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Soft robots are increasingly gaining popularity as a preferred choice for designing medical devices due to their inherently compliant and adaptable nature. As research continues to advance in this field, soft robots are poised to revolutionize healthcare by providing safer, more patient-centric solutions. This paper presents the design of a novel soft corrugated actuator to create a system for positioning the head during head and neck cancer radiation therapy. Simulation and experimental data show that the presented actuator design can achieve linear expansion with respect to pressure in both free and under loading conditions. A machine learning model of the single actuator is created using experimental data (pressure, expansion, and weight) to predict the required pressure. The single actuator model's validity is confirmed by using four actuators to achieve head flexion at a specific angle, illustrating its potential for implementation in a multi-actuator system. The preliminary design of the multi-actuator head and neck positioning system demonstrates its capability to achieve four degrees of freedom. [ABSTRACT FROM AUTHOR]

Introduction: Many guidelines now recommend early rehabilitation for acute stroke patients. However, evidence remains lacking regarding the specific timings for initiation of various rehabilitation steps and management when complications are encountered in acute stroke rehabilitation. This survey aimed to investigate actual clinical situations in acute stroke rehabilitation in Japan and to improve the medical systems for rehabilitation and plan further studies. Methods: This nationwide, cross-sectional, web-based questionnaire survey was administered between February 7, 2022, and April 21, 2022, targeting all primary stroke centers (PSCs) in Japan. Among several components of the survey, this paper focused on the timing of the initiation of three rehabilitation steps (passive bed exercise; head elevation; and out-of-bed mobilization), along with the management of rehabilitation (continued or suspended) in the event of complications during acute stroke rehabilitation. We also investigated the influence of facility features on these contents. Results: Responses were obtained from 639 of the 959 PSCs surveyed (response rate: 66.6%). In cases of ischemic stroke and intracerebral hemorrhage, most PSCs initiated passive bed exercise on day 1, head elevation on day 1, and out-of-bed mobilization on day 2 (with day of admission defined as day 1). In cases with subarachnoid hemorrhage, rehabilitation steps were delayed compared to other stroke subtypes or showed wide variation depending on the facility. Passive bed exercise was accelerated by the presence of protocols for rehabilitation and weekend rehabilitation. Out-of-bed mobilization was accelerated by the presence of a stroke care unit. Facilities with board-certified rehabilitation doctors were cautious regarding the initiation of head elevation. Most PSCs suspended rehabilitation training in the event of symptomatic systemic/neurological complications. Conclusion: Our survey revealed the actual situation of acute stroke rehabilitation in Japan and indicated that some facility features appear to influence early increases in physical activity levels and early mobilization. Our survey provides fundamental data to improve the medical systems for acute stroke rehabilitation in the future. [ABSTRACT FROM AUTHOR]

Soft robots are increasingly gaining popularity as a preferred choice for designing medical devices due to their inherently compliant and adaptable nature. As research continues to advance in this field, soft robots are poised to revolutionize healthcare by providing safer, more patient-centric solutions. This paper presents the design of a novel soft corrugated actuator to create a system for positioning the head during head and neck cancer radiation therapy. Simulation and experimental data show that the presented actuator design can achieve linear expansion with respect to pressure in both free and under loading conditions. A machine learning model of the single actuator is created using experimental data (pressure, expansion, and weight) to predict the required pressure. The single actuator model’s validity is confirmed by using four actuators to achieve head flexion at a specific angle, illustrating its potential for implementation in a multi-actuator system. The preliminary design of the multi-actuator head and neck positioning system demonstrates its capability to achieve four degrees of freedom.

Mobile robotic systems are used in a wide range of applications. Especially in the assistive field, they can enhance the mobility of the elderly and disable people. Modern robotic technologies have been implemented in wheelchairs to give them intelligence. Thus, by equipping wheelchairs with intelligent algorithms, controllers, and sensors, it is possible to share the wheelchair control between the user and the autonomous system. The present research proposes a methodology for intelligent wheelchairs based on head movements and vector fields. In this work, the user indicates where to go, and the system performs obstacle avoidance and planning. The focus is developing an assistive technology for people with quadriplegia that presents partial movements, such as the shoulder and neck musculature. The developed system uses shared control of velocity. It employs a depth camera to recognize obstacles in the environment and an inertial measurement unit (IMU) sensor to recognize the desired movement pattern measuring the user's head inclination. The proposed methodology computes a repulsive vector field and works to increase maneuverability and safety. Thus, global localization and mapping are unnecessary. The results were evaluated by simulated models and practical tests using a Pioneer-P3DX differential robot to show the system's applicability. [ABSTRACT FROM AUTHOR]

Background: Plagiocephaly is defined as an asymmetrical distortion of the skull, resulting in an oblique trapezoid or parallelogram head shape. Deformational plagiocephaly (DP) is caused by forces acting on one side of the back of the head, distorting normal skull symmetry., Objective: The aims of this systematic review and meta-analysis were to critically assess the evidence for nonobstetric risk factors for DP and to make evidence-based recommendations for reducing the prevalence of DP., Methods: The selection criterion was studies reporting risk factors for DP. Case reviews, case series, expert opinions, and systematic reviews were excluded. PubMed and Web of Science were searched from August 21, 2010, to August 21, 2022. Publication bias was assessed using funnel plots. Meta-analyses were presented using forest plots., Results: A total of 19 studies (cohort studies: n=13, 68%; case-control studies: n=5, 26%; and cross-sectional studies: n=1, 5%) with a total of 14,808 participants were included. Of the 43 investigated potential nonobstetric factors, 16 (37%) were associated with DP. Of these 16 factors, 12 (75%) had odds ratios (ORs) with 95% CIs not crossing 1: insufficient vitamin D intake (OR 7.15, 95% CI 3.77-13.54), head position preference (OR 4.75, 95% CI 3.36-6.73), bottle-only feeding (OR 4.65, 95% CI 2.70-8.00), reduced tummy time (OR 3.51, 95% CI 1.71-7.21), sleeping position (OR 3.12, 95% CI 2.21-4.39), fewer motor milestones reached by the age of 6 months (OR 2.56, 95% CI 1.66-3.96), obesity (OR 2.45, 95% CI 1.02-5.90), maternal education level (OR 1.66, 95% CI 1.17-2.37), male sex (OR 1.51, 95% CI 1.07-2.12), formula feeding (OR 1.51, 95% CI 1.00-2.27), head circumference (OR 1.22, 95% CI 1.06-1.40), and mechanical ventilation (OR 1.10, 95% CI 1.00-1.14). No evidence of publication bias was detected., Conclusions: This study provides a comprehensive assessment of the nonobstetric factors associated with DP and presents 11 evidence-based recommendations for reducing its prevalence. The primary limitation is that only publication bias was assessed., Trial Registration: PROSPERO CRD42020204979; https://www.crd.york.ac.uk/prospero/display_record.php? ID=CRD42020204979., (©Christopher Robert Timothy Hillyar, Natalie Bishop, Anjan Nibber, Frances Jean Bell-Davies, Juling Ong. Originally published in the Interactive Journal of Medical Research (https://www.i-jmr.org/), 18.09.2024.)

Background and purpose: Head down tilt 15° (HDT15°), applied before recanalization, increases collateral flow and improves outcome in experimental ischemic stroke. For its simplicity and low cost, HDT15° holds considerable potential to be developed as an emergency treatment of acute stroke in the prehospital setting, where hemorrhagic stroke is the major mimic of ischemic stroke. In this study, we assessed safety of HDT15° in the acute phase of experimental intracerebral hemorrhage. Methods: Intracerebral hemorrhage was produced by stereotaxic injection of collagenase in Wistar rats. A randomized noninferiority trial design was used to assign rats to HDT15° or flat position (n = 64). HDT15° was applied for 1 h during the time window of hematoma expansion. The primary outcome was hematoma volume at 24 h. Secondary outcomes were mass effect, mortality, and functional deficit in the main study and acute changes of intracranial pressure, hematoma growth, and cardiorespiratory parameters in separate sets of randomized animals (n = 32). Results: HDT15° achieved the specified criteria of noninferiority for hematoma volume at 24 h. Mass effect, mortality, and functional deficit at 24 h showed no difference in the two groups. HDT15° induced a mild increase in intracranial pressure with respect to the pretreatment values (+2.91 ± 1.76 mmHg). HDT15° had a neutral effect on MRI‐based analysis of hematoma growth and cardiorespiratory parameters. Conclusions: Application of HDT15° in the hyperacute phase of experimental intracerebral hemorrhage does not worsen early outcome. Further research is needed to implement HDT15° as an emergency collateral therapeutic for acute stroke. [ABSTRACT FROM AUTHOR]

Background and Purpose: Head positioning is an important aspect for surgical planning in any cranial procedure. However, in neurointerventional cases, this is an afterthought due to advances in biplane imaging. We aim to present that the concept of head positioning may be applied to neurointerventional procedures to obtain optimal working projections to aide in the treatment of neurovascular pathology.Methods: The operative log of the senior author was reviewed between 2016 and 2019. Seventeen patients were identified who required readjustment of head position to allow for ideal working projection during treatment. The reports and imaging of these patients were reviewed and categorized based on repositioning adjustments applied.Results: Three specific head adjustments were performed to obtain working projections using biplanar angiography: head flexed position, head extended position, or extended-tilt positioning. All patients underwent endovascular coiling treatment for a variety of intracranial aneurysms.Conclusion: In select cases, ideal views of vascular pathology can be difficult to obtain due to limitations of biplane rotation or patient-specific anatomy. Simple maneuvers in head positioning can be done to achieve better working projections for optimized endovascular treatment. [ABSTRACT FROM AUTHOR]

To investigate the effects of different positioning on the volume/location of the internal jugular vein (IJV) using 2-dimensional (2D) tracked ultrasound. This was a prospective, observational study. Local research institute. Healthy volunteers. Twenty healthy volunteers were scanned in the following 6 positions: (1) supine with head neutral, rotated 15 and 30 degrees to the left and (2) 5-, 10-, and 15-degree Trendelenburg position with head neutral. In each position the volunteer's neck was scanned using a 2D ultrasound probe tracked with a magnetic tracker. These spatially tracked 2D images were collected and reconstructed into a 3D volume of the IJV and carotid artery. This 3D ultrasound volume then was segmented to obtain a 3D surface on which measurements and calculations were performed. The measurements included average cross-section area (CSA), CSA along the length of IJV, and average overlap rate. CSA (mm2) in the supine and 5-, 10-, and 15-degree Trendelenburg positions were as follows: 86.7 ± 44.8, 104.3 ± 54.5, 119.1 ± 58.6, and 133.7 ± 53.3 (p < 0.0001). CSA enlarged with the increase of Trendelenburg degree. Neither Trendelenburg position nor head rotation showed a correlation with overlap rate. Trendelenburg position significantly increased the CSA of the IJV, thus facilitating IJV cannulation. This new 3D reconstruction method permits the creation of a 3D volume through a tracked 2D ultrasound scanning system with image acquisition and integration and may prove useful in providing the user with a "road map" of the vascular anatomy of a patient's neck or other anatomic structures. [ABSTRACT FROM AUTHOR]

Purpose: Accuracy of panoramic radiographs is essential for distance measurements during implant planning, but it might be compromised by various factors. The aim of the present study was to evaluate the effect of vertical and horizontal head positioning on area-dependent enlargement ratios of digital panoramic radiography. Materials and Methods: The mandible of a dry skull was marked with small steel globes. The skull was moved 1 to 4 degrees in 1-degree increments to the left and right and up and down. A series of 17 panoramic radiographs was obtained with the same digital radiographic device. For the rotated skull, horizontal and vertical distances, indicated by the steel globes, were compared to the distances with the ideal positioning of the skull. The results were analyzed statistically. Results: Head positioning and angulation, anatomical site, and distance orientation influenced horizontal measurements. Enlargement ratios of horizontal distances of the right canine and first molar regions (skull rotation to the right 2 to 4 degrees) were significantly lower than those for the corresponding anatomical sites on the left side. Horizontal distance measurements of the different anatomical sites of the left and the right jaw did not differ significantly from each other when the skull was moved downward. When the skull was rotated upward, no significant differences were obtained for corresponding anatomical sites of the right and left arches. Enlargement ratios of vertical distances of different anatomical sites, as well as within the same anatomical site, were not significantly different from each other for the given skull rotations. Conclusions: Ideal head positioning for digital panoramic radiographs is mandatory to avoid improper enlargement ratios of horizontal distances, which can be important in implant dentistry. [ABSTRACT FROM AUTHOR]

Abstract Background To compare the primary anatomical outcome of pars plana vitrectomy, 360° peripheral endolaser, and 15% octafluoropropane C3F8 gas tamponade in patients with uncomplicated rhegmatogenous detachment and inferior retinal breaks, after 24-h postoperative prone positioning to similar patients with 1 week postoperative prone positioning. Methods Records of 5500 patients who underwent pars plana vitrectomy between 2008 and 2015 were retrieved. Collected data included age, gender, number of retinal quadrants with retinal breaks, number of retinal breaks, macula status on presentation (attached or detached), phakic status (phakic, pseudophakic, or aphakic), and primary anatomical outcome (at 1 and 3 months post-operative). Results 270 patients met the study inclusion criteria (78 females, and 192 males). In the 24-h positioning arm (183 patients), the overall anatomical success rate was 96.2% at 1 month and 83.6% at 3 months. In the 1-week positioning group (87 patients), the overall anatomical success rate was 93% at 1 month and 79% at 3 months. Both positioning groups did not show statistical difference in outcome at 1 month (p-value = 0.7) or at 3 months (p-value = 0.39). Logistic regression analysis found that the number of retinal breaks correlates with the postoperative anatomical success at 3 months (odd ratio 0.8, p-value = 0.016). Conclusion This short term retrospective study demonstrated that patients with uncomplicated rhegmatogenous retinal detachment due to inferior retinal breaks, who underwent pars plana vitrectomy, 360° endolaser, 15% C3F8 gas, and limited (24-h) prone positioning did not show statistical difference in the anatomical outcome (at 1, and 3 months) when compared with 1 week postoperative positioning. Larger prospective studies are warranted to further elucidate positioning role.

Abstract Background Cephalometric radiography has been used for orthodontic and surgical treatment planning and assessment, and for quantifying mandibular growth. However, it remains unclear how head positioning errors and the level of examiner experience affect the reliability of such morphometric measurements. The current study aimed to bridge the gap by determining the intra-, inter-rater, and inter-session reliability of measurements of mandibular morphology with random head positioning errors as measured by a junior and a senior dentist. Methods Cone-beam computed tomography data of twelve mandibles were obtained with each rotated randomly away from the neutral position within the range of +3 and −3° along each of the anatomical axes to simulate six imaging trials. A synthetic cephalogram for each trial was obtained via a digitally reconstructed radiography (DRR) technique and eleven landmarks for twelve morphological parameters on the cephalogram were identified manually six times by a junior and a senior dentist. The procedure was repeated on another day within 5 days. Test–retest reliability was assessed in terms of an intra-class correlation coefficient (ICC) using a two-way mixed-effects model. Results Good to very good intra-rater (senior: ICC > 0.92; junior: ICC > 0.78), inter-rater (ICC > 0.70 for most parameters) and inter-session reliability (senior: ICC > 0.84; junior: ICC > 0.62) were found. Bland & Altman plots of inter-rater comparisons show that there were systematical biases between the examiners on most parameters, except for the distance between Gonion and Pogonion. Conclusions The current results suggest that good to very good intra-rater, inter-rater and inter-session reliability can be achieved for most parameters with randomized head positioning errors; higher inter-session reliability can be achieved by more experienced examiners; and that long-term monitoring of mandibular growth based on cephalographic measurements should be made by the same more experienced examiner. The current DRR-based approach can be used to evaluate individual factors that affect the morphological measurements.

Background: Anterior cervical discectomy and fusion (ACDF) is a commonly implemented surgical intervention for a variety of pathologies affecting the cervical spine. The current literature and daily practice reveal variations on patient head positioning for this procedure with both rigid fixations in the Mayfield skull clamp as well as use of a padded headrest being used. In this study, we therefore examine whether patients undergoing surgery using head positioning in the Mayfield skull clamp versus a padded headrest differ in regard to adverse events, surgical parameters and clinical outcome., Methods: A single-center, retrospective analysis of 121 patients treated with ACDF for degenerative disease, traumatic cervical spine injury and infectious disease between November 2019 and March 2023 was performed. Clinical and imaging data for 59 patients positioned in the Mayfield skull clamp and 62 patients positioned in a padded headrest were evaluated using electronic medical records. In addition to demographic data, surgical indications, procedures performed were analyzed for both groups. Level of training (chief, attending and resident), length of surgery and intraoperative radiation exposure (measured by dose area product and total radiation time) were also examined. Finally, modified Rankin Scale (mRS) preoperatively and at last follow-up as well as adverse events were compared between groups., Results: We found no statistically significant differences between the Mayfield and headrest groups regarding surgical indications (P=0.583), procedures performed (P=0.069), level of training of the surgeon (P=0.218), length of surgery (P=0.752), adverse events (P=0.619) or neurological impairment (P=0.080) following surgical intervention. There was a significant difference regarding dose area product between both groups with patients positioned in the Mayfield skull clamp showing lower mean levels of radiation than those in the headrest group (99 versus 131 cGy/cm 2 ; P=0.003)., Conclusions: Patient positioning using the Mayfield skull clamp may reduce required radiation exposure during ACDF procedures versus use of a padded headrest., Competing Interests: Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://jss.amegroups.com/article/view/10.21037/jss-23-117/coif). The authors have no conflicts of interest to declare., (2024 Journal of Spine Surgery. All rights reserved.)

In this paper, we applied the Hilbert–Huang transform (HHT) to the time series of the torque exerted on the carriage arm of a hard disk drive, which was calculated using the finite-element analysis. Then, a Fourier transform (FT) was implemented to perform frequency analysis; the results were subsequently compared with the HHT results. A comparison of both spectra revealed the superior ability of HHT to perform frequency analysis of flow phenomena via disturbance torque analysis. Furthermore, the HHT results confirmed that to achieve more precise head positioning, it is necessary to decrease torque fluctuations induced by the non-stationary phenomena that are not always observed in the power spectrum obtained via the FT analysis, such as vortex shedding around an arm. [ABSTRACT FROM AUTHOR]

Objective Several recent intraventricular hemorrhage prevention bundles include midline head positioning to prevent potential disturbances in cerebral hemodynamics. We aimed to study the impact of head position change on regional cerebral saturations SctO2 in preterm infants (< 30 weeks gestational age) during the first 3 days of life. Study Design Bilateral SctO2 was measured by near-infrared spectroscopy. The infant's head was turned sequentially to each side from midline (baseline) in 30-minute intervals while keeping the body supine. Bilateral SctO2 before and after each position change were compared using paired t-test. Results In relatively stable preterm infants (gestational age 26.5 ± 1.7 weeks, birth weight 930 ± 220 g; n = 20), bilateral SctO2 remained within normal range (71.1-75.3%) when the head was turned from midline position to either side. Conclusion Stable preterm infants tolerated brief changes in head position from midline without significant alternation in bilateral SctO2; the impact on critically ill infants needs further evaluation. [ABSTRACT FROM AUTHOR]

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In flying insects, head stabilization is an essential reflex that helps to reduce motion blur during fast aerial manoeuvres. This reflex is multimodal and requires the integration of visual and antennal mechanosensory feedback in hawkmoths, each operating as a negative-feedback-control loop. As in any negative-feedback system, the head stabilization system possesses inherent oscillatory dynamics that depend on the rate at which the sensorimotor components of the reflex operate. Consistent with this expectation, we observed small-amplitude oscillations in the head motion (or head wobble) of the oleander hawkmoth, Daphnis nerii, which are accentuated when sensory feedback is aberrant. Here, we show that these oscillations emerge from the inherent dynamics of the multimodal reflex underlying gaze stabilization, and that the amplitude of head wobble is a function of both the visual feedback and antennal mechanosensory feedback from the Johnston's organs. Our data support the hypothesis that head wobble results from a multimodal, dynamically stabilized reflex loop that mediates head positioning.

Purpose: The objective of the present study was to evaluate the risk of pneumocephalus, venous air embolism (VAE), and intracranial hemorrhage in subthalamic nucleus (STN) deep brain stimulation (DBS) patients operated in the strict supine (head and body flat) position. Methods: This was a retrospective review of clinical records and brain imaging of patients who underwent STN DBS between January 2007 and June 2009 at the University of Kansas Medical Center. Results: A total of 61 patients underwent 114 lead implantations (53 staged bilateral and 8 unilateral). No case involved a transventricular route. Intracranial air volumes ranged from 0 to 7.02 cm (mean 0.98 ± 1.42 cm). Pneumocephalus volumes were highly skewed with no air present after 44 (38.6%) lead implantations, >0 to 1 cm in 35 (30.7%), >2 to 3 cm in 17 (14.9%), and >3 cm (average 4.97 cm) in 9 (7.9%). There was no incidence of clinically apparent VAE or symptomatic intracranial hemorrhage. There was no association between age, degree of atrophy, sagittal angle of surgical approach, number of microelectrode runs (MERs), distance of gyrus from inner skull bone at the entry point, or surgical side and pneumocephalus. However, the majority of lead implantations (100 leads; 88%) required only one MER and there were minimal measurable distances between entered gyrus and adjacent bone. Conclusions: Our data suggest that strict supine positioning during STN DBS surgery results in minimal intracranial air and is not associated with VAE or symptomatic intracranial hemorrhage when the operative method described is used. [ABSTRACT FROM AUTHOR]

Purpose: Pseudoexfoliation (PEX) is a condition characterized by widespread intraocular and systemic production and deposition of an abnormal fibrillar extracellular material. Zonular instability is frequently associated with PEX. Anterior chamber depth (ACD) and intraocular pressure (IOP) changes in normotensive eyes with PEX after prone position was investigated in this study. Methods: Thirty subjects with normotensive pseudoexfoliative eyes and 30 healthy control subjects were enrolled. None of the eyes had cataract or posterior synechia. Central ACD, axial length (AL), and IOP were measured 5 min after supine and prone positions by using A-scan ultrasonography and TonoPen. Results: Mean ACD decreased from 2.89 ± 0.27 mm to 2.71 ± 0.23 mm in eyes with PEX and from 2.94 ± 0.25 mm to 2.84 ± 0.30 mm in normal eyes with postural change. The ACD decreased significantly in both group of eyes in prone position ( p < 0.001 in PEX group, p = 0.005 in normal group), but the decrease in ACD in eyes with PEX was significantly greater than the decrease in normal control eyes ( p = 0.03). Mean IOP was 16.9 ± 2.1 mmHg after supine position and 17.1 ± 2.04 mmHg after prone position in eyes with PEX, 16.1 ± 2.7 mmHg after supine position and 16.3 ± 2.6 mmHg after prone position in normal eyes. Postural changes in IOP and AL were not statistically significant in both groups of eyes ( p = 0.096 in the PEX group and p = 0.484 in the normal group for IOP; p = 0.177 in the PEX group and p = 0.276 in the normal group for AL). Conclusion: The lens is more mobile in pseudoexfoliative eyes than normal eyes after supine to prone position. Although the ACD of pseuodoexfoliative eyes decreased statistically significantly after 5 min of prone position, IOP did not change significantly. [ABSTRACT FROM AUTHOR]

Objective: Various methods have been reported for the detection of unknown primaries in cervical lymph node metastasis. Recently, we applied new optical devices and modifications of endoscopic techniques for the detection of primary lesions, and obtained excellent results. The detection rate of the new method was compared with that of previous methods. Study Design: Retrospective. Methods: A total of 51 patients with cervical lymph node metastasis from an unknown primary site (CUP) were referred to our hospital between January 2000 and May 2009, and were retrospectively analyzed. Between 2000 and 2005, the observation by normal video-endoscope in straight head position was performed to detect the primary lesions in the outpatient setting. Since 2006, a new method for detection of primary lesions has been employed. The method includes the use of new optical devices (hooded video-endoscope and narrow-band imaging endoscope) and different head positions (head torsion technique, Valsalva maneuver, and the Killian position). Results: The detection rate of primary lesions using the new method was 71% (15 of 21), which was better than the 30% (10 of 30) obtained with the conventional method. All primary lesions identified using the new method were located in the hypopharynx. Conclusions: The new method was able to detect primary lesions in 71% of cases with CUP. The higher rate achieved with the new method was probably due to the clear visualization of the hypopharynx. Thus, the new method was shown to be useful for the detection of primary lesions in cases of CUP. Laryngoscope, 2010 [ABSTRACT FROM AUTHOR]

Considerable forces are exerted on oropharyngeal tissues during microlaryngoscopic procedures. Although it is generally accepted that positioning of the patient’s head influences the quantity of these forces and the easiness of the exposure of the anterior glottis, there is a lack of systematic studies on this topic. The aim of our study was to measure the forces occurring during microlaryngoscopy in different positions. This should result in a recommendation for a “low-pressure” position which minimises the risk of postoperative complications due to tissue trauma. Thirty consecutive patients planned for microlaryngoscopy underwent study procedures. During general anaesthesia, measurements were taken using a tension spring balance in neutral position, during extension of the cervical spine, as well as under moderate and maximum flexion. Elevation of the patient’s head thus flexing the cervical spine reduced the occurring forces significantly. Maximum elevation allowed a full exposure of the anterior commissure in all cases, whereas exposure of the anterior commissure was not possible even with maximum external counterpressure in almost 40% of cases with maximum extended cervical spine. The largest differences were observed between extension, neutral and flexion position, whereas the differences between moderate and maximum flexion were not significant. Elevation of the patient’s head with consecutive flexion of the cervical spine allows for better exposure in microlaryngoscopy and reduces significantly the pressure exerted on the oropharyngeal tissues thus minimising the risk of tissue injury. A slight modification of standard instruments can be necessary when using this “low-pressure” position. [ABSTRACT FROM AUTHOR]

This paper considers the determination of reference trajectories for use with a two-degree of-freedom (2-DOF) controller for the head positioning of hard disk drives (HDD). The reference trajectories are designed in two stages-off-line simulation and online reference generation. The HDD model used for the design includes the back electromotive force of the voice coil motor. In the second stage, the idea of structural vibration minimized acceleration trajectory is utilized to adjust the errors at the end of the trajectories. 2-DOF control with the proposed reference trajectory is compared to conventional mode-switching control, and its effectiveness is verified [ABSTRACT FROM PUBLISHER]

High track density has been achieved by adopting an H∞ controller with a feeds forward compensator using adaptive filter theory in a sector servo system. in applying the H∞ control theory, a state-space model of an augmented plant was constructed considering the input location of the disturbance. Moreover, to reduce repeatable runout, an experiment involving a feed-forward control system including an adaptive FIR filter was performed. As * result, the head-positioning accuracy was improved by approximately 15 percent compared to the case without feed forward. A 0. 15-μm head-positioning accuracy was achieved. This level of accuracy means that a track density of 310 tracks/mm (8100 TPI) can be realized. [ABSTRACT FROM AUTHOR]

Background: The retrosigmoid approach is a common route to the cerebellopontine angle and lateral clivus. Patient's head positioning just before the operation is crucial to perform the procedure effectively and safely. Aim: The aim of the study is to determine the positional angle of the head on preoperative axial sequences of the cranial magnetic resonance imaging (MRI). Materials and Methods: The angle between the line drawn along the petrous bone ventral to the internal auditory canal and the line drawn parallel to the dorsal face of the clivus on the axial view of MRI sequences was measured. Results: This method of patient positioning has resulted in minimal cerebellar retraction, less time in the preoperative preparation period and less postoperative headache and neck pain. Conclusions: This method can provide quick and better exposure of the cerebellopontine angle. Preoperative measurement of positional angle on axial MRI sequences is a very simple and sufficient way to determine the angle of the head that is turned to the contralateral side. [ABSTRACT FROM AUTHOR]

It is generally agreed that optimal head positioning is an important consideration in acute stroke management regime. However, there is limited literature investigating the effect of head positioning changes on cerebrovascular physiology in acute ischemic stroke (AIS). We aim to assess cerebral autoregulation (CA) and associated hemodynamic responses during gradual head positioning (GHP) changes, between AIS and controls. Cerebral blood flow velocity (CBFV, transcranial Doppler), blood pressure (BP, Finometer) and end-tidal CO 2 (capnography) were recorded between lying flat (0°) and sitting up (30°) head position, in 16 controls (8 women, mean age 57 ± 16 yrs) and 15 AIS patients (7 women, 69 ± 8 yrs). AIS patients carried out three visits at 13.3 ± 6.9 h, 4.8 ± 3.2 days and 93.9 ± 11.5 days from symptom onset, respectively. AIS patients were significantly hypertensive (p = 0.005), hypocapnic (p < 0.001), and had lower CBFV (p = 0.02) compared to controls, in both head positions. When comparing 5-min FLAT to SIT head position, reductions in BP (both AIS and controls, p < 0.001) and CBFV (controls only: dominant hemisphere p = 0.001 and non-dominant hemisphere p = 0.05) were demonstrated. Of note, a reduction in autoregulation index was observed in AIS, after 5-min SIT head positioning, at all 3 visits (p = 0.018). Conclusion: Key hemodynamic changes were demonstrated when the head position changes from 5-min FLAT to SIT head position (GHP) in mildly affected stroke patients. Importantly, these were associated with non-significant changes in CBFV but reduced measures of CA following AIS, which may be relevant in determining the optimal head position and the ideal timing of mobilisation. Clinical Trial Registration – URL: http://www.clinicaltrials.gov. Unique Identifier: NCT02932540 • There is an ongoing debate regarding the optimal head positioning in ischemic stroke patients • Cerebral hemodynamic was studied in ischemic stroke patients, between lying flat (0°) and sitting up (30°) head position • Reduction in autoregulation index were observed when head position changes from (0°) to (30°) in ischemic stroke patients • Understand cerebral hemodynamics in head positionings may provide optimal mobilisation timing in ischemic stroke patients [ABSTRACT FROM AUTHOR]

A 39-year-old man with acquired torticollis suffering from cervicobrachialgia and neurological deficits is presented. Due to a change in head position a transient reproducible tetraplegia and severe vegetative dysfunctions were caused. The origin of this uncommon serious combination of symptoms and signs was a chordoma of the upper cervical spine. After surgical decompression the patient was free of neurological deficit and pain. Review of the literature did not reveal any similar case. [ABSTRACT FROM AUTHOR]