Mullan's triangle or anteromedial triangle of the middle cranial fossa: a cadaveric study with its surgical importance.

BACKGROUND: Surgical approaches to the cavernous sinus (CS) and middle cranial fossa (MCF) can be challenging, particularly for young neurosurgeons. The anteromedial (Mullan's) triangle is a triangle by the side of the CS and constitutes part of the floor of the MCF. The contents include the sphenoid sinus, superior ophthalmic vein, and sixth cranial nerve. The literature contains very little research that has precisely defined and measured the anteromedial triangle while considering anatomical variances minimally. METHODOLOGY: The present study was conducted on the skulls of 25 adult human cadavers which were dissected to expose the anteromedial (Mullan's) triangle on both sides. After precisely defining the triangle on each side, measurements of the three borders were taken, and using Heron's formula, the area of each triangle was calculated. RESULTS: On average, the length of the medial border was 12.5 (+ 3.1 mm); the length of the lateral border was 9.9 (+ 3.1 mm); the length of the base was 10.75 (+ 2.4 mm) and the area of the anteromedial triangle was 43.9 (+ 15.06 mm2). CONCLUSION: Precise anatomical knowledge of the Mullan's triangle enables the treatment of disorders in often deformed anatomy or difficult-to-access structures. That is the reason it is important to gain a thorough understanding of the surgical anatomy and to adopt a safe procedure.

Neuroendoscopic cysto-cisternostomy for middle cranial fossa arachnoid cysts: a systematic review of the practice principles from 169 cases.

INTRODUCTION: Arachnoid cysts are primarily dysembryogenetic splitting or duplication of the embryonic meningeal mesenchyme, hence the paediatric preponderance. Neuroendoscopic cysto-cisternostomy is now the favoured treatment option. We pooled data on middle fossa arachnoid cysts (MCFAC) demographics, clinical presentations, cyst characteristics, neuro-endoscopic cysto-cisternostomy and its outcomes. EVIDENCE ACQUISITION: Using search words (from the keywords; 'endoscopic treatment' and 'middle fossa arachnoid cysts') combined using Boolean operators, a systematic review of the PubMed and Cochrane CENTRAL was started on 1st February 2023, as per protocol (PROSPERO CRD42023394345); 65 records and then 46 reports were screened, 169 cases were pooled from the 19 recruited reports for the qualitative and quantitative syntheses, after methodological assessment (significantly excellent 57.9% quality) using the Joanna Briggs Institute critical appraisal tools. EVIDENCE SYNTHESIS: The male-to-female ratio was 2.4:1, with a weighted average-age of 11.25 years in the modal childhood (32.0%) age-group. Headaches (53/29.3%), seizures (30/16.6%) and macrocephaly (25/13.8%) were the commonest presentations. Right-sided (30/55.6%) and Galassi II (55/48.3%) and III (53/46.5%) lesions were common. Rigid (124/93.9%) endoscopes aided cysto-cisternostomy using mostly bipolar diathermy (31/43.7%) and ventriculostomy forceps (18/25.4%); creating one (22/18.3%), two (14/11.6%) or more (78/65.0%) stomas. Fenestration sites were specifically CNIII&ICA (32/25.8%), CNII&ICA (27/21.8%), CNIII&tentorium cerebelli (23/18.6%), CNIII&PCA (1/0.8%) and through the side of CNVI (1/0.8%) into the pre-pontine cistern. Good clinical and radiological outcomes were reported. CONCLUSIONS: Largely excellent-to-good quality, low-level evidence reported MCFACs presenting in childhood with headaches, seizures and macrocephaly. At least two fenestrations using bipolar-diathermy/forceps and balloon-catheter expansion were used for cysto-cisternostomy, with good outcomes.

The Use of Synthetic, Nonabsorbable Graft for Middle Fossa Repair in Patients With Spontaneous Cerebrospinal Fluid Leak: A Pilot, Prospective Study.

OBJECTIVE: To evaluate the efficacy of a nonabsorbable, synthetic graft for the reconstruction of spontaneous middle fossa (sMF) cerebrospinal fluid (CSF) leaks. PATIENTS: Six adult patients (age ≥16 yr) who had sMF CSF leaks surgically repaired within an 18-month period at a single university hospital using synthetic, nonbiological, nonabsorbable graft (Neuro-Patch) and a retrospective control group of five patients undergoing multilayer MF repair with autologous grafts. INTERVENTIONS: MF repair through a combined transmastoid/MF approach using Neuro-Patch or multilayer autologous grafts. MAIN OUTCOME MEASURES: The incidence of postoperative leak within 6 months postoperatively was the main outcome measure; we also recorded the need for lumbar drain, additional hearing loss, length of inpatient stay, body mass index, previous meningitis, preoperative increased intracranial pressure, and age. RESULTS: In the Neuro-Patch group, there was no postoperative CSF leak without the need for lumbar drain. We observed no additional hearing loss; patients were monitored for 2 days without any readmissions. Increased intracranial pressure (four of six), previous episodes of meningitis (two of six) or obesity (five of six) did not affect patient outcomes. Demographic and prognostic factors were the same for the control group. However, one patient needed lumbar drain postoperatively because of residual leak; lumbar drain was used in one more case (two of five cases), whereas three of five patients had to stay for longer than 2 days (5 d). CONCLUSIONS: Our pilot study suggests the use of Neuro-Patch via combined transmastoid/MF approach as an effective technique with minimum, if any morbidity; it could be of particular benefit for patients with larger MF dura defects. A larger number of patients are required to strengthen the evidence.

Spontaneous Intraventricular Tension Pneumocephalus.

Here, we report a very rare case of spontaneous intraventricular tension pneumocephalus. This case concerns a 40-year-old patient with medical history of a tumor of the pineal region and a secondary hydrocephalus treated by multiple ventriculoperitoneal shunts. He presented in the emergency room because of unusual headaches, nausea, and visual loss. In addition, he reported slight rhinorrhea in the past few weeks. The initial brain computed tomography scan revealed a spontaneous intraventricular tension pneumocephalus. There was no history of recent head trauma and no sign of disconnection of the shunt system. A complementary radiologic assessment including a thin-slice bone computed tomography scan and a radioisotope cisternography revealed an osseous defect and an isotope leakage at the junction between the tegmen tympani and the squamous part of the left temporal bone. A middle cranial fossa surgery was performed to repair the osteo-meningeal breach.

Audiometric outcomes following surgery for spontaneous temporal bone cerebrospinal fluid leaks - A single institution study.

PURPOSE: To assess the audiometric outcomes following surgical repair of spontaneous temporal bone cerebrospinal fluid otorrhea and compare different surgical approaches. MATERIALS AND METHODS: Retrospective review of adults (≥18 years old) who underwent repair of spontaneous CSF leak between 2011 and 2022. Audiometric outcomes were compared across the three surgical groups: transmastoid, middle cranial fossa and combined. RESULTS: Thirty-nine patients (40 ears) met the inclusion criteria (71.8 % females; mean age 59.77 +/- 12.4). Forty-two percent underwent transmastoid, 12.5 % middle cranial fossa and 45 % transmastoid-middle cranial fossa. Four patients (10 %) had recurrence, 3 in the transmastoid group and 1 in the combined approach. The mean change in air-bone gap (ABG) for all patients (postoperative-preoperative) was -7.4 (paired t-test, p-value = 0.0003). The postoperative ABG was closed in 28 (70 %) ears (postoperative ABG ≤ 15). The mean change in pure tone average (PTA) for all patients (postoperative-preoperative) was -4.1 (paired t-test, p-value = 0.13). The mean change in word recognition scores (WRS) for all patients (postoperative-preoperative) was -3 (paired t-test, p-value = 0.35). On multivariable analysis (controlling for site and reconstruction material), there was no significant difference in ABG, PTA and WRS change between surgical groups. CONCLUSIONS: Transmastoid, middle cranial fossa and combined approaches are all effective in treatment of spontaneous CSF leaks and all showed mean decrease in post-operative ABG. Transmastoid approach showed the greatest decrease in ABG and PTA (although middle cranial fossa approach shows the greatest decrease, when excluding profound hearing loss in a patient with superior canal dehiscence). Further studies comparing audiometric outcomes are needed.

Quality of Life for Patients with Sporadic Small Vestibular Schwannomas Following Middle Fossa Craniotomy.

OBJECTIVE: To evaluate quality-of-life outcomes for patients with vestibular schwannomas (VS) undergoing a middle cranial fossa (MCF) approach. STUDY DESIGN: Prospective study from 2018 to 2023. SETTING: Tertiary academic institution. PATIENTS: Adults with sporadic VS. INTERVENTIONS: MCF. MAIN OUTCOME MEASURES: The primary outcome measure was the change in preoperative and 1-year postoperative Penn Acoustic Neuroma Quality-of-life (PANQOL) scores. Secondary outcome measures included hearing preservation and facial nerve function. RESULTS: Of the 164 patients who underwent MCF for sporadic VS, 78 patients elected to voluntarily complete preoperative PANQOL assessments prior to surgery. Seventy-one (91%) of those 78 patients completed postoperative PANQOL surveys. Fifty (70%) of the respondents were female and the median age was 48 years (range, 27-71 years). Overall, at 1-year postsurgery, a minimal clinically important difference (MCID) was obtained in the hearing (mean difference, 10.5; 95% confidence interval [CI], 4.3-16.7) and anxiety (mean difference, 18.8; 95% CI, 11.7-25.9) domains. For patients with hearing preservation (n = 48, 68%), MCIDs were reached in the hearing (mean difference, 13.4; 95% CI, 6.3-20.6), anxiety (mean difference, 20.8; 95% CI, 11.8-29.9), energy (mean difference, 13.7; 95% CI, 3.6-23.8), pain (mean difference, 13.7; 95% CI, 3.6-23.8) domains, and overall PANQOL scores (mean difference, 12.7; 95% CI, 7.1-18.3). Postoperatively, 64 (90%) patients maintained a House-Brackmann I. CONCLUSIONS: To our knowledge, this is the largest study examining disease-specific QOL for VS patients undergoing MCF. Based on our institution's experience, MCF approach for small VS is associated with clinically meaningful improvements in QOL, hearing preservation, and excellent facial nerve outcomes.

Anatomical Analysis of the Eustachian Tube in the Temporal Bone Through the Middle Fossa Window.

PURPOSE: This cadaveric anatomical study aimed to explore precise morphometric measurements of the eustachian tube (ET) and adjacent structures in the middle cranial fossa, focusing on identifying reliable surgical landmarks when traditional markers are compromised due to tumors or trauma. METHODS: Twenty-two temporal bones from 11 adult cadavers (mean age: 75.70 ± 13.75 yr, range: 40-90 yr; sex: 5 females and 6 males) were dissected bilaterally. Surgical tools, including an operation microscope, endoscope, and digital caliper, were used for meticulous measurements. Parameters such as ET dimensions, distances between key points, and relevant angles were quantified, ensuring precise anatomical data. RESULTS: ET width at the foramen spinosum (FS) level, the midline level, and the eustachian orifice level were measured as 2.18 ± 0.68, 2.42 ± 0.70, and 2.30 ± 0.74 mm, respectively. The distances from the zygomatic root (ZR) to FS, ET, superior semicircular canal (SSC), and internal carotid artery (ICA) were 29.61 ± 2.56, 23.28 ± 2.61, 26.53 ± 2.56, and 32.61 ± 3.69 mm, respectively. The angles between SSC-ZR-ICA and FS-ZR-ICA were measured as 36.57 ± 10.32 and 13.63 ± 3.72 degrees, respectively. No statistical difference was found between right-left or male-female measurements ( p > 0.05). CONCLUSION: The present study offers invaluable insights for neurotological surgeons performing middle fossa approaches. ET and ZR may serve as crucial reference points, enhancing surgical orientation and minimizing risks during complex procedures. These precise anatomical data may empower surgeons, ensuring safer and more confident middle cranial fossa operations, even in challenging clinical scenarios.

The endaural subtemporal keyhole: a novel minimally invasive approach to the middle cranial fossa.

OBJECTIVE: The goal of this study was to evaluate the feasibility of a minimally invasive approach to the middle cranial fossa using a novel endaural keyhole. METHODS: The charts of all patients who underwent this novel minimally invasive approach to the middle cranial fossa were retrospectively reviewed. In addition, cadaveric dissection was performed to demonstrate the feasibility of the endaural keyhole to the middle cranial fossa. RESULTS: Six patients (5 female and 1 male; age range 47-77 years) who underwent craniotomy for CSF leak (n = 3), intracerebral hematoma evacuation (n = 2), and tumor resection (n = 1) via the endaural subtemporal approach were identified. There were no approach-related complications noted. Representative imaging from cadaveric dissection is provided with a stepwise discussion of the procedure. CONCLUSIONS: The endaural subtemporal keyhole craniotomy provides a novel approach to middle fossa skull base pathology, as well as a minimally invasive approach to intra-axial pathology of the temporal lobe and basal ganglia. Further research is needed to establish the limitations and potential complications of this novel approach.

Comparing Approaches for Repair of Superior Semicircular Canal Dehiscence.

OBJECTIVE: Compare outcomes for subjects who underwent middle cranial fossa (MCF) or transmastoid (TM) repair of superior semicircular canal dehiscence (SSCD). STUDY DESIGN: Retrospective cohort study. SETTING: Quaternary-care, academic neurotology practice. METHODS: Subjects who underwent MCF or TM repair of SSCD between December 1999 and April 2023 were identified. Main outcome measures included demographic data, length of surgery and hospital stay, clinical presentation, and audiometric testing. RESULTS: Ninety-three subjects (97 ears) who underwent surgery for SSCD met inclusion criteria: 58.8% (57) via MCF, 39.2% (38) via TM, and 2.0% (2) via TM + MCF. Median operative time was shorter for the TM (35) compared to the MCF (29) approach (118 vs 151 minutes, P < .001). Additionally, median hospital stays were shorter for TM (36) compared to the MCF (56) approach (15.3 vs 67.7 hours, P < .001). Overall, 92% (49/53) of MCF and 92% (33/36) of TM surgeries resulted in an improvement or resolution of one or more symptoms (P = .84). There was no significant preoperative to postoperative change in the median air conduction pure-tone average (PTA), air-bone gap, or word recognition score in both the MCF and TM groups (P > .05). Improvements of >10 dB in the pre- to postoperative absolute change in bone conduction PTA were noted in 3 subjects in the MCF group and 4 subjects in the TM group (P = .49). CONCLUSION: The TM approach for SSCD demonstrates shorter operative times and length of hospital stay. The TM and MCF approaches have comparable audiometric and clinical outcomes.

Absence and Duplicate Foramen Spinosum in the Same Patient: An Extremely Rare Variation.

The foramen spinosum, one of the important openings at the base of the cranium, is the opening through which the middle meningeal artery enters the cranium. The variations of the foramen spinosum should be well known to be an important landmark in middle fossa surgeries and to understand better the clinical conditions related to the middle meningeal artery passing through it. A total of 35 bones (32 cranial base and 3 separate sphenoid bones) of individuals of unknown age, sex, and ethnicity in the Laboratory of the Department of Anatomy, Gaziantep University, Faculty of Medicine were examined bilaterally in this study. One of the 35 bones was found to have a duplicated foramen spinosum on the left side and an absence foramen spinosum on the right side. Foramen spinosum variations should be considered in middle fossa approaches and procedures involving the middle meningeal artery.

Temporal lobe injury with middle fossa approach to intracanalicular vestibular schwannomas: a systematic review.

There are several surgical approaches for vestibular schwannoma (VS) resection. However, management has gradually shifted from microsurgical resection, toward surveillance and radiosurgery. One of the arguments against microsurgery via the middle fossa approach (MFA) is the risk of temporal lobe retraction injury or sequelae. Here, we sought to evaluate the incidence of temporal lobe retraction injury or sequela from a MFA via a systematic review of the existing literature. This systematic review was conducted according to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) guidelines. Relevant studies reporting temporal lobe injury or sequela during MFA for VS were identified. Data was aggregated and subsequently analyzed to evaluate the incidence of temporal lobe injury. 22 studies were included for statistical analysis, encompassing 1522 patients that underwent VS resection via MFA. The overall rate of temporal lobe sequelae from this approach was 0.7%. The rate of CSF leak was 5.9%. The rate of wound infection was 0.6%. Meningitis occurred in 1.6% of patients. With the MFA, 92% of patients had good facial outcomes, and 54.9% had hearing preservation. Our series and literature review support that temporal lobe retraction injury or sequelae is an infrequent complication from an MFA for intracanalicular VS resection.

[Microanatomical Investigation of the Subtemporal Transtentorial Approach]. / é¢žä¸‹ç»å°è„‘å¹•å ¥è·¯çš„æ˜¾å¾®è§£å‰–å­¦ç ”ç©¶.

Objective: To study the microanatomic structure of the subtemporal transtentorial approach to the lateral side of the brainstem, and to provide anatomical information that will assist clinicians to perform surgeries on the lateral, circumferential, and petroclival regions of the brainstem. Methods: Anatomical investigations were conducted on 8 cadaveric head specimens (16 sides) using the infratemporal transtentorial approach. The heads were tilted to one side, with the zygomatic arch at its highest point. Then, a horseshoe incision was made above the auricle. The incision extended from the midpoint of the zygomatic arch to one third of the mesolateral length of the transverse sinus, with the flap turned towards the temporal part. After removing the bone, the arachnoid and the soft meninges were carefully stripped under the microscope. The exposure range of the surgical approach was observed and the positional relationships of relevant nerves and blood vessels in the approach were clarified. Important structures were photographed and the relevant parameters were measured. Results: The upper edge of the zygomatic arch root could be used to accurately locate the base of the middle cranial fossa. The average distances of the star point to the apex of mastoid, the star point to the superior ridge of external auditory canal, the anterior angle of parietomastoid suture to the superior ridge of external auditory canal, and the anterior angle of parietomastoid suture to the star point of the 10 adult skull specimens were 47.23 mm, 45.27 mm, 26.16 mm, and 23.08 mm, respectively. The subtemporal approach could fully expose the area from as high as the posterior clinoid process to as low as the petrous ridge and the arcuate protuberance after cutting through the cerebellar tentorium. The approach makes it possible to handle lesions on the ventral or lateral sides of the middle clivus, the cistern ambiens, the midbrain, midbrain, and pons. In addition, the approach can significantly expand the exposure area of the upper part of the tentorium cerebelli through cheekbone excision and expand the exposure range of the lower part of the tentorium cerebelli through rock bone grinding technology. The total length of the trochlear nerve, distance of the trochlear nerve to the tentorial edge of cerebellum, length of its shape in the tentorial mezzanine, and its lower part of entering into the tentorium cerebelli to the petrosal ridge were (16.95±4.74) mm, (1.27±0.73) mm, (5.72±1.37) mm, and (4.51±0.39) mm, respectively. The cerebellar tentorium could be safely opened through the posterior clinoid process or arcuate protrusion for localization. The oculomotor nerve could serve as an anatomical landmark to locate the posterior cerebral artery and superior cerebellar artery. Conclusion: Through microanatomic investigation, the exposure range and intraoperative difficulties of the infratemporal transtentorial approach can be clarified, which facilitates clinicians to accurately and safely plan surgical methods and reduce surgical complications.

Retrosigmoid versus middle fossa approach for hearing and facial nerve preservation in vestibular schwannoma surgery: A systematic review and comparative meta-analysis.

BACKGROUND: Vestibular schwannomas (VS) are benign tumors arising from vestibular nerve's Schwann cells. Surgical resection via retrosigmoid (RS) or middle fossa (MF) is standard, but the optimal approach remains debated. This meta-analysis evaluated RS and MF approaches for VS management, emphasizing hearing preservation and Cranial nerve seven (CN VII) outcomes stratified by tumor size. METHODS: Systematic searches across PubMed, Cochrane, Web of Science, and Embase identified relevant studies. Hearing and CN VII outcomes were gauged using the American Academy of Otolaryngology-Head and Neck Surgery, Gardner Robertson, and House-Brackmann scores. RESULTS: Among 7228 patients, 56 % underwent RS and 44 % MF. For intracanalicular tumors, MF recorded 38 % hearing loss, compared to RS's 54 %. In small tumors (<1.5 cm), MF showed 41 % hearing loss, contrasting RS's lower 15 %. Medium-sized tumors (1.5 cm-2.9 cm) revealed 68 % hearing loss in MF and 55 % in RS. Large tumors (>3cm) were only reported in RS with a hearing loss rate of 62 %. CONCLUSION: Conclusively, while MF may be preferable for intracanalicular tumors, RS demonstrated superior hearing preservation for small to medium-sized tumors. This research underlines the significance of stratified outcomes by tumor size, guiding surgical decisions and enhancing patient outcomes.

Anterolateral keyhole transorbital routes to the skull base: a comparative anatomical study.

OBJECTIVE: Although keyhole transorbital approaches are gaining traction, their indications have not been adequately studied comparatively. In this study the authors have defined them also as transwing approaches-meaning that they use the different facies of the sphenoid wing for cranial entry-and sought to compare the four major ones: 1) lateral orbitocraniotomy through a lateral canthal incision (LatOrb); 2) modified orbitozygomatic approach through a palpebral incision (ModOzPalp); 3) modified orbitozygomatic approach through an eyebrow incision (ModOzEyB); and 4) supraorbital craniotomy through an eyebrow incision (SupraOrb), coupled with its expanded version (SupraTransOrb). METHODS: Cadaveric dissections were performed at the neuroanatomy lab. To delineate the skull base exposure, four formalin-fixed heads were used, with two sides dedicated to each approach. The outer limits were assessed via image guidance and were mapped and illustrated accordingly. A fifth head was dissected purely endoscopically, just to facilitate an overview of the transwing concept. Qualitative features were also rigorously examined. RESULTS: The LatOrb proves to be more versatile in the middle cranial fossa (MCF), whereas the anterior cranial fossa (ACF) exposure is limited to a small area above the sphenoid ridge. An anterior clinoidectomy is possible; however, the exposure of the roof of the optic canal is suboptimal. The ModOzPalp adequately exposes both the ACF and MCF. Its lateral trajectory allows the inferior to superior view, yet there is restricted access to the medial anterior skull base (olfactory groove). The ModOzEyB also provides extensive exposure of the ACF and MCF, but has a more superior to inferior trajectory compared to the ModOzPalp, making it more appropriate for pathology reaching the medial anterior skull base or even the contralateral side. The anterior clinoidectomy is performed with improved visualization of the optic canal. The SupraOrb provides mainly anterior cranial base exposure, with minimal middle fossa. An anterior clinoidectomy can be performed, but without any direct observation of the superior orbital fissure. Some MCF access can be accomplished if the lateral sphenoid wing is drilled inferiorly, leading to its highly versatile variant, the SupraTransOrb. CONCLUSIONS: All the aforementioned approaches use the sphenoid wing as skull base corridor from a specific orientation point; hence these are designated as transwing approaches. Their peculiarities mandate careful case selection for the effective and safe completion of the surgical goals.

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.

360° around the orbit: key surgical anatomy of the microsurgical and endoscopic cranio-orbital and orbitocranial approaches.

OBJECTIVE: Several pathologies either invade or arise within the orbit. These include meningiomas, schwannomas, and cavernous hemangiomas among others. Although several studies describing various approaches to the orbit are available, no study describes all cranio-orbital and orbitocranial approaches with clear, surgically oriented anatomical descriptions. As such, this study aimed to provide a comprehensive guide to the microsurgical and endoscopic approaches to and through the orbit. METHODS: Six formalin-fixed, latex-injected cadaveric head specimens were dissected in the surgical anatomy laboratory at the authors' institution. In each specimen, the following approaches were modularly performed: endoscopic transorbital approaches (ETOAs), including a lateral transorbital approach and a superior eyelid crease approach; endoscopic endonasal approaches (EEAs), including those to the medial orbit and optic canal; and transcranial approaches, including a supraorbital approach, a fronto-orbital approach, and a 3-piece orbito-zygomatic approach. Each pertinent step was 3D photograph-documented with macroscopic and endoscopic techniques as previously described. RESULTS: Endoscopic endonasal approaches to the orbit afforded excellent access to the medial orbit and medial optic canal. Regarding ETOAs, the lateral transorbital approach afforded excellent access to the floor of the middle fossa and, once the lateral orbital rim was removed, the cavernous sinus could be dissected and the petrous apex drilled. The superior eyelid approach provides excellent access to the anterior cranial fossa just superior to the orbit, as well as the dura of the lesser wing of the sphenoid. Craniotomy-based approaches provided excellent access to the anterior and middle cranial fossa and the cavernous sinus, except the supraorbital approach had limited access to the middle fossa. CONCLUSIONS: This study outlines the essential surgical steps for major cranio-orbital and orbitocranial approaches. Endoscopic endonasal approaches offer direct medial access, potentially providing bilateral exposure to optic canals. ETOAs serve as both orbital access and as a corridor to surrounding regions. Cranio-orbital approaches follow a lateral-to-medial, superior-to-inferior trajectory, progressively allowing removal of protective bony structures for proportional orbit access.

Optimizing the Endoscopic Transorbital Approach: MacCarty Keyhole for Enhanced Surgical Exposure in the Opticocarotid Region.

BACKGROUND: In recent years, the endoscopic transorbital (TO) approach has gained increasing interest for the treatment of middle cranial fossa lesions. We propose a technical refinement to the conventional superior eyelid TO approach, which improves the surgical exposure and augments the working angles when targeting the opticocarotid region. METHODS: Four embalmed adult cadaveric specimens (8 sides) were dissected at the Laboratory of Surgical Neuroanatomy of our institution. A TO approach was performed, with removal of the anterior clinoid process and the lateral orbital rim. Subsequently, the MacCarty keyhole was drilled in the superolateral orbital wall. Given that the lesser sphenoid wing was already drilled in the conventional TO craniectomy, the opening of the keyhole was essentially a lateral extension of the craniectomy. RESULTS: The procedure was successfully conducted in all 4 orbits. Clinoidectomy was performed either before or after extending the craniectomy to the MacCarty point. Extending the craniectomy made anterior clinoidectomy easier, by increasing the surgical exposure, and allowing a more lateral entrance for the endoscope. The extension also facilitated frontal lobe retraction, and it facilitated the optic nerve and carotid artery manipulation. Postoperative computed tomography scans showed a minimal 10-mm craniectomy extension, which remained covered by the temporal muscle after reconstruction. CONCLUSIONS: The modified endoscopic TO approach with the extension of the craniectomy to MacCarty point improves surgical access and visualization of the opticocarotid region. This facilitates anterior clinoidectomy and optic nerve decompression. Although it implies judicious instrument manipulation and a larger incision size, further studies can define its potential benefits.

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.