Muscle fibre composition and electromyographic features of cervical muscles following prolonged head extension in growing rats.
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Soft tissue stretching has been proposed as one of the control factors in craniofacial morphogenesis. However, its mechanism remains unclear. The present study investigated electromyographic (EMG) activity and muscle fibre composition of cervical muscles following prolonged head extension in growing rats. Thirty-six male Wistar rats were divided into two experimental (E1, E2) and one control (C) group at 25 days of age. To induce head extension, the experimental rats were raised in cylindrical cages, which were positioned horizontally for group E1 and tilted upward at 45 degrees for group E2. At 55 days of age, EMG activity was recorded from the anterior digastricus (AD), sternohyoideus (SH), sternomastoideus (SM), longus capitis (LC), and biventer cervicis (BC) muscles in the rest position and passive head extension. EMG activity was analysed on its integrated values (IEMG), and composition of muscle fibres was evaluated by myosin ATPase reaction and fibre cross-sectional areas were calculated. Group E1 showed a higher percentage of type I fibres and lower IEMG during passive head extension in AD. In group E2 there was a higher percentage of type I fibres, a higher IEMG at rest, and a lower IEMG during passive head extension in BC. The experimental groups demonstrated altered proportions of type IIA and IIB fibres in SM and LC. They also showed higher percentages of subtype fibres and reduced cross-section areas of type II fibres in most of the muscles investigated. These findings suggest that head extension affects fibre transition, distribution, cross-section area, and recruitment pattern in cervical muscles. (+info)
Vibration-induced ocular torsion and nystagmus after unilateral vestibular deafferentation.
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Vibration is an excitatory stimulus for both vestibular and proprioceptive afferents. Vibration applied either to the skull or to the neck muscles of subjects after unilateral vestibular deafferentation induces nystagmus and a shift of the subjective visual horizontal. Previous studies have ascribed these effects to vibratory stimulation of neck muscle proprioceptors. Using scleral search coils, we recorded three-dimensional eye movements during unilateral 92 Hz vibration of the mastoid bone or of the sternocleidomastoid (SCM) muscle in 18 subjects with chronic unilateral vestibular deficits after vestibular neurectomy or neuro-labyrinthitis. Nine subjects had lost function of all three semicircular canals (SSCs) on one side, and the other nine had lost function of only the anterior and lateral SSCs. Vibration of the mastoid bone or of the SCM muscle on either side induced an ipsilesional tonic shift of torsional eye position of up to 6.5 degrees during visual fixation, as well as a nystagmus with horizontal, vertical and torsional components in darkness. Subjects who had lost function of all three SSCs on one side showed a larger shift in ocular torsion in response to SCM vibration than did subjects who had lost function of only two SSCs. The difference between ocular torsion produced by ipsilesional muscle or bone vibration was not significantly different from that produced by contralesional bone or muscle vibration. The vibration-induced nystagmus rotation axis tended to align with the pitch (y) axis of the head in subjects who had lost only anterior and lateral SSC function, and with the roll (x) axis of the head in subjects who had lost function of all three SSCs. We propose that the previously described vibration-induced shift of the subjective visual horizontal can be explained by the vibration-induced ocular torsion, and that the magnitude of ocular torsion is related to the extent of the unilateral vestibular deficit. While altered proprioceptive inputs from neck muscles might be important in the mechanism of vibration-induced ocular torsion and nystagmus after unilateral vestibular deafferentation, vibratory stimulation of vestibular receptors in the intact labyrinth also appears to have an important role. (+info)
Initial experience with oral contrast in PET/CT: phantom and clinical studies.
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The aims of the study were to evaluate the effects of oral contrast on apparent tracer activity measured with PET/CT when using CT attenuation correction and to report our initial experience in the use of oral contrast with PET/CT. METHODS: Phantom studies with (18)F activity and saline bags or syringes filled with barium or gastrografin of varying densities were performed using a PET/CT scanner (CT attenuation correction). In the study, 91 clinical patients received dilute oral contrast and were evaluated by whole-body (18)F-FDG PET. RESULTS: A phantom experiment with CT contrast (1.3% weight/volume [w/v] barium) showed a "cold" area in the cold stomach whereas a phantom with high-density barium (98% w/v) showed an artifactual focus of intense "activity" in the cold stomach. In clinical studies, stomach and right colon were opacified by CT contrast. Maximal measured contrast density was 239 Hounsfield units. CONCLUSION: High-density barium causes overestimation of tissue (18)F-FDG concentration. Low-density barium does not cause significant artifacts and appears suitable for clinical use. (+info)
Respiratory effects of the scalene and sternomastoid muscles in humans.
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Previous studies have shown that in normal humans the change in airway opening pressure (DeltaPao) produced by all the parasternal and external intercostal muscles during a maximal contraction is approximately -18 cmH(2)O. This value is substantially less negative than DeltaPao values recorded during maximal static inspiratory efforts in subjects with complete diaphragmatic paralysis. In the present study, therefore, the respiratory effects of the two prominent inspiratory muscles of the neck, the sternomastoids and the scalenes, were evaluated by application of the Maxwell reciprocity theorem. Seven healthy subjects were placed in a computed tomographic scanner to determine the fractional changes in muscle length during inflation from functional residual capacity to total lung capacity and the masses of the muscles. Inflation induced greater shortening of the scalenes than the sternomastoids in every subject. The inspiratory mechanical advantage of the scalenes thus averaged (mean +/- SE) 3.4 +/- 0.4%/l, whereas that of the sternomastoids was 2.0 +/- 0.3%/l (P < 0.001). However, sternomastoid muscle mass was much larger than scalene muscle mass. As a result, DeltaPao generated by a maximal contraction of either muscle would be 3-4 cmH(2)O, which is about the same as DeltaPao generated by the parasternal intercostals in all interspaces. (+info)
Geniohyoid muscle function in awake canines.
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The geniohyoid (Genio) upper airway muscle shows phasic, inspiratory electrical activity in awake humans but no activity and lengthening in anesthetized cats. There is no information about the mechanical action of the Genio, including length and shortening, in any awake, nonanesthetized mammal during respiration (or swallowing). Therefore, we studied four canines, mean weight 28.8 kg, 1.5 days after Genio implantation with sonomicrometry transducers and bipolar electromyogram (EMG) electrodes. Awake recordings of breathing pattern, muscle length and shortening, and EMG activity were made with the animal in the right lateral decubitus position during quiet resting, CO2-stimulated breathing, inspiratory-resisted breathing (80 cmH2O. l-1. s), and airway occlusion. Genio length and activity were also measured during swallowing, when it shortened, showing a 9.31% change from resting length, and its EMG activity increased 6.44 V. During resting breathing, there was no phasic Genio EMG activity at all, and Genio showed virtually no movement during inspiration. During CO2-stimulated breathing, Genio showed minimal lengthening of only 0.07% change from resting length, whereas phasic EMG activity was still absent. During inspiratory-resisted breathing and airway occlusion, Genio showed phasic EMG activity but still lengthened. We conclude that the Genio in awake, nonanesthetized canines shows active contraction and EMG activity only during swallowing. During quiet or stimulated breathing, Genio is electrically inactive with passive lengthening. Even against resistance, Genio is electrically active but still lengthens during inspiration. (+info)
A new minimally invasive posterior approach for the treatment of cervical radiculopathy and myelopathy: surgical technique and preliminary results.
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Degenerative cervical disorders predominantly lead to anterior spinal cord compression (by bony spurs at the posterior margin of the vertebral body or by degenerated disc), which may be central and/or foraminal. In a smaller percentage of cases, there is encroachment of the canal mainly from posterior by bulging yellow ligaments or bony appositions, resulting in compression syndromes of roots or spinal cord. The aim of this work is to present a minimally invasive posterior approach avoiding detachment of muscles for the treatment of cervical radiculopathy and myelopathy. Thirteen patients suffering from cervical radiculopathy (four patients) or myelopathy (nine patients) were operated according to this technique. In principle, the technique secures access to the diseased spinal segment via a percutaneously placed working channel (11 mm outer diameter and 9 mm inner diameter). The cervical paraspinal muscles are not deflected, but just spread between their fibres by special dilators. All further steps are performed through this channel under control of three-dimensional vision through the operating microscope. The mean follow-up period was 17 months (one patient died 9 months postoperatively), and patients were evaluated using a modified version of the Oswestry Index, called the Neck Disability Index (NDI), and the visual analogue scale (VAS) for neck and arm pain. The mean NDI (P<0.0001) improved from 13.2 (preoperatively) to 4.8 (postoperatively). The VAS for arm pain (P<0.001) and for neck pain (P<0.001) also showed marked postoperative improvement. Complete recovery of the preoperative neurological deficit was found in four patients, while the remaining eight patients showed improvement of the neurological symptoms during the follow-up period. There were no intra-operative or postoperative complications and no re-operation. The preliminary experience with this technique, and the good clinical outcome, seem to promise that this minimally invasive technique is a valid alternative to the conventional open exposure for treatment of lateral disc prolapses, foraminal bony stenosis and central posterior ligamentous stenosis of the cervical spine. (+info)
Absence of scalenus anterior muscle.
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A rare anomaly of the scalenus muscles is described. In this case, the right scalenus anterior muscle was absent. As a substitute for this muscle, some aberrant muscle slips arose from the lower vertebrae and descended in front of the ventral rami of the lower cervical nerves. These aberrant slips then ran between the ventral rami of the the eighth cervical and first thoracic nerves, and were fused with the right scalenus medius muscle. Thus, the subclavian artery and vein ran in front of the aberrant slips, together with the ventral ramus of the first thoracic nerve. The aberrant muscle slips issued 2 accessory bundles. One bundle ran between the ventral rami of the fourth and fifth cervical nerves and was fused with the scalenus medius muscle; the other bundle ran between the ventral rami of the fifth and sixth cervical nerves and was fused with the scalenus medius muscle. (+info)
Compensatory increase of the cervico-ocular reflex with age in healthy humans.
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The cervico-ocular reflex (COR) is an ocular stabilization reflex that is elicited by rotation of the neck. It works in conjunction with the vestibulo-ocular reflex (VOR) and the optokinetic reflex (OKR) in order to prevent visual slip over the retina due to self-motion. The gains of the VOR and OKR are known to decrease with age. We have investigated whether the COR, a reflexive eye movement elicited by rotation of the neck, shows a compensatory increase and whether a synergy exists between the COR and the other ocular stabilization reflexes. In the present study 35 healthy subjects of varying age (20-86 years) were rotated in the dark in a trunk-to-head manner (the head fixed in spaced with the body passively rotated under it) at peak velocities between 2.1 and 12.6 deg s-1 as a COR stimulus. Another 15 were subjected to COR, VOR and OKR stimuli at frequencies between 0.04 and 0.1 Hz. Three subjects participated in both tests. The position of the eyes was recorded with an infrared recording technique. We found that the COR-gain increases with increasing age and that there is a significant covariation between the gains of the VOR and COR, meaning that when VOR increases, COR decreases and vice versa. A nearly constant phase lag between the COR and the VOR of about 25 deg existed at all stimulus frequencies. (+info)