Thickness of the lateral surface of the temporal bone in children

Age estimation in infant and prenatal individuals through the metric development of the pars petrosa and squamosal portion of the temporal bone

This study proposes an assessment of the accuracy of the Fazekas and Kósa and Nagaoka methods by measuring the squamosal and petrous portions of the temporal bone, whose application in the Mediterranean population is not recommended. Therefore, our proposal is a new formula to estimate the age of skeletal remains from individuals at 5 months gestational age to 1.5 postnatal years with the temporal bone. The proposed equation was calculated on a Mediterranean sample identified from the cemetery of San José, Granada (n = 109). The mathematical model used is the exponential regression of the estimated age for each measure and sex, and both in combination, using an inverse calibration and cross-validation model. In addition, the estimation errors and the percentage of individuals within a 95% confidence interval were calculated. The lateral development of the skull, especially the growth of the length of the petrous portion, showed the greatest accuracy, while its counterpart, the width of the pars petrosa, showed the lowest accuracy, so its use is discouraged. The positive results from this paper should be useful in both forensic and bioarchaeological contexts.

A concise guide to transtemporal contrast-enhanced ultrasound in children

Brain contrast-enhanced ultrasound offers insights into the brain beyond the anatomic information offered by conventional grayscale ultrasound. In infants, the open fontanelles serve as acoustic windows. In children, whose fontanelles are closed, the temporal bone serves as the ideal acoustic window due to its relatively smaller thickness than the other skull bones. Diagnosis of common neurologic diseases such as stroke, hemorrhage, and hydrocephalus has been performed using the technique. Transtemporal ultrasound and contrast-enhanced ultrasound, however, are rarely used in children due to the prevalent notion that the limited acoustic penetrance degrades diagnostic quality. This review seeks to provide guidelines for the use of transtemporal brain contrast-enhanced ultrasound in children.

Transtemporal brain contrast-enhanced ultrasound in children: preliminary experience in patients without neurological disorders

AIM

To evaluate the use of transtemporal brain contrast-enhanced ultrasound (CEUS) to assess cerebral blood perfusion in a cohort of children without neurological disorders.

METHODS

We included pediatric patients who were undergoing a clinically-indicated CEUS study. Brain scans were performed with a Siemens Sequoia scanner and a 4V1 transducer, that was placed on the left transtemporal bone. Brain scans were performed simultaneously with the images of the clinically-indicated organ of interest. Qualitative and quantitative analysis was performed to evaluate the hemispherical blood flow at the level of the midbrain during the wash-in and wash-out phases of the time-intensity curve. Clinical charts were reviewed to evaluate post-CEUS adverse events.

RESULTS

Five patients were evaluated (mean age 5.8 ± 5.1 years). Qualitatively, more avid enhancement in the midbrain than the cortex was observed. Structures depicted ranged between the centrum semiovale at the level of the lateral ventricles and the midbrain. A quantitative analysis conducted on four patients demonstrated less avid perfusion on the contralateral (i.e. right) side, with a mean left/right ratio ranging between 1.51 and 4.07. In general, there was a steep positive wash-in slope starting at approximately 10 s after contrast injection, reaching a peak intensity around 15-26 s on the left side, and 17-29 s on the right side. No adverse events were reported.

CONCLUSION

Transtemporal brain CEUS is feasible and safe in the pediatric population and allows qualitative and quantitative assessment of cerebral perfusion.

In Silico Assessment of Safety and Efficacy of Screw Placement for Pediatric Image-Guided Otologic Surgery

Introduction: Current high-accuracy image-guided systems for otologic surgery use fiducial screws for patient-to-image registration. Thus far, these systems have only been used in adults, and the safety and efficacy of the fiducial screw placement has not yet been investigated in the pediatric population.

Materials and Methods: In a retrospective study, CT image data of the temporal region from 11 subjects meeting inclusion criteria (8–48 months at the time of surgery) were selected, resulting in n = 20 sides. These datasets were investigated with respect to screw stability efficacy in terms of the cortical layer thickness, and safety in terms of the distance of potential fiducial screws to the dura mater or venous sinuses. All of these results are presented as distributions, thickness color maps, and with descriptive statistics. Seven regions within the temporal bone were analyzed individually. In addition, four fiducial screws per case with 4 mm thread-length were placed in an additively manufactured model according to the guidelines for robotic cochlear implantation surgery. For all these screws, the minimal distance to the dura mater or venous sinuses was measured, or if applicable how much they penetrated these structures.

Results: The cortical layer has been found to be mostly between 0.7–3.3 mm thick (from the 5^th to the 95^th percentile), while even thinner areas exist. The distance from the surface of the temporal bone to the dura mater or the venous sinuses varied considerably between the subjects and ranged mostly from 1.1–9.3 mm (from the 5^th to the 95^th percentile). From all 80 placed fiducial screws of 4 mm thread length in the pediatric subject younger than two years old, 22 touched or penetrated either the dura or the sigmoid sinus. The best regions for fiducial placement would be the mastoid area and along the petrous pyramid in terms of safety. In terms of efficacy, the parietal followed by the petrous pyramid, and retrosigmoid regions are most suited.

Conclusion: The current fiducial screws and the screw placement guidelines for adults are insufficiently safe or effective for pediatric patients.

Quantitative Analysis of Temporal Bone Density and Thickness for Robotic Ear Surgery

Background and Objective: Quantitative assessment of bone density and thickness in computed-tomography images offers great potential for preoperative planning procedures in robotic ear surgery. Methods: We retrospectively analyzed computed-tomography scans of subjects undergoing cochlear implantation (N = 39). In addition, scans of Thiel-fixated ex-vivo specimens were analyzed (N = 15). To estimate bone mineral density, quantitative computed-tomography data were obtained using a calibration phantom. The temporal bone thickness and cortical bone density were systematically assessed at retroauricular positions using an automated algorithm referenced by an anatomy-based coordinate system. Two indices are proposed to include information of bone density and thickness for the preoperative assessment of safe screw positions (Screw Implantation Safety Index, SISI) and mass distribution (Column Density Index, CODI). Linear mixed-effects models were used to assess the effects of age, gender, ear side and position on bone thickness, cortical bone density and the distribution of the indices. Results: Age, gender, and ear side only had negligible effects on temporal bone thickness and cortical bone density. The average radiodensity of cortical bone was 1,511 Hounsfield units, corresponding to a bone mineral density of 1,145 mg HA/cm³. Temporal bone thickness and cortical bone density depend on the distance from Henle's spine in posterior direction. Moreover, safe screw placement locations can be identified by computation of the SISI distribution. A local maximum in mass distribution was observed posteriorly to the supramastoid crest. Conclusions: We provide quantitative information about temporal bone density and thickness for applications in robotic and computer-assisted ear surgery. The proposed preoperative indices (SISI and CODI) can be applied to patient-specific cases to identify optimal regions with respect to bone density and thickness for safe screw placement and effective implant positioning.

Cochlear implant fixation using resorbable mesh

In this article we describe a new method of cochlear implant receiver-stimulator fixation using a resorbable poly (D,L) lactic acid mesh. We conducted a retrospective case review at a tertiary referral center; 10 pediatric and 4 adult patients had undergone cochlear implantation during the period from February to October 2008. Resorbable poly (D,L) lactic acid mesh and pins were used for fixation of the cochlear implant receiver stimulator. The receiver stimulator was assessed for stability/migration, and the scalp flap/incision were evaluated for allergic reactions, infections, and healing problems. With an average follow-up of 17.2 months, no patients had migration of the receiver stimulator, and there was no evidence of infection, wound dehiscence, or allergic reaction. Early results indicate that fixation of a cochlear implant receiver stimulator using resorbable mesh is well tolerated and provides good stability without device migration. Resorbable mesh fixation of the receiver stimulator is a reasonable alternative technique for cochlear implantation.

Determining the influence of population variation on compliance with radiofrequency exposure limits: proposed study

Currently, compliance with safety limits for human exposure to radiofrequency (RF) fields is demonstrated by methods that rely on certain assumptions and approximations, which include among other things, human anatomical features, tissue types and the dielectric properties of these tissues. This paper reviews some of the available data and outlines a proposal for an encompassing study to investigate which of these assumptions are appropriate; what approximation can be used in physical and computational modeling of humans for specific energy absorption rate (SAR) calculations (a key compliance metric); and what trade-offs can be made between accuracy and modeling requirements for practical considerations. Key issues to be investigated are how SAR varies between children and adults, between males and females, and how to model SAR in the fetus of pregnant females. It is hoped that the proposed study will produce models and methods which allow for faster, more accurate and more efficient compliance with radiofrequency exposure limits.

Differences in RF energy absorption in the heads of adults and children

There has been a long and controversial debate on possible differences in electromagnetic (EM) energy absorption between adults and children during cell phone usage. Some published studies report higher specific absorption rate (SAR) in children and explain this based on smaller head size. More recently, age dependent changes of the dielectric tissue parameters have again ignited the discussion. This study intends to give a comprehensive review of the current state of knowledge about the parameters and mechanisms affecting the exposure of the mobile phone user with special focus on the exposure of children. Discussed are the absorption mechanism, tissue parameters, the effect of the pinna, and the uncertainties associated with head models based on spheroids, scaled adult heads, and magnetic resonance imaging (MRI) data of children. The conclusions of the review do not support the assumption that the energy exposure increases due to smaller heads, but identifies open issues regarding the dielectric tissue parameters and the thickness of the pinna.

Comparisons of peak SAR levels in concentric sphere head models of children and adults for irradiation by a dipole at 900 MHz

The aim of this study is to examine the scale and significance of differences in peak specific energy absorption rate (SAR) in the brains of children and adults exposed to radiofrequency emissions from mobile phones. Estimates were obtained by method of multipole analysis of a three layered (scalp/cranium/brain) spherical head exposed to a nearby 0.4 lambda dipole at 900 MHz. A literature review of head parameters that influence SAR induction revealed strong indirect evidence based on total body water content that there are no substantive age-related changes in tissue conductivity after the first year of life. However, it was also found that the thickness of the ear, scalp and cranium do decrease on average with decreasing age, though individual variability within any age group is very high. The model analyses revealed that compared to an average adult, the peak brain 10 g averaged SAR in mean 4, 8, 12 and 16 year olds (yo) is increased by a factor of 1.31, 1.23, 1.15 and 1.07, respectively. However, contrary to the expectations of a recent prominent expert review, the UK Stewart Report, the relatively small scale of these increases does not warrant any special precautionary measures for child mobile phone users since: (a) SAR testing protocols as contained in the CENELEC (2001) standard provide an additional safety margin which ensures that allowable localized SAR limits are not exceeded in the brain; (b) the maximum worst case brain temperature rise (approximately 0.13 to 0.14 degrees C for an average 4 yo) in child users of mobile phones is well within safe levels and normal physiological parameters; and (c) the range of age average increases in children is less than the expected range of variation seen within the adult population.

Developmental changes in distinguishing concurrent auditory objects

Children have considerable difficulties in identifying speech in noise. In the present study, we examined age-related differences in central auditory functions that are crucial for parsing co-occurring auditory events using behavioral and event-related brain potential measures. Seventeen pre-adolescent children and 17 adults were presented with complex sounds containing multiple harmonics, one of which could be 'mistuned' so that it was no longer an integer multiple of the fundamental. Both children and adults were more likely to report hearing the mistuned harmonic as a separate sound with an increase in mistuning. However, children were less sensitive in detecting mistuning across all levels as revealed by lower d' scores than adults. The perception of two concurrent auditory events was accompanied by a negative wave that peaked at about 160 ms after sound onset. In both age groups, the negative wave, referred to as the 'object-related negativity' (ORN), increased in amplitude with mistuning. The ORN was larger in children than in adults despite a lower d' score. Together, the behavioral and electrophysiological results suggest that concurrent sound segregation is probably adult-like in pre-adolescent children, but that children are inefficient in processing the information following the detection of mistuning. These findings also suggest that processes involved in distinguishing concurrent auditory objects continue to mature during adolescence.