Tomasz Szmuda, Shan Ali, and Paweł Słoniewski
Ossama Al-Mefty, Edward R. Laws, and A. John Popp
As it does periodically, the United States healthcare system is, yet again, undergoing a period of change on multiple fronts, including internal initiatives in education, quality, and the workforce, as well as external pressure responding to changes in reimbursement and oversight. In such times, looking back at the foundations of our specialty is helpful, allowing often-beleaguered neurosurgeons to reflect upon what it means to be a neurosurgeon, and how they can be assured that our specialty will continue to flourish in the future. Harvey Cushing envisioned, espoused, and developed neurological surgery as a “special field”—a comprehensive, encompassing, and distinct discipline that studies the nervous system and manages neurological disorders. It provides surgical intervention for the treatment of neurological disorders; it by no means was meant to be developed as a mere technical or procedural skill; it is neither a subspecialty of surgery nor a branch of neurology; it is a “special field” that has flourished to become a crown jewel in the realm of medicine. Herein is a perspective that brings the inception and future of this concept to light. A specialty that is to live and flourish should stand on and recognize its roots.
Marcio S. Rassi, Sashank Prasad, Anil Can, Svetlana Pravdenkova, Rami Almefty, and Ossama Al-Mefty
Although meningiomas frequently involve the optic nerve, primary optic nerve sheath meningiomas (ONSMs) are rare, accounting for only 1% of all meningiomas. Given the high risk of vision loss with these tumors, surgical intervention is seldom considered, and radiation or observation is commonly applied. Here, the authors describe the visual outcomes for a series of patients who were treated with surgery aiming at maximal tumor resection and highlight their prognostic factors.
The authors retrospectively analyzed the data for 8 patients with intracanalicular ONSMs who had been surgically treated by the senior author (O.A.) between 1998 and 2016. Meningiomas extending into the optic canal from the intracranial cavity (i.e., clinoid, sphenoid wing, tuberculum sellae, diaphragma sellae) were excluded. Diagnosis was based on ophthalmological, radiological, and intraoperative findings, which were confirmed by the typical histological findings. Preoperative, postoperative, and follow-up visual assessments were performed by neuro-ophthalmologists in all cases.
The patients included 7 females and 1 male. The mean age at diagnosis was 45.1 years (range 25.0–70.0 years). Mean duration of follow-up was 38.9 months (range 3.0–88.0 months). All patients reported visual complaints, and all had objective evidence of optic nerve dysfunction. Their evaluation included visual field, visual acuity, funduscopy, and retinal fiber thickness. Total resection was obtained in 4 cases. Comparing preoperative and postoperative visual function revealed that 4 patients had improvement at the last follow-up, 1 patient had stable vision, and 3 patients had decreased function but none had total vision loss. All patients with good preoperative visual acuity maintained this status following surgical treatment. There was no surgical mortality or infection. Operative complications included binocular diplopia in 4 patients, which remitted spontaneously.
Surgery can play a beneficial role in the primary treatment of ONSM, especially lesions located in the posterior third of the nerve. Total removal can be achieved with vision preservation or improvement, without major surgical complications, especially at early stages of the disease. Patients with good preoperative vision and CSF flow in the optic sheath have better chances of a favorable outcome than those with poor vision.
Walid I. Essayed, Prashin Unadkat, Ahmed Hosny, Sarah Frisken, Marcio S. Rassi, Srinivasan Mukundan Jr., James C. Weaver, Ossama Al-Mefty, Alexandra J. Golby, and Ian F. Dunn
Endoscopic endonasal approaches are increasingly performed for the surgical treatment of multiple skull base pathologies. Preventing postoperative CSF leaks remains a major challenge, particularly in extended approaches. In this study, the authors assessed the potential use of modern multimaterial 3D printing and neuronavigation to help model these extended defects and develop specifically tailored prostheses for reconstructive purposes.
Extended endoscopic endonasal skull base approaches were performed on 3 human cadaveric heads. Preprocedure and intraprocedure CT scans were completed and were used to segment and design extended and tailored skull base models. Multimaterial models with different core/edge interfaces were 3D printed for implantation trials. A novel application of the intraoperative landmark acquisition method was used to transfer the navigation, helping to tailor the extended models.
Prostheses were created based on preoperative and intraoperative CT scans. The navigation transfer offered sufficiently accurate data to tailor the preprinted extended skull base defect prostheses. Successful implantation of the skull base prostheses was achieved in all specimens. The progressive flexibility gradient of the models’ edges offered the best compromise for easy intranasal maneuverability, anchoring, and structural stability. Prostheses printed based on intraprocedure CT scans were accurate in shape but slightly undersized.
Preoperative 3D printing of patient-specific skull base models is achievable for extended endoscopic endonasal surgery. The careful spatial modeling and the use of a flexibility gradient in the design helped achieve the most stable reconstruction. Neuronavigation can help tailor preprinted prostheses.
Omar Arnaout and Ossama Al-Mefty
The authors present the case of a 56-year-old patient who presented with a large petroclival meningioma and clinical symptoms of brainstem compression and hydrocephalus. The authors describe a two-stage combined petrosal approach for complete resection of the tumor. The nuances of the approach and microsurgical technique are discussed, as well as the radiographic and clinical outcomes.
The video can be found here: https://youtu.be/T90vUIPKQsA.
Christos Koutsarnakis, Aristotelis V. Kalyvas, and George Stranjalis
Yasser Jeelani, Abdulkerim Gokoglu, Tomer Anor, Ossama Al-Mefty, and Alan R. Cohen
Conventional approaches to the atrium of the lateral ventricle may be associated with complications related to direct cortical injury or brain retraction. The authors describe a novel approach to the atrium through a retrosigmoid transtentorial transcollateral sulcus corridor.
Bilateral retrosigmoid craniotomies were performed on 4 formalin-fixed, colored latex–injected human cadaver heads (a total of 8 approaches). Microsurgical dissections were performed under 3× to 24× magnification, and endoscopic visualization was provided by 0° and 30° rigid endoscope lens systems. Image guidance was provided by coupling an electromagnetic tracking system with an open source software platform. Objective measurements on cortical thickness traversed and total depth of exposure were recorded. Additionally, the basal occipitotemporal surfaces of 10 separate cerebral hemisphere specimens were examined to define the surface topography of sulci and gyri, with attention to the appearance and anatomical patterns and variations of the collateral sulcus and the surrounding gyri.
The retrosigmoid approach allowed for clear visualization of the basal occipitotemporal surface. The collateral sulcus was identified and permitted easy endoscopic access to the ventricular atrium. The conical corridor thus obtained provided an average base working area of 3.9 cm2 at an average depth of 4.5 cm. The mean cortical thickness traversed to enter the ventricle was 1.4 cm. The intraventricular anatomy of the ipsilateral ventricle was defined clearly in all 8 exposures in this manner. The anatomy of the basal occipitotemporal surface, observed in a total of 18 hemispheres, showed a consistent pattern, with the collateral sulcus abutted by the parahippocampal gyrus medially, and the fusiform and lingual gyrus laterally. The collateral sulcus was found to be caudally bifurcated in 14 of the 18 specimens.
The retrosigmoid supracerebellar transtentorial transcollateral sulcus approach is technically feasible. This approach has the potential advantage of providing a short and direct path to the atrium, hence avoiding violation of deep neurovascular structures and preserving eloquent areas. Although this approach appears unconventional, it may provide a minimally invasive option for the surgical management of selected lesions within the atrium of the lateral ventricle.
Wenya Linda Bi, Malak Abedalthagafi, Peleg Horowitz, Pankaj K. Agarwalla, Yu Mei, Ayal A. Aizer, Ryan Brewster, Gavin P. Dunn, Ossama Al-Mefty, Brian M. Alexander, Sandro Santagata, Rameen Beroukhim, and Ian F. Dunn
Meningiomas are the most common primary intracranial neoplasms in adults. Current histopathological grading schemes do not consistently predict their natural history. Classic cytogenetic studies have disclosed a progressive course of chromosomal aberrations, especially in high-grade meningiomas. Furthermore, the recent application of unbiased next-generation sequencing approaches has implicated several novel genes whose mutations underlie a substantial percentage of meningiomas. These insights may serve to craft a molecular taxonomy for meningiomas and highlight putative therapeutic targets in a new era of rational biology-informed precision medicine.
Emad Aboud and Ossama Al-Mefty
Mohammad Abolfotoh, Wenya Linda Bi, Chang-Ki Hong, Kaith K. Almefty, Abraham Boskovitz, Ian F. Dunn, and Ossama Al-Mefty
The combined microscopic and endoscopic technique has shown significant advantages in the management of various lesions through different approaches. Endoscopic-assisted techniques have frequently been applied to cerebellopontine angle (CPA) surgery in the context of minimally invasive craniotomies. In this paper the authors report on the use of the endoscope in the CPA as a tool to increase the extent of resection, minimize complications, and preserve the function of the delicate CPA structures. They also describe a technique of the simultaneous use of the microscope and endoscope in the CPA and dissection of CPA tumors under tandem endoscopic and microscopic vision to overcome the shortcomings of introducing the endoscope alone in the CPA. The reliability of using the microscope alone in dissecting CPA tumors is evaluated, as is the effectiveness of the combined technique in increasing the resectability of various types of CPA tumors.
The authors conducted a retrospective analysis of 50 patients who underwent combined microscopic-endoscopic resection of CPA tumors by the senior author over a period of 3 years (February 2011 to February 2014) at Brigham and Women's Hospital, Harvard Medical School. The reliability of the extent of microscopic removal was evaluated with endoscopic exploration. Additional resection was performed with both microscopic and the combined microscopic-endoscopic technique. Endoscopically verified total resection was validated by intraoperative or postoperative MRI. The function of the cranial nerves was evaluated to assess the impact of the combined technique on their function.
A tumor remnant was endoscopically identified in 69% of the 26 patients who were believed to have microscopic total resection. The utilization of the endoscopic visualization and dissection increased endoscopically verified total removal to 38 patients, and 82% of these patients had no sign of residual tumor on postoperative imaging. The technique was most effective with epidermoid tumors. There were a total of 17 new cranial nerve deficits in 10 patients. Preoperative fifth cranial nerve deficits improved in 52% and hearing improved in 29% of patients after surgery.
This method provides simultaneous microscopic and endoscopic visualization and dissection techniques through skull-base approaches to CPA tumors. It overcomes some of the shortcomings of endoscopic-assisted surgery, further extends the surgical field, and increases the radicality of tumor resection with good functional outcomes.