SSA, both during and after vibration; the influence of vision; and integration between incoming proprioceptive information and working memory traces of visual information.

Adult↗
PubMed2002

Involvement of the medial pallidum in focal myoclonic dystonia: A clinical and neurophysiological case study.

We successfully treated a patient with familial myoclonic dystonia (FMD), which primarily affected his neck muscles, with bilateral deep brain stimulation (DBS) to the medial pallidum, and investigated the role of the medial pallidum in FMD. A patient with FMD underwent bilateral implantation of DBS electrodes during which field potentials (FPs) in the medial pallidum and electromyograms (EMGs) from the affected neck muscles were recorded. The effects of high-frequency DBS to the medial pallidum on the FMD were also assessed by recording EMGs during and immediately after implantation, as well as 6 days and 8 weeks postoperatively. During spontaneous myoclonic episodes, increased FPs oscillating at 4 and 8 Hz were recorded from the medial pallidum; these correlated strongly with phasic EMG activity at the same frequencies in the contralateral affected muscles. The EMG activity was suppressed by stimulating the contralateral medial pallidum at 100 Hz during the operation and continuous bilateral DBS from an implanted stimulator abolished myoclonic activity even more effectively postoperatively. The phasic pallidal activity correlated with and led the myoclonic muscle activity, and the myoclonus was suppressed by bilateral pallidal DBS, suggesting that the medial pallidum was involved in the generation of the myoclonic activity. High-frequency DBS may suppress the myoclonus by desynchronising abnormal pallidal oscillations. This case study has significant clinical implications, because at present, there is no effective treatment for focal myoclonic dystonia.

Adult↗
PubMed1997

Kinematics of the freely moving head and neck in the alert cat.

In this study we examined connections between the moment-generating capacity of the neck muscles and their patterns of activation during voluntary head-tracking movements. Three cats lying prone were trained to produce sinusoidal (0.25 Hz) tracking movements of the head in the sagittal plane, and 22.5 degrees and 45 degrees away from the sagittal plane. Radio-opaque markers were placed in the cervical vertebrae, and intramuscular patch electrodes were implanted in five neck muscles, including biventer cervicis, complexus, splenius capitis, occipitoscapularis, and rectus capitis posterior major. Videofluoroscopic images of cervical vertebral motion and muscle electromyographic responses were simultaneously recorded. A three-dimensional biomechanical model was developed to estimate how muscle moment arms and force-generating capacities change during the head-tracking movement. Experimental results demonstrated that the head and vertebrae moved synchronously, but neither the muscle activation patterns nor vertebral movements were constant across trials. Analysis of the biomechanical model revealed that, in some cases, modification of muscle activation patterns was consistent with changes in muscle moment arms or force-generating potential. In other cases, however, changes in muscle activation patterns were observed without changes in muscle moment arms or force-generating potential. This suggests that the moment-generating potential of muscles is just one of the variables that influences which muscles the central nervous system will select to participate in a movement.

Animals↗
PubMed2005

Comparison of tap-evoked and tone-evoked postural reflexes in humans.

To find an easy clinical test of postural reflexes, we compared tone and tap stimuli for eliciting postural reactions in leg muscles in 13 healthy subjects during upright stance. Tones (1000 Hz, 90 dB nHl) were presented monaurally via headphones; taps were applied with a reflex hammer to the forehead. Surface EMG was recorded from the medial gastrocnemius and the sternocleidomastoid muscles, and rectified and averaged. Tapping the forehead of a standing subject evoked leg muscle reflexes that began 50 ms after the stimulus in all subjects. Tone-evoked leg muscle reflexes behaved differently, i.e., they had smaller amplitudes and could be recorded in only 5 of 13 subjects. However, this same acoustic stimulus elicited reflex activity in the neck muscles of all subjects. There were also other differences (amplitudes, dependence on pre-activation) between these two reflexes. Tone-evoked leg muscle responses and tone-evoked neck muscle responses seem to be mediated by different structures, i.e., the latter by an oligosynaptic pathway and the former by polysynaptic neural circuits. We conclude that tap-evoked leg muscle responses are not or not solely mediated by saccular receptors but other receptors (i.e., proprioceptors, semicircular canals) are probably also involved.

Acoustic Stimulation↗
PubMed1993

[The relationship between experimental changes in the stress-strain distribution and the tissues structural abnormalities of the cervical column].

Using 45 rabbits, the authors made a research on the relationship between the experimental change of the stress-strain distribution and the tissues structural abnormalities of the cervical column. After having changed the stress and strain distribution on the rabbits' cervical vertebrae by letting them bow their heads, we measured the strain distribution in Vivo with resistant strain gauges, inspected the pathological changes of the cervical vertebrae, the nuchal ligaments, the capsular ligaments, the neck muscles and the attachments of the capsular ligament to bones, by ligh microscope and electron microscope. We found that the greater the level of the strain and the longer time the strain was loaded, the more evident the morphological abnormalities of the cervical vertebrae. The increase of the stress and strain could also cause degeneration of the nuchal ligaments, capsular ligaments and neck muscles. We believe that the abnormalities of the of the soft tissues around the cervical vertebral bones play an important part in the development of the cervical spondylosis. We think that the morphological changes of the cervical column is the basis of the biomechanical pathogenesis of the cervical spondylosis.

Animals↗
PubMed2006

Postural reactions to neck vibration in Parkinson's disease.

To test the hypothesis that reduced reactions to proprioceptive input signals contribute to postural instability in Parkinson's disease (PD), pulses of mechanical vibration were applied to the neck muscles of PD patients and healthy controls. This stimulus elicits postural reactions in standing subjects. Participating were 13 moderately affected PD patients, 13 severely affected PD patients, and 13 age-matched healthy subjects. Patients were tested on and off medication. Three-second-long pulses of vibration were regularly (10 times) applied to the posterior neck muscles while subjects kept their eyes open or closed. Postural responses to the stimuli were measured by static posturography. No intergroup difference in the pattern and latencies of responses was found. However, the amplitudes of the postural reactions (shift of center of foot pressure) were significantly larger in advanced PD patients; those of moderately affected PD patients did not differ from those of control subjects. Moreover, the size of postural responses in both latter groups decreased across the trial contrary to that of advanced PD patients. Comparison of the measures during on and off testing revealed no significant differences. These results indicate that neither afferent proprioceptive deficits nor central integrative functions but rather scaling and habituation of erroneous proprioceptive information are disturbed in the postural control of advanced PD. Nondopaminergic structures seem to be responsible for this impairment.

Afferent Pathways↗
PubMed1983

Afferent projections from the rat longus capitis muscle studied by transganglionic transport of HRP.

Using the method of transganglionic transport of horseradish peroxidase (HRP) according to Mesulam (1978), the course and central terminations of the afferents from the longus capitis muscle were studied in the rat. Application of HRP to the cut muscle nerves was followed by heavy labeling of a considerable number of cell bodies of different sizes in the spinal ganglia C2 and C3. The labeled central processes follow two distinct main routes: one to the external cuneate nucleus, which is known to project ipsilaterally to the cerebellum, the other to the central cervical nucleus (CCN) of the spinal cord. The latter nucleus contains dense arborizations and terminals of muscle afferents in close relationship to medium sized cells which project contralaterally to the cerebellum. This could be shown in double labeling experiments with HRP as a tracer for primary afferents and Nuclear yellow for the cerebellar pathway. The labeled area of CCN extends from the fourth cervical segment up to the medulla oblongata where it lies laterally adjacent to the hypoglossal nucleus, though clearly separated from the latter. In the cervical part of CCN, dendrites of neck muscle motoneurons arborize within the area of afferent terminals. Besides the external cuneate and the central cervical nuclei, afferent projections were seen in lamina X, partly in close contact with the central canal, and in more lateral areas of lamina VII. In contrast to results from studies on other neck muscles, no reaction product was observed in dorsal horn laminae I-VI.

Afferent Pathways↗
PubMed2001

[Influence of vibration on the equilibrium of patients with unilateral labyrinthine dysfunction].

To determine the role of proprioceptors of different skeletal muscles in posture control in patients with unilateral labyrinthine dysfunction (ULD), we studied the effect of vibration on those muscles by postulography. Subjects were 59 healthy people and 20 ULD patients. We measured the length of the displacement of the center of gravity, maximum sway length, and sway area. Significant differences were observed between healthy and ULD subjects on stimulation of the muscle groups of the upper and lower extremity during vibration. In patients with ULD, vibration to the dorsal neck muscles caused a deviation toward the diseased side. We speculate that the upper dorsal neck muscle plays an important role in maintaining body balance in the frontal plane in patients with ULD. The upper and lower extremity muscles play a significant role in adjusting standing posture.

Adult↗