The Posterior Auricularis Muscle as Superficial Landmark for the Sigmoid Sinus and Transverse-Sigmoid Sinus Junction: An Anatomical Study.

OBJECTIVE: Neuronavigation systems coupled with previously reported external anatomical landmarks assist neurosurgeons during intracranial procedures. We aimed to verify whether the posterior auricularis muscle (PAM) could be used as an external landmark for identifying the sigmoid sinus (SS) and the transverse-sigmoid sinus junction (TSSJ) during posterior cranial fossa surgery. METHODS: The PAM was dissected in 10 adult cadaveric heads and after drilling the underlying bone, the relationships with the underlying SS and TSSJ were noted. The width and length of the PAM, and the distance between the muscle and reference points (asterion, mastoid tip, and midline), were measured. RESULTS: The PAM was identified in 18 sides (9 left, 9 right). The first 20 mm of the muscle length (mean 28.28 mm) consistently overlay the mastoid process anteriorly and the proximal half of the SS slightly posteriorly on all sides. The superior border was a mean of 2.22 mm inferior to the TSSJ and, especially when the muscle length exceeded 20 mm, this border extended closer to the transverse sinus; it was usually found at a mean of 3.11 mm (range 0.0-13.80 mm) inferior to the distal third of the transverse sinus. CONCLUSIONS: Superficial landmarks give surgeons improved surgical access, avoiding overexposure of deep neurovascular structures and reducing brain retraction. On the basis of our cadaveric study, the PAM is a reliable and accurate direct landmark for identifying the SS and TSSJ. The PAM could potentially be used for guiding the retrosigmoid approach.

Sex Estimation From Measurements of the Mastoid Triangle and Volume of the Mastoid Air Cell System Using Classical and Machine Learning Methods: A Comparative Analysis.

ABSTRACT: Previous studies on the sexual dimorphism of the mastoid triangle have typically focused on linear and area measurements. No studies in the literature have used mastoid air cell system volume measurements for direct anthropological or forensic sex determination. The aims of this study were to investigate the applicability of mastoid air cell system volume measurements and mastoid triangle measurements separately and combined for sex estimation, and to determine the accuracy of sex estimation rates using machine learning algorithms and discriminant function analysis of these data. On 200 computed tomography images, the distances constituting the edges of the mastoid triangle were measured, and the area was calculated using these measurements. A region-growing algorithm was used to determine the volume of the mastoid air cell system. The univariate sex determination accuracy was calculated for all parameters. Stepwise discriminant function analysis was performed for sex estimation. Multiple machine learning methods have also been used. All measurements of the mastoid triangle and volumes of the mastoid air cell system were higher in males than in females. The accurate sex estimation rate was determined to be 79.5% using stepwise discriminant function analysis and 88.5% using machine learning methods.

An anatomical study of the sigmoid sinus artery: Application to the transmastoid approach.

INTRODUCTION: We aimed to investigate the morphological features of the artery that traverse the sigmoid sinus's lateral surface and to discuss this structure's clinical relevance. METHODS: Ten sides from five cadaveric Caucasian heads were used for gross anatomical dissection to investigate the morphological features of the sigmoid sinus artery (SSA), and additional five sides were used for histological observation. RESULTS: The SSA was found on eight out of ten sides (80%). The mean diameter of the SSA was 0.3 mm. The mean distance from the tip of the mastoid process to the artery was 20.3 mm. Histological observation identified extradural and intradural courses of SSA. The intradural course was further categorized into protruding and non-protruding types. In the protruding type, the SSA traveled within the dura but indented into the bone, making it more or less an intraosseous artery. In the non-protruding type, the SSA traveled within the dura but did not protrude into the bone but rather indented into the lumen of the SS. In all sections, both intradural and extradural courses were identified simultaneously. CONCLUSIONS: When the mastoid foramen is observed, it does not always only carry an emissary vein but also an artery. The SSA could be considered a "warning landmark" during bone drilling for the transmastoid approach.

Morphometric and morphological evaluation of mastoid emissary canal using cone-beam computed tomography.

OBJECTIVES: This study aimed to determine mastoid emissary canal's (MEC) and mastoid foramen (MF) prevalence and morphometric characteristics on cone-beam computed tomography (CBCT) images to underline its clinical significance and discuss its surgical consequences. METHODS: In the retrospective analysis, two oral and maxillofacial radiologists analyzed the CBCT images of 135 patients (270 sides). The biggest MF and MEC were measured in the images evaluated in MultiPlanar Reconstruction (MPR) views. The MF and MEC mean diameters were calculated. The mastoid foramina number was recorded. The prevalence of MF was studied according to gender and side of the patient. RESULTS: The overall prevalence of MEC and MF was 119 (88.1%). The prevalence of MEC and MF is 55.5% in females and 44.5% in males. MEC and MF were identified as bilateral in 80 patients (67.20%) and unilateral in 39 patients (32.80%). The mean diameter of MF was 2.4 ± 0.9 mm. The mean height of MF was 2.3 ± 0.9. The mean diameter of the MEC was 2.1 ± 0.8, and the mean height of the MEC was 2.1 ± 0.8. There is a statistical difference between the genders (p = 0.043) in foramen diameter. Males had a significantly larger mean diameter of MF in comparison to females. CONCLUSION: MEC and MF must be evaluated thoroughly if the surgery is contemplated. Radiologists and surgeons should be aware of mastoid emissary canal morphology, variations, clinical relevance, and surgical consequences while operating in the suboccipital and mastoid areas to avoid unexpected and catastrophic complications. CBCT may be a reliable imaging diagnostic technique.

Statistical classification methods for estimating sex based on five skull traits: A nonmetric assessment using 3D CT models.

Five cranial nonmetric traits for sex estimation for sex estimation are classified by score according to geometry. The population of origin is one of the factors influencing cranial nonmetric traits. Moreover, among the five cranial traits, the robust traits for estimating sex varied across population. The aim of this study is to suggest the most useful method for sex estimation and demonstrate the need of a suitable method for each population. One-hundred thirty-five three-dimensional skull images from 21st century Korean autopsy cadavers were evaluated using the ordinal scoring system of five cranial nonmetric traits as outlined in Buikstra & Ubelaker (1994). All scores of each trait were analyzed by linear discriminant and decision tree analyses for sex estimation. The frequency of each trait was analyzed and compared to populations from other studies. The accuracy for both sexes was 88.1% by discriminant analysis and 90.4% by decision tree. The traits with the highest accuracy were the glabella and mastoid process in both discriminant analysis and decision tree. Sex estimation in modern Korean cadavers using the cranial nonmetric method was shown to be highly accurate by both discriminant analysis and decision tree. When comparing the pattern of frequency scores in this study with those of other populations, the pattern of trait scores for estimating sex was different for each population, even among populations in the same Asian region, which suggests the need for methods suited for specific populations.

Anatomy of the mastoid triangle and morphometric sex differences.

OBJECTIVE OF THE STUDY: This study aimed to quantify the area of the mastoid triangle (MT) and assess potential morphometric differences between males and females. PATIENTS: The sample consisted of 244 dry human skulls, with biological sex known based on genetic analysis, collected from a medicolegal osteological database from Central-Western Brazil. MATERIALS AND METHODS: The study was observational, analytical, and cross-sectional. The skulls were analyzed using Heron's equation to calculate the area of the MT. The landmarks connecting each of the sides of the triangle were: Porion (Po)>Mastoidale (Ma)>Asterion (Ast). Morphometric references were calculated and compared based on sex. RESULTS: The area of the MT was nearly 14% larger in males compared to females (p<0.05). The mean MT area for the right and left sides of males were 684.11±93.25mm2 and 668.94±111.95mm2, respectively. In females, the mean MT for the right and left sides were 588.93±91.09mm2 and 582.88±102.98mm2, respectively. Right and left side measurements were significantly different (p<0.05), except for Po-Ast (p=0.232). CONCLUSION: Morphometric features regarding the MT were slightly different between males and females. Application of the MT as a dimorphic tool should be adjuvant. Moreover, this tool should be considered carefully, especially because the sex-based differences were statistically significant, but discrete between males and females.

Clinical applications of the mastoid emissary vein.

PURPOSE: During retrosigmoid craniotomy, the mastoid emissary vein (MEV) can be a source of considerable bleeding during the operation, especially when the larger diameter MEV or sigmoid sinus is torn. In this study, we evaluated the relevant structure of the MEV for their anatomy and applied the data in surgery to summarize their clinical significance. METHODS: The posterior craniocervical regions of 15 silicon-injected Chinese human cadaver specimens were dissected to expose the MEV and adjacent structures. Fifty-one patients who were scheduled to undergo retrosigmoid craniotomy were selected. All patients underwent preoperative routine CT of the head. The relevant data were collected on cadaveric anatomy and CT. Eventually, all patients underwent retrosigmoid craniotomy and the MEV was observed during the operation. RESULTS: In cadaver specimens, the prevalence of the MEV was 90.0%. It originated from the middle and lower parts of the posterior wall of the sigmoid sinus and extended in the posterior direction in the mastoid process, usually having 1-2 external openings (86.7%) and only 1 internal opening. The intraosseous courses of the MEV were classified as straight and curved. The straight type accounted for 57.9%, and the curved type for 42.1%. The mean diameter of the MEV was 1.84 ± 0.85 mm, and the straight length of the MEV inside the mastoid process was 11.93 ± 3.58 mm. In 16.7% and 6.7% of all cadaver specimens, the MEV diameter was greater than 2.5 and 4 mm, respectively. In 51 patients (bilateral), routine head CT scan showed the MEV in 49.0% of the patients, and the MEV diameter was greater than 2.5 and 4 mm, respectively, in 17.6% (18/102) and 3.9% (4/102) of the cases. During surgery (unilateral) in the 51 patients, 48 had the MEV and 3 had no MEV. None of the patients had sigmoid sinus tears or massive bleeding. CONCLUSION: In the process of retrosigmoid craniotomy, detailed anatomical knowledge of the MEV, well-planned CT scan, and meticulous microsurgical techniques are key for successful operation, which can reduce the occurrence of complications.

Air spaces of the temporal bone: a morphometric analysis with clinical implications.

BACKGROUND: The main objective of the present study was to analyse the morphological variations of the air spaces of the temporal bone, that is, the pneumatized and air-filled spaces of the temporal bone cavities. MATERIALS AND METHODS: A total of 99 sides were analysed. Temporal bone pneumatic spaces (TBPS) were defined as the free spaces inside the cavities of the temporal bone filled with air, excluding the volume of the structures present in the investigated region. Total volumes of TBPS were calculated as the sum of total volumes of mastoid air cells (MAC), tympanic cavity (TC), and external auditory canal (EAC). Analyses were performed considering the general population and the female and male subgroups. RESULTS: The overall results obtained on Polish population were set as follows: the median total volume of TBPS was demonstrated at 7882.58 mm3 (lower quartile [LQ]: 6200.56 mm3; higher quartile [HQ]: 10393.16 mm3). The median volume of MAC was set at 5813.05 mm3 (LQ: 4224.94 mm3; HQ: 8181.81 mm3). The median of the total volume of the EAC was demonstrated at 1294.36 mm3 (LQ: 1099.68 mm3; HQ: 1627.84 mm3). CONCLUSIONS: In the present study, the morphometric properties of the temporal bone cavities were analysed. The results showed that the total volume of the MAC was, on average, lower in women than in men. This should be taken into account when performing procedures on the mastoid, such as mastoidectomies. It is hoped that the results of this study can help reduce potential surgical complications associated with otological procedures.

Determination of age and sex using bimastoid diameter: a cone beam computed tomography Study / Deteminación de la edad y el sexo mediante el diámetro bimastoide: un estudio en tomografía computarizada de haz cónico (CBCT)

Abstract This study aimed to investigate the possibility of age and sex determination using bimastoid diameter with cone-beam computed tomography (CBCT). This retrospective study investigated 100 female and 100 male patients aged 18-83 years (mean age: 45.55±16.28 years). To measure bimastoid diameter, the appropriate image was chosen from sagittal, coronal, and axial images of CBCT in which the measurement points could be best detected. The distance between the points of the mastoid process was measured using three-dimensional coronal reconstruction. The mean bimastoid breadth was 106.12±6.22mm. The bimastoid diameter in male cases was higher than that in female cases (110.69±4.53mm vs. 101.65±4.00mm). There was no significant difference in bimastoid breadth with advancing age. For sex determination, morphometric measurements of bimastoid diameter ensured a high rate of dimorphism in the Turkish subpopulation. CBCT morphometric analysis may be reliable and convenient for evaluating sex and may be recommended to compare population data.

Resumen Este estudio tuvo como objetivo investigar la posibilidad de determinar la edad y el sexo utilizando el diámetro bimastoideo con tomografía computarizada de haz cónico (CBCT). Este estudio retrospectivo investigó a 100 mujeres y 100 hombres de entre 18 y 83 años (edad media: 45,55±16,28 años). Para medir el diámetro bimastoideo, se eligió la imagen adecuada de las imágenes sagital, coronal y axial de CBCT en las que los puntos de medición se podían detectar mejor. La distancia entre los puntos del proceso mastoideo se midió mediante reconstrucción coronal tridimensional. La amplitud media del bimastoide fue de 106,12± 6,22mm. El diámetro del bimastoide en los casos masculinos fue mayor que en los casos femeninos (110,69±4,53 mm frente a 101,65±4,00mm). No hubo diferencias significativas en la amplitud del bimastoide con la edad. Para la determinación del sexo, las mediciones morfométricas del diámetro bimastoide aseguraron una alta tasa de dimorfismo en la subpoblación turca. El análisis morfométrico CBCT puede ser confiable y conveniente para evaluar el sexo y puede recomendarse para comparar datos poblacionales.

The Intersection Between the Sternocleidomastoid and Splenius Capitis as the Anatomical Landmark to Facilitate Occipital Artery Harvest: A Retrospective Clinical Study.

BACKGROUND: Occipital artery (OA)-posterior inferior cerebellar artery (PICA) bypass is a challenging procedure and is not frequently performed owing to the difficulty of OA harvest. To facilitate harvest, the intersection between the sternocleidomastoid and splenius capitis (the OA triangle) is used as the anatomical landmark to identify the OA segment that carries the highest risk of damage. This clinical study aimed to demonstrate efficacy and safety of OA harvest using this landmark. METHODS: The study included 18 patients who underwent OA harvest using the OA triangle as a landmark for treatment of vertebral artery and PICA aneurysms. Patients were retrospectively evaluated for safety and patency of OA after harvest and OA-PICA bypass. RESULTS: Of 18 patients with ruptured and unruptured vertebral artery and PICA aneurysms, 13 (72.2%) underwent OA-PICA bypass and 5 (27.8%) did not undergo bypass. The OA was completely harvested without damage in all patients. After harvest, the OA was patent in 17 patients (94.4%) and was occluded in 1 patient owing to vasospasm; this patient then underwent recanalization resulting in good patency of the OA-PICA bypass. The patency rate of the OA-PICA bypass was 100%. CONCLUSIONS: The OA triangle, which is the anatomical landmark of the proximal end of the transitional segment of the OA, facilitated OA harvest using the distal-to-proximal harvest technique with safety and good patency. To the best of our knowledge, this is the first study of OA harvest in clinical cases.

Prognostic factors of early-onset otitis media with effusion in children treated using tympanostomy.

BACKGROUND: Predicting the prognosis of early-onset otitis media with effusion (OME) in children is difficult. OBJECTIVES: To investigate the prognostic factors of OME in children undergoing tympanostomy at 1 year of age. MATERIAL AND METHODS: We examined 66 children (123 ears) followed up to 6 years of age. OME prognosis was determined by a history of re-tympanostomy at the last examination. We retrospectively analysed the prognostic factors based on the duration of first ventilation tube (VT) placed, history of otorrhea, asthma, adenoidectomy, and mastoid air cell system (MACS) size at 1 year before tympanostomy and at 3 years. RESULTS: While 25 ears underwent re-tympanostomy (group 1), 98 did not (group 2). The mean duration of VT placed was 21 months and 25, and the mean MACS size at 3 years was 314 mm2 and 441, respectively, in the corresponding groups. MACS size at 3 years was significantly smaller in group 1 than in group 2. The combination of MACS size at 3 years and duration of VT placed showed the best value of area under the curve. CONCLUSION AND SIGNIFICANCE: The most probable prognostic factor was the combination of the MACS size at 3 years and duration of VT placed.

Mastoid and opisthion-bimastoid triangles for sex determination in a Brazilian sample / Triangulos mastoideo y opistión-bimastoideo para la determinación del sexo en una muestra brasileña

SUMMARY: Human identification involving mutilation, advanced decomposition, and skeletonized materials is a challenge for professionals in forensic medicine and dentistry. This study was aimed at a morphometric analysis of the mastoid and bimastoid triangles to determine sex in a Brazilian population. The sample included 80 human skulls (34 females and 46 males; age: 18 to 60 years) from individuals with death certificates. Linear measurements (mm) of the mastoid process - right (n=3) and left (n=3) - and the opisthion- bimastoid (n=3) triangles were taken (digital caliper) by two previously trained researchers. Three cranial points - asterion, porion and process - were determined for the right and left mastoid triangle and three others - (1) opisthion and (2) right and (3) left mastoid - for the bimastoid triangle. Heron's formula was used to calculate the area of the triangles assessed. Data were submitted to the Shapiro- Wilk normality test, followed by the unpaired Student's t test or the Mann-Whitney U test, depending on the data distribution verified in the normality test (GraphPad Prism 5.01; p<0.05). The ROC curve was used to measure the accuracy of the variables toward sex determination. The opisthion-bimastoid triangle showed high accuracy and significant differences in all the variables assessed and thus was considered a potential element for sex determination in the Brazilian population assessed.

RESUMEN: La identificación humana que comprende la mutilación, descomposición avanzada y materiales esqueletizados, es un desafío para los profesionales de la medicina forense y de la odontología. Este estudio tuvo como objetivo un análisis morfométrico de los triángulos mastoideo y bimastoideo para determinar el sexo en una población brasileña. La muestra incluyó 80 cráneos humanos (34 mujeres y 46 hombres; edad: 18 a 60 años) de sujetos con certificado de defunción. Se tomaron las medidas lineales (mm) del proceso mastoides - derecha (n = 3) e izquierda (n = 3) - y los triángulos opistion-bimastoide (n = 3) (caliper digital) por dos investigadores previamente entrenados. Se determinaron tres puntos craneales - asterion, porion y proceso mastoides - para el triángulo mastoideo derecho e izquierdo y otros tres - (1) opistion y (2) proceso mastoides derecho e izquierdo - para el triángulo bimastoideo. Se utilizó la fórmula de Heron para calcular el área de los triángulos evaluados. Los datos se analizaron con la prueba de normalidad de Shapiro-Wilk, seguida de la prueba t de Student para datos no apareados o la prueba U de Mann-Whitney, según la distribución de datos verificada en la prueba de normalidad (GraphPad Prism 5.01; p <0.05). La curva ROC se utilizó para medir la precisión de las variables hacia la determinación del sexo. El triángulo opistion-bimastoide mostró una alta precisión y diferencias significativas en todas las variables evaluadas, por lo que se consideró un elemento probable para la determinación del sexo en la población brasileña evaluada.

Sexual dimorphism in mastoid process volumes measured from 3D models of dry crania from mediaeval Croatia.

3D analysis of skeletal volumes has become an important field in digital anthropology studies. The volume of the mastoid process has been proposed to display significant sexual dimorphism, but it has a complex shape and to date no study has quantified the full mastoid volume for sex estimation purposes. In this study we compared three different ways to isolate the volume of the mastoid process from digital 3D models of dry crania, and then evaluated the performance of the three different volume definitions for sex estimation purposes. A total of 170 crania (86 male, 84 females) excavated from five medieval Croatian sites were CT-scanned and used to produce 3D stereolitographic models. The three different isolation techniques were based on various anatomical landmarks and planes, as well as the anatomy of the mastoid process itself. Measurements of the three different mastoid volumes yielded different accuracies and precisions. Interestingly, anatomical structures were sometimes more useful than classical landmarks as demarcators of mastoid volume. For all three volume definitions, male mastoid volumes were significantly larger than female volumes, in both relative and absolute numbers. Sex estimation based on mastoid volume showed a slightly higher precision and better accuracy (71% correct classifications) than visual scoring techniques (67%) and linear distance measurements (69%) of the mastoid process. Sex estimation based on cranial size performed even better (78%), and multifactorial analysis (cranium size + mastoid volume) reached up to 81% accuracy. These results show that measurements of the mastoid volume represent a promising metric to be used in multifactorial approaches for sex estimation of human remains.

Retromastoid Craniotomy: An Adaptable and Panoramic Approach to the Cerebellopontine Angle.

There are many approaches to the cerebellopontine angle, all of which involve different degrees of disruption of the normal anatomy. The retromastoid craniotomy has stood the test of time for the efficiency, panoramic exposure, and flexibility it provides while allowing excellent control over the vital cerebrovascular structures including the brainstem. This approach allows the surgeon not to get distracted by how to get there but instead to focus on what to do when he or she is there. Herein, I discuss the nuances of this simple approach with its "extended" variations.

Anatomo-sonographic identification of the longissimus capitis and splenius cervicis muscles: principles for possible application to ultrasound-guided botulinum toxin injections in cervical dystonia.

OBJECTIVE: The main objective of this study was to define and verify anatomo-sonographic landmarks for ultrasound-guided injection of botulinum toxin into the longissimus capitis (LC) and splenius cervicis (SC) muscles. METHODS AND RESULTS: After a preliminary work of anatomical description of the LC and SC muscles, we identified these muscles on two cadavers and then on a healthy volunteer using ultrasound and magnetic resonance imaging (MRI) to establish a radio-anatomical correlation. We defined an anatomo-sonographic landmark for the injection of each of these muscles. The correct positioning of vascular glue into the LC muscle and a metal clip into the SC muscle of a fresh cadaver as verified by dissection confirmed the utility of the selected landmarks. DISCUSSION: For the LC muscle, the intramuscular tendon of the cranial part of the muscle appears to be a reliable anatomical landmark. The ultrasound-guided injection can be performed within the cranial portion of the muscle, between the intra-muscular tendon and insertion into the mastoid process at dens of the axis level. For the SC muscle, the surface topographic landmarks of the spinous processes of the C4-C5 vertebrae and the muscle body of the levator scapulae muscle seem to be reliable landmarks. From these, the ultrasound-guided injection can be carried out laterally by transfixing the body of the levator scapulae. CONCLUSION: The study defined two cervical anatomo-sonographic landmarks for injecting the LC and SC muscles.

Evaluation of the relationship of chronic otitis media with the Körner's septum, auditory tube angle, and tubotympanic angle.

PURPOSE: This study aimed to evaluate the relationships between chronic otitis media (COM) and the characteristics of Auditory tube (Eustachian) angle (ATa), tubotympanic angle (TTa), and Körner's septum (KS). METHODS: A retrospective research was conducted between January 2019 and October 2019. The computed tomography (CT) results and medical files of 210 patients were evaluated. According to CT results and medical files, the patients were evaluated regarding the presence of COM, KS, ATa, and TTa. RESULTS: There were 113 (53.81%) males and 97 (46.19%) females in the study group, and the mean age of the patients was 42.05 ± 10.77 years. The frequency of the KS was significantly higher in patients who were diagnosed with COM (35.66% vs. 7.41%, p < 0.001). The patients diagnosed with COM were found to have a narrower ATa and a wider TTa than the patients who were not diagnosed with COM. ATa was narrower and TTa was wider in patients with KS. The presence of KS and higher TTa value were considered as risk factors for COM (p < 0.001, p < 0.001, respectively) CONCLUSION:  Our findings indicate that ATa was narrower, TTa was wider and KS was more frequent in patients with COM. Analysis of risk factors demonstrated that increased TTa and the presence of KS were associated with increased risk for COM.

Anterior epitympanic recess volume and Cog process length in temporal bones with Körner's septum: A radio- anatomical investigation.

OBJECTIVE: Körner's septum is a dense bony lamina dividing the mastoid cavity into superficial squamous and deeper petrosal portions at the level of antrum. In this study, we aimed at investigating the association of the Körner's septum with the length of the Cog process and the volume of anterior epitympanic recess (AER), using the 3-dimensional reconstruction models based on high resolution computed tomography sections of the temporal bone. METHODS: Using OsiriX software for MacOS (version 3.8.1, Pixmeo), we measured the volumes from three- dimensional models of anterior epitympanic recess. Anterior epitympanic recess volumes and Cog process lengths of the temporal bones with and without Körner's septum were compared. RESULTS: Cog process length was significantly higher, and AER volume was significantly lower in patients with Körner's septum compared to the patients without. (p < 0.001). Additionally, Cog process length was significantly (p = 0.008), negatively, but weakly (rho= -0.24) correlated with AER volume. CONCLUSION: Temporal bones with Körner's septum had a longer Cog process and a smaller AER.

Comprehensive review of the mastoid foramen.

Anatomical variations of the mastoid foramen have been observed to vary in a number of qualities including size, number, and location. These variants have the potential to become problematic during surgical approaches to the posterior cranial fossa and mastoid part of the temporal bone, and should thus be appreciated by the surgeon. Herein, we discuss the mastoid foramen in detail including issues with such foramina that should be known to the neurosurgeon.

The Role of the Parotid-Mastoid Fascia in Identification of the Facial Nerve Trunk During Parotidectomy.

OBJECTIVE: We aim to describe the parotid fascia as a landmark that can help identify the immediately underlying facial nerve trunk. METHODS: Dissection of the parotid fascia and identification of the facial nerve trunk were carried out on 8 fresh cadaveric parotid glands. The attachments and arrangement of the parotid gland and its fascia were evaluated and histologically assessed, with special attention to the fascia overlying the facial nerve trunk. RESULTS: The parotid fascia envelops the posterior aspect of the parotid gland in an open-book fashion. Posteriorly, it connects to the anterior and medial aspect of the mastoid tip. Posterosuperiorly, it attaches to the inferior aspect of the tragal pointer. Directly medial to the fascia lies the facial nerve trunk. CONCLUSION: The parotid fascia, particularly the parotid-mastoid segment overlying the facial nerve trunk, can be utilized as an additional landmark of depth to help identify the facial nerve trunk during a parotidectomy in conjunction with other commonly used standard anatomic landmarks. The parotid fascia sling spans from the mastoid and tragal pointer to the parotid gland and can be easily palpated intraoperatively. Once the fascia is removed, the facial nerve trunk is identified.

The effect of anatomical variables and use of the Lifts system on hearing outcomes after implantation of an active transcutaneous bone conduction device in bilateral congenital conductive hearing loss.

BACKGROUND: Malformations of the temporal bone present different challenges to the implantation of a transcutaneous active bone conduction device, such as Bonebridge (Med-el, Innsbruck, Austria). This study aims to describe the benefits of high-resolution computed tomography (HRCT) in preoperative assessment and to analyze whether characteristics of the mastoid process, intraoperative compression of the dura or sigmoid sinus, and the use of the Lifts system, lead to differences in audiological performance after implantation. METHODS: We examined 110 cases of congenital microtia. The structure of the temporal bone was examined using HRCT and a 3D simulation software program. The mean anteroposterior mastoid bone thickness from the external auditory canal to the sigmoid sinus was measured (a measurement referred to as "AP", hereafter). Sound field threshold (SFT), speech reception threshold (SRT) in noise, and word recognition score (WRS) in quiet, before and after implantation, were also measured. Independent variables were recorded in all patients: mastoid type (well pneumatized or poorly pneumatized), the presence of dural or sigmoid sinus compression, and the use of the Lifts system. RESULTS: We found that the mean AP in the non-compression group was 16.2 ± 2.3 mm and in the compression group, 13.1 ± 2.9 mm (p < 0.001). We analyzed the hearing improvement of patients grouped by mastoid development, dural or sigmoid sinus compression, and use of the Lifts system, and found that these factors did not interact and that they had no influence on the hearing outcomes (p > 0.05). CONCLUSIONS: The AP dimension in the non-compression group was significantly larger than that in the compression group. This finding combined with the ROC curve analysis revealed the AP dimension was a high-accuracy predictor of potential surgical complications involving the dura and sigmoid sinus compression. Further analysis revealed that there was no interaction between the chosen variables: mastoid type, dural or sigmoid sinus compression, and the use of the Lifts system, and that all of these factors had no significant impact on hearing performance. Bonebridge was shown to produce effective and stable bone conduction and to improve patients' hearing performance.