Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Surgical Anatomy of the Middle Fossa Approaches and Anterior Petrosectomy, Surgical Principles, and Illustrative Cases

Introduction The middle fossa (MF) approaches encompass a group of versatile surgical accesses to pathologies in the MF, internal auditory canal (IAC), and superomedial aspect of the posterior fossa. Although many descriptions of the MF approaches have been published, a practical surgical guide that allows an easy understanding for Skull Base trainees is needed.

Methods Three formalin-fixed, colored-injected specimens were dissected under microscopic magnification (six sides). A MF craniotomy followed by IAC drilling was performed on three sides, and anterior petrosectomy (AP) was performed in the remaining three sides. The anatomical dissection was documented in stepwise three-dimensional photographic images. Following dissection, representative case applications were reviewed.

Results The MF approach provides direct access to the MF structures and IAC. The AP provides excellent access to the superomedial aspect of the posterior fossa. Key common steps include: positioning and skin incision; scalp and muscle flaps; burr holes; craniotomy flap elevation; dural dissection along the petrous ridge; division of the middle meningeal artery; and exposure of the greater superficial petrosal nerve, tegmen tympani, and V3. Then, to approach the IAC: superior IAC drilling, and longitudinal dura opening. The area drilled in the AP approach forms a pentagon limited by the petrous internal carotid artery, cochlea, IAC, petrous ridge, and lateral border of V3.

Conclusion The MF approaches are challenging. Operatively oriented skull base dissections provide a crucial foundation for learning these techniques. We describe comprehensive step-by-step approaches intended to develop familiarity in the cadaver laboratory and facilitate understanding of their potential for skull base disorders. Basic surgical principles are described to help in the operating room as well as illustrative cases.

Endoscopic Endonasal Approaches to the Clivus with No Violation of the Nasopharynx: Surgical Anatomy and Clinical Illustration

Background Despite the use of vascularized intranasal flaps, endoscopic endonasal posterior fossa defects remain surgically challenging with high rates of postoperative cerebrospinal fluid leak.

Objective The aim of the study is to describe a novel surgical technique that allows complete drilling of the clivus and exposure of the craniovertebral junction with preservation of the nasopharynx.

Methods Two formalin-fixed latex-injected anatomical specimens were used to confirm feasibility of the technique. Two surgical approaches were used: sole endoscopic endonasal approach and transnasion approach. The sole endonasal approach was used in a patient with a petroclival meningioma.

Results In both anatomical dissections, the inferior clivectomy with exposure of the foramen magnum was achieved with a sole endoscopic endonasal approach. The addition of the transnasion approach helped to complete drilling of the inferior border of the foramen magnum and exposure of the arch of C1.

Conclusion This study shows the anatomical feasibility of total clivectomy and exposure of the craniovertebral junction with preservation of the nasopharynx. A more favorable anatomical posterior fossa defect for the reconstruction is achieved with this technique. Further clinical studies are needed to assess if this change would impact the postoperative CSF leak rate.

Cerebral sinus thrombosis as an initial symptom of acute promyelocytic leukemia: Case report and literature review

Background:

Cerebral sinus thrombosis as presentation of acute promyelocytic leukemia (AMPL) is exceptional, with only three cases registered in the literature.

Case Description:

A 24-year-old female patient was transferred to our center after a car accident. The patient had a witnessed generalized seizure while driving. Computerized tomography (CT) demonstrated a temporal intraparenchymal hemorrhage and CT venogram diagnosed a cerebral sinus thrombosis on the left transverse and sigmoid sinus. The patient underwent surgical evacuation of the hematoma and was treated with anticoagulation 48 h after surgery. Pancytopenia alerted of a possible hematological disorder. The patient was subsequently diagnosed with AMPL and treated with arsenic trioxide. The patient had a complete neurological recovery with no postoperative complications.

Conclusion:

The management of cerebral sinus thrombosis in patients with AMPL remains controversial. The previous reported cases of cerebral sinus thrombosis preceding the diagnosis of AMPL are reviewed and treatment of cerebral sinus thrombosis with anticoagulation in the setting of intraparenchymal hemorrhage and bleeding disorders is also discussed.

Anatomical Step-by-Step Dissection of Complex Skull Base Approaches for Trainees: Endoscopic Endonasal Approach to the Orbit

Introduction  Although endonasal endoscopic approaches (EEA) to the orbit have been previously reported, a didactic resource for educating neurosurgery and otolaryngology trainees regarding the pertinent anatomy, techniques, and decision-making pearls is lacking. Methods  Six sides of three formalin-fixed, color latex-injected cadaveric specimens were dissected using 4-mm 0- and 30-degree rigid endoscopes, as well as standard endoscopic equipment, and a high-speed surgical drill. The anatomical dissection was documented in stepwise three-dimensional (3D) endoscopic images. Following dissection, representative case applications were reviewed. Results  EEA to the orbit provides excellent access to the medial and inferior orbital regions. Key steps include positioning and preoperative considerations, middle turbinate medialization, uncinate process and ethmoid bulla removal, complete ethmoidectomy, sphenoidotomy, maxillary antrostomy, lamina papyracea resection, orbital apex and optic canal decompression, orbital floor resection, periorbita opening, dissection of the extraconal fat, and final exposure of the orbit contents via the medial-inferior recti corridor. Conclusion  EEA to the orbit is challenging, in particular for trainees unfamiliar with nasal and paranasal sinus anatomy. Operatively oriented neuroanatomy dissections are crucial didactic resources in preparation for practical endonasal applications in the operating room (OR). This approach provides optimal exposure to the inferior and medial orbit to treat a wide variety of pathologies. We describe a comprehensive step-by-step curriculum directed to any audience willing to master this endoscopic skull base approach.

Intraoperative use of heads-up display in skull base surgery

In this video, the authors highlight the applications of virtual reality and heads-up display in skull base surgery by presenting the case of a 45-year-old woman with an incidental large clinoid meningioma extending into the posterior fossa. The patient underwent preoperative endovascular tumor embolization to facilitate tumor resection and reduce blood loss, followed by a right pterional craniotomy. The use of intraoperative Doppler, intraoperative neurophysiological monitoring, and endoscope-assisted microsurgery is also featured. A subtotal resection was planned given tumor encasement of the posterior communicating and anterior choroidal arteries. No new neurological deficits were noted after the surgical procedure.

The video can be found here: https://stream.cadmore.media/r10.3171/2021.10.FOCVID21177

Neuronavigated Ultrasound in Neuro-Oncology: A True Real-Time Intraoperative Image

OBJECTIVE

Ultrasound is considered a real-time imaging method in neuro-oncology because of its highly rapid image acquisition time. However, to our knowledge, there are no studies that analyze the additional surgical time that it requires.

METHODS

A prospective study of 100 patients who underwent intra-axial brain tumor resection with navigated intraoperative ultrasound. The primary outcomes were lesion visibility grade on ultrasound and concordance with preoperative magnetic resonance imaging (MRI) scan, intraoperative ultrasound usage time, and percentage of tumor resection on ultrasound and comparison with postoperative MRI scan.

RESULTS

The breakdown of patients included the following: 53 high-grade gliomas, 26 metastases, 14 low-grade gliomas, and 7 others. Ninety-six percent of lesions were clearly visualized. The tumor border was clearly delimited in 71%. Concordance with preoperative MRI scan was 78% (P < 0.001). The mean time ± SD for sterile covering of the probe was 2.16 ± 0.5 minutes, and the mean image acquisition time was 2.49 ± 1.26 minutes. Insular tumor location, low-grade glioma, awake surgery, and recurrent tumor were statistically associated with an increased ultrasound usage time. Ultrasound had a sensitivity of 94.4% and a specificity of 100% for residual tumor detection.

CONCLUSIONS

Neuronavigated ultrasound can be considered a truly real-time intraoperative imaging method because it does not increase surgical time significantly and provides optimal visualization of intra-axial brain lesions and residual tumor.

Benign notochordal cell tumor of the clivus with chordoma component: report of 2 cases

Benign notochordal cell tumors (BNCTs) are considered to be benign intraosseous lesions of notochord origin; however, recent spine studies have suggested the possibility that some chordomas arise from BNCTs. Here, the authors describe two cases demonstrating histological features of BNCT and concomitant chordoma involving the clivus, which, to the best of the authors' knowledge, have not been previously documented at this anatomical site.An 18-year-old female presented with an incidentally discovered clival mass. Magnetic resonance imaging revealed a 2.8-cm nonenhancing lesion in the upper clivus that was T2 hyperintense and T1 hypointense. She underwent an uneventful endoscopic transsphenoidal resection. Histologically, the tumor demonstrated areas of classic chordoma and a distinct intraosseous BNCT component. The patient completed adjuvant radiation therapy. Follow-up showed no recurrence at 18 months.A 39-year-old male presented with an incidentally discovered 2.8-cm clival lesion. The nonenhancing mass was T2 hyperintense and T1 hypointense. Surgical removal of the lesion was performed through an endoscopic transsphenoidal approach. Histological analysis revealed areas of BNCT with typical features of chordoma. Follow-up did not demonstrate recurrence at 4 years.These cases document histologically concomitant BNCT and chordoma involving the clivus, suggesting that the BNCT component may be a precursor of chordoma.

[Non-aneurysmal subarachnoid haemorrhage secondary to panarteritis nodosa at paediatric age: a case report]

INTRODUCTION

Polyarteritis nodosa is a necrotizing vasculitis that mainly affects small and medium-sized arteries in skin and internal organs. Neurological involvement is reported in around 25% of cases: ischemic stroke is relatively common, but haemorrhagic lesions are extremely rare. Subarachnoid haemorrhage in polyarteritis nodosa is an uncommon expression of this disease, mostly associated with aneurism rupture. To the best of the authors' knowledge, there is just one published case in pediatric age with polyarteritis nodosa and subarachnoid haemorrhage with no underlying aneurismal disease.

CASE REPORT

A 7-year-old girl, who presented a non-aneurismal subarachnoid haemorrhage with intraparenchymal extension in the left basal ganglia. She was previously diagnosed with polyarteritis nodosa and prothrombotic condition, being under immunosuppressive and anti-platelet treatment at that moment.

CONCLUSIONS

The clinical features of polyarteritis nodosa together with continued anti-platelet therapy to prevent thromboembolic disease in this patient could have predisposed to the haemorrhagic event in the process of cerebral vasculitis. Standard subarachnoid haemorrhage management is initially required in such cases as cerebral aneurysms are the most common cause of haemorrhage in the context of polyarteritis nodosa disease.