Three-Dimensional High-Resolution Temporal Bone Histopathology Identifies Areas of Vascular Vulnerability in the Inner Ear

<b><i>Objectives:</i></b> Hypothesized causes of vestibular neuritis/labyrinthitis include neuroinflammatory or vascular disorders, yet vascular disorders of the inner ear are poorly understood. Guided by known microvascular diseases of the retina, we developed 2 hypotheses: (1) there exist vascular vulnerabilities of artery channels in cases of hypothetical nerve swelling for the superior, inferior, and vestibulocochlear artery and (2) there are arteriovenous crossings that could compromise vascular flow in disease states. <b><i>Methods:</i></b> Two fully mounted and stained temporal bones were used to render three-dimensional reconstructions of the labyrinth blood supply. Using these maps, areas of potential vascular compression were quantified in 50 human temporal bones. <b><i>Results:</i></b> Although inner ear arteries and veins mostly travel within their own bony channels, they may be exposed (1) at the entrance into the otic capsule, and (2) where the superior vestibular vein crosses the inferior vestibular artery. At the entry into the otic capsule, the ratio of the soft tissue to total space for the superior vestibular artery was significantly greater than the inferior vestibular artery/cochleovestibular artery (median 44, interquartile range 34–55 vs. 14 [9–17], <i>p</i> &#x3c; 0.0001). <b><i>Conclusions:</i></b> Three-dimensional reconstruction of human temporal bone histopathology can guide vascular studies of the human inner ear. Studies of retinal microvascular disease helped identify areas of vascular vulnerability in cases of hypothetical nerve swelling at the entrance into the otic capsule and at an arteriovenous crossing near the saccular macula. These data may help explain patterns of clinical findings in peripheral vestibular lesions.

Hand Motion Analysis Illustrates Differences When Drilling Cadaveric and Printed Temporal Bone

Objective: Temporal bone simulation is now commonly used to augment cadaveric education. Assessment of these tools is ongoing, with haptic modeling illustrating dissimilar motion patterns compared to cadaveric opportunities. This has the potential to result in maladaptive skill development. It is hypothesized that trainee drill motion patterns during printed model dissection may likewise demonstrate dissimilar hand motion patterns. Methods: Resident surgeons dissected 3D-printed temporal bones generated from microCT data and cadaveric simulations. A magnetic position tracking system (TrakSTAR Ascension, Yarraville, Australia) captured drill position and orientation. Skill assessment included cortical mastoidectomy, thinning procedures (sigmoid sinus, dural plate, posterior canal wall) and facial recess development. Dissection was performed by 8 trainees (n = 5 < PGY3 > n = 3) using k-cos metrics to analyze drill strokes within position recordings. K-cos metrics define strokes by change in direction, providing metrics for stroke duration, curvature, and length. Results: T-tests between models showed no significant difference in drill stroke frequency (cadaveric = 1.36/s, printed = 1.50/s, P < .40) but demonstrate significantly shorter duration (cadaveric = 0.37 s, printed = 0.16 s, P < .01) and a higher percentage of curved strokes (cadaveric = 31, printed = 67, P < .01) employed in printed bone dissection. Junior staff used a higher number of short strokes (junior = 0.54, senior = 0.38, P < .01) and higher percentage of curved strokes (junior = 35%, senior = 21%, P < .01). Conclusions: Significant differences in hand motions were present between simulations, however the significance is unclear. This may indicate that printed bone is not best positioned to be the principal training schema.

Post-traumatic tension pneumocephalus and cystic angiomatosis of the skull: case report

Background Tension pneumocephalus is an increasing air trapped intracranially. Either spontaneous, post-traumatic or iatrogenic in origin. Cystic angiomatosis is a benign vascular hamartoma of the skeleton, when acquired it is either due to trauma or infection. This is the second report in English literature of post-traumatic delayed tension pneumocephalus with the development of cystic angiomatosis of the skull bone. Case presentation A 55-year-old gentlemen, presented with scalp swelling of 6-month duration with history of head trauma 2 years back. The swelling was increasing and associated with progressive walking difficulties and left hearing loss. CT scan and MRI revealed extradural pneumocephalus, parietal and occipital pneumatocele, and multiple lytic bony lesions, left mastoid hyperpneumatization with inner table defect communicating with the extradural space. Diagnosis of delayed extradural tension pneumocephalus was made. Surgical exploration revealed multiple bony defects of parietal, temporal and squamous part of left temporal bones, confirmed extradural pneumocephalus with intact dura. Repair of mastoid defect of (0.5 × 0.5 cm), excision of pneumatocele and removal of lytic bones were performed. Defective bone “cribriform-like” was identified at occipital and parietal regions centrally with a defect of nearly 7 × 7 cm. Future cranioplasty was considered after 6 months. Histology of bony chips and surrounding soft tissues is recognized as cystic angiomatosis. Conclusions The present case developed two very rare complications, following trivial head trauma; the first complication was delayed extradural tension pneumocephalus with pneumatocele which presented 2 years after trauma, the origin of air was from a defect of the inner table of the mastoid, the second complication was cystic angiomatosis of the skull bones. Both complications were managed surgically in one operative session as a combined neurosurgery and otolaryngology teams approach.

The effect of virtual reality on temporal bone anatomy evaluation and performance

Purpose There is only limited data on the application of virtual reality (VR) for the evaluation of temporal bone anatomy. The aim of the present study was to compare the VR environment to traditional cross-sectional viewing of computed tomography images in a simulated preoperative planning setting in novice and expert surgeons. Methods A novice (n = 5) and an expert group (n = 5), based on their otosurgery experience, were created. The participants were asked to identify 24 anatomical landmarks, perform 11 distance measurements between surgically relevant anatomical structures and 10 fiducial markers on five cadaver temporal bones in both VR environment and cross-sectional viewings in PACS interface. The data on performance time and user-experience (i.e., subjective validation) were collected. Results The novice group made significantly more errors (p < 0.001) and with significantly longer performance time (p = 0.001) in cross-sectional viewing than the expert group. In the VR environment, there was no significant differences (errors and time) between the groups. The performance of novices improved faster in the VR. The novices showed significantly faster task performance (p = 0.003) and a trend towards fewer errors (p = 0.054) in VR compared to cross-sectional viewing. No such difference between the methods were observed in the expert group. The mean overall scores of user-experience were significantly higher for VR than cross-sectional viewing in both groups (p < 0.001). Conclusion In the VR environment, novices performed the anatomical evaluation of temporal bone faster and with fewer errors than in the traditional cross-sectional viewing, which supports its efficiency for the evaluation of complex anatomy.

Analysis of tympanic sinus shape for purposes of intraoperative hearing monitoring: a microCT study

Purpose Sinus tympani is the space in the retrotympanum, with variable morphology. Computed tomography is a common tool to investigate sinus tympani anatomy. During cochlear implantation or tympanoplasty, electrocochleography can be used for hearing monitoring. In such a surgical strategy the electrode is placed in the round window’s region throughout posterior tympanotomy. Common accessible needle-shaped electrodes using is difficult in achieving intraoperative stabilization. The aim of the study is to assess the dimensions and shape of sinus tympani, basing on the micro computed tomography scans for purposes of establishing the possible new electrocochleography electrode shape. Materials and methods Sixteen fresh frozen cadaveric temporal bones were dissected. MicroCT measurements included the depth and the width of sinus tympani, width of facial canal with stapedius muscle chamber. Obtained data were analyzed statistically with the use of RStudio 1.3.959 software. Results The highest average width of sinus tympani amounted for 2.68 mm, depth measured at the round window plane for 3.19 mm. Width of facial canal with stapedius muscle chamber highest average values at the round window plane- 3.32 mm. The lowest average minimum and maximum values were calculated at the 1 mm above the round window plane. The highest average posterior tympanotomy width was 2.91 mm. Conclusions The shape of the tympanic sinus is like a trough with the narrowest and deepest dimensions in the middle part. The ST shape and dimensions should be taken into account in constructing the ECochG electrode, designed for optimal placement through posterior tympanotomy approach.

Fusion of Technology in Cochlear Implantation Surgery: Investigation of Fluoroscopically Assisted Robotic Electrode Insertion

The HEARO cochlear implantation surgery aims to replace the conventional wide mastoidectomy approach with a minimally invasive direct cochlear access. The main advantage of the HEARO access would be that the trajectory accommodates the optimal and individualized insertion parameters such as type of cochlear access and trajectory angles into the cochlea. To investigate the quality of electrode insertion with the HEARO procedure, the insertion process was inspected under fluoroscopy in 16 human cadaver temporal bones. Prior to the insertion, the robotic middle and inner ear access were performed through the HEARO procedures. The status of the insertion was analyzed on the post-operative image with Siemens Artis Pheno (Siemens AG, Munich, Germany). The completion of the full HEARO procedure, including the robotic inner ear access and fluoroscopy electrode insertion, was possible in all 16 cases. It was possible to insert the electrode in all 16 cases through the drilled tunnel. However, one case in which the full cochlea was not visible on the post-operative image for analysis was excluded. The post-operative analysis of the electrode insertion showed an average insertion angle of 507°, which is equivalent to 1.4 turns of the cochlea, and minimal and maximal insertion angles were recorded as 373° (1 cochlear turn) and 645° (1.8 cochlear turn), respectively. The fluoroscopy inspection indicated no sign of complications during the insertion.

Improved visualization of the chorda tympani nerve using ultra‐high-resolution computed tomography

Background Recognition of the anatomical course of the chorda tympani nerve (CTN) is important for preventing iatrogenic injuries during middle-ear surgery. Purpose This study aims to compare visualization of the CTN using two computed tomography (CT) methods: conventional high-resolution CT (C-HRCT) and ultra‐high-resolution CT (U-HRCT). Materials and methods We performed a retrospective visual assessment of 59 CTNs in normal temporal bones of 54 consecutive patients who underwent both C-HRCT and U-HRCT. After dividing CTN into three anatomical segments (posterior canaliculus, tympanic segment, and anterior canaliculus), two neuroradiologists scored the visualizations on a four-point scale. Results On C-HRCT, the visual scores of the posterior canaliculus, tympanic segment, and anterior canaliculus were 3.5 ± 0.7, 1.6 ± 0.6, and 3.1 ± 0.7, respectively. The respective values were significantly higher in all segments on U-HRCT: 3.9 ± 0.2, 2.4 ± 0.6, 3.5 ± 0.6 ( p < 0.01). Although the difference in scores between methods was greatest for the tympanic segment, the visual score on U-HRCT was lower for the tympanic segment than for the anterior and posterior segments ( p < 0.01). Conclusion Ultra‐high-resolution CT provides superior visualization of the CTN, especially the tympanic segment.

The skull

The human skull is the skeleton of the head and is considered along with the mandible. It consists of paired bones and unpaired midline bones that contribute to the muscular attachments for mastication and facial expression, a bony foundation for the upper aerodigestive tract and support and housing for the special sensory organs, brain and other structures susceptible to trauma. The skull without the mandible is termed the cranium and consists of the neurocranium and viscerocranium (facial skeleton). The upper third of the skull is principally formed by the frontal bones and exaggerated at the superciliary ridges of the superior orbit and smooth glabella region centrally. The paired maxillary bones form the middle third, creating the circumference of the piriform aperture between, and are separated from the frontal and temporal bones by the zygoma laterally. They house the maxillary sinuses and meet in the midline inferiorly to form the upper jaw and most of the hard palate at the intermaxillary suture.