The thickness of the skull in Korean adults

Multiple-Point Metamaterial-Inspired Microwave Sensors for Early-Stage Brain Tumor Diagnosis

Simple, instantaneous, contactless, multiple-point metamaterial-inspired microwave sensors, composed of multi-band, low-profile metamaterial-inspired antennas, were developed to detect and identify meningioma tumors, the most common primary brain tumors. Based on a typical meningioma tumor size of 5-20 mm, a higher operating frequency, where the wavelength is similar or smaller than the tumor target, is crucial. The sensors, designed for the microwave Ku band range (12-18 GHz), where the electromagnetic property values of tumors are available, were implemented in this study. A seven-layered head phantom, including the meningioma tumors, was defined using actual electromagnetic parametric values in the frequency range of interest to mimic the actual human head. The reflection coefficients can be recorded and analyzed instantaneously, reducing high electromagnetic radiation consumption. It has been shown that a single-band detection point is not adequate to classify the nonlinear tumor and head model parameters. On the other hand, dual-band and tri-band metamaterial-inspired antennas, with additional detecting points, create a continuous function solution for the nonlinear problem by adding extra observation points using multiple-band excitation. The point mapping values can be used to enhance the tumor detection capability. Two-point mapping showed a consistent trend between the S11 value order and the tumor size, while three-point mapping can also be used to demonstrate the correlation between the S11 value order and the tumor size. This proposed multi-detection point technique can be applied to a sensor for other nonlinear property targets. Moreover, a set of antennas with different polarizations, orientations, and arrangements in a network could help to obtain the highest sensitivity and accuracy of the whole system.

Ballistic trauma caused by military rifles: experimental study based on synthetic skull proxies

Rifles are often involved in violent deaths such as homicide and suicide. Consequently, expert knowledge and experimental forensic investigations are important to clarify the nature of ballistic trauma when applied to the human head and neurocranium. This study investigated differences in entrance wound morphology with Synbone® spheres which are described as being comparable to human flat bones. A series of ballistic experiments were conducted using two different rifle calibers (5.56 × 45 mm and 7.62 × 39 mm Full Metal Jacket (FMJ)). Synbone® spheres were used for close-range 0.3 m simulated executions as well as at 25 m and 35 m to simulate urban and military engagements. Results were compared with previously published experimental studies using similar military ammunition. In our study, entry wound morphology closely resembles real forensic cases compared to exit wound and overall shape morphology independently of the distance and the caliber. Circumferential delamination was clearly visible with full metal jacket (FMJ) rounds, yielding similar damage pattern morphology to the human crania. This study documented the presence of hydraulic burst or shock in all ten rounds from all three distances. Krönlein shots were also observed in some cases. Synbone® spheres constitute an acceptable synthetic surrogate for ballistic experiments. The present study offers new initial data on the behavior of Synbone® proxies in ballistic testing of military ammunitions; FMJ gunshot injuries to the human head, for distances that have not previously been published, suggesting that efficient tests can take place under these conditions. Further research on experimental ballistics with a larger number of controlled factors and multiple repetitions is recommended to verify the results of this pilot study before applied in forensic simulations.

Upper facial surgery: simultaneous hairline-lowering surgery during endoscopic forehead lifting

Background Endoscopic forehead lifting is one of the most common procedures in the field of upper facial surgery. The upper third of the face determines the facial expression and plays a key role in the appearance of facial youth. After the forehead, a high hairline is one of the most important features of the upper third of the face contributing to age identification. The combined evaluation of these two features should be a basic premise of upper facial surgery.Methods The authors present a surgical sequence in which endoscopic forehead lifting and lowering of the high hairline by means of a scalp flap advancement are carried out during the same operation. The incision line is located along the hairline. After the scalp and forehead flap are moved, they are fixed using the bone tunnel fixation method.Results In total, 194 patients were treated with endoscopic forehead lifting and simultaneous hairline lowering between August 2018 and July 2020. On average, the patients’ hairlines were 18 mm lower and their eyebrows were 5 mm higher. No patients had serious complications.Conclusions Endoscopic forehead lifting and simultaneous hairline lowering surgery make it possible to address the entire upper third of the face in a single facial rejuvenation operation.

Positions and Types of Pterion in Adult Human Skulls: A Preliminary Study

BACKGROUND

A trauma to the skull in the area of the pterion usually causes rupture of the middle meningeal artery leading to life- threatening epidural hematoma. The objective of the study is to assess the prevalence of different types of pterion and to determine its location using valuable bony landmarks.

METHODS

On 90 dry adult human skulls of unknown sex, age and nationality the distance of different landmarks from pterion was measured using stainless steel sliding Vernier caliper. The data were analyzed using SPSS version-20 and an independent t-test analysis was implemented. A value of P< 0.05 was considered as statistically significant.

RESULTS

A higher occurrence of sphenoparietal type of pterion with the absence of frontotemporal type was noted. About 23% and 77% of the suture types are found to be unilateral and bilateral, respectively. There was a statistically significant difference between right and left sides of the skull in distances from the center of pterion to frontozygomatic suture, root of zygomatic arch, inion and in central thickness pterion.

CONCLUSION

This study showed that the most prevalent type of pterion is sphenoparietal, and revealed asymmetry in the distances from center of pterion to frontozygomatic suture, root of zygomatic arch and inion, and its central thickness. Such findings could offer worthy information about the type and location of pterion, which could be relevant to anatomists, neurosurgeons, forensic medicine specialist and anthropologists.

Nasopharyngeal electrodes in temporal lobe epilepsy: A reappraisal of their diagnostic utility

OBJECTIVE

To compare electroencephalography (EEG) recordings with nasopharyngeal electrodes (NPEs) plus anterior temporal electrodes (ATEs) (NPE recordings) and those with only ATEs (non-NPE recordings) for the detection of interictal epileptiform discharges (IEDs) in patients with suspected temporal lobe epilepsy (TLE).

METHODS

We retrospectively analyzed the initial EEGs of 229 patients that were recorded simultaneously with ATEs and NPEs in addition to the electrodes of the 10-20 system of electrode placement. Two data sets of NPE and non-NPE recordings were reviewed independently by three interpreters with differing degrees of experience. Discordant findings in the interpretation among the three interpreters were resolved by a consensus to yield final results.

RESULTS

IEDs were detected in 76.4% of patients with NPE recordings compared to 55.5% with non-NPE recordings (p < 0.01). Bilateral independent IEDs were found in 26.2% and 11.4% of EEGs with NPE and non-NPE recordings (p < 0.01). The degree of agreement for the detection of IEDs among the three interpreters was higher with the NPE than with non-NPE recordings (κappa score, 0.70 vs. 0.54). The increased diagnostic yield of NPE recordings for the detection of IEDs was particularly prominent in patients with mesial and non-lesional TLEs.

CONCLUSIONS

EEG recordings using NPEs are useful to improve the sensitivity and level of agreement among interpreters for the detection of IEDs in patients with TLE.

SIGNIFICANCE

NPE recordings may be recommended in routine EEGs for the evaluation of patients with suspected TLE.

A Pilot Study Comparing Effects of Bifrontal Versus Bitemporal Transcranial Direct Current Stimulation in Mild Cognitive Impairment and Mild Alzheimer Disease

OBJECTIVE

While transcranial direct current stimulation (tDCS) can enhance aspects of memory in patients with mild cognitive impairment (MCI) and Alzheimer disease (AD), there has been wide variability in both the placement of tDCS electrodes and treatment response. This study compared the effects of bifrontal (anodal stimulation over the dorsolateral prefrontal cortices), bitemporal (anodal stimulation over the temporal cortices), and sham tDCS on cognitive performance in MCI and AD.

METHODS

Seventeen patients diagnosed with MCI or mild AD received 3 sessions of anodal tDCS (bifrontal, bitemporal, 2 mA for 20 minutes; and sham) in random order. Sessions were separated by 1 week. The Alzheimer's Disease Assessment Scale-Cognitive Word Recognition Task, Alzheimer's Disease Assessment Scale-Cognitive Word Recall Task, 2-back, and Montreal Cognitive Assessment were used to assess cognition.

RESULTS

There was a significant effect of stimulation condition on 2-back accuracy (F2,28 = 5.28 P = 0.01, ηp = 0.27), with greater improvements following bitemporal tDCS compared with both bifrontal and sham stimulations. There were no significant changes on other outcome measures following any stimulation. Adverse effects from stimulation were mild and temporary.

CONCLUSIONS

These findings demonstrate that improvements in specific memory tasks can be safely achieved after a single session of bitemporal tDCS in MCI and mild AD patients.

Viability of Bos taurus scapulae as a flat bone proxy for ballistic testing

BACKGROUND

Handguns and rifles are often involved in violent deaths such as homicide and suicide. Consequently, forensic investigations are important to clarify the nature of ballistic trauma.

METHODS

This study investigated the differences in entrance and exit wound morphology with Bos taurus (bovine) scapulae that have two cortical layers surrounding a central cancellous bone section which are comparable with human flat bones, with a series of experiments using six different calibres (0.22 Long Rifle, 9×19 mm North Atlantic Treaty Organization, 0.40 Smith & Wesson, 0.45 Automatic Colt Pistol, 5.56×45 mm and 7.62×51 mm). B. taurus (bovine) scapulae were used for closed range 30 cm simulated executions.

RESULTS

The ballistic experiments presented similarities in entrance wound morphology and exit wound bevelling with that of recognised forensic cases. As muzzle velocity increased, bevelling increased. Circumferential delamination is clearly visible with full metal jacket rounds, yielding similar bone damage morphology as human crania.

CONCLUSION

Bovine scapulae seem appropriate for ballistic simulations of flat bone injuries on the macroscopic level, if the correct portion of the scapulae is deployed. More research is needed to further substantiate these interpretations.

Reappraising the neurosurgical significance of the pterion location, morphology, and its relationship to optic canal and sphenoid ridge and neurosurgical implications

Frontolateral craniotomy procedures have advanced from conventional craniotomy to mini-craniotomy, and to contemporary keyhole surgery. In this context, it is important for the neurosurgeon to precisely locate the pterion. The distance of the pterion center from midpoint of zygomatic arch and posterolateral margin of frontozygomatic suture was studied bilaterally in 50 whole adult skulls in Indian ethnic group. The depth of optic canal and sphenoid ridge from the pterion was recorded bilaterally in fifty cut adult skulls and fifteen three-dimensional computed tomography scans. The suture length, thickness, and morphology were studied. The data were analyzed using SPSS software, two-tailed Student's t test, binary logistic regression and receiver operating characteristic curve for sexual dimorphism. The pterion center was located at a mean distance of 37.02 mm above the midpoint of zygomatic arch, 28.20 mm behind the posterolateral margin of frontozygomatic suture, 42.73 mm lateral to the optic canal and 10.59 mm from the sphenoid ridge. The location did not exhibit sexual dimorphism. In 20% cases the pterion center was 40 mm or more above the midpoint of the zygomatic arch and in 5% cases 35 mm or more posterior to the posterolateral margin of frontozygomatic suture. The mean suture length was 10±3 mm. The mean thickness at the center of the pterion was 3.52±1.45 mm. The commonest variety was sphenoparietal followed by frontotemporal, epipteric, and stellate types. A thorough knowledge of these dimensions has innumerable neurosurgical implications in resection of sellar, parasellar, and paraclinoid tumors and circulatory aneurysms.

Model of Steady-state Temperature Rise in Multilayer Tissues Due to Narrow-beam Millimeter-wave Radiofrequency Field Exposure

The assessment of health effects due to localized exposures from radiofrequency fields is facilitated by characterizing the steady-state, surface temperature rise in tissue. A closed-form analytical model was developed that relates the steady-state, surface temperature rise in multilayer planar tissues as a function of the spatial-peak power density and beam dimensions of an incident millimeter wave. Model data was derived from finite-difference solutions of the Pennes bioheat transfer equation for both normal-incidence plane waves and for narrow, circularly symmetric beams with Gaussian intensity distribution on the surface. Monte Carlo techniques were employed by representing tissue layer thicknesses at different body sites as statistical distributions compiled from human data found in the literature. The finite-difference solutions were validated against analytical solutions of the bioheat equation for the plane wave case and against a narrow-beam solution performed using a commercial multiphysics simulation package. In both cases, agreement was within 1-2%. For a given frequency, the resulting analytical model has four input parameters, two of which are deterministic, describing the level of exposure (i.e., the spatial-peak power density and beam width). The remaining two are stochastic quantities, extracted from the Monte Carlo analyses. The analytical model is composed of relatively simple functions that can be programmed in a spreadsheet. Demonstration of the analytical model is provided in two examples: the calculation of spatial-peak power density vs. beam width that produces a predefined maximum steady-state surface temperature, and the performance evaluation of various proposed spatial-averaging areas for the incident power density.

Hairline Lowering Surgery With Bone Tunneling Suture Fixation: Effectiveness and Safety in 91 Patients

BACKGROUND

People with a wide forehead often look older. Hairline lowering surgery is a good treatment option, which is generally performed utilizing Endotine.

OBJECTIVES

We describe our hairline lowering surgical technique involving bone tunneling without Endotine, a method designed to produce comparable outcomes with fewer side effects. We evaluated the effectiveness and safety of our technique.

METHODS

Charts of 91 patients who underwent hairline lowering surgery without Endotine were reviewed retrospectively. We utilized standardized preoperative and postoperative photographs to measure the proportions of 3 face parts and the length of the forehead. We also determined changes in forehead length at various times after surgery, occurrence of postoperative complications, and overall patient satisfaction with their surgical results.

RESULTS

Of the 91 patients, 80 were female and the mean age was 28.67 ± 7.15 years. Preoperatively, the mean forehead length was 8.09 ± 0.69 cm and ratio of facial part lengths was 1.08:1:0.99 (cranial to caudal). The hairline was advanced 18.37 ± 2.90 mm. One month postoperatively, the mean forehead length was 6.57 ± 0.52 cm and facial parts ratio was 1:1:0.99. Compared with preoperatively, forehead length was significantly reduced at 1, 3, 6, and 12 months postoperatively. Forehead length was not significantly different at 1 and 12 months postoperatively. All patients were satisfied or very satisfied with their overall surgical results.

CONCLUSIONS

Hairline lowering surgery with bone tunneling was effective and safe, and patients were satisfied with the results. The effects appeared immediately following surgery and were sustained over time.

LEVEL OF EVIDENCE: 4

Cranial trauma in handgun executions: Experimental data using polyurethane proxies

Gun violence is a global phenomenon with regional variation in frequency and severity. Handguns are often used in violent deaths such as suicides and homicides. Hence, ballistic trauma is a critical subject of forensic investigations. Trauma patterns are fundamental evidence for the reconstruction of the incident and for the determination of the manner of death. This study investigated the differences in trauma patterns with a series of experiments using six different calibers (.22 LR, .38 Special, .380 ACP, 9×19mm, .40 S&W, and .45 ACP) and four different bullet types. Synbone^® spheres (polyurethane bone proxies) were used for close range 30cm simulated executions. The polyurethane spheres constitute an excellent proxy for human crania at the macroscopic level as suggested by other studies. The results showed that the radius of the entrance wound is positively correlated (Pearson's correlation coefficient R=0.846, p<0.05) with the caliber dimension. As muzzle velocity increased, endocranial beveling increased. Bullet weight, conversely, does not seem to have an effect on the size of the endocranial beveling present in Synbone^® spheres. The ballistic experiments exhibited similarities in entrance wound morphology; radial and concentric fracture patterns, hydraulic burst effect, circumferential delamination, and endocranial beveling with that of documented forensic cases with corresponding caliber shot. Synbone spheres seem appropriate for ballistic simulations of cranial injuries; yet, more research is needed to verify these observations.

A validation method for near-infrared spectroscopy based tissue oximeters for cerebral and somatic tissue oxygen saturation measurements

We describe the validation methodology for the NIRS based FORE-SIGHT ELITE^® (CAS Medical Systems, Inc., Branford, CT, USA) tissue oximeter for cerebral and somatic tissue oxygen saturation (StO₂) measurements for adult subjects submitted to the United States Food and Drug Administration (FDA) to obtain clearance for clinical use. This validation methodology evolved from a history of NIRS validations in the literature and FDA recommended use of Deming regression and bootstrapping statistical validation methods. For cerebral validation, forehead cerebral StO₂ measurements were compared to a weighted 70:30 reference (REF CX_B) of co-oximeter internal jugular venous and arterial blood saturation of healthy adult subjects during a controlled hypoxia sequence, with a sensor placed on the forehead. For somatic validation, somatic StO₂ measurements were compared to a weighted 70:30 reference (REF CX_S) of co-oximetry central venous and arterial saturation values following a similar protocol, with sensors place on the flank, quadriceps muscle, and calf muscle. With informed consent, 25 subjects successfully completed the cerebral validation study. The bias and precision (1 SD) of cerebral StO₂ compared to REF CX_B was −0.14 ± 3.07%. With informed consent, 24 subjects successfully completed the somatic validation study. The bias and precision of somatic StO₂ compared to REF CX_S was 0.04 ± 4.22% from the average of flank, quadriceps, and calf StO₂ measurements to best represent the global whole body REF CX_S. The NIRS validation methods presented potentially provide a reliable means to test NIRS monitors and qualify them for clinical use.

Simultaneous head tissue conductivity and EEG source location estimation

Accurate electroencephalographic (EEG) source localization requires an electrical head model incorporating accurate geometries and conductivity values for the major head tissues. While consistent conductivity values have been reported for scalp, brain, and cerebrospinal fluid, measured brain-to-skull conductivity ratio (BSCR) estimates have varied between 8 and 80, likely reflecting both inter-subject and measurement method differences. In simulations, mis-estimation of skull conductivity can produce source localization errors as large as 3cm. Here, we describe an iterative gradient-based approach to Simultaneous tissue Conductivity And source Location Estimation (SCALE). The scalp projection maps used by SCALE are obtained from near-dipolar effective EEG sources found by adequate independent component analysis (ICA) decomposition of sufficient high-density EEG data. We applied SCALE to simulated scalp projections of 15cm(2)-scale cortical patch sources in an MR image-based electrical head model with simulated BSCR of 30. Initialized either with a BSCR of 80 or 20, SCALE estimated BSCR as 32.6. In Adaptive Mixture ICA (AMICA) decompositions of (45-min, 128-channel) EEG data from two young adults we identified sets of 13 independent components having near-dipolar scalp maps compatible with a single cortical source patch. Again initialized with either BSCR 80 or 25, SCALE gave BSCR estimates of 34 and 54 for the two subjects respectively. The ability to accurately estimate skull conductivity non-invasively from any well-recorded EEG data in combination with a stable and non-invasively acquired MR imaging-derived electrical head model could remove a critical barrier to using EEG as a sub-cm(2)-scale accurate 3-D functional cortical imaging modality.

Creating a normative database of age-specific 3D geometrical data, bone density, and bone thickness of the developing skull: a pilot study

OBJECT

Finite element models (FEMs) of the head are used to study the biomechanics of traumatic brain injury and depend heavily on the use of accurate material properties and head geometry. Any FEM aimed at investigating traumatic head injury in children should therefore use age-specific dimensions of the head, as well as age-specific material properties of the different tissues. In this study, the authors built a database of age-corrected skull geometry, skull thickness, and bone density of the developing skull to aid in the development of an age-specific FEM of a child's head. Such a database, containing age-corrected normative skull geometry data, can also be used for preoperative surgical planning and postoperative long-term follow-up of craniosynostosis surgery results.

METHODS

Computed tomography data were processed for 187 patients (age range 0-20 years old). A 3D surface model was calculated from segmented skull surfaces. Skull models, reference points, and sutures were processed into a MATLAB-supported database. This process included automatic calculation of 2D measurements as well as 3D measurements: length of the coronal suture, length of the lambdoid suture, and the 3D anterior-posterior length, defined as the sum of the metopic and sagittal suture. Skull thickness and skull bone density calculations were included.

RESULTS

Cephalic length, cephalic width, intercoronal distance, lateral orbital distance, intertemporal distance, and 3D measurements were obtained, confirming the well-established general growth pattern of the skull. Skull thickness increases rapidly in the first year of life, slowing down during the second year of life, while skull density increases with a fast but steady pace during the first 3 years of life. Both skull thickness and density continue to increase up to adulthood.

CONCLUSIONS

This is the first report of normative data on 2D and 3D measurements, skull bone thickness, and skull bone density for children aged 0-20 years. This database can help build an age-specific FEM of a child's head. It can also help to tailor preoperative virtual planning in craniosynostosis surgery toward patient-specific normative target values and to perform objective long-term follow-up in craniosynostosis surgery.

Cortical thickness parameters for endoscopic browlift fixation

BACKGROUND

Techniques for endoscopic browlift include bony fixation over the lateral frontal region and soft tissue fixation over the temporal region. Although bony fixation over the lateral frontal region is advocated universally, limited information exists about bicortical thickness in this area.

OBJECTIVES

The authors provide bicortical thickness measurements between the frontal midline and the most inferior temporal region to assist surgeons in identifying appropriate fixation planes.

METHODS

Bicortical thickness was measured in the hemicraniums of 13 female cadavers, along the coronal planes that travel through the anterior border of the mandibular condyles and at the junction of the posterior mandibular condyles and the external auditory meatuses. Measurements began at the midline and coursed laterally at 1-cm intervals.

RESULTS

Average cranial thickness along the frontal region ranged from 8.9 ± 2.4 mm to 6.4 ± 2.8 mm over the anterior coronal line and 8.8 ± 2.2 mm to 5.6 ± 1.8 mm over the posterior line. Average thickness along the temporal region ranged from 5.6 ± 2.8 mm to 2.8 mm ± 1.4 mm over the anterior coronal line and 5.1 ± 1.8 mm to 3.4 ± 1.4 mm over the posterior line. Minimum thickness was 3.7 mm and 1.3 mm over the frontal and temporal regions, respectively. There was no significant difference between left and right hemicranial thickness.

CONCLUSIONS

To avoid violation of the inner cortex during surgery, endoscopic browlift procedures should include measurement of cortical thickness at various fixation points. Bony fixation over the temporal region should be avoided. Minimal bicortical thickness was observed in the lateral frontal region.

Determination of the absorbed dose rate to water for the 18-mm helmet of a gamma knife

PURPOSE

To measure the absorbed dose rate to water of (60)Co gamma rays of a Gamma Knife Model C using water-filled phantoms (WFP).

METHODS AND MATERIALS

Spherical WFP with an equivalent water depth of 5, 7, 8, and 9 cm were constructed. The dose rates at the center of an 18-mm helmet were measured in an 8-cm WFP (WFP-3) and two plastic phantoms. Two independent measurement systems were used: one was calibrated to an air kerma (Set I) and the other was calibrated to the absorbed dose to water (Set II). The dose rates of WFP-3 and the plastic phantoms were converted to dose rates for an 8-cm water depth using the attenuation coefficient and the equivalent water depths.

RESULTS

The dose rate measured at the center of WFP-3 using Set II was 2.2% and 1.0% higher than dose rates measured at the center of the two plastic phantoms. The measured effective attenuation coefficient of Gamma Knife photon beam in WFPs was 0.0621 cm(-1). After attenuation correction, the difference between the dose rate at an 8-cm water depth measured in WFP-3 and dose rates in the plastic phantoms was smaller than the uncertainty of the measurements.

CONCLUSIONS

Systematic errors related to the characteristics of the phantom materials in the dose rate measurement of a Gamma Knife need to be corrected for. Correction of the dose rate using an equivalent water depth and attenuation provided results that were more consistent.

Validation of a noninvasive neonatal optical cerebral oximeter in veno-venous ECMO patients with a cephalad catheter

INTRODUCTION

Cerebral Oximetry is an optical technique that allows for noninvasive and continuous monitoring of brain oxygenation by determining tissue oxygen saturation (SctO2). In conjunction with pulse oximetry, cerebral oximetry offers a promising method to estimate cerebral venous oxygen saturation (SvO2).

OBJECTIVE

The aim of this study was to validate the cerebral oximetry measurements with the cerebral oxygen saturation measured from blood drawn in neonates on veno-venous ECMO with existing cephalad catheter with a prototype neonatal cerebral oximeter developed by CAS Medical Systems (Branford, CT, USA).

STUDY DESIGN

After obtaining informed consent, neonates undergoing VV-ECMO with cephalad catheterization were monitored by the CAS cerebral oximeter. Cephalad blood samples were periodically obtained to validate the monitor's accuracy.

RESULTS

Seventeen neonates were studied with 1718 h of cerebral oximetry data collected. Compared to the reference values, the bias+/-precision for cerebral oximetry SctO2 was 0.4+/-5.1% and derived SvO2 was 0.6+/-7.3%.

CONCLUSION

We recommend the use of this noninvasive method as an alternative to blood draws for cerebral venous saturation measurements in neonates requiring extracorporeal life support.

Cranial Thickness in Superior Canal Dehiscence Syndrome

OBJECTIVE

To use morphometric analyses of cranial thickness to investigate 2 cases of unanticipated calvarial bone resorption in superior canal dehiscence (SCD) resurfacing surgery.

DESIGN

Retrospective morphometric analysis of high-resolution computed tomography (CT) temporal bone scans in normal and control subjects with accompanying case reports.

SETTING

Tertiary care referral center.

PATIENTS

Two patients with SCD and failed resurfacing because of bone resorption. Temporal bone CT scans from 30 sex-matched controls.

INTERVENTION

Resurfacing of SCD via a middle fossa approach using a split thickness calvarial graft from the craniotomy site.

MAIN OUTCOME MEASURE

Mean cross-sectional area of the middle fossa craniotomy bone flap and mean cranial thickness at 30 and 45 degrees above the middle fossa floor.

RESULTS

Two patients had delayed failure of SCD resurfacing surgery as manifested by return of symptoms. High-resolution CT scans in both, and intraoperative confirmation in one, confirmed resorption of the bone graft. Measurements of cross-sectional area of the middle fossa craniotomy on high-resolution CT scans demonstrated significantly reduced values in the two SCD patients as compared with normal controls (Mann-Whitney U test, p<0.05). Cranial thickness outside the squamous temporal bone was reduced but did not reach statistical significance.

CONCLUSION

Morphometric measurements of the calvarium have demonstrated that the squamous temporal bone is thinner in patients with SCD as compared with controls. Thus, the process leading to defects in the tegmen extends beyond the petrous pyramid. This suggests that there may be extratemporal factors leading to the development of a dehiscence. These findings also have implications for the surgical treatment of this disorder. Resurfacing methods may have a higher failure rate as the bone graft has reduced mass and maybe prone to resorption. Canal plugging methods may provide a more definitive means of addressing the dehiscent labyrinth than resurfacing.

The pterion in Turkish male skulls

This study was conducted to determine the location and type of pterion in Turkish males. The importance of the pterion is its relation to the middle meningeal artery, Broca's motor speech area on the left side, and surgical interventions relating to pathologies of the sphenoid ridge and optic canal. Specific measurements were taken on both sides of 26 Turkish human male skulls, none of which showed any obvious pathology or trauma. The sphenoparietal type of pterion was the most common (96% right side, 79% left side), followed by the frontotemporal (4% right side, 17% left side), and finally the epipteric type (4% left side only). The distances on the right and left sides respectively from the center of the pterion to the frontozygomatic suture were 3.30+/-0.40 cm and 3.44+/-0.39 cm, to the zygomatic arch 4.05+/-0.39 cm and 3.85+/-0.25 cm, to the optic canal 4.39+/-0.40 cm and 4.36+/-0.40 cm, and to the sphenoid ridge 1.40+/-0.33 cm and 1.48+/-0.32 cm. The thickness of the skull at the center of the pterion was 0.41+/-0.14 cm and 0.39+/-0.12 cm on the right and left sides respectively. These findings should be of use in surgical approaches and interventions via the pterion.

Anatomical variations of the frontal and supraorbital transcranial passages

In this study, 500 frontal and supraorbital transcranial passages were studied in 50 cadavers and 200 crania of 500 samples. One hundred six specimens had a frontal foramen (notch), and all the samples had a supraorbital foramen (notch). The frontal passage was a foramen in 7 samples and a notch in 99 samples. As for the supraorbital passage, it was found as a foramen in 133 of specimens and as a notch in 358 of specimens. In 9 of the specimens, there were double notches or foramina. The distances from the foramina (notches) to angulus oculi medialis were measured in the cadavers. The average distance from the angulus oculi medialis to the frontal foramen (notch) was 4.50 mm, and the average distance to the supraorbital foramen (notch) was 9.87 mm. The distances from the foramina (notches) to the midline were measured in the crania. The average distances from the midline to the frontal foramen (notch) and the supraorbital foramen (notch) were 20.24 mm and 25.23 mm, respectively. The average distance between the frontal foramen (notch) and supraorbital foramen (notch) was 5.37 mm in cadavers and 4.99 mm in crania. In 200 crania, the distances of the frontal and supraorbital transcranial passages to the midline were measured. Types of these passages were also evaluated, and frequencies were calculated. Measurements were made using a digital compass, and the student t test was used in the statistical evaluation of results.