Localization of Maxillary Artery for Cerebral Revascularization: L-Shaped Perpendicular Two-Step Drilling Technique Stretching from the Foramen Ovale to Rotundum

BACKGROUND

The use of the maxillary artery (MA) as a donor has increasingly become an alternative method for cerebral revascularization. Localization difficulties emerge due to rich infratemporal anatomical variations and the complicated relationships of the MA with neuromuscular structures. We propose an alternative localization method via the interforaminal route along the middle fossa floor.

METHODS

Five silicone-injected adult cadaver heads (10 sides) were dissected. Safe and effective localization of the MA was evaluated.

RESULTS

The MA displayed anatomical variations in relation to the lateral pterygoid muscle (LPM) and the mandibular nerve branches. The proposed L-shaped perpendicular 2-step drilling technique revealed a long MA segment that allowed generous rotation to the intracranial area for an end-to-end anastomosis. The first step of drilling involved medial-to-lateral expansion of foramen ovale up to the lateral border of the superior head of the LPM. The second step of drilling extended at an angle approximately 90° to the initial path and reached anteriorly to the foramen rotundum. The MA was localized by gently retracting the upper head of the LPM medially in a posterior-to-anterior direction.

CONCLUSIONS

Considering all anatomical variations, the L-shaped perpendicular 2-step drilling technique through the interforaminal space is an attainable method to release an adequate length of MA. The advantages of this technique include the early identification of precise landmarks for the areas to be drilled, preserving all mandibular nerve branches, the deep temporal arteries, and maintaining the continuity of the LPM.

Giant primary intracranial multi-fossa leiomyosarcoma involving the frontal sinus, ethmoid air cells, anterior fossa, middle fossa, and intraventricular space: A case report and literature review

Background

Leiomyosarcomas (LMSs) is a type of sarcoma that arises from smooth muscle and generally presents in the abdomen. Although intracranial LMS has been identified before, most reported presentations have been in immunocompromised patients. Here, we present an intracranial LMS in an immunocompetent patient.

Case Description

A 22-year-old male with a history of an atypical pineal parenchymal tumor of intermediate differentiation resected by suboccipital craniotomy at the age of 12 followed by adjuvant radiation therapy, presented with 3 weeks of decreased appetite, weight loss, and lethargy. He subsequently underwent transbasal approach skull base tumor resection. Histologic examination of the mass along with the patient's history of radiation was supportive of a low-grade, radiation-induced LMS arising from the anterior fossa of the skull or meninges and extends to the frontal sinus and ethmoid air cells.

Conclusion

Primary intracranial LMS is an extremely rare diagnosis and presenting symptoms vary with the location and size of the tumor. Due to the poor specificity of clinical symptoms, diagnosis is often based on histology. The most common treatment is surgical resection. Adjuvant chemotherapy with various agents has been found to be somewhat effective outside the central nervous system. When LMS does occur, a history of immunocompromised state or previous radiation exposure is often present. Pathological confirmation is required for an appropriate diagnosis.

Endoscopic Lateral and Superior Cerebellar Keyhole Approach to the Anterior and Middle Incisural Space and Meckel Cave: An Anatomic Study

OBJECTIVE

We sought to assess the feasibility of endoscopic lateral and superior cerebellar keyhole approach for exposure of the anterior and middle incisural space and Meckel cave.

METHODS

The endoscopic lateral and superior cerebellar keyhole approach was performed in 6 cadaveric heads (12 sides) using 0- and 30-degree endoscopes, respectively. The anatomic structures for this approach to the anterior and middle incisural space and Meckel cave were observed.

RESULTS

By grinding out the suprameatal tubercle and petrous apex and incising the tentorium, the anatomic structures in the anterior incisural space were visualized. The mean area exposed with a 0-degree endoscope in the anterior incisural space was 212.50 ± 6.04 mm2, significantly less than that exposed with a 30-degree endoscope (233.83 ± 8.72 mm2) (P < 0.05). The anatomic distance of the Meckel cave in the depth was the same between a 0-degree endoscope and a 30-degree endoscope; however, the distance in the width was 9.48 and 12.32 mm, respectively (P < 0.01). The area of petrous window grinded by a 30-degree endoscope was only increased by 5.83 mm2, compared with a 0-degree endoscope (P > 0.05).

CONCLUSIONS

This approach provides access to the anterior and middle incisural space and Meckel cave, which is feasible to clearly expose the anatomic structures in those regions with minimal invasiveness. Additionally, better visualization and surgical space can be achieved under a 30-degree endoscope.

Middle Fossa Approach for Resection of a Petrous Bone Hemangioma Compressing the Geniculate Ganglion

Facial nerve hemangiomas are a rare entity of skull base lesions that arise within the temporal bone and affect the seventh cranial nerve.1 They are vascular malformations arising from the vascular plexuses surrounding the nerve. Although slow growing and overall benign in nature, they can cause significant facial nerve dysfunction even at small sizes.2 Facial nerve hemangiomas can arise within different segments of the facial nerve within the temporal bone, but most commonly arise near the geniculate ganglion.3 We describe the case of a 34-year-old female who presented with progressive right facial palsy (House-Brackmann 4) and a calcified lesion arising from the petrous temporal bone. Resection of the lesion was performed with a posterior to anterior middle fossa approach, with identification of the greater superficial petrosal nerve and geniculate ganglion, sectioning of the middle meningeal artery, and identification of V2 and V3 segments of the trigeminal nerve (Video 1). The bony mass was peeled off the petrous temporal bone and the geniculate ganglion without sacrifice of the facial nerve. Postoperative imaging showed gross total resection, and the patient's facial palsy improved to House-Brackmann 1. A comprehensive literature review on surgical approaches and outcomes for the resection of hemangiomas involving the geniculate ganglion or the facial nerve is also provided.2,4-18 The case presentation, surgical anatomy, operative nuances with technical considerations, and postoperative course with imaging are reviewed. The patient and family provided informed consent for the procedure and publication of patient images.

Microsurgical and illustrative anatomy of the cavernous sinus, middle fossa, and paraclival triangles: a straightforward, comprehensive review

The middle fossa, cavernous sinus, and paraclival triangles consist of ten triangles. Their use in a surgical approach is vast; most are used as landmarks to access and identify other structures of surgical interest. Multiple labels, borders, and contents mentioned by different authors make understanding and reproduction challenging and confusing. This study aims to organize and clarify recent or most relevant publications and disclose our portrayal of the ten triangles using cadaveric dissection and simple and practical figures. Four middle fossa triangles, four cavernous sinus triangles, and two paraclival triangles were dissected and delineated in a cadaveric specimen. Drawings were simplified to eliminate confusion and evaluate the triangles effortlessly. Similarities and differences in triangle names, border limits, and contents are described in a precise form. The recognition of triangle landmarks allows for treating pathologies in a frequently distorted anatomy or challenging to access structure. That is why an accurate knowledge of the surgical anatomy should be mastered, and a safe approach should be accomplished.

Scratching in the minefield: using intertriangles line to safely perform anterior petrosectomy

PURPOSE

The transpetrosal-transtentorial approach provides a practical and safe surgical corridor for the treatment of petroclival region lesions. Any inaccuracies while performing this surgical technique can result in catastrophic results; nevertheless, this can be prevented under the guidance of a detailed anatomical orientation. An "intertriangles line" was defined to preserve the internal auditory canal (IAC) and cochlea during extradural bone drilling.

METHODS

The anatomical study consisted of two groups: the cadaveric head and the skull group. A literature-based landmark and criteria list was created to examine the borders of the Kawase triangle/space and evaluate the anatomical structures that may be at risk during drilling for anterior petrosectomy.

RESULTS

A total of 20 cadaveric head sides and 30 dried skull sides were examined. The rhomboid area was divided into two triangles with a common the intertriangles line. In all dissections, the IAC was found to be localized posterior to the "intertriangle line". A minimum distance of 1 mm for the Internal Carotid artery and 2 mm for the IAC can serve as threshold values to be considered by the surgeon during drilling for petrosectomy.

CONCLUSIONS

Kawase's area resembles a minefield, in which every step and manipulation should be considered. A minimal but effective resection of the cranial base is needed to increase safety and decrease morbidity during skull base surgery. Furthermore, this study investigated accessible and prominent landmarks to establish a feasible area of triangles and define the intertriangles line to guide the neurosurgeon under microscope and avoid IAC injury.

Middle fossa triangles - A step-by-step dissection

Background

The anatomy and surgical approach to the cavernous sinus and the middle fossa can constitute a considerable challenge, specially for young surgeons. Although their surgical explorations have gone through a popular phase in the past, to this date, they remain an uncomfortable subject for many neurosurgeons. The aim of this paper is to systematically review its anatomy and multiple corridors through a step-by-step dissection of the middle fossa triangles, providing a roadmap for surgeons.

Methods

A step-by-step dissection of the cavernous sinus was performed in two fresh-frozen cadavers aiming to describe the anatomy of ten different middle fossa triangles, demonstrating the feasibility of the use of their spaces while surgically approaching this area.

Results

The intradural opening of the roof of the cavernous sinus was obtained by dissection of clinoidal, carotid-oculomotor, supratrochlear, optic-carotideal, and oculomotor triangles, allowing an expanded superior view. On the counterpart, the extradural exploration of the lateral wall through the middle fossa floor peeling exposed the infratrochlear, anteromedial, and anterolateral triangles. The middle fossa floor itself was the door to approaching posterior fossa through anterior petrosectomy. The dissection of each individual triangle can be amplified exponentially with exploration of its adjacents, providing broader surgical corridors.

Conclusion

The cavernous sinus still remains far from an "every man's land," but its systematic study based on direct approaches can ease the challenges of its surgical exploration, allowing surgeons to feel more comfortable with its navigation, with consequently benefit in the treatment of patients.

Trigeminal Schwannoma Surgery: Challenges in Preserving Facial Sensation

Treatments of schwannoma have dramatically improved in the previous few decades, but preservation of the functions of the originating nerve, such as facial sensation in trigeminal schwannomas, still remains challenging. As the preservation of facial sensation in trigeminal schwannomas has not been analyzed in detail, we here review our surgical experience of more than 50 trigeminal schwannoma patients, particularly focusing on their facial sensation. Since the facial sensation in each trigeminal division showed a different perioperative course even in a single patient, we investigated patient-based outcomes (average of the three divisions in each patient) and division-based outcomes separately. In the evaluation of patient-based outcomes, facial sensation remained postoperatively in 96% of all the patients, and improved in 26% and worsened in 42% of patients with preoperative hypesthesia. Posterior fossa tumors tended to most rarely disrupt facial sensation preoperatively, but were the most difficult to preserve facial sensation postoperatively. Facial pain was relieved in all six patients with preoperative neuralgia. In the division-based evaluation, facial sensation remained postoperatively in 83% of all the trigeminal divisions, and improved in 41% and worsened in 24% of the divisions with preoperative hypesthesia. The V3 region was most favorable before and after surgery, with the most frequent improvement and the least frequent functional loss. To clarify current treatment outcomes of the facial sensation and to achieve more effective preservation, standardized assessment methods of perioperative facial sensation may be required. We also introduce detailed MRI investigation methods for schwannoma, including contrast-enhanced heavily T2-weighted (CISS) imaging, arterial spin labeling (ASL), and susceptibility-weighted imaging (SWI), preoperative embolization for rare vascular-rich tumors, and modified techniques of the transpetrosal approach.

Direct Comparison Between the Kawase Approach and Retrosigmoid Intradural Suprameatal Corridor to Access the Petroclival Region Using Computed Tomography Quantitative Volumetric Analysis: A Cadaveric Study

OBJECTIVE

The anterior petrosectomy, also known as the Kawase approach, and the retrosigmoid intradural suprameatal approach (RISA) have both been used to reduce the petrous apex and access the petroclival region. Our goal was to compare the volumes and 3-dimensional shapes of bony resection obtained through each approach while trying to resemble realistic surgical settings.

METHODS

Five cadaveric specimens totaling 10 sides were dissected and analyzed. In every specimen, 1 side was used for the Kawase approach while the opposite side was used for the RISA. Petrosectomy volumes were assessed by comparing preoperative and postoperative thin-sliced computed tomography scans.

RESULTS

Petrosectomy volumes were significantly larger through the Kawase approach than through the RISA (0.82 ± 0.11 vs. 0.49 ± 0.07 cm³, P < 0.001). In addition, surgical maneuverability and freedom were greater in the Kawase operative variant. Lastly, the morphology of the bony window achieved through each approach was clearly different: trapezoid for the anterior petrosectomy versus elongated ellipsoid for the RISA.

CONCLUSIONS

The Kawase approach invariably results in larger volumes of bony removal than the RISA operative variant, and the volume of petrosectomy that is spatially congruent is only partially identical. The Kawase corridor is best suited for middle fossa lesions that extend into the posterior fossa, while the RISA is suitable for pathologies mainly residing in the posterior fossa and extending into the Meckel cave.

Severe headache and seizure free after microscopic fenestration craniotomy of middle Fossa arachnoid cyst: Case series

Introduction

Arachnoid cyst in the middle fossa can cause many symptoms include headache and seizure. When drugs therapy can not relieve or control the symptoms, it is necessary to determine whether the surgical procedure can improve patient's outcome.

Case presentation

First case, 28 years old female suffered from severe headache and sometimes unconsciousness for a few minutes. Magnetic resonance images showed the lesion hypo-intense on T1-weight and hyper-intense on T2-weight images. Left M1 middle cerebral artery lay down inside the cyst.

The second case, a man 18 years old had seizures every three months. He took phenytoin 600 mg a day but in the last one month seizures repeated up to five times. The brain MRI results showed a hypointense lesion of T1-weight and hyperintense at T2-weight in the right temporal region measuring approximately 5 × 4 cm and compressing the temporal bone to form a convex shape.

The third case, a man 23 years old had complaints of seizures since 6 months. The patient received the drug phenytoin 3x200mg and valproic acid 1 g daily but the seizures still exist. The brain MRI showed hyperintense lesion in the right temporal region.

Microscopic fenestration craniotomy was performed in all cases and at one year of follow-up the headache disappeared. Seizure attacks have never occurred again with only low doses of phenytoin.

Conclusion

The result of microscopic fenestration craniotomy in patients with headaches and seizures due to middle fossa arachnoid cysts is good and can be considered for controlling seizures in selected cases.

•

This study reports of arachnoid cyst with seizures and successfully treated by microscopic fenestration surgery

•

Brain imaging is very important not only to make a diagnosis but also to determine whether surgery is necessary or not

•

Surgery in patients with headaches and seizures due to middle fossa arachnoid is highly recommended in selected cases [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12], [13], [14]

Cochlear Fibrosis after Vestibular Schwannoma Resection via the Middle Cranial Fossa Approach

OBJECTIVE

The aim of this study was to determine the incidence of cochlear fibrosis after vestibular schwannoma (VS) resection via middle cranial fossa (MCF) approach.

DESIGN

A retrospective case review was conducted.

SETTING

The review was conducted in a tertiary care academic medical center.

PARTICIPANTS

Patients who (1) underwent resection of VS via MCF approach between 2013 and 2018, (2) had complete pre- and post-audiometric testing, and (3) had clinical follow-up with magnetic resonance imaging (MRI) for at least 1 year after surgery were included.

MAIN OUTCOME MEASURE(S)

The main outcome of this study was cochlear fibrosis as assessed by MRI 1 year after surgery.

RESULTS

Fifty-one patients underwent VS resection via MCF technique during the study period. Of 31 patients with AAO-HNS class A or B preoperative hearing ability, 18 (58.0%) maintained class A, B, or C hearing postoperatively. Of 16 patients who lost hearing and had MRI 1 year after surgery, 11 (61.1%) had MRI evidence of fibrosis in at least some portion of the labyrinth and 4 (22.2%) showed evidence of cochlear fibrosis. Of 16 patients with preserved hearing and MRI 1 year after surgery, 4 (25%) had fibrosis in some portion of the labyrinth, with no fibrosis in the cochlea.

CONCLUSIONS

In patients who lose hearing during VS resection with the MCF approach, there is usually MRI evidence of fibrosis in the labyrinth 1 year after surgery. However, there is also, but less commonly, fibrosis involving the cochlea. It is unclear if this will affect the ability to insert a cochlear implant electrode array.

Middle fossa approach for a facial nerve schwannoma: how I do it

BACKGROUND

Facial nerve schwannomas can extend to the middle fossa or the cerebellopontine angle through the labyrinthine and cisternal segments of the facial nerve. The middle fossa approach (MFA) and its extensions provide a wide approach to deal with a large variety of lesions located in the middle and posterior cranial fossa junction.

METHODS

We describe the MFA along with its advantages and limitations to treat a facial nerve schwannoma involving the middle and posterior cranial fossa.

CONCLUSIONS

The MFA is a well-established route to surgically deal with tumors located in and around the proximal four segments of the facial nerve.

Resection of a Dumbbell-Shaped Facial Nerve Schwannoma With Preservation of Facial Nerve Function Through the Extended Middle Fossa Approach: 2-Dimensional Operative Video

Facial nerve schwannomas are rare and can arise from any segment along the course of the facial nerve.1 Their location and growth patterns present as distinct groups that warrant specific surgical management and approaches.2 The management challenge arises when the facial nerve maintains good function (House-Brackmann grade I-II).3 Hence, a prime goal of management is to maintain good facial animation. In large tumors, however, resection with facial nerve function preservation should be sought and is achievable.4,5  While tumors originating from the geniculate ganglion grow extradural on the floor of the middle fossa, they may extend via an isthmus through the internal auditory canal to the cerebellopontine angle forming a dumbbell-shaped tumor. Despite the large size, they may present with good facial nerve function. These tumors may be resected through an extended middle fossa approach with preservation of facial and vestibulocochlear nerve function.  The patient is a 62-yr-old man who presented with mixed sensorineural and conductive hearing loss and normal facial nerve function. Magnetic resonance imaging (MRI) revealed a large tumor involving the middle fossa, internal auditory meatus, and cerebellopontine angle.  The tumor was resected through an extended middle fossa approach with a zygomatic osteotomy and anterior petrosectomy.6 A small residual was left at the geniculate ganglion to preserve facial function. The patient did well with hearing preservation and intact facial nerve function. He consented to the procedure and publication of images.  Image at 1:30 © Ossama Al-Mefty, used with permission. Images at 2:03 reprinted from Kadri and Al-Mefty,6 with permission from JNSPG.

Microsurgical Resection of Trigeminal Schwannoma via Anterior Petrosal Approach: 2-Dimensional Operative Video

Trigeminal schwannomas are complex lesions that may be related to many critical neurovascular structures. We present the case of a 59-year-old male presenting a history of left-sided trigeminal neuralgia. Preoperative imaging demonstrated a mass highly suggestive of a trigeminal schwannoma, and microsurgical resection was indicated considering the progressive symptomatology and important mass effect (Video 1). A middle fossa route including an anterior petrosectomy was chosen. The patient was placed supine with the head rotated to the contralateral side, and an arcuate incision was performed. A V-shaped zygomatic osteotomy was done to mobilize the temporalis muscle more inferiorly and better expose the middle fossa floor. Following craniotomy, peeling of the dura propria from the lateral wall of cavernous sinus was carried out starting by coagulation of middle meningeal artery. Some tumor was already identified and removed, and then the anterior petrosectomy was performed until we exposed the posterior fossa dura. The middle fossa dural incision was connected with the other one at the posterior fossa dura, by coagulation of the superior petrosal sinus. The tentorium was completely cut toward the incisura. After lesion debulking, the tumor was progressively removed by peeling the arachnoid from the lesion to maintain arachnoid planes and preserve the nerves and their blood supply. Postoperative imaging demonstrated complete tumor resection. The patient's symptoms improved, and there were no neurologic deficits on follow-up. Extensive laboratory training is fundamental to be familiarized with the normal anatomic nuances and prepared to face the anatomy distorted by lesion. Informed consent was obtained from the patient for the procedure and publication of this operative video.

Venous Anatomy Influence on the Approach Selection of a Petroclival Clear Cell Meningioma With Associated Multiple Spinal Meningiomas: 2-Dimensional Operative Video

Preoperative careful evaluation of the sigmoid transverse sinus and its tributary veins is paramount for the safe surgical planning of petroclival lesions.1,2 When the vein of Labbé is running within the tentorium, classic petrosal approach involving transection of the tentorium is modified to avoid the risk of postoperative morbid temporal lobe venous infarcts.1-3 Thus, the surgical plan should be tailored to the specific patient anatomy as demonstrated in the presented case during which a transmastoid approach was followed, in the same surgical setting, by a middle fossa approach to resect a large petroclival clear cell meningioma with extension into Meckel cave. These meningiomas are WHO grade II tumors with a propensity to local recurrence and cerebrospinal fluid seeding.4 SMARCE1 mutations define this subtype of meningioma, with frequent familial inheritance, and predispose patients to both skull base and spinal clear cell meningiomas.5,6 Maximal surgical resection is the best initial treatment option allowing to withhold or delay the use of radiation in tumors frequently encountered in young patients.7 In this report, we demonstrate the microsurgical techniques deployed to achieve maximal resection of a petroclival clear cell meningioma and associated lumbar and sacral spinal meningiomas in a 20-yr-old patient with a familial SMARCE1 mutation. The patient agreed to the surgical intervention and to the use of her image.

Extirpation of Recurrent Petrous Apex Cholesterol Granuloma Through the Zygomatic Approach: 2-Dimensional Operative Video

Petrous apex cholesterol granulomas are believed to result from blockage of the normal aeration of the petrous air cells, resulting in a repetitive cycle of mucosal engorgement, hemorrhage, and granuloma formation.1 The lesion usually progressively expands causing compressive symptoms. The thick granulomatous wall envelopes various ages of breakdown products, including a cholesterol-containing fluid, which is typically hyperintense on T1 and T2 weighted magnetic resonance imaging. Drainage procedures, regardless of the route (endoscopic, endonasal, or transtemporal), with or without stenting or marsupialization, will only temporarily drain this cholesterol-containing fluid, with consequently frequent recurrences.2-5 A total exoneration of the granuloma and obliteration of the cavity with vascularized tissue will assure a more durable outcome.1 The extradural zygomatic/middle fossa approach provides a short distance to the petrous apex and is purely extradural. By sectioning the zygoma, temporal lobe retraction is avoided.6 We present a case of a 29-yr-old male who presented in the year 2000 with progression of a left petrous apex cholesterol granuloma despite 2 previous drainage and stenting procedures.  The patient consented for surgery and photo publication. Images in video at 2:41 © JNSPG, republished from Eisenberg et al1 with permission.

Modern endoscopic skull base neurosurgery

INTRODUCTION

Since the early use of the endoscopic view for treating simple intrasellar pituitary adenomas, the skull base surgery has experienced an unprecedented revolution elevating the treatment of skull base lesions to the next level in proficiency and excellence of care.

METHODS

We have reviewed the preclinical and clinical evidence supporting the use of the endoscope in the treatment of skull base lesions. In this article, we aim to discuss and provide a wide view of the current indications and future perspectives of the endoscopic endonasal approaches (EEA) and of the endoscopic transcranial approaches.

RESULTS

As in the development of any other technique, EEA have gone through a transformation process from theoretical anatomic models to a pragmatic clinical use. Along the way, EEA have required several modifications, as well as pushbacks in the application of this technique in some indications. This process has resulted in the provision of an additional tool to the current surgical armamentarium that allows the skull base surgeon to face most challenging lesions along the skull base.

CONCLUSIONS

The judicious combination of transcranial and endoscopic-transnasal approaches warrants highest chances of achieving satisfactory tumors resection with a reduced risk of complications.

The BONEBRIDGE active transcutaneous bone conduction implant: effects of location, lifts and screws on sound transmission

BACKGROUND

The BONEBRIDGE (MED-EL, Innsbruck, Austria) is a bone-conduction implant used in the treatment of conductive and mixed hearing loss. The BONEBRIDGE consists of an external audio processor and a bone-conduction floating mass transducer that is surgically implanted into the skull in either the transmastoid, retrosigmoid or middle fossa regions. The manufacturer includes self-tapping screws to secure the transducer; however, self-drilling screws have also been used with success. In cases where the skull is not thick enough to house the transducer, lifts are available in a variety of sizes to elevate the transducer away from the skull. The objective of the present study was to investigate the effects of screw type, lift thickness, and implant location on the sound transmission of the BONEBRIDGE.

METHOD

Six cadaveric temporal bones were embalmed and dried for use in this study. In each sample, a hole was drilled in each of the three implant locations to house the implant transducer. At the middle fossa, six pairs of screw holes were pre-drilled; four pairs to be used with self-tapping screws and lifts (1, 2, 3, and 4 mm thick lifts, respectively), one pair with self-tapping screws and no lifts, and one pair with self-drilling screws and no lifts. At the transmastoid and retrosigmoid locations, one pair of screw holes were pre-drilled in each for the use of the self-tapping screws. The vibration of transmitted sound to the cochlea was measured using a laser Doppler vibrometry technique. The measurements were performed on the cochlear promontory at eight discrete frequencies (0.5, 0.75, 1, 1.5, 2, 3, 4 and 6 kHz). Vibration velocity of the cochlear wall was measured in all samples. Measurements were analyzed using a single-factor ANOVA to investigate the effect of each modification.

RESULTS

No significant differences were found related to either screw type, lift thickness, or implant location.

CONCLUSIONS

This is the first known study to evaluate the effect of screw type, lift thickness, and implant location on the sound transmission produced by the BONEBRIDGE bone-conduction implant. Further studies may benefit from analysis using fresh cadaveric samples or in-vivo measurements.

Microsurgical Techniques for Exposing the Internal Maxillary Artery in Cerebral Revascularization Surgery: A Comparative Cadaver Study

BACKGROUND

The internal maxillary artery (IMAX) is currently considered one of the main donor vessels in extracranial-to-intracranial bypass surgeries. Four main techniques for harvesting the IMAX have been described: via the anterior medial infratemporal fossa (AMITF), the middle infratemporal fossa (MITF), the anterior lateral middle fossa (ALMF), and the lateral middle fossa (LMF). The advantages and limitations of these techniques have not yet been systematically evaluated and compared.

METHODS

Twenty-five cadaver specimens were used to evaluate the harvesting technique. The length and the caliber of the targeted IMAX segments, as well as the depth from the operating plane to the IMAX, surgical time, and surgical area of exposure, were analyzed.

RESULTS

The MITF technique provided the greatest operating area of exposure (mean, 3.88 ± 0.97 cm²). The LMF and MITF techniques provided the largest IMAX caliber (mean, 3.1 ± 0.4 mm and 3.0 ± 0.3 mm, respectively). The ALMF technique provided the shallowest operative depth as well as the least time of exposure (21.8 minutes). The MITF technique exposed the longest IMAX segment (mean, 18.8 ± 3.5 mm).

CONCLUSIONS

Advantages of the AMITF and MITF techniques include anatomic simplicity, absence of skull base drilling, and greater discretion in muscle dissection. These properties can simplify the anastomosis procedure compared with the ALMF and LMF techniques. Identification of the IMAX pattern is important before selecting the approach for this bypass operation.

Extended Anterior Petrosectomy Through the Transcranial Middle Fossa Approach and Extended Endoscopic Transsphenoidal-Transclival Approach: Qualitative and Quantitative Anatomic Analysis

BACKGROUND

Petroclival tumors and ventrolateral lesions of the pons present unique surgical challenges. This cadaveric study provides qualitative and quantitative anatomic comparison for an anterior petrous apicectomy through the transcranial middle fossa (TMF) and expanded endoscopic transsphenoidal-transclival approaches.

METHODS

In 10 silicone-injected heads, the petrous apex and clivus were drilled extradurally using middle fossa and endonasal approaches. With in situ and frameless stereotactic navigation, we defined consistent points to compare working areas, bone removal volumes, approach angles, and surgical freedom.

RESULTS

Mean exposed TMF area (21.03 ± 3.46 cm²) achieved a 44.71 ± 4.13° working angle to the brainstem between cranial nerves V and VI. Kawase's rhomboid area measured 1.76 ± 0.34 cm², and bone removal averaged 1.20 ± 0.12 cm³ at the petrous apex. Surgical freedom on the lateral brainstem was higher halfway between cranial nerves V and VI at the center of the rhomboid compared with midline at the basilar sulcus (P < 0.01). After clivectomy and petrous apicectomy, mean exposed expanded endoscopic transsphenoidal-transclival area was 5.29 ± 0.66 cm². Approach from either nostril showed no statistically significant differences in surgical freedom at the foramen lacerum and midpoint basilar sulcus. At the petrous apex, bone volume removed and area exposed were significantly larger for the TMF approach (P < 0.001).

CONCLUSIONS

Expanded transclival anterior petrosectomy through the TMF approach provides an adequate corridor to lesions in the upper ventrolateral pons. The expanded endoscopic transsphenoidal-transclival approach better fits midline lesions not extending laterally beyond cranial nerve VI and C3 carotid when evaluating normal anatomic parameters.

The extended eyebrow approach a cadaveric stepwise dissection

BACKGROUND

The eyebrow incision supraorbital approach is limited by the lack of exposure of the sylvian fissure exposure. By extending the skin incision 15 mm posteriorly and the supraorbital craniotomy beneath the superior temporal line, proximal sylvian dissection is achievable, and the surgical exposure is drastically improved.

METHODS

Throughout a cadaveric stepwise dissection and a pertinent anatomical analysis, we describe in detail the surgical technique of the extended eyebrow approach (xEBA). We additionally highlight main anatomical elements involved in this approach and provide technical nuances to avoid complications.

CONCLUSION

xEBA is a versatile technique that uses the pretemporal, transylvian, and subfrontal corridor to enhance surgical exposure around the anterior cranial fossa.

Middle fossa meningiomas

The middle cranial fossa is bounded anteriorly by the sphenoid ridge, medially by the lateral wall of the cavernous sinus and Meckel's cave, posteriorly by the sphenoid wing and petrous bone, and laterally by the greater wing of sphenoid and squamous temporal bone. In normal individuals, unnamed venous channels within the dura and arachnoid granulations can be seen on the floor of this fossa by the operating surgeon. Meningiomas arising mainly from the dura of the floor are uncommon, and middle fossa meningiomas have been arbitrarily named so based on an attachment of more than 75% to this location. They tend to present clinically at a large size and require special considerations for surgical treatment.

Possible cerebrospinal fluid pathways in the middle fossa floor and pterional diploe: a magnetic resonance imaging study

PURPOSE

There has not been a study documenting the distribution of cerebrospinal fluid (CSF) pathways in the anterolateral base of the middle fossa (ALB) and diploe of the pterional region (Pt). The present study aimed to delineate these pathways using magnetic resonance imaging.

METHODS

Thin-sliced, axial, and coronal T2-weighted sequences were performed for a total of 358 outpatients, including 20 pediatric patients.

RESULTS

Adult population: CSF-filled channels were identified on axial images in the ALB in 57% and in the diploe of the Pt in 65% of 338 patients. These pathways showed variable morphology and number bilaterally. CSF-filled channels were identified on coronal images in the ALB in 14% and in the diploe of the Pt in 100% of 59 patients. These were delineated as linear structures of variable number and thickness. Eleven percent of the pathways identified in the ALB was connected with extracranial channels. Pediatric population: CSF-filled channels were identified on axial images in the ALB in 75% and in the diploe of the Pt in 80% of 20 patients.

CONCLUSIONS

The ALB and diploe of the Pt may function as CSF pathways in children and adults. The pathways in the ALB can be a CSF-drainage route connecting to the extracranial sites.

Cochlear implantation via middle fossa approach - a case report

Objective: Cochlear implantation is routinely performed all over the world via the post-auricular, facial recess approach. Our case study describes the middle fossa approach for the management of bilateral profound sensorineural hearing loss in a female child with multiple external, middle and inner ear malformations. The middle fossa approach has been reported sporadically and has been used inconsistently in patients with chronic otitis media and inner ear malformations. Case study: A 3-year-old female child presented with bilateral profound sensorineural hearing loss, bilateral anotia, right cochlear nerve agenesis, right facial paralysis, bilateral mild inner ear dysplasia and an aberrant left facial nerve covering the left round window. Further tests indicated that she was a suitable candidate for cochlear implantation and was medically cleared for surgery. In view of the multiple malformations and high risk of injury to her only functioning left facial nerve on the side with a cochlear nerve, cochlear implantation via a middle fossa approach was performed. Conclusion: Middle fossa approach to cochlear implantation is challenging but can be safely performed even in children and offers an option in patients when a routine mastoidectomy, facial recess and round window approach cannot be undertaken.

Endoscopic treatment of middle fossa arachnoid cysts

BACKGROUND

Endoscopic treatment of middle fossa arachnoid cysts is an alternative option to microsurgical fenestration and shunting procedures. The procedure is minimally invasive and obviates the morbidity of craniotomy and shunting.

METHODS

Operative charts and videos of patients undergoing endoscopic fenestration of middle fossa arachnoid cysts were retrieved from the senior author's database of endoscopic procedures and reviewed. Description of the surgical techniques was then formulated.

CONCLUSIONS

Endoscopic fenestration of middle fossa arachnoid cysts entails communicating the cyst cavity to the basal cisterns via multiple fenestrations that should be made as large as possible with care to avoid injury of the juxtaposed neurovascular structures.

Resolution of Middle Fossa Arachnoid Cyst after Minor Head Trauma - Stages of Resolution on MRI: Case Report and Literature Review

Arachnoid cysts (ACs) are frequently encountered in pediatric neurosurgical practice. Their natural history and optimum treatment are not well determined. The authors describe a resolution of asymptomatic middle fossa AC after trivial head trauma in a 7-year-old child. Intracystic bleeding was noticed on interval MRI. Serial MRI follow-up demonstrates stages of resolution of the AC that did not require surgical intervention. Few cases of nonsurgical AC disappearance have been reported, much fewer with trauma as a triggering factor. Here, we present the stages of resolution in images.

Transmastoid resurfacing versus middle fossa plugging for repair of superior canal dehiscence: Comparison of techniques from a retrospective cohort

Objective

To compare and contrast our experience with middle cranial fossa approach (MFR) and transmastoid approach with capping of the dehiscence (TMR) of superior semicircular canal dehiscence and to determine guidelines to help guide management of these patients.

Methods

All patients from 2005 to 2014 with symptomatic superior semicircular canal dehiscence syndrome with dehiscence demonstrated on CT scan of the temporal bone who underwent surgical repair and had a minimum 3 months of follow up. Surgical repair via the MFR or TMR, preoperative CT temporal bone, preoperative, and postoperative cervical vestibular evoked myogenic potential (cVEMP) testing and anterior canal video head thrust testing (vHIT). Success of repair was stratified as complete success, moderate success, mild success, or failure based on resolution of all symptoms, the chief complaint, some symptoms, or no improvement, respectively.

Results

A total of 29 ears in 27 patients underwent surgical repair of canal dehiscence. Complete or moderate success was seen in 71% of the MFR group compared to 80% of the TMR group. There were zero failures with the MFR group and no major intracranial complications. There were 2 failures out of 15 ears that underwent the TMR. Residual symptoms were most commonly vertigo or disequilibrium in the MFR and aural fullness or autophony in the TMR groups, respectively. MFR hospital stay was approximately 2 days longer. Average cVEMP threshold shifted 18 dB with surgical correction in the MFR group. A 29 dB average shift was seen in the TMR group. The MFR group had a significant reduction in their anterior canal gain compared to the TMR group.

Conclusions

TMR is a less invasive alternative to MFR. However, in our series, we have not seen any intracranial complications (aphasia, stroke, seizures, etc.) in our MFR patients. Interestingly, vestibular symptoms were better addressed than audiological symptoms by the TMR suggesting its usefulness as a less invasive option for patients with primarily vestibular complaints. Residual auditory symptoms in TMR patients may be due to the flow of acoustic energy from the superior canal to the mastoid cavity through an incompletely sealed third window.

Pediatric neurofibromatosis type 2: clinical and molecular presentation, management of vestibular schwannomas, and hearing rehabilitation

OBJECTIVE

This study aims to describe the clinical and molecular presentation of pediatric neurofibromatosis type 2 (NF2) and the subsequent management of vestibular schwannomas (VS) and hearing rehabilitation.

METHODS

This is a single-center retrospective study of neurofibromatosis type 2 diagnosed before the age of 18 years old from 1997. Natural history of vestibular schwannomas and surgical outcomes were evaluated using volumetric MRI, hearing, and facial nerve assessment. Patients included in chemotherapy protocols were excluded.

RESULTS

From a database of 80 patients followed up for NF2 on a regular basis, 25 patients were eligible (11 sporadic cases, 14 inherited in five families). The mean age at diagnosis was 11.6 years old. The average clinical follow-up was 6.5 years. NF2 mutation was identified in 81 % of the probands. The average growth rate based on the maximum linear diameter (DGR) was 1.68 mm/year (n = 33, average follow-up 4.22 years) and 545 mm³/year in volumetric assessment (VGR) for VS larger than 1 cm (n = 21, average follow-up 3.4 years). In unoperated ears, hearing was stable in about 50 % of ears. The mean change in dB HL was 9.5 dB/year for pure-tone average and 3.5 for speech-recognition threshold (n = 34, 5.5 years 1-12). Eight children required removal through a translabyrinthine approach (mean follow-up was 4.5 years), six patients were operated on for hearing preservation (mean postoperative follow-up 4.3 years). Six patients were eligible for hearing rehabilitation with cochlear implantation (I), and five received placement of an auditory brainstem implant.

CONCLUSION

Early diagnosis and treatment of small growing VS should be carefully discussed considering familial history and possible rehabilitation with a CI.

Long-term results of middle fossa plugging of superior semicircular canal dehiscences: clinically and instrumentally demonstrated efficiency in a retrospective series of 16 ears

The objective of this study is to report the surgical outcome after middle fossa approach (MFA) plugging in patients suffering from a superior semi-circular canal dehiscence (SCD) syndrome. This is a retrospective case review. Tertiary referral center. Sixteen ears in 13 patients with a SCD syndrome suffering from severe and disabling vestibular symptoms with a bony dehiscence on CT scan >3 mm and decreased threshold of cervical vestibular evoked potentials (cVEMPs). We assessed preoperatively: clinical symptoms, hearing, cVEMPs threshold, size of dehiscence and videonystagmography (VNG) with caloric and 100 Hz vibratory tests. Postoperatively, we noted occurrences of neurosurgical complication, evolution of audiological and vestibular symptoms, and evaluation of cVEMP data. Tullio’s phenomenon was observed in 13 cases (81.3 %) and subjectively reported hearing loss in seven (43.7 %). All patients were so disabled that they had to stop working. No neurosurgical complications were observed in the postoperative course. In three cases (16.6 %), an ipsilateral and transitory immediate postoperative vestibular deficit associated with a sensorineural hearing loss (SNHL) was noted, which totally resolved with steroids and bed rest. All patients were relieved of audiological and vestibular symptoms and could return to normal activity with a mean follow-up of 31.1 months (range 3–95). No patient had residual SNHL. cVEMPs were performed in 14 ears postoperatively and were normalized in 12 (85.7 %). Two of the three patients operated on both sides kept some degree of unsteadiness and oscillopsia. MFA plugging of the superior semi-circular canal is an efficient and non-hearing deteriorating procedure.

Lateral transzygomatic middle fossa approach and its extensions: surgical technique and 3D anatomy

BACKGROUND

Various approaches to lesions involving the middle fossa and cavernous sinus (CS), with and without posterior fossa extension have been described. In the present study, we describe the surgical technique for the extradural lateral tranzygomatic middle fossa approach and its extensions, highlight relevant 3D anatomy.

METHODS

Simulations of the lateral transzygomatic middle fossa approach and its extensions were performed in four silicon-injected formalin fixed cadaveric heads. The step-by-step description and relevant anatomy was documented with 3D photographs.

RESULT

The lateral transzygomatic middle fossa approach is particularly useful for lesions involving the middle fossa with and without CS invasion, extending to the posterior fossa and involving the clinoidal region. This approach incorporates direct lateral positioning of patient, frontotemporal craniotomy with zygomatic arch osteotomy, extradural elevation of the temporal lobe, and delamination of the outer layer of the lateral CS wall. Extradural drilling of the sphenoid wing and anterior clinoid process allows entry into the CS through the superior wall and exposure of the clinoidal segment of the ICA. Posteriorly, drilling the petrous apex allows exposure of the ventral brainstem from trigeminal to facial nerve and can be extended to the interpeduncular fossa by division of the superior petrosal sinus.

CONCLUSION

The present study illustrates 3D anatomical relationships of the lateral transzygomatic middle fossa approach with its extensions. This approach allows wide access to different topographic areas (clinoidal region and clinoidal ICA, the entire CS, and the posterior fossa from the interpeduncular fossa to the facial nerve) via a lateral trajectory. Precise knowledge of technique and anatomy is necessary to properly execute this approach.