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PubMed1996

Electromyography of levator scapulae: new findings allow tests of a head stabilization model.

OBJECTIVE: Understanding the recruitment patterns of shoulder girdle prime-mover muscles will allow meaningful exploration of non-prime-mover neck muscle activity during arm and shoulder efforts. This study identifies exercises that isolate recruitment of levator scapulae from recruitment of upper trapezius. The exercises will be used for electromyographic experiments in which the head stabilizing roles of other neck muscles will be explored. DESIGN: Right levator scapulae and upper trapezius were electromyographically monitored with indwelling, fine-wire, bipolar electrodes. Subjects performed isometric arm exercises and movements of the upper limb, shoulder and head. SETTING: Electromyography facilities of the department of Anatomical Sciences of the State University of New York at Stony Brook were used. PARTICIPANTS: Six adult subjects participated; one had reduced shoulder girdle mobility and a history of multiple shoulder separations. MAIN OUTCOME MEASURES: Raw electromyographic data were scored visually on a scale from 0 to 4, with 4 being the signal observed in a maximal voluntary contraction. RESULTS: All subjects recruited levator scapulae alone during arm extension. Only the subject with reduced shoulder mobility recruited levator scapulae during scapular plane arm elevation and arm abduction. CONCLUSIONS: The levator scapulae torque to be counteracted in arm extension produces ipsilateral rotation, lateral flexion and extension of the neck; trapezius rotates the head contralaterally during scapular plane arm elevation. These distinct and relatively simple cases (one shoulder girdle prime-mover affecting head posture at a time) are appropriate exercises for experimental exploration of the recruitment patterns of potential head stabilizers during arm/shoulder efforts.

Adult↗

PubMed2006

Myofascial trigger points and their relationship to headache clinical parameters in chronic tension-type headache.

OBJECTIVE: To assess the presence of trigger points (TrPs) in several head and neck muscles in subjects with chronic tension-type headache (CTTH) and in healthy subjects; and to evaluate the relationship of these TrPs with forward head posture (FHP), headache intensity, duration, and frequency. BACKGROUND: Tension-type headache (TTH) is a headache in which myofascial TrPs in head and neck muscles might play an important etiologic role. DESIGN: A blinded, controlled, pilot study. METHODS: Twenty-five CTTH subjects and 25 matched controls without headache were studied. TrPs in bilateral upper trapezius, sternocleidomastoids, and temporalis muscles were identified according to Simons et al's diagnostic criteria: tenderness in a hyperirritable spot within a palpable taut band, local twitch response elicited by snapping palpation, and elicited referred pain with palpation. A TrP was considered active if the subject recognized the evoked referred pain as familiar headache. If the evoked referred pain was not recognized as familiar headache, the TrP was considered as latent. Side-view pictures of each subject were taken in both sitting and standing positions in order to assess FHP by measuring the cranio-vertebral angle. Both measurements were made by a blinded assessor. A headache diary was kept for 4 weeks in order to assess headache intensity, frequency, and duration. RESULTS: The mean number of TrPs on each CTTH subject was 3.9 (SD: 1.2), of which 1.9 (SD: 1.2) were active TrPs and 1.9 (SD: 0.8) were latent TrPs. Control subjects only exhibited latent TrPs (mean: 1.4; SD: 0.8). There was a significant difference between the CTTH group and the controls for active TrPs (P < .001), but not for latent TrPs (P > .05). Differences in the distribution of active and latent TrPs within each muscle were also significant for all the analyzed muscles (P < .01). CTTH subjects with active TrPs in the right upper trapezius muscle or left sternocleidomastoid muscle showed a greater headache intensity and duration, but not headache frequency, compared to those with latent TrPs (P < .05). Active TrPs in the right temporalis muscle were associated with longer headache duration (P < .01), whereas active TrPs in the left temporalis muscle were associated with greater headache intensity (P < .05). CTTH subjects with active TrPs in the analyzed muscles had a greater FHP than those with latent TrPs in both sitting and standing positions. Differences were only significant for TrPs in the left sternocleidomastoid and FHP in the sitting position (P < .01). CONCLUSIONS: Active TrPs in upper trapezius, sternocleidomastoid, and temporalis muscles were associated with CTTH. CTTH subjects with active TrPs usually reported a greater headache intensity and longer headache duration than those with latent TrPs. CTTH subjects with active TrPs tended to have a greater FHP than CTTH subjects with latent TrPs.

Adolescent↗

PubMed1986

ECoG sleep-waking rhythms and bodily activity in the cerveau isolé rat.

In rats with a high mesencephalic transection, isolating both the locus coeruleus and raphe nuclei from the forebrain, Electrocorticogram (ECoG) and Electromyogram (EMG) of the neck muscles were continuously recorded. Normal sleep-waking ECoG changes with a significant circadian rhythm reappeared in 4 to 9 days after transection. Neck muscle EMG and bodily movements were independent of the ECoG changes and did not show any significant circadian rhythm. In these high mesencephalic rats with sleep-waking ECoG changes, large bilateral hypothalamic lesions were made by passing DC current either in the preoptic area or in the posterior hypothalamus. After the preoptic area lesions the amount of low voltage fast ECoG per day markedly increased, whereas after the posterior hypothalamic lesions, the total amount of low voltate fast wave per day decreased showing long-lasting slow wave sleep pattern. These results support an idea that the forebrain, especially in the hypothalamus including the preoptic area, a mechanism inducing sleep-waking ECoG changes is localized.

Animals↗

PubMed1998

Interdependence of spatial properties and projection patterns of medial vestibulospinal tract neurons in the cat.

Activity of vestibular nucleus neurons with axons in the ipsi- or contralateral medial vestibulospinal tract was studied in decerebrate cats during sinusoidal, whole-body rotations in many planes in three-dimensional space. Antidromic activation of axon collaterals distinguished between neurons projecting only to neck segments from those with collaterals to C6 and/or oculomotor nucleus. Secondary neurons were identified by monosynaptic activation after labyrinth stimulation. A three-dimensional maximum activation direction vector (MAD) summarized the spatial properties of 151 of 169 neurons. The majority of secondary neurons (71%) terminated above the C6 segment. Of these, 43% had ascending collaterals to the oculomotor nucleus (VOC neurons), and 57% did not (VC neurons). The majority of VOC and VC neurons projected contralaterally and ipsilaterally, respectively. Most C6-projecting neurons could not be activated from oculomotor nucleus (V-C6 neurons) and projected primarily ipsilaterally. All VO-C6 neurons projected contralaterally. The distributions of MADs for secondary neurons with different projection patterns were different. Most VOC (84%) and contralaterally projecting VC (91%) neurons had MADs close to the activation vector of a semicircular canal pair, compared with 54% of ipsilaterally projecting VC (i-VC) and 39% of V-C6 neurons. Many i-VC (44%) and V-C6 (48%) neurons had responses suggesting convergent input from horizontal and vertical canal pairs. Horizontal and vertical gains were comparable for some, making it difficult to assign a primary canal input. MADs consistent with vertical-vertical canal pair convergence were less common. Type II yaw or type II roll responses were seen for 22% of the i-VC neurons, 68% of the V-C6 neurons, and no VOC cells. VO-C6 neurons had spatial properties between those of VOC and V-C6 neurons. These results suggest that secondary VOC neurons convey semicircular canal pair signals to both ocular and neck motor centers, perhaps linking eye and head movements. Secondary VC and V-C6 neurons carry more processed signals, possibly to drive neck and forelimb reflexes more selectively. Two groups of secondary i-VC neurons exhibited vertical-horizontal canal convergence similar to that present on neck muscles. The vertical-vertical canal convergence present on many neck muscles, however, was not present on medial vestibulospinal neurons. Spatial transformations achieved by the vestibulocollic reflex may occur in part on secondary neurons but further combination of canal signals must take place to generate compensatory muscle activity.

Animals↗

PubMed1989

Operant conditioning of head-waving in Aplysia. I. Identified muscles involved in the operant response.

A basic goal in the neurosciences is to understand the cellular mechanisms underlying associative learning. The 2 major forms of associative learning are classical conditioning and operant conditioning. In recent years considerable progress has been made towards a cellular analysis of classical conditioning in a number of different preparations. In contrast, the cellular mechanisms underlying operant conditioning are poorly understood. Since the marine mollusc Aplysia has proved to be a powerful preparation for studying cellular and molecular mechanisms of a variety of forms of learning, including classical conditioning, we asked whether Aplysia might also be capable of exhibiting operant conditioning. In previous experiments we found that a naturally occurring behavior, the head-waving response of Aplysia, could be operantly conditioned (Cook and Carew, 1986). In the present paper we have carried out a quantitative analysis of the horizontal and vertical components of the head-waving response at the level of individual muscle groups. We have identified a discrete, bilateral band of neck muscles, the lateral columellar muscles (LCMs), whose electromyographic (EMG) activity is significantly correlated with the horizontal component of head-waving, the component modified by operant conditioning. Since head-waving is a complex behavioral response involving a variety of different muscle groups, using a restricted system such as the LCMs as an analog of the head-waving response will greatly facilitate a cellular analysis of operant conditioning in Aplysia.

Animals↗

PubMed2002

Effects of inertial load and cervical-spine orientation on a head-tracking task in the alert cat.

Simultaneous video-fluoroscopic and neck muscle EMG data were recorded from one cat performing +/-15 degrees sinusoidal (0.25 Hz) head-tracking movements in the sagittal plane in a standing body posture with two initial neck orientations and four inertial loads. Radio-opaque markers were inserted into the anterior/posterior and lateral aspects of the occipital ridge and C(1)-C(7) to measure vertebral displacement. Kinematic data were analyzed, and a computer model was applied to the data to characterize the limits of movement in the cervical spine and to estimate the moment arms of the neck muscles at different orientations of head-neck movement. For each initial neck orientation, the cat utilized a distinct set of vertebral alignments, relative joint movements, and muscle-activation patterns to achieve the same movement outcome. As inertial load increased, vertebral alignments and relative joint movements were constant with a vertically oriented neck but differed when the neck was more horizontally oriented. Different muscle-activation patterns were used to maintain the same kinematic pattern with increased inertial loads. Some muscle EMG response gains (rectus capitis major and splenius capitis) increased with increasing mass, while others (biventer cervicis and occipitoscapularis) demonstrated an initial increase and then a plateau. EMG phases were not affected by changing the mass of the system but were affected by changing neck orientation. The model predicted that muscle moment arms would vary little for the different vertebral alignments, suggesting a robust biomechanical system minimally compensates for small changes in task geometry.

Animals↗

PubMed2006

Auditory startle alters the response of human subjects exposed to a single whiplash-like perturbation.

STUDY DESIGN: Human volunteers were exposed to a single whiplash-like perturbation. OBJECTIVE: To determine how muscle and kinematic responses are affected by the superposition of a rear-end collision and loud startling noise. SUMMARY OF BACKGROUND DATA: Many whiplash studies use forward perturbations without reproducing the sound of a car crash. Loud sounds are known to evoke startle responses in the neck muscles and therefore could affect whiplash injuries. METHODS: Sixty-five subjects (30 female, 35 male) were exposed to a single forward horizontal perturbation. Head and torso kinematics, and electromyographic activity in the sternohyoid, sternocleidomastoid, scalenus, and cervical paraspinal muscles were measured. Two awareness conditions (deceived and unaware subjects) nested in two startle conditions (with or without a 40 milliseconds, 124 dB sound) were tested. RESULTS: Startle and gender affected the amplitude and timing of numerous kinematic and muscle variables. Awareness affected only one muscle variable. Startled individuals exhibited greater peak head and trunk accelerations, increased activity of the cervical paraspinal muscles, and a reduced head retraction and trunk angle. CONCLUSIONS: An acoustic startle alters the neck muscle and kinematic responses and may be as important as gender in the genesis of whiplash injury.

Acoustic Stimulation↗

PubMed2006

Cervical dystonia responsive to acoustic and galvanic vestibular stimulation.

We examined the effects of acoustic and galvanic vestibular stimulation in a patient with cervical dystonia. Acoustic stimulation consisted of three conditions: "baseline" (no stimulation), "vestibular" (500 Hz bone-conducted tone bursts), and "control" (5,000 Hz tone bursts). Rectified electromyographic activity in the sternocleidomastoid was measured. Galvanic stimulation (1.5-2.5 mA current steps) was delivered to the mastoids, and head acceleration was measured. Vestibular acoustic stimulation reduced neck muscle activity between 16% and 44% (P < 0.001), and galvanic stimulation reduced head acceleration by 22.5% (P = 0.028). The patient reported subjective improvement in head control. Vestibular stimulation can reduce neck muscle activity in cervical dystonia and give symptomatic relief.

Acoustic Stimulation↗

PubMed2003

Preventive measures for axial symptoms following cervical laminoplasty.

We have modified the operative procedure of laminoplasty and changed the postoperative therapy since 1997. In the modified group, several modifications were incorporated. The open door type of cervical en bloc laminoplasty was performed. 1) Bone grafts in the open gap were placed at three levels only. 2) Bone grafting in the hinged side was not performed. 3) The neck collar was worn for only 1 month. 4) The doctors explained the importance of the neck muscle and advised patients to perform early exercise of the posterior neck muscle. The patients who had the original operation and postoperative therapy served as the control (control group). The original operation and postoperative therapy were as follows: Bone grafts from dissected spinous processes were put in the opened laminae and fixed with braided wires or nylon threads. Bone grafts in the open gap were placed to extend from three to five levels. Bone chips were also placed in the hinged side. The orthosis was applied for up to 1 months after surgery, and a neck collar was recommended for 1 additional month. Postoperative neurologic recovery and axial symptoms after cervical laminoplasty were compared between the two groups. There was no statistical difference in postoperative neurologic recovery. However, the incidence of axial symptoms was much lower in the modified group compared with the control group. Radiologic examination showed that postoperative range of motion of the cervical spine in the modified group was significantly well preserved and the number of postoperative fused laminae in the modified group was less than that in the control group. Based on these results, we concluded that the modified method is beneficial for the postoperative status of cervical laminoplasty patients.

Adult↗

PubMed1994

[Specifics of innervation of the cranio-cervical transition].

Innervation at the craniocervical transition differs from other regions of the body in certain respects. In particular, thick-calibre neck muscle afferents project directly to the external cuneate nucleus and to the vestibular nuclear complex. This projection is most prominent in segments C2 and 3 and is sparse or absent in more caudal segments. Thus, proprioceptive neck muscle afferents gain direct access to vestibulospinal, vestibulooculomotor and other secondary or even higher-order vestibular neurons. There is extensive convergence of proprioceptive neck and labyrinthine afferents on these neurons, which plays an important role in the control of balance, posture and movements. It can be assumed that dysfunction of this cervicovestibular network results in a variety of clinical problems, in particular, so-called cervical balance disorders.

Afferent Pathways↗

PubMed2000

Multi-muscle control of head movements in monkeys: the referent configuration hypothesis.

It is suggested that the nervous system may specify a referent configuration (R) of the body determined by the set of the threshold joint angles at which all skeletal muscles may be silent. At the same time, electromyographic (EMG) activity and forces are generated to resist deflections of the body from this configuration. The R configuration may thus be considered an internal geometric image with which the actual body configuration (Q) is compared. Thereby the difference between the R and Q is a major factor determining the recruitment and gradation of the activity of each skeletal muscle. Control systems may produce movements by changing the R configuration according to task demands. The referent hypothesis predicts that when the R and Q configurations match each other, a global minimum in the EMG activity of all muscles involved should occur, an event most likely observed in movements with reversal in direction. To test the validity of the R hypothesis for head movements, three-dimensional kinematics and EMG activity of 14 functionally diverse neck muscles were analysed in monkeys during head rotations to and from fruit targets placed beyond the oculomotor range. Despite the functional and anatomical diversity of the neck muscles, the activity of all muscles was minimised at a reversal point of the movement trajectory, as predicted by the R hypothesis. This study thus illustrates the notion that a change in the internal geometric image of a biomechanical system may underlie movement production.

Animals↗

PubMed2000

Trapezius muscle activity, neck and shoulder pain, and subjective experiences during monotonous work in women.

The electromyographic (EMG) activity patterns of 18 female supermarket employees reporting neck and shoulder pain were compared with those of 6 of their female colleagues reporting no pain when doing cash-register work. It was found that the EMG activity of the trapezius muscle tended to show a lack of low and high levels among pain subjects, and that the time the trapezius muscle was at rest was longer in the group reporting no pain. In the non-dominant side, the muscle rest time was significantly longer (P < 0.05) in the group reporting no pain, and this group also showed a larger EMG activity difference between the dominant and non-dominant sides, indicating a less static bilateral muscle activation. Self-reports of negative experiences (stressed, exhausted and tense) were somewhat higher in the group reporting pain, while positive experiences during work (concentrated, stimulated and happy) appeared to be similar in the two groups of supermarket employees.

Adult↗

PubMed1993

Deep and superficial noxious stimulation increases Fos-like immunoreactivity in different regions of the midbrain periaqueductal grey of the rat.

UNLABELLED: We have reported that the lateral region of the caudal third of the midbrain periaqueductal grey (PAG), which mediates flight and hypertension, receives inputs from lamina I and IIo and the lateral cervical nucleus (LCN) of the upper cervical spinal cord (UCC); whereas the ventrolateral PAG region, which mediates hypotension, quiescence and immobility, is targeted by cells in laminae VII, VIII and X. In the UCC the cells of laminae VII and VIII receive a significant afferent input from the deep neck muscles, whereas cells of laminae I and IIo and the LCN receive a large input from cutaneous nociceptors. Thus we investigated the hypothesis that nociceptive activation of the deep neck muscles would activate the spinal-ventrolateral PAG projection, whereas cutaneous nociceptive stimulation would activate the spinal-lateral PAG projection, by examining the expression of Fos protein. We found that deep noxious stimulation led to Fos-positive cells predominantly in the ventrolateral PAG and superficial noxious stimulation led to Fos-positive cells predominantly in the lateral PAG. THE RESULTS: (i) indicate that the UCC afferent regulation of the PAG arises from topographically separable and functionally dissociable populations of neurons and (ii) raise the possibility that the ventrolateral and lateral PAG play important but different roles in mediating the distinctive affective, emotional and autonomic responses evoked by pain arising from deep or superficial structures.

Animals↗

PubMed1999

Neck-proprioceptive influence on auditory lateralization.

The effect of transcutaneous vibration of the posterior neck muscles on the lateralization of dichotic sound was investigated in human subjects. Two-alternative forced-choice (left/right) judgements were made on acoustic stimuli presented with different interaural level differences via headphones during neck-muscle vibration. A shift of the subjective auditory median plane toward the side contralateral of vibration was found, indicating that the sound was perceived as shifted toward the side of vibration. The mean magnitude of the vibration-induced intracranial shift was 1.5 dB. The results demonstrate a neck-proprioceptive influence on sound lateralization and suggest that this proprioceptive input is used for a central-nervous transformation of auditory spatial coordinates onto a body-centered frame of reference.

Acoustic Stimulation↗

PubMed1997

Comparative measurement of visual stability in Earth and cosmic space.

Three theories have been suggested as to the cause of space motion sickness: 1) eye and vestibular sensory mismatch, 2) abnormal shift of body fluids producing increased intracranial pressure and 3) pre-warning signals for unpleasant physical situations by self-produced neurotoxic substances released in the body. We are interested in the possible functional disabilities/incongruities of eye, head and body movements in 0-G. Space motion sickness might be explained from the viewpoint of lack of coordination of the movements of the eye and head. It is important to ascertain the significance of gravity in the maintenance of human visual stability. We will examine the coordination of Japanese Payload Specialist (JPS) eye and head movement by electrooculogram and neck muscle electromyogram recordings, as well as obtaining a subjective evaluation of visual stability from the PS during space flight. We hypothesize that 1) poor performance of the eye movement will be observed, 2) unusual neck muscle activity will be observed and 3) there will be decreased visual stability in micro gravity. We obtained all digital data and VCR taped image data in [TEXT MISSING]

Aerospace Medicine↗

PubMedDate not supplied

The control of head movements during human balance corrections.

The assumption that the CNS regulates head stability during human balance corrections is explored in this review (an outgrowth of discussions initiated during the Head/Neck meeting held in Vail, Colorado, USA, July 1995). Two major questions were considered. First, how do the vestibulocollic (VCR) and cervicocollic (CCR) reflexes interact with intrinsic mechanical properties of the head neck system to control head position during balance corrections? Second, how is this interaction affected by factors such as vestibular loss, aging, and changes in behavioral goals or central set? The authors conclude that head velocities observed during balance corrections depend to a large extent on the movements of the head-neck mass-viscoelastic system whose properties could be altered by cocontracting the neck muscles. For experiments involving stance perturbations, much of the corrective response in neck muscles appeared to be triggered by trunk and leg proprioceptive signals, and a major role for the VCR was not established. Evidence consistent with a role for the vestibular system was found in other experimental paradigms in which the head was perturbed directly. In these paradigms the VCR modulates the amplitude of functionally stabilizing responses and damps mechanically induced instability of the head and neck.

Adult↗

PubMed2005

Postural responses and spatial orientation to neck proprioceptive and vestibular inputs during locomotion in young and older adults.

Both vestibular and neck proprioceptive inputs contribute towards maintaining a walking trajectory. We investigated how aging alters neck proprioceptive and vestibular interaction for preserving equilibrium and spatial orientation during locomotion. Young and healthy elderly were exposed to two sensory manipulations as they walked, eyes closed, to a target located straight ahead: (1) right side dorsal neck muscle vibration (Vib), and (2) Vib + transmastoidal galvanic vestibular stimulation (Vib + GVS). The maximum path deviation, average frontal centre of mass velocity and average trunk roll were evaluated. Trunk yaw rotation was computed at every metre of the path. We observed that directional responses to neck muscle stimulation were very sensitive to the reference frame generated by vestibular information. The attenuation of path deviation in older adults can be attributed to a reduced sensitivity of the neck proprioceptive system rather than the vestibular system.

Adult↗

PubMed1998

Electromyography in cervical dystonia: changes after botulinum and trihexyphenidyl.

BACKGROUND: The value of physical examination in detecting involved neck muscles in cervical dystonia (CD) is uncertain and little is known about changes in electromyographic (EMG) features after botulinum toxin type A (BTA) treatment. METHODS: In a double-blind, randomized study we recorded the EMG activities of 420 neck muscles in 42 patients with CD before and after treatment with BTA or trihexyphenidyl. We regarded any needle EMG activity higher than 100 microV as the gold standard for involuntary involvement of a muscle in the dystonic posture and compared this with the results of physical examination. We calculated EMG total scores by adding the scores of the individual muscles. RESULTS: Physical examination had a low predictive value in the detection of involved muscles. There was a significant correlation between changes in EMG total scores and changes in clinical measurements. We observed increased EMG activity in 20% of noninjected muscles after BTA treatment and in 27% of noninjected muscles after trihexyphenidyl treatment. A switch from one most active muscle to another was seen equally in both groups and had no influence on clinical response. CONCLUSION: Physical examination alone is not sufficient to detect involved muscles, and repeated, simultaneous EMG-guided application of BTA may be helpful. In addition to clinical measurements, changes in EMG activity due to treatment can be used as a physiologic measure in evaluating treatment response. Increased activity of noninjected muscles and a switch from one most active muscle to another are not related to BTA treatment, but are probably pathophysiologic phenomena of CD itself.

Botulinum Toxins, Type A↗