Referred pain in headache

A technique consisting of the application of digital pressure to posterior neck muscles was applied at the time of headache to 82 neuropsychiatric patients observed at a Veterans Administration Mental Hygiene Clinic. Results indicated correlation between sustained muscular contraction of neck muscles and pain in the head. Certain commonalities among the Minnesota Multiphasic Personality Inventory profiles of the patients were noted and a new scale of items was developed which may prove useful in identifying headache-prone persons and their psychological characteristics. Repression was not found to be higher than the populational mean.     

Relationship between reaction time of eye movement and activity of the neck extensors

This study investigated the relationship between the reaction time of eye movement (RTEM) and activity of the superficial neck extensor muscles when the shoulder girdle elevator muscles contracted isometrically. The results were compared with those of a previous study in which the subjects's head was fixed and loaded with the neck flexed. When the shoulder girdle elevator muscles contracted isometrically, RTEM decreased significantly in comparison to RTEM at rest. This demonstrated that the reaction time significantly decreased not only as a result of the neck in flexion, which activated the deep and superficial neck extensor muscles, but also from contraction of the shoulder girdle elevator muscles which mainly activated the superficial extensor muscles. The relationship between RTEM and relative muscle load of the shoulder girdle elevator muscles showed that RTEM decreased up to 30% loading, and with loading above 40% the RTEM was longer than with 30%. The relative muscle load for the shortest RTEM demonstrated a subject-to-subject variance ranging from 24.7% to 49.6%. The difference between RTEM at rest and at their shortest reaction time was approximately 20 ms, which was consistent with the data for the neck in flexion. However, the relative muscle load for the shortest RTEM differed between the current and previous studies. The parameters obtained in this study were higher than for those in the previous study.     

Sequential maturation of skeletal muscle groups during postnatal ontogenesis of rats]

Experiments were conducted on rats during the early postnatal period; a study was made of the membrane potential (MP) establishment of the fibers of the skeletal muscles of the neck, the anterior and the posterior limbs. At birth the most mature were the muscles of the neck, and the least -- the muscles of the posterior limb. Establishment of the stationary MP level in the muscles of the neck occurred during the first week after birth, in the muscles of the anterior limbs -- by the 10th-12th day, and of the posterior limbs -- by the 15th-20th day. The order of maturation of various groups of the skeletal muscles was associated with the peculiarities of the neuro-trophic influences at various age periods. Muscles of the neck were characterized at all the developmental stages by a rhythmic low-frequency electromyographic activity. In the muscles of the limbs the rhythmic electromyographic activity was transformed into the discharge high-frequency activity by the period of termination of increase of the MP of the muscles.     

Contractile characteristics and operating lengths of canine neck inspiratory muscles

The neck inspiratory muscles are recruited to support breathing under numerous conditions. To gain insight into their synergistic actions we examined the isometric contractile properties of bundles from canine scalene and sternomastoid muscles. In addition, we also related the length of the neck muscles, measured sonomicrometrically in vivo at different lung volumes and body positions, to their optimal force-producing length (Lo) determined in vitro. We found that the speed of the sternomastoid is somewhat faster than that of the scalene owing to a shorter relaxation rate; the sternomastoid generates higher forces at submaximal stimulation frequencies than the scalene; the maximal tetanic force corrected for cross-sectional area is the same for both neck muscles; the neck muscles are significantly faster than the canine costal diaphragm; at supine functional residual capacity (FRC), the scalene is operating at a length corresponding to 85% Lo, whereas the sternomastoid is significantly shorter at 75% Lo; increasing lung volume shortens both muscles slightly, the length at supine total lung capacity being approximately 5% shorter than at FRC; and in the upright posture, both neck muscles lengthen toward their Lo, with the sternomastoid lengthening more than the scalene. We conclude that the scalene is a more effective force generator than the sternomastoid with the animal lying supine; the neck muscles appear to maintain their force-generating potential regardless of the lung volume; and the force-generating potential of the neck muscles is greatly enhanced with the animal in the upright vs. the supine position. This may contribute to the augmented rib cage motion characteristic of breathing in the upright posture.     

Problem neck, hyoid bone, and submental myotomy.

Despite significant attention to the cervical region over the last two decades, the hyoid bone has not received deserved recognition. In this report, the anatomy and role of the hyoid bone and suprahyoid muscles in cervicomental morphology are reviewed. From an analysis of cephaloxerograms on 54 patients, it was concluded that on a balanced neck, the most caudal border of the hyoid body is located at or above a line parallel to the Frankfort horizontal line passing through the most caudal border of the mandibular symphysis (menton). Of the muscles that control the position of the hyoid bone, the anterior belly of the diagastric, geniohyoid, and mylohyoid muscles pull the hyoid bone cephalad and anteriorly. The stylohyoid muscles, on the other hand, pull this bone cephalad and posteriorly, while the sternohyoid and omohyoid muscles pull it caudally. Transection of the first three muscles at their attachment to the posterior aspect of the mandible in patients with dysmorphic necks due to caudal and anterior hyoid position will allow posterior and cephalad relocation of this bone, which improves the neck contour. Sixteen patients, with an average follow-up of 27 months, have undergone this procedure, with cervicomental contour improvement in all cases. The degree of improvement ranged from 1 to 5 (5 being excellent): One patient was ranked 1, two patients were ranked 2, two patients were ranked 3, and the rest were ranked 4 or 5. One patient had overcorrection as a result of an aggressive concomitant submental lipectomy. Another patient had central depression in the submental area. None of the patients had difficulties with mandibular movement or swallowing.     

Influence of test position on neck muscle fatigue in healthy controls

BackgroundIt has been suggested that increased fatigue of neck muscles could be related to neck pain. However, studies on the matter present contradicting results which could be explained by the different test positions used.PurposeThe purpose of this study was to investigate the influence of test position on muscle fatigue of neck flexor and extensor muscles in healthy controls.MethodsTwenty-five women without neck pain sustained neck flexion and neck extension isometric contractions at 25% and 75% of their maximal voluntary contraction (MVC) in two test positions: sitting and supine lying. Using surface electromyography, the change over time of the median frequency of the power spectrum (MDF slope) of the myoelectric signal of the sternocleidomastoid and splenius capitis muscles was measured and compared between both positions.ResultsAt 75% MVC, splenius capitis muscles presented higher fatigue in lying compared to sitting, while sternocleidomastoid demonstrated no difference between positions. No statistically significant effect of test position was found at 25% MVC for both sternocleidomastoid and splenius capitis muscles as they generally did not present myoelectric manifestations of fatigue.ConclusionThese results underline the need to standardise the test position when investigating neck muscle fatigue, especially for neck extensors at high loads.     

Neuronal mechanisms of motor signal transmission in the thalamic ventrooral nucleus in spasmodic torticollis patients

A microelectrode technique was used to study the neuronal mechanisms of motor signal transmission in the ventrooral internus nucleus (Voi) of the motor thalamus during voluntary and involuntary pathological (dystonic) movements in patients with spasmodic torticollis. Voi cell elements proved highly reactive to various functional (mostly motor) tests. An activity analysis of 55 Voi neurons detected during nine stereotactic operations revealed, first, a difference in neuronal mechanisms of motor signal transmission for voluntary movements that do or do not involve the affected axial muscles of the neck and for passive and abnormal involuntary dystonic movements. Second, a sensory component was found to play a key role in the mechanisms of sensorimotor interactions during voluntary and involuntary dystonic head and neck movements activating the axial muscles of the neck. Third, rhythmic and synchronized activity of Voi neurons was shown to play an important role in motor signal transmission during voluntary and passive movements. The Voi nucleus was directly implicated in the mechanisms of involuntary head movements and tension of the neck muscles in spasmodic torticollis. The results can be used to identify the Voi nucleus of the thalamus during stereotactic neurosurgery in order to select the optimal destruction or stimulation target and to reduce the postoperative effects in spasmodic torticollis patients.     

Optimal vibration stimulation to the neck extensor muscles using hydraulic vibrators to shorten saccadic reaction time

Optimal vibration stimulation to the neck extensor muscles using hydraulic vibrators to shorten the saccadic reaction time was examined. Subjects were 14 healthy young adults. Visual targets (LEDs) were located 10 degrees left and right of a central point. The targets were alternately lit for random durations of 2-4 seconds in a resting neck condition and various vibration conditions, and saccadic reaction times were measured. Vibration amplitude was 0.5 mm in every condition. The upper trapezius muscles were vibrated at 40, 60, 80, and 100 Hz in a sub-maximum stretch condition in which the muscles were stretched at 70% of maximum stretch. In addition, the muscles were vibrated at 60 Hz with the muscles maximally stretched, with 70% vertical pressure without stretching, and with vibration applied to the skin in the same area as the muscle vibration. At 60, 80, and 100 Hz at 70% maximum stretch, saccadic reaction time shortened significantly compared with the resting neck condition. However, no significant difference in the reaction time was observed among the frequencies. The saccadic reaction times in the maximum stretch condition, muscle pressure condition, and skin contact condition did not differ significantly from that in the resting neck condition. Vibration stimulation to the trapezius with 60-100 Hz frequencies at 0.5 mm amplitude in the sub-maximum stretch condition was effective for shortening saccadic reaction time. The main mechanism appears to be Ia information originating from the muscle spindle.     

Electromyographic investigations in torticollis.

In 13 patients with torticollis, the electromyographic (EMG) activity in the neck muscles at rest was investigated before, during and after stimulation of the H1 bundle (in horizontal torticollis) and inner part of oral ventral nucleus (in the rotatory form), as well as after coagulation. Three EMG types of torticollis-spasmodic, myoclonic and mixed - could be differentiated. During the 8-, 25- and 50-Hz stimulations, a diminution in the amplitude and frequency of muscle potentials, followed by electric silence, was most often obtained; in general, the electric silence was preceded by a rhythmic activity of grouped potentials. Following coagulation, no spontaneous EMG activity was any longer recorded in the neck muscles, in the majority of the cases.     

Electromyography of superficial and deep neck muscles during isometric, voluntary, and reflex contractions

Increasingly complex models of the neck neuromusculature need detailed muscle and kinematic data for proper validation. The goal of this study was to measure the electromyographic activity of superficial and deep neck muscles during tasks involving isometric, voluntary, and reflexively evoked contractions of the neck muscles. Three male subjects (28-41 years) had electromyographic (EMG) fine wires inserted into the left sternocleidomastoid, levator scapulae, trapezius, splenius capitis, semispinalis capitis, semispinalis cervicis, and multifidus muscles. Surface electrodes were placed over the left sternohyoid muscle. Subjects then performed: (i) maximal voluntary contractions (MVCs) in the eight directions (45 deg intervals) from the neutral posture; (ii) 50 N isometric contractions with a slow sweep of the force direction through 720 deg; (iii) voluntary oscillatory head movements in flexion and extension; and (iv) initially relaxed reflex muscle activations to a forward acceleration while seated on a sled. Isometric contractions were performed against an overhead load cell and movement dynamics were measured using six-axis accelerometry on the head and torso. In all three subjects, the two anterior neck muscles had similar preferred activation directions and acted synergistically in both dynamic tasks. With the exception of splenius capitis, the posterior and posterolateral neck muscles also showed consistent activation directions and acted synergistically during the voluntary motions, but not during the sled perturbations. These findings suggest that the common numerical-modeling assumption that all anterior muscles act synergistically as flexors is reasonable, but that the related assumption that all posterior muscles act synergistically as extensors is not. Despite the small number of subjects, the data presented here can be used to inform and validate a neck model at three levels of increasing neuromuscular-kinematic complexity: muscles generating forces with no movement, muscles generating forces and causing movement, and muscles generating forces in response to induced movement. These increasingly complex data sets will allow researchers to incrementally tune their neck models' muscle geometry, physiology, and feedforward/feedback neuromechanics.     

Reflex constriction of human limb resistance vessels to head-down neck flexion

The effect of head-down neck flexion on forearm and calf blood flow was determined in 10 healthy male subjects. The subject lay prone, with the neck slightly extended and the chin resting on a soft-padded support at the edge of the table. The chin support was then removed, and the subject maximally flexed and lowered the neck. This was followed by return to the initial position. Neck flexion caused a rapid decrease in blood flow in both forearm and calf; at 30 s this averaged 39 and 35%, respectively. The flow in both forearm and calf gradually recovered as the neck flexion was sustained and approached the control values at the end of 10 min. The blood flow at the ankle was unchanged, indicating that the decrease occurred in the skeletal muscles. The arterial blood pressure and heart rate were unchanged; thus the decrease in flow was due to vasoconstriction. The fact that the decrease was evident as soon as the head was lowered indicated that it was nervously mediated. Neither contraction of the flexor muscles of the neck nor venous congestion of the head, in the absence of the head-down position, altered the blood flow. Although the mechanism of the decrease in flow has not been determined, the studies demonstrate that in response to certain stimuli, the resistance vessels in the skeletal muscles of the forearm and calf undergo a similar nervously mediated vasoconstriction.     

Post natal development of the neck system in the chicken (Gallus domesticus)

The lengths of several neck muscles and tendons and the length, width, and height of the cervical vertebrae and some additional distances were measured in the chicken in six post-hatching ontogenetic stages and adults. Each vertebra is characterized by a unique combination of growth rates. All increase most in length. Cranial and caudal width as well as height decreases relative to length during ontogeny. When the long dorsal neck muscles are assumed to provide the support for the weight of the head and half of the weight of the neck, the neck system evidently develops according to McMahon's elastic similarity theory. The assumption is justified also because the weights of head and neck together appeared to scale as predicted by elastic similarity. Short neck muscles show negative and tendons positive allometric growth, and long neck muscles grow isometrically relative to neck length. This growth pattern of the muscles and tendons is a direct consequence of the geometric relations of the different growth rates of the vertebrae.     

Activation of Neck and Low-Back Muscles Is Reduced with the Use of a Neck Balance System Together with a Lumbar Support in Urban Drivers

Driving is associated with high activation of low-back and neck muscles due to the sitting position and perturbations imposed by the vehicle. The aim of this study was to investigate the use of a neck balance system together with a lumbar support on the activation of low-back and neck muscles during driving. Twelve healthy male subjects (age 32±6.71 years) were asked to drive in two conditions: 1) with devices; 2) without devices. During vehicle accelerations and decelerations root mean square (RMS) of surface electromyography (sEMG) was recorded from the erector spinae, semispinalis capitis and sternocleidomastoid muscles and expressed as a percentage of maximal voluntary contraction (MVC). The pitch of the head was obtained by means of an inertial sensor placed on the subjects’ head. A visual analog scale (VAS) was used to assess the level of perceived comfort. RMS of the low back muscles was lower with than without devices during both acceleration and deceleration of the vehicle (1.40±0.93% vs 29 2.32±1.90% and 1.88±1.45% vs 2.91±2.33%, respectively), while RMS of neck extensor muscles was reduced only during acceleration (5.18±1.96% vs 5.91±2.16%). There were no differences between the two conditions in RMS of neck flexor muscles, the pitch of the head and the VAS score. The use of these two ergonomic devices is therefore effective in reducing the activation of low-back and neck muscles during driving with no changes in the level of perceived comfort, which is likely due to rebalancing weight on the neck and giving a neutral position to lumbar segments.     

Complex innervation of three neck muscles by motor and dorsal unpaired median neurons in crickets

Summary In the crickets, Gryllus campestris and Gryllus bimaculatus, the innervation of the dorso-ventral neck muscles M62, M57, and M59 was examined using cobalt staining via peripheral nerves and electrophysiological methods. M62 and M57 are each innervated by two motoneurons in the suboesophageal ganglion. The four motoneurons project into the median nerve to bifurcate into the transverse nerves of both sides. M62 and M57 are the only neck muscles innervated via this route. These bifurcating axon-projections are identical to those of the spiracular motoneurons in the prothoracic ganglion innervating the opener and closer muscle of the first thoracic spiracle in the cricket. The morphology of their branching pattern is described. The neck muscle M57 and the opener muscle of the first thoracic spiracle are additionally innervated by one mesothoracic motoneuron each, with similar morphology. These results suggest, that in crickets, the neck muscles M57 and M62 are homologous to spiracular muscles in the thoracic segments. The two neck muscles M62 and M59 (the posterior neighbour of M57) receive projections from a prothoracic dorsal unpaired median (DUM) neuron that also innervates dorsal-longitudinal neck muscles but not M57. In addition, one or two mesothoracic DUM neurons send axon collaterals intersegmentally to M59. This is the first demonstration of the innervation of neck muscles by DUM neurons.     

Relation Between Testosterone Levels in Serum and Proteolytic Activity in the Neck Muscles of the Norwegian Reindeer (Rangifer tarandus tarandus)

The characteristic hypertrophying of the male reindeer neck muscles during the rutting period, which coincides with the rise in serum testosterone levels, is found to be accompanied by a significant decrease in lysosomal proteolytic activity of the neck muscle cells. Conversely, during the period of neck muscle involution following the rapid decline in serum testosterone after the rut, a marked increase in neck muscle proteolytic activity is found. These changes in lysosomal activity do not parallel the changes in feed consumption and nutritional stage of the animals during the rutting period. The lysosomal proteolytic activity of the male reindeer neck muscles thus may be, at least partly, under the control of sex steroid hormones.     

Cervical and axioscapular muscle stiffness measured with shear wave elastography: A comparison between different levels of work-related neck disability

Assessing muscle mechanical properties in terms of stiffness may provide important insights into mechanisms underlying work-related neck pain. This study compared stiffness of cervical and axioscapular muscles between 92 participants (sonographers) with no (n = 31), mild (n = 43) or moderate/severe (n = 18) neck disability. It was hypothesized that participants with more severe neck pain and disability would present with altered distribution of stiffness in cervical and axioscapular muscles than those with no disability. Using shear wave elastography, the shear modulus (kPa) of five cervical and six axioscapular muscles or muscle segments were measured in a relaxed seated upright or side-lying position. Muscle activity was measured simultaneously using surface electromyography during the elastography measurements and scapular depression was measured using a measurement tape and inclinometer before the elastography measurements to evaluate their potential confounding influences on shear modulus. Increased shear modulus was found in deeper than superficial cervical muscles and more cranial than caudal axioscapular muscles. However, no differences in shear modulus of the cervical or axioscapular muscles were found between sonographers with varying levels of disability. This study suggests no alterations in stiffness of cervical and axioscapular muscles were associated with work-related neck pain and disability.     

Moment arms of the human neck muscles in flexion, bending and rotation

There is a paucity of data available for the moment arms of the muscles of the human neck. The objective of the present study was to measure the moment arms of the major cervical spine muscles in vitro. Experiments were performed on five fresh-frozen human head-neck specimens using a custom-designed robotic spine testing apparatus. The testing apparatus replicated flexion-extension, lateral bending and axial rotation of each individual intervertebral joint in the cervical spine while all other joints were kept immobile. The tendon excursion method was used to measure the moment arms of 30 muscle sub-regions involving 13 major muscles of the neck about all three axes of rotation of each joint for the neutral position of the cervical spine. Significant differences in the moment arm were observed across sub-regions of individual muscles and across the intervertebral joints spanned by each muscle (p<0.05). Overall, muscle moment arms were larger in flexion-extension and lateral bending than in axial rotation, and most muscles had prominent moment arms in at least 2 out of the 3 joint motions investigated. This study emphasizes the importance of detailed representation of a muscle's architecture in prediction of its torque capacity about the individual joints of the cervical spine. The dataset produced may be useful in developing and validating computational models of the human neck.     

Influence of the neck muscles deafferentation on the natural head-forelimb coordination in dogs

We studied the influence of the neck muscles deafferentation on the natural head-forelimb coordination. This coordination exists in intact dogs at the early stage of acquisition of the instrumental feeding reaction of tonic forelimb flexion aimed at holding a cup with meat during eating when the head is bent down to foodwell. In untrained dogs, the forelimb flexion is preceded by lifting the head bent down to the food; the following lowering of the head leads to extension of the flexed forelimb. For performing the instrumental reaction, the innate coordination has to be rearranged into the opposite one. It is achieved only by learning. It was shown that deafferentation of the neck muscles, which leads to a loss of the neck reflex, did not destroy the innate coordination and did not facilitate its rearrangement during the instrumental conditioning.     

Investigation of the Differential Contributions of Superficial and Deep Muscles on Cervical Spinal Loads with Changing Head Postures

Cervical spinal loads are predominately influenced by activities of cervical muscles. However, the coordination between deep and superficial muscles and their influence on the spinal loads is not well understood. This study aims to document the changes of cervical spinal loads and the differential contributions of superficial and deep muscles with varying head postures. Electromyography (EMG) of cervical muscles from seventeen healthy adults were measured during maximal isometric exertions for lateral flexion (at 10°, 20° and terminal position) as well as flexion/extension (at 10°, 20°, 30°, and terminal position) neck postures. An EMG-assisted optimization approach was used to estimate the muscle forces and subsequent spinal loads. The results showed that compressive and anterior-posterior shear loads increased significantly with neck flexion. In particular, deep muscle forces increased significantly with increasing flexion. It was also determined that in all different static head postures, the deep muscle forces were greater than those of the superficial muscle forces, however, such pattern was reversed during peak efforts where greater superficial muscle forces were identified with increasing angle of inclination. In summary, the identification of significantly increased spinal loads associated with increased deep muscle activation during flexion postures, implies higher risks in predisposing the neck to occupationally related disorders. The results also explicitly supported that deep muscles play a greater role in maintaining stable head postures where superficial muscles are responsible for peak exertions and reinforcing the spinal stability at terminal head postures. This study provided quantitative data of normal cervical spinal loads and revealed motor control strategies in coordinating the superficial and deep muscles during physical tasks.     

Air-righting responses to chronic hindlimb suspension and ambulation recovery in adult rats.

Laouris et al. (1990) reported that the development of air-righting in growing new-born rats was clearly suppressed when their neck and/or back rotations were prevented. Thus, it is suggested that the neck and back muscles play an important role for a quick righting in response to drop from supine position. Further, we reported that an inhibiton of posture adjustment in response to head-down drop from a height of approximately 30 cm following chronic hindlimb suspension of adult rats was accompanied by a decrease of electromyogram (EMG) activity in both neck and back muscles (Kawano et al., 2002). However, it is still unclear how the air-righting performance is influenced by hindlimb suspension in adult rats. Thus, the effects of chronic hindlimb suspension of adult rats on the patterns and time of air-righting and role of neck and back muscles in the air-righting were investigated in the current study.