The lateral retrocanthal transorbital endoscopic approach to the middle fossa: cadaveric stepwise approach and review of quantitative cadaveric data.

OBJECTIVE: The lateral retrocanthal transorbital endoscopic approach (LRCTEA) facilitates trajectory to the middle fossa, preserving the lateral canthal tendon and thus avoiding postoperative complications such as eyelid malposition. Here, the authors sought to define the surgical anatomy and technique of LRCTEA using a stepwise approach in cadaveric heads and offer an in-depth examination of existing quantitative data from cadaveric studies. METHODS: The authors performed LRCTEA to the middle cranial fossa under neuronavigation in 7 cadaveric head specimens that underwent high-resolution (1-mm) CT scans preceding the dissections. RESULTS: The LRCTEA provided access to middle fossa regions including the cavernous sinus, Meckel's cave, and medial temporal lobe. The trajectories and endpoints of the approach were confirmed using electromagnetic neuronavigation. A stepwise approach was delineated and recorded. CONCLUSIONS: The authors' cadaveric study delineates the surgical anatomy and technique of the LRCTEA, providing a stepwise approach for its implementation. As these approaches continue to evolve, their development and refinement will play an important role in expanding the surgical options available to neurosurgeons, ultimately improving outcomes for patients with complex skull base pathologies. The LRCTEA presents a promising advancement in skull base surgery, particularly for accessing challenging middle fossa regions. However, surgeons must remain vigilant to potential complications, including transient diplopia, orbital hematoma, or damage to the optic apparatus.

Open-door extended endoscopic transorbital technique to the paramedian anterior and middle cranial fossae: technical notes, anatomomorphometric quantitative analysis, and illustrative case.

OBJECTIVE: The superior eyelid endoscopic transorbital approach (SETOA) provides a direct and short minimally invasive route to the anterior and middle skull base. Nevertheless, it uses a narrow corridor that limits its angles of attack. The aim of this study was to evaluate the feasibility and potential benefits of an "extended" conservative variant of the "standard" endoscopic transorbital approach-termed "open-door"-to enhance the exposure of lesions affecting the paramedian aspect of the anterior and middle cranial fossae. METHODS: First, the authors described the technical nuances of the open-door extended transorbital approach (ODETA). Next, they documented its morphometric advantages over standard SETOA. Finally, they provided a clinical-anatomical application to demonstrate enhanced exposure and better angles of attack to treat lesions occupying the paramedian anterior and middle cranial fossae. Five adult cadaveric specimens (10 sides) initially underwent standard SETOA and then extended open-door SETOA (ODETA to the paramedian anterior and middle fossae). The adjunct of hinge-orbitotomy, through three surgical steps and straddling the frontozygomatic suture, converted conventional SETOA to its extended open-door variant. CT scans were performed before dissection and uploaded to the neuronavigation system for quantitative analysis. The angles of attack on the axial plane that addressed four key landmarks, namely the tip of the anterior clinoid process (ACP), foramen rotundum (FR), foramen ovale (FO), and trigeminal impression (TI), were calculated for both operative techniques and compared. RESULTS: Hinge-orbitotomy of the extended open-door SETOA resulted in several surgical, functional, and esthetic advantages: it provided wider axial angles of attack for each of the target points, with a gain angle of 26.68° ± 1.31° for addressing the ACP (p < 0.001), 29.50° ± 2.46° for addressing the FR (p < 0.001), 19.86° ± 1.98° for addressing the FO (p < 0.001), and 17.44° ± 2.21° for addressing the lateral aspect of the TI (p < 0.001), while hiding the skin scar, avoiding temporalis muscle dissection, preserving flap vascularization, and decreasing the rate of bone infection and degree of orbital content retraction. CONCLUSIONS: The extended open-door technique may be specifically suited for selected patients affected by paramedian anterior and middle fossae lesions, with prevalent anteromedial extension toward the anterior clinoid, the foremost compartment of the cavernous sinus and FR and not completely controlled with the pure endoscopic transorbital approach.

Inner Ear Breaches from Vestibular Schwannoma Surgery: Revisiting the Incidence of Otologic Injury from Retrosigmoid and Middle Cranial Fossa Approaches.

OBJECTIVE: To assess the rate of iatrogenic injury to the inner ear in vestibular schwannoma resections. STUDY DESIGN: Retrospective case review. SETTING: Multiple academic tertiary care hospitals. PATIENTS: Patients who underwent retrosigmoid or middle cranial fossa approaches for vestibular schwannoma resection between 1993 and 2015. INTERVENTION: Diagnostic with therapeutic implications. MAIN OUTCOME MEASURE: Drilling breach of the inner ear as confirmed by operative note or postoperative computed tomography (CT). RESULTS: 21.5% of patients undergoing either retrosigmoid or middle fossa approaches to the internal auditory canal were identified with a breach of the vestibulocochlear system. Because of the lack of postoperative CT imaging in this cohort, this is likely an underestimation of the true incidence of inner ear breaches. Of all postoperative CT scans reviewed, 51.8% had an inner ear breach. As there may be bias in patients undergoing postoperative CT, a middle figure based on sensitivity analyses estimates the incidence of inner ear breaches from lateral skull base surgery to be 34.7%. CONCLUSIONS: A high percentage of vestibular schwannoma surgeries via retrosigmoid and middle cranial fossa approaches result in drilling breaches of the inner ear. This study reinforces the value of preoperative image analysis for determining risk of inner ear breaches during vestibular schwannoma surgery and the importance of acquiring CT studies postoperatively to evaluate the integrity of the inner ear.

Subdural hemorrhage in middle cranial fossa arachnoid cysts: a report of two cases at two ends of the spectrum.

Arachnoid cysts are usually asymptomatic, benign lesions commonly occurring in the middle cranial fossa. However, the cysts may rupture in rare cases causing intracystic or subdural hemorrhages with significant mass effect. We report two cases of middle cranial fossa arachnoid cyst with subdural hemorrhage with very different clinical course. The first case presented with significant mass effect with cerebral herniation and had significant neurological morbidity post-surgery. The second case had minimal symptoms and was managed conservatively with offer of elective surgery. The report underscores the importance of prompt diagnosis and appropriate surgical intervention in managing arachnoid cysts with hemorrhage, highlighting the potential for diverse clinical presentations and outcomes.

Video article: the subtemporal extradural approach to cavernous sinus tumour.

OBJECTIVE: Here we demonstrate via operative video the subtemporal extradural approach to a tumour in the cavernous sinus. METHODS: The extradural approach is performed here in a paediatric patient (a 15-year-old child) via a right extended pterional osteoplastic craniotomy with removal of the zygomatic arch. The operative microscope is introduced, and the dura is divided at the superior orbital fissure into endosteal and meningeal layers using a diamond knife. The middle cranial fossa floor is drilled flat to increase access, and the plane is further developed towards the cavernous sinus. The tumour is seen bulging from within the cavernous sinus, and the cavernous sinus is opened in the anteromedial triangle between cranial nerves Vi and Vii. After biopsy, the tumour is debulked with an ultrasonic aspirator. Doppler is used to identify the internal carotid artery and preserve it. The bone flap is replaced, and the wound is closed in layers in standard fashion. RESULTS: The patient recovered well and was discharged on post-operative day 3. Persistent sixth nerve palsy (present pre-operatively) was present; however, otherwise, there was good recovery from surgery. Good resection of tumour is demonstrated on post-operative MR imaging. CONCLUSIONS: This approach is uncommon but important as it enables extradural access to the cavernous sinus, minimising the complications associated with an intradural approach such as cortical injury. In this video, we also demonstrate the fundamental anatomy using annotation and cadaveric images to enhance understanding required for the neurosurgeon to successfully complete this approach. The patient consented to the procedure in the standard fashion.

Communication between the temporomandibular joint articular space and the extradural space in patients with temporal bone pneumatization: implications for temporomandibular joint surgery.

The pneumatization of the articular portion of the temporal bone is an anatomical variant that can modify the barrier between the articular space and the middle cranial fossa. Thus, this study aimed to identify the presence and degree of pneumatization, as well as the existence of pneumatic cell dehiscence towards the extradural or articular space determining whether it could lead to direct communication between the articular and extradural spaces. Hence, One-hundred skull computed tomography images were selected. The presence and extension of pneumatization were classified according to scores 0, 1, 2, and 3. Dehiscence towards extradural and articular spaces was recorded. In total, 200 TMJ from 100 patients were assessed and 40.5% of pneumatization cases were observed. The most prevalent score was 0 (restricted to the mastoid process), while the least prevalent score was 3 (extending beyond the crest of articular eminence). Dehiscence of the pneumatic cells towards the extradural space is more common than towards the articular space. One complete communication between the extradural and articular spaces was observed. Considering the results, it was concluded that to avoid neurological and ontological complications, awareness of the potential anatomical communications between articular and extradural spaces, particularly in patients with extensive pneumatisation, is necessary.

A Three-Dimensional Anterior and Middle Cranial Fossa Model for Skull Base Surgical Training with Two Layers of the Colored Dura Mater.

BACKGROUND: Adequate epidural procedures and anatomical knowledge are essential for the technical success of skull base surgery. We evaluated the usefulness of our three-dimensional (3D) model of the anterior and middle cranial fossa as a learning tool in improving knowledge of anatomy and surgical approaches, including skull base drilling and dura matter peeling techniques. METHODS: Using a 3D printer, a bone model of the anterior and middle cranial fossa was created based on multi-detector row computed tomography data, incorporating artificial cranial nerves, blood vessels, and dura mater. The artificial dura mater was painted using different colors, with 2 pieces glued together to allow for the simulation of peeling the temporal dura propria from the lateral wall of the cavernous sinus. Two experts in skull base surgery and 1 trainee surgeon operated on this model and 12 expert skull base surgeons watched the operation video to evaluate this model subtlety on a scale of 1 to 5. RESULTS: A total of 15 neurosurgeons, 14 of whom were skull base surgery expert, evaluated, scoring 4 or higher on most of the items. The experience of dural dissection and 3D positioning of important structures, including cranial nerves and blood vessels, was similar to that in actual surgery. CONCLUSIONS: This model was designed to facilitate teaching anatomical knowledge and essential epidural procedure-related skills. It was shown to be useful for teaching essential elements of skull-base surgery.

Giant Cell Tumor of the Temporal Bone and Skull Base.

Giant cell tumor (GCT) is a benign tumor that originates from undifferentiated mesenchymal cells of the bone marrow. The craniums as well as temporal bone are extremely rare locations for GCTs. Clinical, radiological, and anatomical diagnosis of this locally aggressive disease poses a major challenge in clinical practice. In this article, we present a clinical study for a 35-year-old female who was found to have left-sided temporal bone GCT with extension to middle cranial fossa and temporomandibular joint (TMJ) with its clinical features and management.

Idiopathic Unilateral Intracranial Condylar Dislocation: A Case Report.

Intracranial condylar dislocation to the middle fossa is rare, as it is not reported often. Known cases have an etiology, identified as erosion of the glenoid cavity from joint prostheses and/or traumatic events. As such, this case aims to offer a predisposing reason for the idiopathic condylar dislocation to the middle cranial fossa with nonfunctional limitations.

Modified Lateral Orbitotomy Approach to Lesions of the Orbital Apex, Superior Orbital Fissure, Cavernous Sinus, and Middle Cranial Fossa.

BACKGROUND: The lateral orbitotomy approach (LOA) provides minimally invasive access to the orbit, cavernous sinus region, and middle cranial fossa. Orbital retraction with this approach can nonetheless injure orbital structures, causing unnecessary morbidity. OBJECTIVE: To describe our clinical experience with the modified LOA (mLOA), wherein the medial aspect of the lateral orbital wall posterior to the orbital rim is preserved. METHODS: This is a retrospective, single-institution case series of patients undergoing a mLOA for lesions of the orbital apex, superior orbital fissure, cavernous sinus, and middle cranial fossa. The dimensions and variance of selected anatomic parameters relevant to this approach (orbital rim-superior orbital fossa depth, lateral orbital wall angle) were also analyzed using computed tomography scans from 30 adult patients. RESULTS: Eight patients underwent a mLOA (mean age 54.0 ± 19.6 years; 3 males). Surgical targets included the superior orbital fissure (2; cavernoma and meningioma), sphenoid wing with or without the orbital apex (2; meningioma), cavernous sinus (2; rule out carcinoma and smooth muscle tumor), and anterior/mesial temporal lobe (2; cavernoma). Visual acuity/fields and diplopia was stable or improved in all patients postoperatively. One patient experienced a cerebrospinal fluid leak. On computed tomography analysis, the relevant bony anatomy displayed limited variability, with a mean orbital fossa depth of 42.7 ± 2.8 mm and a lateral orbital wall angle of 44.4° ± 2.7°. CONCLUSION: The mLOA can provide safe, minimally invasive access to select lesions of the orbital apex, superior orbital fissure, cavernous sinus, and middle cranial fossa. The operative corridor has relatively consistent bony anatomy.

The "Crista Ovale": A Reliable Anatomical Landmark in Transorbital Endoscopic Approaches to the Middle Cranial Fossa.

BACKGROUND: Transorbital endoscopic approaches (TOEAs) have emerged as adjunct and alternatives for accessing the middle cranial fossa (MCF). Nuances of the skull base anatomy from a ventral transorbital endoscopic viewpoint remain to be fully described. OBJECTIVE: To assess the anatomy of the "crista ovale" (COv), described transcranially as the midsubtemporal ridge (MSR), from a ventral transorbital perspective and evaluate its role as a landmark in TOEA to the MCF. METHODS: Lateral TOEAs to the MCF were performed in 20 adult cadaveric heads (40 sides). The presence of the COv/MSR was evaluated under endoscopic visualization. Anatomic relationships between COv/MSR and surrounding structures were assessed. The presence of COv/MSR was also examined in 30 cadaveric head computed tomography (CT) scans (60 sides). RESULTS: The COv/MSR was identified in 98% (39/40) of sides at the MCF, as 1 of 4 major configurations. The COv/MSR was found anterolateral to the foramen ovale and foramen spinosum (mean distance: 9.2 ± SD 2.4 mm and 12.3 ± SD 2.6 mm, respectively) directly anterior or anteromedial to the petrous apex (mean distance: 26.2 ± SD 2.6 mm) and at a mean 47.6 ± SD 4.7 mm from the approach's surgical portal. It was recognized in 95% (57/60) of CT scans. CONCLUSION: The COv/MSR can be readily identified during TOEA to the MCF and on CT. It serves as a reliable landmark to localize the foramen ovale, foramen spinosum, and petrous apex. Further studies may confirm its surgical significance in transorbital endoscopic procedures.

Evaluation of anterior and middle cranial fossa intraosseous arachnoid granulations with 3D T2-SPACE sequence.

OBJECTIVES: Arachnoid granulations (AG) can be located anywhere outside the dural sinuses. Their presence is thought to be associated with idiopathic intracranial hypertension (IIH) and cerebrospinal fluid (CSF) leaks. It was aimed to evaluate the intraosseous AGs located in the middle and anterior cranial fosses in detail with three-dimensional T2-SPACE (Sampling Perfection with Application optimized Contrasts using different flip angle Evolution-Siemens) imaging and to investigate their clinical significance. MATERIALS AND METHODS: Sixty-five intraosseous AG of 46 patients were included in this retrospective study. The highest diameter, bone indentation degree (in the inner tabula, diploe distance, reaching and exceeding the outer tabula), content (CSF/+parenchyma) of each AG were evaluated by 2 experienced radiologists. In addition, the presence of other MRI findings supporting IIH was examined. RESULTS: Additional signs of IIH were detected in 25 patients, and they were statistically significantly more common in the middle cranial fossa. Parenchymal herniation (in four patients) was more common in the young population. CONCLUSIONS: Intraosseous AGs can be evaluated in detail with T2-SPACE imaging. Determining intraosseous AG is very important both as an indicator of IIH and in terms of its content. T2-SPACE imaging is superior to CT and conventional sequences in this regard.

Postoperative Outcomes of Patients with Thin Bone Overlying the Superior Semicircular Canal: A Single Institution's Experience.

BACKGROUND: Superior semicircular canal dehiscence (SSCD) is defined by a bony defect overlying the superior semicircular canal (SSC) in the middle cranial fossa floor, causing a myriad of vestibular and auditory symptoms. Patients with thin bone without full dehiscence overlying the SSC also present with similar symptoms. There are currently no guidelines for surgical management of patients with thin bone. The authors offer their experience with thin bone patients to characterize their symptomatology and explore whether these patients benefit from surgical intervention typically offered to SSCD patients. METHODS: Two hundred fifty-six patients evaluated for SSCD from 2011 to 2019 were reviewed. High-resolution coronal computed tomography scans with 0.6-mm slice thickness of the temporal bones were assessed to determine whether the patient had a true dehiscence or a thin bone covering overlying the SSC. Bone that was ≤0.5 mm was considered to be "thin bone." Parameters of interest included patient demographics as well as preoperative and postoperative symptomatology. A P value < 0.05 was considered statistically significant. RESULTS: Forty-eight patients met inclusion criteria of having "thin bone." The mean age was 48.13 ± 12.03 years, and 65.5% of patients were female. Of the preoperative symptoms evaluated, the greatest postoperative symptomatic resolution was noted in hearing loss (92.3%), vertigo (94.4%), and oscillopsia (100%). Dizziness (56.5%) had the lowest symptomatic resolution rate. CONCLUSIONS: Surgical management of thin bone patients via middle fossa craniotomy, a similar technique to SSCD repair, provides significant symptomatic resolution. Therefore, surgery should be considered in thin bone patients with debilitating symptoms, albeit not having a true dehiscence.

"Sagittal Crest": Definition, Stepwise Dissection, and Clinical Implications From a Transorbital Perspective.

BACKGROUND: The recent development of the superior eyelid endoscopic transorbital approach (SETOA) offered a new route for the management of cavernous sinus and middle cranial fossa tumors. As a result, a constant anatomic landmark of the surgical pathway after drilling the medial edge of the greater sphenoid wing (GSW) is represented by a triangular-shaped bone ridge appearing as a "crest." OBJECTIVE: To perform an anatomic study to define this surgical landmark, named the "sagittal crest" (SC) as seen from the transorbital endoscopic view. METHODS: Four adult cadaveric specimens (8 sides) were dissected performing an endoscopic transorbital approach to the middle fossa and the SC was removed to perform interdural opening of the cavernous sinus. Computed tomography scans were made before and after removal of the SC to perform quantitative analysis and building a 3-dimensional model of the bone resection of the GSW via the SETOA. RESULTS: The SC is a bone ridge triangle shaping dorsally the superior orbital fissure resulting as the residual fragment after drilling the lateral aspect of the greater sphenoid wing. Predissection and postdissection computed tomography scans allowed to objectively assess SC features and dimensions (mean 1.08 ± 0.2 cm). CONCLUSION: The SC is a constant anatomic landmark constituted of the residual medial portion of the GSW. Complete resection of this key landmark provides adequate working space and appears to be mandatory during SETOA to guide the subsequent interdural dissection of the lateral wall of cavernous sinus.

Three-dimensional imaging for the localization of related anatomical structures during surgery on the internal auditory canal.

BACKGROUND: The Fisch infra-temporal fossa approach (Fisch's method), first proposed in 1970, is commonly used during internal auditory canal (IAC) surgery with an approach that advances through the middle cranial fossa. This study was designed to address the technical difficulties encountered in recognizing and localizing the arcuate eminence with respect to the superior semicircular canal (SSC). METHODS: Forty men and 40 women (18-57 years of age) without space-occupying lesions in the petrous part of the temporal bone were selected for the study. In total, 160 samples were obtained from both sides of the temporal bone. The temporal bone in these 160 samples was scanned using computed tomography, and a three-dimensional coordinate system was established to measure the three-dimensional coordinate values of structures adjacent to the arcuate eminence, the SSC, and the IAC. RESULTS: The results showed that the shape of the arcuate eminence is highly variable. Approximately 23.12% of samples had no obvious arcuate eminence, which prevented the use of Fisch's method to localize the SSC. The arcuate eminence was difficult to identify in 37 samples. CONCLUSIONS: Analysis samples showed that the SSC was located in a fan ring centered at the midpoint of the upper edge of the petrous portion of the temporal bone. The arcuate eminence did not correspond directly with the SSC, as the former was located posterolateral to the latter in 85.83% of samples. The angle between the SSC and the IAC ranged from 0° to 60° degrees, as reported previously by Fisch. However, the angle typically ranged from 10-30° in our study.

Resection of Vestibular Schwannoma Through Middle Cranial Fossa Approach with Endoscopic Assistance.

OBJECTIVE: We sought to report the outcome of resection of vestibular schwannomas (VSs) originating from the inferior vestibular nerve that extended into the fundus of the internal auditory canal through the middle cranial fossa (MCF) approach with endoscopic assistance. METHODS: Seven patients with VSs who underwent resection through MCF approach with endoscope assistance and 12 patients with conventional microsurgery in our department were enrolled in this study. These patients' characteristics were acquired, and the surgical outcomes, as well as postoperative complications, were evaluated. RESULTS: In the endoscope group, the VS was first removed by a conventional microscopic procedure and then an endoscope was used to find and remove any residue lesions. In 3 of 7 patients, residue tumor in the space below transverse crest was found and completely removed under endoscope. Six of 7 patients (85.7%) had House-Brackmann grade I at the time of last follow-up in the endoscope group compared with 10 of 12 patients (83.3%) in the conventional microsurgery group. Serviceable hearing was successfully maintained in 2 of 3 patients (66.7%) in the endoscope group compared with 6 of 10 patients (60%) in the conventional microsurgery group. Total resections were achieved in all the patients (100%) in the endoscope group compared with 9 of 12 patients (75%) in the conventional microsurgery group. CONCLUSIONS: Using an endoscope in VS resection through the MCF approach could facilitate complete removal of the lesion while minimizing the risk of hearing loss and facial paralysis. The endoscope-assisted MCF approach is especially suitable for removing an intracanalicular VS with lateral extension involving the space below the transverse crest.

Ruptured middle cranial fossa arachnoid cysts after minor trauma in adolescent boys presenting with subdural hygroma: two case reports.

BACKGROUND: Intracranial arachnoid cysts are common, cerebrospinal fluid-filled, innocent lesions that are usually detected incidentally on brain imaging. They may rupture and complicate due to subdural hematoma or hygroma after minor trauma. Authors present two cases of ruptured middle cranial fossa arachnoid cysts in adolescent (12-year-old and 15-year-old) Afghan boys presenting with subdural hygroma after minor trauma. CONCLUSION: Imaging work-up is necessary for symptomatic patients following minor head trauma as incidentally detected ruptured intracranial arachnoid cysts can be responsible for the symptoms.

Are arachnoid cysts actually clinically mute in relation to neuropsychological symptoms? Cognitive functioning in children with AC of middle and cranial fossa.

Aiming at being part of the discussion about the cognitive functioning of patients with arachnoid cysts (AC) and the value of neuropsychological testing in these patients, we present our study in which we investigated the cognitive functioning of 32 children with ACs of the middle cranial fossa. We compared the Stanford Binet 5 (SB 5) results obtained by the patients with the population mean values and analysed the relation between the patients' clinical details and the results of SB 5. The main conclusions of this research are: (1) In SB 5 tasks, the tested group performed worse than the population mean, which could be related to AC of the middle cranial fossa. Deficits concern especially visuospatial reasoning, quantitative reasoning, and knowledge. The obtained results indicate the coexistence of cognitive impairment and AC of the middle cranial fossa. (2) In patients with AC, neuroimaging information has only limited predictive ability regarding cognitive syndromes. (3) The complaints reported in the interview are not necessarily objectively reflected in the clinical assessment. Neuropsychological assessment should be part of the management of all patients with AC. (4) Cognitive deficits in patients with AC may become more pronounced with age. Accordingly, increasing school difficulties in these patients should be expected. In light of the above, there is a clear indication of the need for neuropsychological support and support in school functioning for patients with AC. (5) Neuropsychological control in patients with AC is crucial not only with regard to treatment decisions but primarily for monitoring school performance and providing these patients with adequate neuropsychological and psychological support.