Supramarginal resection of skull base chordomas: proof of concept and preliminary outcomes.

OBJECTIVE: The mainstay of treatment for skull base chordoma (SBC) is maximal safe resection followed by radiotherapy. However, even after gross-total resection (GTR), the recurrence rate is high due to microscopic disease in the resection margins. Therefore, supramarginal resection (SMR) could be beneficial, as has been shown for sacral chordoma. The paradigm of postoperative radiation therapy for every patient has also begun to change, as molecular profiling has shown variability in the risk of recurrence. The aim of this study was to present the concept of SMR applied to SBC, along with an individualized decision for postoperative radiation therapy. METHODS: This is a retrospective analysis of all SBCs operated on by the senior author between 2018 and 2023. SMR was defined as negative histological margins of bone and/or dura mater, along with evidence of bone resection beyond the tumor margins in the craniocaudal and lateral planes on postoperative imaging. Tumors were classified into 3 molecular recurrence risk groups (group A, low risk; group B, intermediate risk; and group C, high risk). Postoperative radiation therapy was indicated in group C tumors, in group B chordomas without SMR, or in cases of patient preference. RESULTS: Twenty-two cases of SBC fulfilled the inclusion criteria. SMR was achieved in 12 (55%) cases, with a mean (range) amount of bone resection beyond the tumor margins of 10 (2-20) mm (+40%) in the craniocaudal axis and 6 (1-15) mm (+31%) in the lateral plane. GTR and near-total resection were each achieved in 5 (23%) cases. Three (19%) tumors were classified as group A, 12 (75%) as group B, and 1 (6%) as group C. Although nonsignificant due to the small sample size, the trends showed that patients in the SMR group had smaller tumor volumes (13.9 vs 19.6 cm3, p = 0.35), fewer previous treatments (33% vs 60% of patients, p = 0.39), and less use of postoperative radiotherapy (25% vs 60%, p = 0.19) compared to patients in the non-SMR group. There were no significant differences in postoperative CSF leak (0% vs 10%, p = 0.45), persistent cranial nerve palsy (8% vs 20%, p = 0.57), and tumor recurrence (8% vs 10%, p = 0.99; mean follow-up 15 months) rates between the SMR and non-SMR groups. CONCLUSIONS: In select cases, SMR of SBC appears to be feasible and safe. Larger cohorts and longer follow-up evaluations are necessary to explore the benefit of SMR and individualized postoperative radiation therapy on progression-free survival.

How I do it: endoscopic endonasal chiasmopexy for optic chiasm prolapse.

BACKGROUND: Prolapse of the optic system into an empty sella is an unusual complication of the management of pituitary tumors. METHOD: We described the technical nuances for an endoscopic endonasal chiasmopexy, the indications for the procedure, and the caveats on the diagnosis of optic chiasm prolapse. CONCLUSION: The endoscopic endonasal chiasmopexy provides a direct route to lift the optic system. In most cases, the procedure may be achieved extradurally, protecting the chiasm from manipulation and postoperative fibrosis.

How I do it: endoscopic endonasal approach to the orbital apex.

BACKGROUND: The endoscopic endonasal approach provides an option to approach the medial and inferior orbital apex, with less manipulation of intraorbital structures. METHOD: We described the advantages, complications, caveats, and indications of the endoscopic endonasal approach to the orbital apex. An intraorbital extraconal cavernous malformation is shown as example. CONCLUSION: The endoscopic endonasal approach is a good corridor to the medial and inferior orbital apex, providing good exposure and little manipulation of the intraorbital contents.

Cerebellopontine angle schwannomas arising from the intermediate nerve: a scoping review.

Intermediate nerve schwannomas (INS) are extremely rare lesions in literature. They have been described mimicking facial nerve schwannomas, but not vestibular schwannomas (VS). We aimed to review the previously published cases, as well as the evidence to believe that they are far more common, though usually misdiagnosed as facial or VS. We performed a review of PubMed/Medline and Embase of "intermediate nerve schwannoma," "facial nerve schwannoma," "greater superficial petrosal nerve schwannoma," "geniculate ganglion schwannoma," and "chorda tympani schwannoma" to identify all cases of INS, following the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews (PRISMA-ScR) statement. Furthermore, 2 cases operated at our center are shown to exemplify the proposed hypotheses. No article was excluded from review. Thirteen cases of INS, 11 cases of chorda tympani schwannoma, and 18 cases of greater superficial petrosal nerve schwannoma were found in literature. In facial nerve schwannomas, the predilection of schwannomas for sensory nerves, and the ability to preserve the motor facial nerve during tumor resection support the hypothesis of intermediate nerve as the nerve of origin. For VSs, the different arachnoidal arrangement of medial VS, the sharing of pia mater by the intermediate nerve and vestibular nerve, and the medial Obersteiner-Redlich zone of the intermediate nerve, support the hypothesis of intermediate nerve origin of some VS. The correct identification of the intermediate nerve as a nerve of origin of cerebellopontine angle schwannomas is of uttermost importance, especially when mistaken for VS, as this may account for the heterogeneity of facial and cochlear outcomes after surgery.

How I do it: retrosigmoid suprajugular approach to the jugular foramen.

BACKGROUND: The retrosigmoid suprajugular approach provides a less-aggressive approach for a subset of tumors of the jugular foramen. METHOD: We described the retrosigmoid suprajugular approach with its advantages, caveats, and indications. A Samii-B2 glossopharyngeal nerve schwannoma is shown to exemplify the procedure. CONCLUSION: The retrosigmoid suprajugular approach provides an excellent option for tumors with a variable extension into the cerebellopontine cistern and limited extension into the jugular foramen. It is less destructive than the other approaches and allows a good exposure to the posterior part of the jugular foramen.

Endoscopic endonasal pituitary sacrifice for select tumors with retrochiasmatic and/or retrosellar extension: surgical anatomy, operative technique, and case series.

OBJECTIVE: Tumors located in the retrochiasmatic region with extension to the third ventricle might be difficult to access when the pituitary-chiasmatic corridor is narrow. Similarly, tumor extension into the interpeduncular and retrosellar space poses a major surgical challenge. Pituitary transposition techniques have been developed to gain additional access. However, when preoperative pituitary function is already impaired or the risk of postoperative panhypopituitarism (PH) is considered to be particularly high, removal of the pituitary gland (PG) might be the preferred option to increase the working corridor. The aim of this study was to describe the relevant surgical anatomy, operative steps, and clinical experience with the endoscopic endonasal pituitary sacrifice (EEPS) and transsellar approach. METHODS: This study comprised anatomical dissections to highlight the relevant surgical steps and a retrospective case series reporting clinical characteristics, indications, and outcomes of patients who underwent EEPS. The surgical technique is as follows: both lateral opticocarotid recesses are exposed laterally, the limbus sphenoidale superiorly, and the sellar floor inferiorly. After opening the dura, the PG is detached circumferentially and mobilized off the medial walls of the cavernous sinuses. The descending branches of the superior hypophyseal artery are coagulated, and the stalk is transected. After removal of the PG, drilling of the dorsum sellae and bilateral posterior clinoidectomies are performed to gain access to the hypothalamic region, interpeduncular, and prepontine cisterns. RESULTS: From 2018 to 2023, 11 patients underwent EEPS. The cohort comprised mostly tuberoinfundibular craniopharyngiomas (n = 8, 73%). Seven (64%) patients had partial or complete anterior PG dysfunction preoperatively, while 4 (36%) had preoperative diabetes insipidus. Because of the specific tumor configuration, the chance of preserving endocrine function was estimated to be very low in patients with intact function. The main reasons for pituitary sacrifice were impaired visibility and surgical accessibility to the retrochiasmatic and retrosellar spaces. Gross-total tumor resection was achieved in 10 (91%) patients and near-total resection in 1 (9%) patient. Two (18%) patients experienced a postoperative CSF leak, requiring surgical revision. CONCLUSIONS: When preoperative pituitary function is already impaired or the risk for postoperative PH is considered particularly high, the EEPS and transsellar approach appears to be a feasible surgical option to improve visibility and accessibility to the retrochiasmatic hypothalamic and retrosellar spaces, thus increasing tumor resectability.

Leukocyte-Rich and Platelet-Rich Fibrin for Skull Base Reconstruction After Endoscopic Endonasal Skull Base Surgery.

BACKGROUND: Postoperative cerebrospinal fluid (CSF) leak is one of the most common complications after endoscopic endonasal approach to the skull base. OBJECTIVE: To analyze the effect of leukocyte-rich and platelet-rich fibrin (L-PRF) as part of a standardized endonasal skull base repair protocol on postoperative infection and CSF leak rate. METHODS: One hundred three patients who underwent an endoscopic endonasal approach and were reconstructed using a standard technique (Group A) were compared with 139 patients using the same protocol with the addition of L-PRF (Group B). Postoperative intracranial infection and CSF leak at 6 months were analyzed. RESULTS: In patients with intraoperative CSF leak, postoperative leak occurred in 10.8% in Group A and 2.6% in Group B ( P .024), and in patients with intraoperative high-flow leaks, the incidences were 11.7% and 3.1%, respectively ( P .048). L-PRF reduced postoperative CSF leak by 76% in cases with intraoperative CSF leak (relative risk 0.24, 95% CI 0.06-0.87) and by 73% of patients with high-flow leak (relative risk 0.27, 95% CI 0.07-0.99). In patients undergoing surgery for diagnoses other than adenomas, there were no cases of postoperative leak in Group B, whereas in Group A occurred in 13.4% of those with intraoperative leaks ( P .047) and 15.8% with high-flow intraoperative leaks ( P .033). No significant differences were found in patients with pituitary adenoma. Meningitis occurred in 0.97% in Group A vs 2.16% in Group B ( P .639), without differences between subgroups. CONCLUSION: L-PRF reduced the rate of postoperative CSF leaks in patients with intraoperative leaks, without differences on postoperative meningitis.

Intracanalicular vestibular schwannomas: facial and hearing outcomes according to the location of the tumor in relation to the nerves of the internal auditory canal.

OBJECTIVE: The objective was to evaluate whether the position of the nerves within the internal auditory canal (IAC) has any effect on preoperative and postoperative cochlear and facial nerve function in patients with intracanalicular vestibular schwannoma (VS) resected through the retrosigmoid transmeatal approach. METHODS: Forty-four patients with sporadic intracanalicular VS, from a series of 710 patients with VS who underwent operations from January 1993 to April 2022, were retrospectively reviewed. The pattern of displacement of the cranial nerves and tumor within the IAC was recorded. Tumors were divided into 2 types: type T1A lesions had only anteriorly displaced nerves, and type T1B had posteriorly displaced vestibular nerves and anteriorly displaced facial and cochlear nerves. Differences in surgical outcomes between groups in terms of facial nerve function and hearing preservation were evaluated. RESULTS: Thirty-five cases (79.5%) were T1A tumors and 9 were T1B (20.5%). Gross-total resection and anatomical preservation of the facial and cochlear nerves were achieved in all patients. Postoperatively, all patients with T1A VS maintained normal facial nerve function; however, among T1B VS patients, 6 (67%) retained House-Brackmann grade I, 2 worsened to grade II, and 1 worsened to grade III at 6 months (p = 0.006). The 27 T1A VS patients with serviceable hearing maintained this status, and an additional patient with nonserviceable hearing improved to serviceable hearing; among T1B VS patients, only 2 of the 5 patients with serviceable hearing remained as such, 2 evolved to nonserviceable hearing, and 1 lost hearing after surgery (p = 0.0022). T1B VS patients had a 24-fold risk of facial nerve deterioration (relative risk [RR] 25.2, 95% CI 1.42-448.57, p = 0.028) and a 32-fold risk of hearing deterioration (RR 32.7, 95% CI 1.93-553, p = 0.016) after surgery. CONCLUSIONS: In intracanalicular VS, postoperative cochlear and facial nerve function are directly related to the location of the tumor in relation to the nerves, with worse outcomes in cases where the tumor is located between the vestibular and facial-cochlear nerves.

Retrosigmoid Craniotomy and Intradural Variations: Role of Patient-Specific Preoperative Imaging to Identify Landmarks and Relevant Structures.

OBJECTIVE: There are several landmarks to safely identify the limits of the retrosigmoid approach and its intradural variations; however, there has been little discussion about how those landmarks may vary among patients. METHODS: Patient positions; surface landmarks for the retrosigmoid craniotomy; and structures to recognize for transmeatal, suprameatal, suprajugular, and transtentorial extensions were reviewed. RESULTS: The position of the dural sinuses in relation to the zygomatic-inion line and digastric notch line is readily identified on magnetic resonance imaging. For transmeatal drilling, the position of the semicircular canals, vestibular aqueduct, and jugular bulb is best evaluated on computed tomography. For suprameatal drilling, the labyrinth and the position and integrity of the carotid canal are relevant for planning the anterior extension of the approach. For transtentorial extension, it is desirable to identify incisural structures. For suprajugular drilling, the position of the jugular bulb, invasion of venous structures, and integrity of the roof of the jugular foramen must be checked preoperatively. CONCLUSIONS: The retrosigmoid approach is the workhorse of posterior skull base surgery. By recognizing patient-specific variations in known landmarks, the approach may be tailored prevent complications.

Perfusion-weighted imaging in vestibular schwannoma: the influence that cystic status and tumor size have on perfusion profiles.

Objective: The perfusion profile of vestibular schwannomas (VSs) and the factors that influence it have yet to be determined. Materials and Methods: Twenty patients with sporadic VS were analyzed by calculating parameters related to the extravascular extracellular space (EES)-the volume transfer constant between a vessel and the EES (Ktrans); the EES volume per unit of tissue volume (Ve); and the rate transfer constant between EES and blood plasma (Kep)-as well as the relative cerebral blood volume (rCBV), and by correlating those parameters with the size of the tumor and its structure (solid, cystic, or heterogeneous). Results: Although Ktrans, Ve, and Kep were measurable in all tumors, rCBV was measurable only in large tumors. We detected a positive correlation between Ktrans and rCBV (r = 0.62, p = 0.031), a negative correlation between Ve and Kep (r = -0.51, p = 0.021), and a positive correlation between Ktrans and Ve only in solid VSs (r = 0.64, p = 0.048). Comparing the means for small and large VSs, we found that the former showed lower Ktrans (0.13 vs. 0.029, p < 0.001), higher Kep (0.68 vs. 0.46, p = 0.037), and lower Ve (0.45 vs. 0.83, p < 0.001). The mean Ktrans was lower in the cystic portions of cystic VSs than in their solid portions (0.14 vs. 0.32, p < 0.001), as was the mean Ve (0.37 vs. 0.78, p < 0.001). There were positive correlations between the solid and cystic portions for Ktrans (r = 0.71, p = 0.048) and Kep (r = 0.74, p = 0.037). Conclusion: In VS, tumor size appears to be consistently associated with perfusion values. In cystic VS, the cystic portions seem to have lower Ktrans and Ve than do the solid portions.

Objetivo: O perfil de perfusão do schwannoma vestibular (SV) não tem sido estudado, nem os fatores que o influenciam. Materiais e Métodos: Vinte pacientes com SV esporádico foram analisados usando Ktrans, Ve, Kep e rCBV e correlacionados com tamanho e estádio cístico. Resultados: Ktrans, Ve e Kep foram medidos em todos os casos. rCBV só foi possível em tumores grandes. Ktrans e rCBV estavam correlacionados positivamente (r = 0,62, p = 0, 0 31 ) . Ve e Kep estavam negativamente correlacionados (r = ­0,51, p = 0,021). Ktrans estava correlacionado positivamente com Ve em SVs sólidos (r = 0,64, p = 0,048). Em SVs pequenos, Ktrans foi menor (0,13 vs 0,029, p < 0,001), Kep foi maior (0,68 vs 0,46, p = 0,037) e Ve foi menor (0,45 vs 0,83, p < 0,001) que nos SVs grandes. Ktrans e Ve foram menores dentro dos cistos que nas porções solidas dos SVs císticos (0,14 vs 0,32, p < 0,001; 0,37 vs 0,78, p < 0.001, respectivamente). Foi encontrada correlação positiva em Ktrans (r = 0,71, p = 0,048) e Kep (r = 0,74, p = 0,037) entre as áreas sólidas e císticas. Conclusão: Nos SVs, o tamanho está consistentemente associado com os valores da perfusão. Nos SVs císticos, as porções císticas parecem ter valores menores de Ktrans e Ve do que nas porções sólidas.

Retrosigmoid Infralabyrinthine (Suprajugular) Approach to the Jugular Foramen: Indications, Limitations, and Surgical Nuances.

BACKGROUND: Among the several approaches described to the jugular foramen (JF), the retrosigmoid infralabyrinthine (suprajugular) approach was one of the most recently described. OBJECTIVE: To describe the indications, limitations, and operative nuances of the suprajugular approach. METHODS: We provided a pertinent review of the anatomy, indications, preoperative evaluation, surgical steps and nuances, and postoperative management. RESULTS: The suprajugular approach is suitable for tumors occupying the intracranial compartment with limited extension into the JF. Volume, width, and configuration of the foramen dictate the feasibility of the approach. Tumors invading the venous system are not suitable for this approach. Preoperative 3-dimensional MRI and computed tomography are used to evaluate intrajugular extension, relationship between the tumor and the jugular bulb (JB), venous system invasion, and shape of the JF. During surgery, exposition of the entire posterior border of the sigmoid sinus is needed and removing the bone over the JB. After identification of the JF, the jugular notch and intrajugular process of the roof of the foramen are removed and intrajugular resection is completed. In cases of high-riding JB, it may be gently pushed down to allow visualization of the anterior foramen. In cases of JB laceration, it may be repaired using a muscle patch and usually does preclude further resection. CONCLUSION: The suprajugular approach is variation of the retrosigmoid approach that, when properly indicated, provides excellent exposure of the medial JF, with most anatomical variations and intraoperative complications predicted by a comprehensive preoperative evaluation.

Relationship between Signal Intensity of the Labyrinth and Cochleovestibular Testing and Morphologic Features of Vestibular Schwannoma.

Objectives The aim of this article was to evaluate the relationship between signal intensity of the labyrinth and vestibulocochlear function and morphologic features of vestibular schwannoma (VS). Design Cross-sectional Study. Setting Tertiary referral center. Participants Fifty-four patients with sporadic, untreated VS. Main Outcome Measure Signal intensity of the cochlea and vestibule (SIRc and SIRv: signal intensity of cochlea/vestibule compared with cerebellar signal intensity; AURc and AURv: SIRc/SIRv of the affected side compared with the unaffected side) in 1.5T T2-weighted images was correlated with size (Hannover classification), cystic status, distance from the fundus of the internal auditory canal, video head impulse test (vHIT), and audiometry. Results Signal intensity of the vestibule was higher than that of the cochlea ( p < 0.01). Large tumors had lower SIRc than smaller tumors ( p = 0.03); Hannover T1 tumors had higher SIRc ( p < 0.01), SIRv ( p < 0.01), AURc ( p < 0.01) and AURv ( p < 0.01) than the rest; heterogenous and cystic tumors had higher SIRv than solid large tumors ( p = 0.02); superior vestibular nerve pattern on vHIT had higher SIRv and AURv than inferior vestibular nerve and mixed patterns ( p = 0.03 and 0.004, respectively); and there was a weak correlation between AURv and speech discrimination ( r = 0.33, p = 0.04). Conclusion A more abnormal signal intensity of the labyrinth is associated with larger size and solid status of VS. There was a positive relationship between signal intensity of the labyrinth and speech discrimination scores on audiogram.

Modified Craniocervical Approach for Resection of the Styloid Process in Patients with Eagle's Syndrome.

Objective Surgical treatment of Eagle's syndrome remains the mainstay of treatment. Palsy of the marginal mandibular branch of the facial nerve is the most significant complication encountered in transcervical resections, due to direct compression during the approach. We proposed a modification of the craniocervical approach to the jugular foramen to resect the styloid process avoiding the marginal mandibular branch and subsequent palsy. Design This is a single-center retrospective cohort study. Setting The research was conducted at a tertiary medical center. Participants From November 2008 to October 2018, 12 patients with Eagle's syndrome underwent treatment using our modified approach. Main Outcome Measures Demographic data, type of Eagle's syndrome, symptomatic side, size of the styloid process, clinical outcomes, and complications were analyzed. Results Mean size of the styloid processes was of 3.34 cm on the operated side (2.3-4.7 cm) and 2.98 cm on the other (2-4.2 cm). Intraoperative facial nerve irritation occurred in one case. Resection of the entire styloid process was achieved in all cases. Eight cases experienced complete improvement, three cases had a partial response, and one case failed to improve. There were no cases of recurrence. Two patients presented transient postoperative auricular paresthesia. There were no cases of mandibular branch palsy, nor any other complications in our series. Conclusions Our modified transcervical approach is effective in avoiding the marginal mandibular branch of the facial nerve, avoiding postoperative palsy.

Pseudo-Cerebrospinal Fluid Leaks of the Anterior Skull Base: Algorithm for Diagnosis and Management.

Objective Pseudo-cerebrospinal fluid (CSF) leaks are a rare cause of unilateral, watery rhinorrhea. We proposed a step-wise approach to evaluate these cases. Design It involves a single-center retrospective cohort study. Setting The setting is that of a tertiary academic medical center. Participants Ten patients with diagnosis of pseudo-CSF leak over a 21-year period were evaluated using our proposed algorithm that includes computed tomography, magnetic resonance imaging, nasal endoscopy, ß-2 transferrin, intrathecal fluorescein, and surgical exploration of the anterior cranial base. Main Outcome Measures The occurrence of intracranial infection and resolution of the symptoms were evaluated at a mean follow-up of 94.4 months. Results Eight patients had history of skull base fracture or surgery. In all patients computed tomography, magnetic resonance imaging, and nasal endoscopy did not show signs of CSF leak. Beta-2 transferrin testing was performed in five patients, being negative in all of them. Intrathecal fluorescein was performed in seven patients, being negative in five and inconclusive in two. Surgical exploration was performed in five patients, definitively ruling out CSF leak. Six patients were treated with intranasal ipratropium, resolving the symptoms in all cases. Conclusion The presented algorithm provides a step-wise approach for patients with unilateral watery rhinorrhea, allowing to safely ruling out CSF leak.

Management of jugular bulb injury during retrosigmoid transmeatal resection of vestibular schwannoma.

Inadvertent laceration of the jugular bulb is a potentially serious complication of the retrosigmoid transmeatal approach to vestibular schwannomas. Here, the authors present the case of a 51-year-old woman with a right Hannover T4a vestibular schwannoma and bilateral high-riding jugular bulb, which was opened during drilling of the internal auditory canal (IAC). They highlight the immediate management of this complication, technical nuances for closing the defect without occluding the jugular bulb, and modifications of the standard technique needed to continue surgical resection. The video can be found here: https://stream.cadmore.media/r10.3171/2021.7.FOCVID2155.

Brainstem hyperintensity in patients with vestibular schwannoma is associated with labyrinth signal on magnetic resonance imaging but not vestibulocochlear tests.

OBJECTIVES: Focal hyperintensity in the dorsal brainstem (HDB) has been described in large cerebellopontine angle tumours and is thought to represent vestibular nuclei degeneration, but its functional significance has not been thoroughly investigated. Our aim was to analyse its relationship to imaging characteristics of the tumour and inner-ear structures and to vestibulocochlear functional tests. METHODS: We retrospectively reviewed 54 patients with a histological diagnosis of vestibular schwannoma (VS). Magnetic resonance imaging tumour characteristics (size, cystic composition and distance from the cochlear aperture), signal intensity ratio of the cochlea and vestibule in fluid-attenuated inversion recovery (FLAIR) and fast imaging employing steady-state acquisition (FIESTA)/fast spin-echo imaging with variable flip angles (CUBE) and vestibulocochlear function tests (audiometry, auditory brainstem response (ABR) and video head impulse testing (vHIT)) were obtained. Statistical analyses were performed to evaluate their relation to focal HDB. RESULTS: Focal HDB was found in 22% of VS. It was significantly associated with large (p < 0.001) and cystic (p = 0.004) tumours and also with tumours located further from the cochlear aperture (p = 0.039). The signal intensity ratio of the cochlea on FLAIR was higher in patients with HDB (p < 0.014), but this difference was not observed in FIESTA/CUBE (p = 0.981). Audiometry, ABR and vHIT results did not significantly differ in patients with HDB, but ABR results were worse in patients with higher cochlear signal intensity on FLAIR sequences (p = 0.026). CONCLUSIONS: Focal HDB in patients with VS was associated with increased signal intensity ratio of the cochlea on FLAIR in patients with VS but not directly to the results of vestibulocochlear function tests.

Microsurgical Anatomy of the Jugular Foramen Applied to Surgery of Glomus Jugulare via Craniocervical Approach.

The jugular foramen remains one of the most complex regions of the human body. Approaching lesions in this area requires extensive anatomical knowledge and experience, due to the many critical neurovascular structures passing through or around the jugular foramen. Here, we present a concise review of the microsurgical anatomy of the jugular foramen in relation to the craniocervical approach.

Video Head Impulse Test to Preoperatively Identify the Nerve of Origin of Vestibular Schwannomas.

BACKGROUND: Identification of the nerve of origin in vestibular schwannoma (VS) is an important prognostic factor for hearing preservation surgery. Thus far, vestibular functional tests and magnetic resonance imaging have not yielded reliable results to preoperatively evaluate this information. The development of the video head impulse test (vHIT) has allowed a precise evaluation of each semicircular canal, and its localizing value has been tested for some peripheral vestibular diseases, but not for VS. OBJECTIVE: To correlate patterns of semicircular canal alteration on vHIT to intraoperative identification of the nerve of origin of VSs. METHODS: A total 31 patients with sporadic VSs were preoperatively evaluated with vHIT (gain of vestibule-ocular reflex, overt and covert saccades on each semicircular canal) and then the nerve of origin was surgically identified during surgical resection via retrosigmoid approach. vHIT results were classified as normal, isolated superior vestibular nerve (SVN) pattern, isolated inferior vestibular nerve (IVN) pattern, predominant SVN pattern, and predominant IVN pattern. Hannover classification, cystic component, and distance between the tumor and the end of the internal auditory canal were also considered for analysis. RESULTS: Three patients had a normal vHIT, 12 had an isolated SVN pattern, 5 had an isolated IVN pattern, 7 had a predominant SVN pattern, and 4 had a predominant IVN pattern. vHIT was able to correctly identify the nerve of origin in 89.7% of cases (100% of altered exams). CONCLUSION: The pattern of semicircular canal dysfunction on vHIT has a localizing value to identify the nerve of origin in VSs.

Video Head Impulse Test in Vestibular Schwannoma: Relevance of Size and Cystic Component on Vestibular Impairment.

OBJECTIVES: Tumor factors that influence vestibular function in vestibular schwannoma (VS) have not been properly described. We evaluated whether cystic VSs have different vestibular function than solid VS. Tumor size on vestibular function was also evaluated. STUDY DESIGN: Cross-sectional study. SETTING: Tertiary referral center. PATIENTS: Forty-one cases of sporadic, untreated VS. INTERVENTION: Evaluation with video head impulse test and MRI. MAIN OUTCOME MEASURES: Tumors were classified as solid, heterogeneous, or cystic and by size using the Hannover classification. Vestibulo-ocular reflex (VOR) gain was correlated to tumor size and cystic status. RESULTS: Large VS had worse VOR gain than small lesions (p < 0.001). Cystic lesions had lower VOR gain than all other tumors (p = 0.001), Hannover T3 and T4 (p = 0.014), Hannover T4 (p = 0.015), solid tumors (p < 0.001), solid Hannover T3 and T4 (p = 0.003), and solid Hannover T4 (p = 0.008). Heterogeneous VSs had lower VOR gain compared to solid tumors (p = 0.02), solid Hannover T3 and T4 (p = 0.08), and solid Hannover T4 (p = 0.14). Heterogeneous and cystic VSs had lower VOR gain than solid tumors (p < 0.001), solid Hannover T3 and T4 (p = 0.004), and solid Hannover T4 (p = 0.02). VOR gain of solid T4 lesions was not significantly lower than solid Hannover T1-T3 (p = 0.33). CONCLUSION: Cystic status is directly associated with a worse vestibular dysfunction. Size did not significantly impact vestibular function in solid VS.

Retrosigmoid Transmeatal Approach with 360-Degree Drilling of the Internal Auditory Canal for the Resection of Intracanalicular Meningioma.

Introduction Vestibular schwannomas are the most common lesions occupying the internal auditory canal (IAC); however, almost in 4 to 5% of meningiomas, metastases, cysts, lipomas, and cavernous malformations have been found in this location, mimicking schwannomas. Even though cerebellopontine angle (CPA) meningiomas with the involvement of the IAC are frequently encountered, the presence of a primary intracanalicular meningioma is rare. Objective To show the technical nuances of the retrosigmoid-transmeatal approach to successfully achieve gross total resection (GTR) with preservation of facial and auditory function. Case Report We present a left intracanalicular meningioma on a 60-year-old man with history of tinnitus and hearing loss. Magnetic resonance imaging (MRI) showed a left intracanalicular lesion completely obliterating the IAC and with minor extension to the CPA cistern, with the vestibulocochlear complex dislocated posteriorly, initially diagnosed as a Hannover's T2 vestibular schwannoma. The patient underwent a left retrosigmoid approach, and during the exposure of the lesion, the diagnosis of a meningioma became evident. The transmeatal phase of the approach was modified with a wide opening of the canal, including the anterior wall. Closure was performed using a muscle graft, duramater flap, and fibrin glue. Results GTR was achieved and the patient developed a mild facial palsy (House-Brackmann grade III) which completely recovered within 3 months. Conclusions The retrosigmoid transmeatal approach is suitable to achieve GTR in intracanalicular meningiomas. Some modifications of the approach intended for vestibular schwannomas are necessary and may be performed during the procedure. The link to the video can be found at: https://youtu.be/A9OXRFIl1e8 .