BACKGROUND: Cochlear duct length (CDL) measurement plays a role in the context of individualized cochlear implant (CI) surgery regarding an individualized selection and implantation of the CI electrode carrier and an efficient postoperative anatomy-based fitting process. The level of detail of the preoperative temporal bone CT scan depends on the imaging modality with major impact on CDL measurements and CI electrode contact position determination. The aim of this study was to evaluate the accuracy of perioperative CDL measurements and electrode contact determination in photon-counting CT (PCCT).
METHODS: Ten human fresh-frozen petrous bone specimens were examined with a first-generation PCCT. A clinically applicable radiation dose of 27.1 mGy was used. Scans were acquired before and after CI insertion. Postoperative measurement of the CDL was conducted using an otological planning software and 3D-curved multiplanar reconstruction. Investigation of electrode contact position was performed by two respective observers. Measurements were compared with a conventional multislice CT and to a high-resolution flat-panel volume CT with secondary reconstructions.
RESULTS: Pre- and postoperative CDL measurements in PCCT images showed no significant difference to high-resolution flat-panel volume CT. Postoperative CI electrode contact determination was also as precise as the flat-panel CT-based assessment. PCCT and flat-panel volume CT were equivalent concerning interobserver variability.
CONCLUSIONS: CDL measurement with PCCT was equivalent to flat-panel volume CT with secondary reconstructions. PCCT enabled highly precise postoperative CI electrode contact determination with substantial advantages over conventional multislice CT scanners.

A comparative analysis of 26 petrous bones and epiphyses of metacarpals from the Second World War era revealed no significant differences in DNA yield or success in STR typing. This unexpected parity in DNA preservation between the petrous bone, a renowned source of endogenous DNA in skeletal remains, and the epiphyses of metacarpals, which are porous and susceptible to taphonomic changes, is surprising. In this study, we introduced ATR-FTIR spectroscopy as an approach to unravel the correlation between bone molecular structure and DNA preservation. Metacarpals and petrous bones with same taphonomic history were sampled and prepared for DNA analyses. While one portion of the sample was used for DNA analysis, the other underwent ATR-FTIR spectroscopic examination. The normalized spectra and FTIR indices between the epiphyses of metacarpals and petrous bones were compared. Because the taphonomic history of the remains used is relatively short and stable, the ATR-FTIR spectroscopy unveiled subtle structural differences between the two bone types. Petrous bones exhibited higher mineralization, whereas epiphyses contained more organic matter. The unexpected preservation of DNA in the epiphyses of metacarpals can likely be attributed to the presence of soft tissue remnants within the trabeculae. Here observed differences in the molecular structure of bones indicate there are different mechanisms enabling DNA preservation in skeletal tissues.

BACKGROUND: The retrolabyrinthine approach provides shorter working distance and less cerebellar retraction compared with the retrosigmoid approach to the internal acoustic canal (IAC) and cerebellopontine angle cistern. However, exposure of the ventral surface of the brainstem and petroclival region may be restricted. Trautmann\'s triangle (TT), an area intimately related to this region, demonstrates significant anatomical variability, which may adversely affect the ease of the approach. The aim of this study is to evaluate anatomic parameters of the posterior fossa that may anticipate a challenging situation in approaching the IAC and the petroclival region through the retrolabyrinthine approach.
METHODS: It was performed a radioanatomic analysis of 75 cerebral angiotomography exams to identify parameters that could potentially reduce areas of surgical exposure.
RESULTS: Large variations were observed in the area of exposure of the TT (553%) and the height of the jugular bulb (234%). Shorter distances from the sigmoid sinus to the posterior semicircular canal and high-riding jugular bulb were associated with smaller areas of exposure. Dominant and laterally positioned sigmoid sinuses and less pneumatized mastoids were associated with potentially unfavorable conditions, including a narrower angle of attack to the IAC. Increased petrous slopes and petroclival angles were associated with smaller petroclival areas and shallower clival depths.
CONCLUSIONS: This study of the posterior fossa reveals remarkable anatomic variation in the region. These findings should be taken into consideration during the preoperative planning of retrolabyrinthine approaches in order to offer safer and more effective surgical procedures.

Identification of human remains using genetic methods is an important task of forensic science. DNA markers are proving essential in the identification of unknown human remains. However, environmental factors can lead to poor preservation of DNA, including in bone material. The aim of this study was therefore to compare two methods of DNA isolation from bone material: the traditional organic method and the new protocol using the EZ2 Connect instrument. The study involved three types of bone material, namely molars/premolars, petrous parts of the temporal bone and femurs, all with an estimated PMI of 70-80 years. Importantly, the biological material was obtained from three different environments, categorized as preserving, neutral and degrading, based on basic physico-chemical tests and the potential impact on the bone. The results obtained show that the DNA was best preserved in the petrous bone, followed by the teeth, and the femur. DNA extraction using the EZ2 Connect instrument with a new protocol gave slightly better results for the petrous bone, comparable results for the teeth and worse results for the femur compared to the organic method. Several protocol modifications were tested and optimal conditions for DNA isolation were proposed for the EZ2 protocol. Furthermore, the use of an automated method facilitated the effective accumulation of isolates and increased the chances of successful identification of unknown human remains.

Due to deep location and for being adjacent to neurovascular structures, petroclival meningiomas (PCMs) are generally considered to be associated with a high rate of recurrence and cranial nerve deficits.1 This video presents a 49-year-old female patient reporting right trigeminal neuralgia for more than 1 year. The incidence of this symptom with PCMs is about 5%.2 According to the classification system proposed by Kawase et al.3 and Ichimura et al.,4 this is a tentorium type PCM. A modified anterior petrosectomy approach was adopted based on the tumor size and its origin. The case presentation, surgical technique, postoperative outcome are reviewed. The treatments to the intraoperative trochlear nerve injury and temporal bridging vein occlusion are displayed (Video 1). The patient gave verbal consent for participating in the procedure and surgical video.

Minimally invasive endoscopic endonasal multiport approaches create additional visualization angles to treat skull base pathologies. The sublabial contralateral transmaxillary (CTM) approach and superior eyelid lateral transorbital approach, frequently used nowadays, have been referred to as the \"third port\" when used alongside the endoscopic endonasal approach (EEA). The endoscopic precaruncular contralateral medial transorbital (cMTO) corridor, on the other hand, is an underrecognized but unique port that has been used to repair CSF rhinorrhea originating from the lateral sphenoid sinus recess. However, no anatomical feasibility studies or clinical experience exists to assess its benefits and demonstrate its potential role in multiport endoscopic access to the other contralateral skull base areas. In this study, the authors explored the application and potential utility of multiport EEA combined with the endoscopic cMTO approach (EEA/cMTO) to three target areas of the contralateral skull base: lateral recess of sphenoid sinus (LRSS), petrous apex (PA) and petroclival region, and retrocarotid clinoidocavernous space (CCS).
Ten cadaveric specimens (20 sides) were dissected bilaterally under stereotactic navigation guidance to access contralateral LRSS via EEA/cMTO. The PA and petroclival region and retrocarotid CCS were exposed via EEA alone, EEA/cMTO, and EEA combined with the sublabial CTM approach (EEA/CTM). Qualitative and quantitative assessments, including working distance and visualization angle to the PA, were recorded. Clinical application of EEA/cMTO is demonstrated in a lateral sphenoid sinus CSF leak repair.
During the qualitative assessment, multiport EEA/cMTO provides superior visualization from a high vantage point and better instrument maneuverability than multiport EEA/CTM for the PA and retrocarotid CCS, while maintaining a similar lateral trajectory. The cMTO approach has significantly shorter working distances to all three target areas compared with the CTM approach and EEA. The mean distances to the LRSS, PA, and retrocarotid CCS were 50.69 ± 4.28 mm (p < 0.05), 67.11 ± 5.05 mm (p < 0.001), and 50.32 ± 3.6 mm (p < 0.001), respectively. The mean visualization angles to the PA obtained by multiport EEA/cMTO and EEA/CTM were 28.4° ± 3.27° and 24.42° ± 5.02° (p < 0.005), respectively.
Multiport EEA/cMTO to the contralateral LRSS offers the advantage of preserving the pterygopalatine fossa contents and the vidian nerve, which are frequently sacrificed during a transpterygoid approach. This approach also offers superior visualization and better instrument maneuverability compared with EEA/CTM for targeting the petroclival region and retrocarotid CCS.

In this study, the authors aimed to describe the endoscopic transorbital approach (ETOA) in children.
Six pediatric patients (2 girls and 4 boys) underwent the ETOA for paramedian skull base lesions at a single institution between September 2016 and February 2023.
The median age at the time of surgery was 7.5 (range 4-18) years. The median follow-up period was 33 (range 9-60) months. In this series, the ETOA level of difficulty included stage 1 (n = 2, 33.3%), stage 3 (n = 3, 50%), and stage 5 (n = 1, 16.7%). The ETOA was performed for tumor resection in 4 cases; the final pathology consisted of fibrous dysplasia, pilocytic astrocytoma, metastatic neuroblastoma, and choroid plexus papilloma. The procedure was also performed for repair of a petrous apex meningocele and for lateral orbital wall decompression of traumatic lateral rectus muscle entrapment. One patient experienced a transient cranial nerve III palsy after the procedure. There were no operative deaths in this series.
In select cases, the ETOA can be considered a minimally invasive alternative for conventional skull base approaches in the armamentarium of pediatric skull base surgery. Further investigation and the accumulation of experience are warranted in the future to enhance the efficacy and applicability of the ETOA in pediatric patients.

BACKGROUND: Petroclival meningiomas are one of the most challenging tumors to be operated in the realm of neurosurgery. Many approaches have been developed over the years.
METHODS: The authors describe the Half & Half (H&H) approach whose main indication is petroclival meningiomas with suprasellar extension. The part of the tumor located above CN III and in the retrochiasmatic space is addressed through a trans-sylvian, while the petroclival portion is through an extradural anterior petrosectomy approach. The wide surgical corridor given by this approach allows extensive tumor resection while avoiding the risk associated with the manipulation of intracavernous neurovascular structures.
CONCLUSIONS: The H&H approach is an effective strategy to maximize the safe resection of petroclival meningiomas.

OBJECTIVE: This study aims to define specific measurements on cranial high-resolution computed tomography (HRCT) images prior to surgery to prove the feasibility of the navigated transmastoid infralabyrinthine approach (TI-A) without rerouting of the facial nerve (FN) and decompression of the jugular bulb (JB) in accessing the extradural-intrapetrous part of petrous bone lesions located at the petrous apex and petroclival junction.
METHODS: Vertical and horizontal distances of the infralabyrinthine space were measured on cranial HRCT images prior to dissection. Subsequently, the area of access was measured on dissected human cadaveric specimens. Infralabyrinthine access to the extradural part of the petrous apex and petroclival junction was evaluated on dissected specimens by two independent raters. Finally, the vertical and horizontal distances were correlated with the area of access.
RESULTS: Fourteen human cadaveric specimens were dissected bilaterally. In 54% of cases, the two independent raters determined appropriate access to the petrous apex and petroclival junction. A highly significant positive correlation (r = 0.99) was observed between the areas of access and the vertical distances. Vertical distances above 5.2 mm were considered to permit suitable infralabyrinthine access to the extradural area of the petrous apex and petroclival junction.
CONCLUSIONS: Prior to surgery, vertical infralabyrinthine distances on HRCT images above 5.2 mm provide suitable infralabyrinthine access to lesions located extradurally at the petrous apex and petroclival junction via the TI-A without rerouting of the FN and without decompression of the JB.

OBJECTIVE: Expanded endonasal approaches (EEAs) have proven safe and effective in treating select petrous apex (PA) pathologies. Angled endoscopes and instruments have expanded indications for such approaches; however, the complex neurovascular anatomy surrounding the petrous region remains a significant challenge. This study evaluates the feasibility, anatomic aspects, and limitations of a contralateral nasofrontal trephination (CNT) route as a complementary corridor improving access to the PA.
METHODS: Expanded endonasal and CNT approaches to the PA were carried out bilaterally in 15 cadaveric heads with endovascular latex injections. The distance to the PA, angle between instruments through the 2 approach portals, and surgical freedom were measured and compared.
RESULTS: Three-dimensional DICOM-based modeling and visualization indicate that the CNT route reduces the distance to the target located within the contralateral PA by an average of 3.33 cm (19%) and affords a significant increase in the angle between instruments (15.60°; 54%). Furthermore, the vertical vector of approach is improved by 28.97° yielding a caudal reach advantage of 2 cm. The area of surgical freedom afforded by 3 different approaches (endonasal, endonasal with an endoscope in CNT portal, and endonasal with an instrument in CNT portal) was compared at 4 points: the dural exit point of the 6th cranial nerve, jugular foramen, foramen lacerum, and petroclival fissure. The mean area of surgical freedom provided by both approaches incorporating the CNT corridor was superior to EEA alone at each of the surgical targets ( P = <.001).
CONCLUSIONS: The addition of a CNT portal provides an additional avenue to expand on the classical EEA to the PA. This study provides insight into the anatomic nuances and potential clinical benefits of a dual-port approach to the PA.