Changes In Head Position Research Articles

Changes in natural head position observed immediately and one year after rapid maxillary expansion

Rapid maxillary expansion (RME) has been shown to increase nasal permeability and reduce nasal airway resistance. A number of studies have examined the relationship between RME and the change in airway resistance, or the relationship between airway resistance and natural head position (NHP). Few studies, to date, have examined the relationship between RME and the change in NHP resulting from the consequent change in airway resistance. A sample of 43 adolescent patients with uni- or bilateral crossbite in the permanent dentition underwent RME as part of normal orthodontic treatment. Cephalograms in NHP were taken before, immediately after expansion, and one year after RME. No significant changes in the craniofacial angles were observed immediately after expansion. One year post-expansion, however, NSL/VER had reduced by 3.14 degrees (P < 0.01), OPT/HOR by 2.13 degrees (P < 0.05), and CVT/HOR by 2.55 degrees (P < 0.05). The results of this study suggest an ongoing change in head posture possibly due to a change in the mode of breathing from oral to nasal as a result of RME, thereby contributing to a change in craniofacial development, supporting and adding to the soft tissue stretching hypothesis.

Cerebellar skew deviation and the torsional vestibuloocular reflex

Skew deviation is typically caused by brainstem damage, and has not been identified with focal cerebellar lesions. This vertical strabismus has been attributed to asymmetric disruption of vestibuloocular reflex (VOR) projections from otolithic receptors of the utricle to ocular motoneurons, but asymmetry of the utriculo-ocular counter-roll reflex has not been detected. Lesions localized to the cerebellum were identified by MRI in five patients with vertical strabismus. Their skew deviation was measured by prism cover tests in all patients and by search coils in three patients. The angular VOR was tested in patients and 10 controls during sinusoidal +/- 10 degree torsional, vertical, and horizontal head-on-body rotations at 0.5, 1, and 2 Hz. Static torsional VOR gain was measured by the change in torsional eye position divided by change in head position during maintained head tilt. Static torsional VOR gains were asymmetric in each patient. Three patterns of asymmetry were identified: 1) decreased static gain in one eye in both directions; 2) decreased gains in both eyes in one direction; and 3) asymmetric gain in one direction in one eye alone. Dynamic torsional VOR gains were symmetrically reduced in both directions in both eyes in all patients. Focal cerebellar lesions can cause skew deviation. The static torsional vestibuloocular reflex (VOR) is linked to cerebellar control of vertical vergence. Asymmetry between the eyes or in direction of the static torsional VOR provides evidence that monocular or binocular imbalance of the utriculo-ocular reflex leads to cerebellar skew deviation.

Benign positional nystagmus

To describe the spatial and temporal characteristics of benign positional nystagmus (BPN) subtypes in benign positional vertigo (BPV) due to vestibular lithiasis affecting one or more semicircular canals (SCCs). Activation of SCC receptors by sequestered otoconia, either freely moving (canalithiasis) or cupula-adherent (cupulolithiasis) during head position changes with respect to gravity, is the accepted cause of BPV. Although accurate identification and interpretation of BPN is critical to BPV therapy, no rigorous, kinematically correct three-dimensional spatio-temporal analysis of BPN in all its forms exists. Using dual-search scleral coils, the authors recorded BPN provoked by Dix-Hallpike or supine ear-down test in a two-axis whole-body rotator in 44 patients with refractory BPV. To localize the SCC affected, BPN rotation axes were compared to SCC axes, axes orthogonal to average SCC planes. Sixteen patients had upbeat, geotropic-torsional BPN in the Dix-Hallpike test to one side and five to both sides, with BPN rotation axes clustered around the lowermost posterior SCC axis. Seven had direction-changing horizontal BPN, three geotropic (canalithiasis) and four apogeotropic (cupulolithiasis), with rotation axes around the lowermost and uppermost horizontal SCC axis. Seven had predominantly downbeating BPN with rotation axes clustered around one superior SCC axis. Nine had upbeat, horizontal-torsional BPN with rotation axes located between posterior and horizontal SCC axes of the lowermost ear suggesting simultaneous lithiasis in both SCCs. BPN vector-guided repositioning therapy was successful in 43 patients. Benign positional vertigo can affect one or more semicircular canals and three-dimensional recording with vector analysis of the benign positional nystagmus (BPN) can guide canalith repositioning therapy especially in refractory cases with atypical BPN.

Change in cranio-cervical angulation following orthognathic surgery

Changes in natural head posture (NHP) were investigated in 33 patients (10 males, 23 females) with an age range of 16-40 years (median 21 years) following orthognathic surgery to change vertical face height. The reproducibility of the radiographer's technique of taking radiographs in NHP was investigated using a photographic method and found to be acceptable. The patients were divided into two groups: group 1, patients who had more than 3 mm of vertical change in anterior total face height (ATFH) and group 2, those who had less than 3 mm vertical change. For group 1 there was a significant relationship between ATFH change and cranio-cervical angulation (NSL/OPT) change (r = 0.532, P = 0.023), compared with group 2 (r = -0.247, P = 0.376). A similar relationship was revealed between lower anterior face height (LAFH)/ATFH ratio and NSL/OPT, where the correlation was also higher in group 1 (r = -0.635, P = 0.005) compared with group 2 (r = -0.182, P = 0.515). The correlation between cranio-vertical angulation (NSL/VER) and ATFH was not significant for group 1 (r = 0.406) or group 2 (r = 0.239) patients. Additionally, NSL/VER and LAFH/ATFH correlation for the two groups was not significant (r = -0.392 and -0.338, respectively). There appears to be a relationship between the reduction in vertical face height following orthognathic surgery and neck posture (as indicated by NSL/OPT). As no significant relationship was found between the reduction in face height and head posture (as indicated by NSL/VER) this suggests that neck posture, rather than head posture, had changed.

Changes in head and neck position affect elbow joint position sense

Changes in the position of the head and neck have been shown to introduce a systematic deviation in the end-point error of an upper limb pointing task. Although previous authors have attributed this to alteration of perceived target location, no studies have explored the effect of changes in head and neck position on the perception of limb position. This study investigated whether changes in head and neck position affect a specific component of movement performance, that is, the accuracy of joint position sense (JPS) at the elbow. Elbow JPS was tested with the neck in four positions: neutral, flexion, rotation and combined flexion/rotation. A target angle was presented passively with the neck in neutral, after a rest period; this angle was reproduced actively with the head and neck in one of the test positions. The potential effects of distraction from head movement were controlled for by performing a movement control in which the head and neck were in neutral for the presentation and reproduction of the target angle, but moved into flexion during the rest period. The absolute and variable joint position errors (JPE) were greater when the target angle was reproduced with the neck in the flexion, rotation, and combined flexion/rotation than when the head and neck were in neutral. This study suggests that the reduced accuracy previously seen in pointing tasks with changes in head position may be partly because of errors in the interpretation of arm position.

Changes in Fetal Position During Labor and Their Association With Epidural Analgesia

To evaluate whether epidural analgesia is associated with a higher rate of abnormal fetal head position at delivery. We conducted a prospective cohort study of 1,562 women to evaluate changes in fetal position during labor by using serial ultrasound examinations. Ultrasound examinations were performed at enrollment, epidural administration, 4 hours after the initial ultrasonography if epidural had not been administered, and late in labor (> 8 cm). Information about fetal head position at delivery was obtained from the provider. Regardless of fetal head position at enrollment (occiput transverse, occiput posterior, or occiput anterior), most fetuses were occiput anterior at delivery (enrollment position: occiput transverse 78%, occiput posterior 80%, occiput anterior 83%, P = .1). Final fetal position was established close to delivery. Of fetuses that were occiput posterior late in labor, only 20.7% were occiput posterior at delivery. Changes in fetal head position were common, and 36% of women had an occiput posterior fetus on at least one ultrasound examination. Women receiving epidural did not have more occiput posterior fetuses at the enrollment (23.4% epidural versus 26.0 no epidural, P = .9) or the epidural/4-hour ultrasound examination (24.9% epidural, 28.3% no epidural), but did have more occiput posterior fetuses at delivery (12.9% epidural versus 3.3% no epidural, P = .002); the association remained in a multivariate model (adjusted odds ratio 4.0, 95% confidence interval 1.4-11.1). Fetal position changes are common during labor, with the final fetal position established close to delivery. Our demonstration of a strong association of epidural with fetal occiput posterior position at delivery represents a mechanism that may contribute to the lower rate of spontaneous vaginal delivery consistently observed with epidural.

Pathomechanics in Atraumatic Shoulder Instability

The objective was to analyze three-dimensional scapular positioning and glenohumeral centering of normal and atraumatic unstable shoulders. We hypothesized that changes of humeral head position correlate with alterations of scapular positioning. The shoulders of 28 healthy volunteers and 14 patients with atraumatic instability were examined in various arm positions using open magnetic resonance imaging. After segmentation and three-dimensional reconstruction, three-dimensional analyses of scapular positioning and humeral head position relative to the glenoid were done. The coefficient of correlation (r) between both parameters was determined using the correlation z test. The glenohumeral to scapulothoracic ratio in the scapular plane was increased in nine of 14 patients and decreased in three patients, whereas the scapular internal rotation in the transverse plane was increased in all unstable shoulders. The unstable shoulders also had malcentering (greater than two times the standard deviation in the healthy volunteers) of the humeral head in the direction of instability during various arm positions. In healthy and unstable shoulders, the correlation between scapular position and glenohumeral positioning was high during passive elevation (r = 0.60-0.87). The high correlation suggests that scapular positioning is relevant for humeral head decentering. Therefore, physiotherapeutic strategy should consider the malpositioning of the scapula and be adapted to the direction of instability.

Studies of Eccentric Gaze Stability: Effects of Pitch Head Position on Horizontal Gaze‐Holding in Patients with Cerebellar Disease

We studied the effects of change of head position in the pitch plane on the ability to hold horizontal eccentric gaze in five patients with cerebellar disorders. All patient showed a change in the time constant of horizontal centripetal drift when the head was pitched forward or back. This result suggests that otolithic inputs can influence the neural integrator for horizontal eye movements and indicates the value of testing horizontal gaze holding in different head positions.

Clinical Features and Pathophysiology of Posterior Canal Benign Positional Vertigo

Benign positional vertigo (BPV) is caused by detached otolith debris that enters the semicircular canal and moves with changes in head position. Movement in the plane of the affected canal triggers brief but violent episodes of vertigo. The posterior semicircular canal variant (PC-BPV) is by far the most common because once the debris enters the canal it becomes trapped and can remain there for months and even years. We are just beginning to understand how the otolithic membrane is formed, how it is maintained and what happens to otolithic debris floating in the endolymphatic space.

Influence of Sleep Position Experience on Ability of Prone-Sleeping Infants to Escape From Asphyxiating Microenvironments by Changing Head Position

Several studies have found that back- or side-sleeping infants who are inexperienced in prone sleeping are at much higher risk for sudden infant death syndrome (SIDS) when they turn to prone or are placed prone for sleep compared with infants who normally sleep prone. Moreover, such inexperienced infants are more likely to be found in the face-down position at death after being placed prone compared with SIDS infants who are experienced in prone sleeping. We hypothesized that lack of experience in prone sleeping is associated with increased difficulty in changing head position to avoid an asphyxiating sleep environment. We studied 38 healthy infants while they slept prone. Half of these were experienced and half were inexperienced in prone sleeping. To create a mildly asphyxiating microenvironment, we placed infants to sleep prone with their faces covered by soft bedding. We recorded inspired CO2 (CO2I), electrocardiogram, and respiration, and we videotaped head movements. Also, we assessed gross motor development (Denver Development Scale). When sleeping prone, with their faces covered by bedding, all infants experienced mild asphyxia as a result of rebreathing. All aroused and attempted escape from this environment. Infants used 3 stereotyped head-repositioning strategies. The least effective was nuzzling into the bedding with occasional brief head lifts. More effective were head lifts combined with a head turn. Some infants, however, could turn only to 1 side, right or left. Infants who were inexperienced in prone sleeping had less effective protective behaviors than experienced infants. Infant age did not correlate with efficacy of protective behaviors. Infants who were experienced in prone sleep had advanced gross motor development compared with inexperienced infants. Infants who are inexperienced in prone sleeping have decreased ability to escape from asphyxiating sleep environments when placed prone. These observations potentially explain the increased risk associated with prone sleep in infants who are inexperienced. The increased occurrence of the face-down position in such infants is also potentially explained. These findings suggest that airway protective behaviors may be acquired through the mechanism of operant conditioning (learning).

Validation of an amphibian sperm inhibition toxicological test method using zinc

Analysis of sperm has been investigated as a possible method to examine the toxicity of environmental contaminants. The amphibian sperm inhibition toxicological test (ASITT) method examines the effects of contaminants on Xenopus laevis (African clawed frog) sperm motility and path trajectories. As part of a preliminary validation of the method, the effects of increasing divalent metal ion, zinc (Zn2+), on X. laevis sperm motility were examined. We hypothesized that Zn2+ concentration would have significant inhibitory effects on percent sperm motility, velocities, and trajectories. The Zn2+ was added to a control solution in concentrations from 0 to 1,417 microg/L. Sperm cells were videotaped at 30 frames per second under x 400 microscope, and percent motility was recorded and paths were mapped by marking the change in position of the sperm head over a period of 1 s. Sperm motility was categorized as progressive, hyperactivated, idle, or nonmotile, and velocities and trajectories were calculated on the basis of x,y coordinates. Increasing Zn2+ concentrations caused a significant exponential decay in percent total motility and progressive motility. Straight-line velocity increased with increasing Zn2+ concentrations. Overall, results suggest that Zn2+ may be interfering with cellular processes, such as cellular respiration, flagellar bending, or ion exchange, thereby inhibiting sperm motility.

Diagnostic, pathophysiologic, and therapeutic aspects of benign paroxysmal positional vertigo

Benign paroxysmal positional vertigo is the most common peripheral vestibular disorder. It can be defined as transient vertigo induced by a rapid head position change, associated with a characteristic paroxysmal positional nystagmus. Canalolithiasis of the posterior semicircular canal is considered the most convincing theory of its pathogenesis and the development of appropriate therapeutic maneuvers resulted in its effective treatment. However, involvement of the horizontal or the anterior canal has been found in a significant rate and the recognition and treatment of these variants completed the clinical picture of the disease. This paper describes the advances in understanding how this disease is generated and discusses the current therapeutic modalities.

Home Treatment for Benign Positional Vertigo

Benign paroxysmal positional vertigo (BPPV) consists of brief episodes of vertigo that are provoked by changes in head position and are associated with

The Epley (canalith repositioning) manoeuvre for benign paroxysmal positional vertigo.

Benign paroxysmal positional vertigo (BPPV) is a syndrome characterised by short-lived episodes of vertigo in association with rapid changes in head position. It is a common cause of vertigo presenting to primary care and specialist otolaryngology clinics. Current treatment approaches include rehabilitative exercises and physical manoeuvres including the Epley manoeuvre. To assess the effectiveness of the Epley manoeuvre compared to other treatments available for posterior canal benign paroxysmal positional vertigo, or no treatment. The Cochrane Central Register of Controlled Trials (CENTRAL) (Cochrane Library Issue 1, 2004), MEDLINE (1966 to 2004), EMBASE (1974 to 2004) and reference lists of identified publications. Date of the most recent search was January 2004. Randomised trials of adults diagnosed with posterior canal BPPV (including a positive Dix-Hallpike test). Comparisons sought: Epley manoeuvre versus placebo Epley manoeuvre versus untreated controls Epley manoeuvre versus other active treatment Outcome measures that were considered include: frequency and severity of attacks of vertigo; proportion of patients improved by each intervention; and conversion of a "positive" Dix-Hallpike test to a "negative" Dix-Hallpike test Both reviewers independently extracted data and assessed trials for quality. Fifteen trials were identified but twelve studies were excluded because of a high risk of bias, leaving three trials in the review. Trials were mainly excluded because of inadequate concealment during randomisation, or failure to blind outcome assessors. The studies included in the review (Lynn 1995; Froehling 2000; Yimtae 2003) addressed the efficacy of the Epley manoeuvre against a sham manoeuvre or control group by comparing the proportion of subjects in each group who had complete resolution of their symptoms, and who converted from a positive to negative Dix-Hallpike test. Individual and pooled data showed a statistically significant effect in favour of the Epley manoeuvre over controls. There were no serious adverse effects of treatment. There is some evidence that the Epley manoeuvre is a safe effective treatment for posterior canal BPPV, although this is based on the results of only three small randomised controlled trials with relatively short follow up. There is no good evidence that the Epley manoeuvre provides a long term resolution of symptoms. There is no good evidence comparing the Epley manoeuvre with other physical, medical or surgical therapy for posterior canal BPPV.

Head tilt–dependent esotropia associated with trisomy 21

Objective To describe a series of patients who used a head tilt to control esotropia. Design Retrospective noncomparative case series. Participants Seven children with esotropia that decreased with their compensatory abnormal head tilt. Six of the patients had trisomy 21. The patients had no other identifiable etiology for their head tilt, including no oblique muscle dysfunction, nystagmus that changed with head tilt, or uncorrected refractive error. Intervention Six patients underwent horizontal extraocular muscle surgery. Preoperative evaluation in 4 patients included assessment of the change in head position with either monocular occlusion or prisms. Main outcome measures Ocular alignment in primary position and improvement in abnormal head tilt after surgery. Results In the 4 patients who underwent preoperative testing, the abnormal head tilt resolved with either monocular occlusion or prisms. The head tilt and esotropia were eliminated or improved in all patients who underwent strabismus surgery. Conclusions Abnormal head tilt may be used as a compensatory maneuver to improve purely horizontal strabismus. This finding appears to be associated with trisomy 21. Horizontal extraocular muscle surgery may improve the head tilt in such patients.

Cardiovascular Modules in the Cerebellum

Mapping with local lesions, electrical or chemical stimulation, or recording evoked field potentials or unit spikes revealed localized representations of cardiovascular functions in the cerebellum. In this review, which is based on literatures in the field (including our own publications), I propose that the cerebellum contains five distinct modules (cerebellar corticonuclear microcomplexes) dedicated to cardiovascular control. First, a discrete rostral portion of the fastigial nucleus and the overlying medial portion of the anterior vermis (lobules I, II and III) conjointly form a module that controls the baroreflex. Second, anterior vermis also forms a microcomplex with the parabrachial nucleus. Third, a discrete caudal portion of the fastigial nucleus and the overlying medial portion of the posterior vermis (lobules VII and VIII) form another module controlling the vestibulosympathetic reflex. Fourth, the medial portion of the uvula may form a module with the nucleus tractus solitarius and parabrachial nucleus. Fifth, the lateral edge of the nodulus and the uvula, together with the parabrachial nucleus and vestibular nuclei, forms a cardiovascular microcomplex that controls the magnitude and/or timing of sympathetic nerve responses and stability of the mean arterial blood pressure during changes of head position and body posture. The lateral nodulus-uvula appears to be an integrative cardiovascular control center involving both the baroreflex and the vestibulosympathetic reflex.

The Dix-Hallpike and Modified Epley Manoeuvres in the diagnosis and management of Benign Paroxysmal Positional Vertigo (BPPV)

Benign Paroxysmal Positional Vertigo (BPPV) is one of the most common balance disorders and one of the easiest to diagnose and treat. It is characterised by short lived episodes of vertigo and geotropic rotatory nystagmus, which occur a few seconds after rapid changes in head position. The vertigo usually lasts no more than a minute and the symptoms reduce in severity with repetitions of the evoking movement.

Quantification and clinical relevance of head motion during computed tomography.

To quantify the 3-dimensional translation and rotation components of head motion during computed tomography and to analyze the influence of such motion on perceptible artifacts and distortion of volume image data sets. Using high-precision optoelectronic motion-capture technology, changes in patient head position during axial CT scanning were registered in 20 cases and 2 phantoms with a spatial relative resolution better than 0.003 cm. Statistical analysis was performed on a base of 6-dimensional measurement-vectors, each with 3 translation and 3 rotation values. Because of the recording frequency of the tracking system, more than 80000 values were included in a statistical analysis. All 20 patients had head motion during the CT scanning, with only 4 of 20 patients showing perceptible motion artifacts. The frequency, the extent, and the direction of the movements did not correlate with either the observations made by the radiologic staff or with the patient's subjective estimation of comfort. Translation movements of the head during CT accounted for a maximum of 0.5 cm and rotations of more than 2 degrees without perceptible motion artifacts. The extent of positional changes of the head was found to correlate with the duration of scanning (Pearson's correlation coefficient: 0.647 for translation shifts, 0.453 for rotation shifts). The mean direction of head motion could be characterized predominantly as a rotation around the longitudinal axis of the body (xy plane) at a significance level of 0.01. Computed tomography evaluations of the head performed without rigid fixation suffer a spatial distortion of the volume image data sets, caused by interimage motion. The absence of motion artifacts is not correlated with the absence of motion.

Effect of complete dentures on dynamic measurement of changing head position: A pilot study

Statement of problem Complete dentures contribute significantly to the facial esthetics of edentulous patients. However, information as to the effect of complete dentures on the natural position of the head is limited. Purpose The purpose of this pilot study was to evaluate the immediate and 30-day effect of wearing complete dentures on the dynamic natural head position measured during walking. Material and methods The sample consisted of a volunteer group of 16 patients, 8 women and 8 men, who received new complete dentures. The ages of the subjects ranged from 45 to 64 years (mean=52 years). Dynamic measurement of head posture was carried out by a specially constructed inclinometer device. Each subject in turn was fitted with the inclinometer system and instructed to walk in a relaxed manner for 5 minutes. The data, measured as degrees, were stored in a pocket data logger. This procedure was repeated before insertion of dentures (T1), immediately after insertion of dentures (T2), and 30 days after insertion of dentures (T3). Stored dynamic head posture data were transferred to computer for analysis. The means of the measurements were statistically compared with Friedman and following Wilcoxon tests (α =.05). Results Twelve of 16 (75%) subjects showed an average of 4.6 degrees of cranial extension immediately after insertion of dentures. Six (37.5%) subjects showed an average of 6.4 degrees of cranial flexion, and 8 (50%) subjects showed an average of 5.2 degrees of cranial extension at T3 relative to the T1 measurement. Dynamic head posture measurements of the other 2 subjects remained unchanged. There were significant differences between different measurements of dynamic head posture positions ( P<.025). However, only the T1 and T2 measurements were significantly different ( P<.015). Conclusion The findings indicate that the statistically significant average extension 4.6 degrees in subjects immediately after insertion of complete dentures was not stable after a 30-day evaluation period and did not produce any statistically significant change. The overall effect of wearing dentures was an irregular flexion or extension pattern on dynamic head posture.

Experimental Study of Speed-dependent Positional Nystagmus in Benign Paroxysmal Positional Vertigo

Objective—One of the clinical characteristics of benign paroxysmal positional vertigo (BPPV) is that the more quickly the head position changes, the more severe the vertigo. This suggests that the velocity of the head change is critical in determining the occurrence and severity of vertigo. The aim of this study was to examine factors determining the symptoms of BPPV using models of canalolithiasis and cupulolithiasis.Material and Methods—Canalolithiasis and cupulolithiasis models were prepared using the bullfrog posterior semicircular canal (PSC). The ampullary nerve discharges were compared between quick and slow positional changes to examine factors determining the symptoms of BPPV.Results—In the canalolithiasis model, the acceleration of the otoconia was greater for the quick positional change. This resulted in a greater discharge with a longer duration. With the slow positional change, the discharges were smaller and shorter. In the cupulolithiasis model, the discharges were sustained and their magnitude did not differ between the quick and slow positional changes. The canalolithiasis model influenced the magnitude of discharge of the PSC depending on the speed of the positional change.Conclusions—Canalolithiasis is the more likely mechanism of BPPV, which is characterized by various degrees of vertigo upon kinetic positional change.