Osteological studies of skull base neurovascular area in reference to infratemporal approach to skull basec

Surgical approaches to the lateral skull base often lead to tearing of vessels and piecemeal removal of the tumour. This study is aimed to delineate exact relationship of the various foramina at the lateral skull base. The coronal dimensions of the jugular foramina are larger as compared to sagittal with right sided dominance also noticed in the case of carotid canal. The width of “Keel” separating the carotid and jugular foramina normally varies from 0.4 to1.4 centimetres and may not always suggest the erosion of the foramen of skull base scans, unless the erosion is associated with irregularity or demineralization the thickness of this keel really depends upon relative size of the vessels and location of foramina. Area between stylomastoid foramen, carotid canal and jugular foramen is roughly wedge shaped. The angle subtended by carotid and jugular at the stylomastoid foramen is about 36.84whereas the location of stylomastoid foramen and internal carotid axis pose an angle of 83:16. The angle subtended by stylomastoid and jugular at carotid on an average 59:31. The space between these structures is measured to be 0.642centimetres which can be verified on tomograms. By using these measurements, the precise location of the upper end of the vessels could be predicted, whereas the superior stump could be clamped with minimal exposure of the skull base and identification and location of the last four cranial nerves is found out. This could avoid injuries and subsequent morbidity while carrying out surgery in this region.

Freehand Stereotactic Image-Guidance Tailored to Neurotologic Surgery

Hypothesis: The use of freehand stereotactic image-guidance with a target registration error (TRE) of μTRE + 3σTRE < 0.5 mm for navigating surgical instruments during neurotologic surgery is safe and useful.Background: Neurotologic microsurgery requires work at the limits of human visual and tactile capabilities. Anatomy localization comes at the expense of invasiveness caused by exposing structures and using them as orientation landmarks. In the absence of more-precise and less-invasive anatomy localization alternatives, surgery poses considerable risks of iatrogenic injury and sub-optimal treatment. There exists an unmet clinical need for an accurate, precise, and minimally-invasive means for anatomy localization and instrument navigation during neurotologic surgery. Freehand stereotactic image-guidance constitutes a solution to this. While the technology is routinely used in medical fields such as neurosurgery and rhinology, to date, it is not used for neurotologic surgery due to insufficient accuracy of clinically available systems.Materials and Methods: A freehand stereotactic image-guidance system tailored to the needs of neurotologic surgery–most importantly sub-half-millimeter accuracy–was developed. Its TRE was assessed preclinically using a task-specific phantom. A pilot clinical trial targeting N = 20 study participants was conducted (ClinicalTrials.gov ID: NCT03852329) to validate the accuracy and usefulness of the developed system. Clinically, objective assessment of the TRE is impossible because establishing a sufficiently accurate ground-truth is impossible. A method was used to validate accuracy and usefulness based on intersubjectivity assessment of surgeon ratings of corresponding image-pairs from the microscope/endoscope and the image-guidance system.Results: During the preclinical accuracy assessment the TRE was measured as 0.120 ± 0.05 mm (max: 0.27 mm, μTRE + 3σTRE = 0.27 mm, N = 310). Due to the COVID-19 pandemic, the study was terminated early after N = 3 participants. During an endoscopic cholesteatoma removal, a microscopic facial nerve schwannoma removal, and a microscopic revision cochlear implantation, N = 75 accuracy and usefulness ratings were collected from five surgeons each grading 15 image-pairs. On a scale from 1 (worst rating) to 5 (best rating), the median (interquartile range) accuracy and usefulness ratings were assessed as 5 (4–5) and 4 (4–5) respectively.Conclusion: Navigating surgery in the tympanomastoid compartment and potentially in the lateral skull base with sufficiently accurate freehand stereotactic image-guidance (μTRE + 3σTRE < 0.5 mm) is feasible, safe, and useful.Clinical Trial Registration:www.ClinicalTrials.gov, identifier: NCT03852329.

Reconstruction of Complex Lateral Skull Base Defects After Oral Cancer Resection With Individualized Anterolateral Thigh Flap

ObjectivesComplex lateral skull base defects resulting from advanced or recurrent oral cancer resection are continuously challenging reconstructive surgeons. This study aimed to use reconstructive methods for lateral skull base defects, explore their feasibility, and evaluate the efficacy of defect reconstruction using anterolateral thigh (ALT) flaps.Patients and MethodsWe performed a retrospective case series of 37 patients who underwent lateral skull base defect reconstruction using the ALT/anteromedial thigh (AMT) flap between March 2016 and May 2021 at the Second Xiangya Hospital. The design and harvest of the flaps, methods for defect reconstruction, and reconstructive efficacy are described.ResultsOf the 37 patients, 3 were women and 34 were men, with a mean age of 51.7 years. Among the defects, 26 were through-and-through defects and were reconstructed using ALT chimeric flaps, double ALT flaps, folded ALT flap, combined ALT chimeric flaps and AMT flaps, or combined ALT chimeric flaps and pectoralis major flaps; the large lateral skull base dead spaces were filled with muscle tissues or fatty tissues. Postoperatively, 38 of the 39 ALT/AMT flaps survived completely, and the remaining flap experienced partial necrosis. Venous compromise occurred in one patient who was salvaged after operative exploration. Oral and maxillofacial wound infections occurred in two patients, salivary fistula in three patients, and thigh wound effusion in three patients. The wounds healed gradually in all patients after repeated dressing changes. Thirty-three patients were followed up for approximately 3–60 months; their oral functions and appearance were acceptable, and thigh motor dysfunction was not observed.ConclusionsWith the convenient flap design and muscle flap harvest, large and individualized tissue supply, feasible combination with other flaps, effective reduction or avoidance of wound complications, and acceptable donor site morbidity, the ALT flap is an appropriate choice for complex lateral skull base defect reconstruction.

Multicranial neuropathy secondary to endolymphatic sac tumor

<p class="abstract">Endolymphatic sac tumors (ELST) are rare neuroectodermal neoplasms arising from the epithelium of the endolymphatic sac or duct. Despite their benign histopathological features, ELSTs frequently demonstrate a locally destructive growth pattern with involvement of the skull base and cranial nerves. While ELSTs may arise sporadically, the majority of cases occur in association with Von Hippel-Lindau (VHL) syndrome. ELSTs are commonly diagnosed late due to their slow growing nature and non-specific symptomatology. Surgical resection is the treatment of choice. However, due to the location of these tumors in the lateral skull base surgical intervention carries a high risk of injury to critical neurovascular structures in close proximity. We presented the case of a 51 years old gentleman with a three-months history of hearing loss and otalgia. He subsequently developed multiple cranial neuropathies and was diagnosed with a sporadic ELST. He underwent a complete surgical resection and received adjuvant radiotherapy. </p>

Phosphaturic Mesenchymal Tumors of the Sinonasal Area and Skull Base: Experience at a Single Institution

Objectives: Phosphaturic mesenchymal tumor (PMT) is a rare, polymorphous neoplasm with a highly variable presentation and natural history and unpredictable clinical course. The primary objective was to describe our clinical experience with and management of 4 markedly different cases of sinonasal and skull base PMT. Methods: A retrospective case series with chart review, and relevant literature review, was performed at a tertiary academic medical center between 1998 and 2020. Adult patients treated for PMTs of the sinonasal area and skull base were included. Our main outcome measures included postoperative laboratory findings and radiological evidence of disease remission. Results: Four patients (2 Males, 2 Females; Mean Age: 63.5 years) with PMTs of the skull base have been managed at our institution since 1998. Patient presentations varied, ranging from severe phosphorus wasting and osteoporosis to symptoms secondary to mass effect, including nasal obstruction and rhinorrhea. All 4 patients were eventually found to have elevated levels of fibroblast growth factor 23. Tumors were located in the sinonasal area (right frontal sinus, right ethmoid sinus, and right nasal cavity, respectively) in 3 patients and in the lateral skull base (right jugular foramen) in 1 patient. All 4 patients underwent complete surgical resection of their tumors. PMT tissue pathology was confirmed in all cases. Gross total resection was achieved in all patients. There was no chemical or radiological evidence of disease recurrence in any patients at follow-up. Conclusions: The presentation of skull base PMT is variable, and it may mimic other mass pathologies of the head and neck. Complete surgical resection with negative margins is potentially curative.

Accuracy of Guided Surgery and Real-Time Navigation in Temporomandibular Joint Replacement Surgery

Background: Sophisticated guided surgery has not been implemented into total joint replacement-surgery (TJR) of the temporomandibular joint (TMJ) so far. Design and in-house manufacturing of a new advanced drilling guide with vector and length control for a typical TJR fossa component are described in this in vitro study, and its accuracy/utilization was evaluated and compared with those of intraoperative real-time navigation and already available standard drilling guides. Methods: Skull base segmentations of five CT-datasets from different patients were used to design drilling guides with vector and length control according to virtual surgical planning (VSP) for the TJR of the TMJ. Stereolithographic models of the skull bases were printed three times for each case. Three groups were formed to compare our newly designed advanced drilling guide with a standard drilling guide and drill-tracking by real-time navigation. The deviation of screw head position, screw length and vector in the lateral skull base have been evaluated (n = 72). Results: There was no difference in the screw head position between all three groups. The deviation of vector and length was significantly lower with the use of the advanced drilling guide compared with standard guide and navigation. However, no benefit in terms of accuracy on the lateral skull base by the use of real-time navigation could be observed. Conclusion: Since guided surgery is standard in implant dentistry and other CMF reconstructions, this new approach can be introduced into clinical practice soon, in order to increase accuracy and patient safety.

Metrological Support of Medical Drillings at the Lateral Skull Base

For minimally invasive drilling processes, the temperature development in the drilling ground is of crucial importance for patient safety. To monitor the temperature during drilling, a drill prototype was developed by BREDEMANN ET AL. which can record the drill temperature in parallel to the process and in real time. The measurement principle of the thermistor (temperature sensor) integrated in the drill could be validated. [1] The prototype must be refined for use in the operating room, as the drill does not yet meet all the medical requirements that need to be fulfilled. In further development, the recorded temperature data in particular must be processed and communicated to the surgeon in order to provide added value for the surgical procedure.