Skull Base Surgical Techniques Research Articles

The development of a pediatric skull base team: how, where and why?

The purpose of this review is to describe the development of pediatric skull base surgical techniques and illustrate the advantages of pediatric endonasal skull base surgery (ESBS) when applied in appropriate settings. Additionally, this manuscript endeavors to define the pediatric skull base team components, highlight circumstances amenable to the development of a pediatric skull base surgery team, and describe the relative advantages of independent pediatric teams versus incorporation with adult skull base practices. Multiple series published within the last decade have described the application of ESBS to the pediatric population, demonstrating adoption of these interventions in many academic centers. Most series include relatively small numbers of patients, highlighting the relative infrequency of anterior skull base pathology in the pediatric patient. Given the relatively low volume and high technical demands of this skillset, general guidelines for the timing, suggested training, and volume necessary to support a pediatric skull base team are offered. The interest in pediatric ESBS continues to expand though case volumes may limit maintenance of skills in lower volume centers. The development of a dedicated pediatric skull base team in areas where sufficient volume exists facilitates concentration of expertise and interdisciplinary relationships necessary to provide the highest level of care. Collaborating with adult skull base teams can enhance the pediatric team experience, increasing exposure to complex surgical planning and radiologic nuances. However, a pediatric-focused skull base team can tailor treatment to meet the specific psychosocial and developmental needs of children.

Current diagnosis and treatment of skull base osteomyelitis

Skull base osteomyelitis is a rare, refractory, and potentially fatal disease primarily caused by otogenic and sino rhinogenic infections. At times, it can mimic neoplasia complicating the diagnosis. With the use of antibiotics, advancements in diagnostic methods, and skull base surgical techniques, the mortality rate has significantly improved. However, the successful diagnosis and treatment of the disease is still challenging due to delayed diagnosis, lengthy treatment course, a tendency for relapse and lack of guidelines. Therefore, this article aims to review the progress in the diagnosis and treatment of skull base osteomyelitis.

History of Skull Base Surgery

Skull base surgery is a surgical field that involves the cooperation of multiple surgical and medical specialties, including neurosurgery, head-neck surgery, plastic-reconstructive surgery, radiation oncology, as well as multiple medical supporting teams. This field has been developed with the collaborative efforts of these medical specialties, and its history can be divided into five phases: Beginning of surgery(Prior to 1940); Early skull base surgery driven by the ENT-HN surgery group(1940-70); Conventional skull base surgery development based on anatomical, physiological knowledge and microsurgical equipment and technique(1970-90); Reflection and consolidation of the surgical dimension(1995-2005); and Evolution of endoscopic and new skull base surgical techniques(2005-). Several topics and advancements have improved this surgical field, such as access to the cavernous sinus, petrosal-temporal bone, and foramen magnum; concepts of minimally invasive surgical techniques; advanced endoscopic instruments; knowledge of biological assessments; and development of surgical robotics. To achieve a safe and effective surgery for cases of difficult cranial base lesions, clinicians must understand the origin of the surgical field, the detailed anatomy and physiology of the skull base, and the basic microsurgical techniques.

Surgical Education using Cadaver Dissection for Modern Practical Skull Base Surgical Techniques

より複雑かつ高度な頭蓋底外科手術を安全に行うための, 現代のcadaver surgical trainingの実際について述べた. 脳除去後の通常ホルマリン固定の献体は, 詳細な解剖の学習や組織学的研究に有用であった. フェノール, エタノール, メタノールを加えた新しい固定法は手術シミュレーションに適していた. 医師が行う解剖を外科手技の発展に活用するためには, 学内の組織構築が必須である.

Surgical Candidacy in Skull Base Paragangliomas: An Institutional Experience.

Objective The aim of the study is to determine the surgical candidacy and nuances of skull base paraganglioma surgery in the era of radiotherapy. Materials and Methods This was a retrospective observational study conducted in patients who presented with skull base paragangliomas between January 2017 and December 2019. Primary data, including indication for surgery, the approach used, the extent of resection, complications, and postoperative lower cranial nerve status were studied. Results A total of 21 cases of skull base paragangliomas were analyzed, including seven cases of tympanic paraganglioma, 10 cases of jugular foramen paraganglioma, three cases of multiple paragangliomas, and one case of vagal paraganglioma. Indications for surgery were young age, bleeding from ear, neck mass with upper aerodigestive pressure symptoms, lower cranial nerve paralysis, and patients with intracranial pressure symptoms. Total excision was done in 11 patients, near-total excision in five patients, subtotal in three patients, and surgery was not done in two patients. Facial nerve paralysis was the most common complication observed, followed by bleeding and flap necrosis. Radiotherapy was considered as adjuvant treatment wherever indicated. Conclusion A thorough knowledge and understanding of the pathophysiology of the skull base paragangliomas and its management strategies can help to achieve excellent results in terms of tumor clearance and reduction in complications. A multidisciplinary team approach and meticulous skull base surgical techniques have a significant role to play in the management of paragangliomas, especially in developing countries where availability of radiosurgery is still a challenge.

Direct CNS delivery of proteins using thermosensitive liposome-in-gel carrier by heterotopic mucosal engrafting.

Delivering therapeutics across the blood-brain barrier (BBB) for treating central nervous system (CNS) diseases is one of the biggest challenges today as the BBB limits the uptake of molecules greater than 500 Da into the CNS. Here we describe a novel trans-nasal mucosal drug delivery as an alternative to the intranasal drug delivery to overcome its limitations and deliver high molecular weight (HMW) therapeutics efficiently to the brain. This approach is based on human endoscopic skull base surgical techniques in which a surgical defect is repaired by engrafting semipermeable nasal mucosa over a skull base defect. Based on endoscopic skull based surgeries, our groups has developed a trans-nasal mucosal rodent model where we have evaluated the permeability of ovalbumin (45 kDa) as a model protein through the implanted mucosal graft for delivering HMW therapeutics to the brain. A thermo sensitive liposome-in-gel (LiG) system was developed for creating a drug depot allowing for a sustained release from the site of delivery to the brain through the implanted nasal graft. We would like to report this as an exploratory pilot study where we are using this novel surgical model to show that the implanted nasal mucosal graft and the LiG delivery system result in an efficient and a sustained brain delivery of HMW proteins. Hence, this study demonstrates that the trans-nasal mucosal engrafting technique could overcome the limitations for intranasal drug delivery and enable the uptake of HMW protein therapeutics into the CNS for the treatment of a wide range of neurodegenerative diseases.

Skull Base Surgery Training and Practice Patterns among Recent Otolaryngology Fellowship Graduates

Background: Skull base surgical techniques, including advanced endoscopic approaches, are now being incorporated into an increasing number of otolaryngology training programs. The purpose of this survey is to collect data on skull base surgery training experiences and current skull base practice patterns of young otolaryngologists.

The combined subtemporal-transfacial approach for the resection of juvenile nasopharyngeal angiofibromas with intracranial extension.

Stage IVb juvenile nasopharyngeal angiofibromas (JNAs) are frequently regarded as unresectable because of their intracranial extension and cavernous sinus invasion. Although radiation has been described to control these tumors, it can leave the adolescent with long-lasting sequelae. Herein, we describe an alternative treatment strategy based on a combined subtemporal-transfacial surgical approach that permits the successful management of advanced stage JNAs by divorcing the intracranial vascular supply to these massive lesions. Four male patients were identified with Andrew's Stage IVB JNAs. All patients were treated by surgical resection using a combined subtemporal-transfacial surgical approach. Parameters assessed included tumor extent, number and types of surgical procedures, extent of resections, complications, and recurrence rate. Near-total tumor resections were achieved in all patients. No cerebrospinal fluid leak or cranial neuropathies were noted. All but one patient had local recurrences, and these could be managed with repetitive endoscopic debridement. No patient required adjuvant radiation treatment to control advanced disease. With the use of modern skull base surgical techniques, coordinated interdisciplinary care, and safe, near-total removal of the tumor mass, adolescent males with advanced JNAs may be spared the long-term morbidities associated with using radiation to treat these benign but aggressive lesions.

Neurotologic Skull Base Access for Primary Tumors of the Temporomandibular Joint

To familiarize the physician with the clinical and radiographic features associated with primary tumors of the temporomandibular joint (TMJ) and to demonstrate the use of the neurotologic skull base techniques in the surgical extirpation of TMJ tumors. This was a retrospective chart review spanning the years 1988 to 2012. Tertiary care academic medical center. Any patient with diagnosis of a primary TMJ tumor who received surgical management at our institution. The surgical approaches used included preauricular infratemporal fossa, postauricular infratemporal fossa, and pterional infratemporal fossa. The most critical assessment measures were postoperative patient morbidity and evidence of disease at follow-up visits. The surgical approach was tailored according to the radiographic mapping of the size and location of the tumor. Trismus and jaw discomfort were the most common postoperative complications. Conductive hearing loss occurred only in patients who underwent oversewing of the cartilaginous ear canal. The presenting signs and symptoms of extremely rare primary TMJ tumors are those often seen by otolaryngologists. Contemporary neurotologic skull base surgical techniques can optimize the successful extirpation of these lesions.

Permeabilization of the Blood-Brain Barrier via Mucosal Engrafting: Implications for Drug Delivery to the Brain

Utilization of neuropharmaceuticals for central nervous system(CNS) disease is highly limited due to the blood-brain barrier(BBB) which restricts molecules larger than 500Da from reaching the CNS. The development of a reliable method to bypass the BBB would represent an enormous advance in neuropharmacology enabling the use of many potential disease modifying therapies. Previous attempts such as transcranial catheter implantation have proven to be temporary and associated with multiple complications. Here we describe a novel method of creating a semipermeable window in the BBB using purely autologous tissues to allow for high molecular weight(HMW) drug delivery to the CNS. This approach is inspired by recent advances in human endoscopic transnasal skull base surgical techniques and involves engrafting semipermeable nasal mucosa within a surgical defect in the BBB. The mucosal graft thereby creates a permanent transmucosal conduit for drugs to access the CNS. The main objective of this study was to develop a murine model of this technique and use it to evaluate transmucosal permeability for the purpose of direct drug delivery to the brain. Using this model we demonstrate that mucosal grafts allow for the transport of molecules up to 500 kDa directly to the brain in both a time and molecular weight dependent fashion. Markers up to 40 kDa were found within the striatum suggesting a potential role for this technique in the treatment of Parkinson’s disease. This proof of principle study demonstrates that mucosal engrafting represents the first permanent and stable method of bypassing the BBB thereby providing a pathway for HMW therapeutics directly into the CNS.

Calcium Pyrophosphate Deposition Disease of the Temporomandibular Joint

Calcium pyrophosphate dihydrate deposition disease (CPDD, tophaceous pseudogout) is a rare crystal arthropathy characterized by calcium pyrophosphate crystal deposition in joint spaces, episodes of synovitis, and radiological features of chondrocalcinosis. We present a case of 61-year-old woman who presented with left temporomandibular joint (TMJ) pain, difficulty chewing, left facial numbness, left-sided hearing loss, and left TMJ swelling. Imaging of the temporal fossa revealed a large mass emanating from the temporal bone at the TMJ, extending into the greater wing of the sphenoid and involving the mastoid bone and air cells posteriorly. Fine needle aspiration demonstrated polarizable crystals with giant cells. Intraoperatively, the TMJ was completely eroded by the mass. Final pathology was consistent with tophaceous pseudogout. CPDD has rarely been reported involving the skull base. None of the cases originally described by McCarty had TMJ pseudogout. Symptoms are generally pain, swelling, and hearing loss. Management is nearly always surgical with many patients achieving symptomatic relief with resection. CPDD is associated with many medical problems (including renal failure, gout, and hyperparathyroidism), but our patient had none of these risk factors. This case demonstrates that CPDD can involve the skull base and is best treated with skull base surgical techniques.

Clinical Course and Autopsy Findings of a Patient with Clival Chordoma Who Underwent Multiple Surgeries and Radiation during a 10-Year Period

The management of clival chordoma remains problematic. We present the case of a 48-year-old woman with clival chordoma who underwent multiple surgeries and radiation therapy, including gamma knife stereotactic radiosurgery (GK-SRS), during a 10-year clinical course. The tumor was initially removed by gross total resection via the trans-sphenoidal approach, followed by external linac radiation therapy. The tumor recurred at the clivus 5 years after the initial operation. After repeated trans-sphenoidal removal of recurrent tumors, she twice underwent GK-SRS for a tumor remnant adjacent to the brainstem. Although this part of the tumor was controlled by GK-SRS, there was further tumor extension toward the sphenoid and maxillary sinuses. Ultimately, lower cranial nerve dysfunction developed due to tumor extension into the lower part of the clivus and the patient died of respiratory failure. Autopsy revealed the tumor to extend from the lower clivus to the bilateral middle fossae. The lower part of the tumor extended to the nasal cavity and to the posterior wall of the pharynx, resulting in compression of the upper pharyngeal region. The tumor around the jugular foramen compressed the lower cranial nerves bilaterally. Tumor cells did not, however, invade the intradural space microscopically. Although chordoma is not biologically malignant, this tumor can show massive extension with destruction of bony structures and extracranial invasion of connective tissues. Therefore, the optimal treatment strategy is to remove the tumor mass as extensively as possible, including normal bony structures and connective tissues surrounding the tumor, using skull base surgical techniques.

Gliosarcoma with infratemporal fossa extension

Gliosarcomas are bimorphic intraaxial tumors. Involvement of the skull base is highly unexpected. The authors present the case of a temporal lobe gliosarcoma with significant infratemporal fossa extension. This 55-year-old man presented with a 1-month history of severe progressive headache. Neurological examination was unremarkable except for bilateral papilledema. Magnetic resonance imaging revealed a 6-cm right temporal mass with extension into the infratemporal fossa. The patient underwent a right frontotemporal craniotomy together with drilling of the sphenoid ridge and middle fossa floor. The tumor consisted of intraaxial, intracranial as well as extradural, and extracranial components with extension to the posterolateral wall of the sphenoid sinus. It had a relatively well-circumscribed dissection plane. Gross-total resection was achieved, and the middle fossa floor was reconstructed using a rotated temporalis muscle flap. The postoperative course was uneventful except for hypesthesia in the distribution of the maxillary division of the right trigeminal nerve. The histopathological diagnosis was consistent with gliosarcoma. Radiotherapy and chemotherapy consisting of temozolomide were administered subsequently, and the patient was recurrence free 12 months after his initial diagnosis. In the presence of a mass lesion with both intraaxial and extracranial involvement, gliosarcoma should be considered among the differential diagnoses. Aggressive resection should be attempted, including the use of skull base surgical techniques to ensure an optimal outcome. The effect of skull base involvement to the overall treatment and outcome of patients with gliosarcomas would be difficult to determine given the rare occurrence of these lesions in such locations.

The history and present status of deep hypothermia and circulatory arrest in cerebrovascular surgery

After the development of deep hypothermia and circulatory arrest for cardiothoracic procedures in the late 1950s, this technique was adopted by several neurosurgeons as an aid to complex cranial surgery. Woodhall and colleagues described its first use for a neurosurgical procedure in 1960. Although their case did not involve a cerebrovascular procedure, the technique was subsequently used for the surgical treatment of cerebrovascular lesions, especially complex and giant aneurysms as well as large and solid hemangioblastomas. At the beginning, incorporation of this technique into common neurosurgical practice was impeded by several factors. For example, postbypass coagulopathy had been a serious source of morbidity. Furthermore, the need for cooperation among multiple subspecialties and the requirements for expensive equipment had further limited the availability of this technique. Subsequent improvements in the technique and advances in the equipment designed for cardiopulmonary bypass have led to its more widespread use starting in the 1980s. Hypothermic circulatory arrest has been described in several reports as a safe and useful tool in the treatment of large and giant aneurysms. Nevertheless, improvements in endovascular procedures and further refinement in skull base surgical techniques have limited the indications for circulatory arrest and deep hypothermia. The authors describe the history of hypothermia and circulatory arrest, its implementation in cerebrovascular surgery, and the changes in indications for and results of its use over time.

Aggressive Syringomatous Carcinoma of the Orbit

A 68-year-old woman with an unusual tumor involving the right orbit presented with painful exophthalmos of the right eye. Excision biopsy of her right eyelid was performed. The specimen showed ductal differentiation with comma-like extensions identical to syringoma. Cellular atypia, an invasive growth pattern, and remarkable perineural invasion led to the diagnosis of syringomatous carcinoma. Magnetic resonance imaging showed that the tumor exhibited maxillary involvement, invading the supraorbital fissure and bone of the middle skull base. The patient underwent craniofacial resection and has been alive with no sign of recurrence for 2 years. This case suggests that wide excision of these tumors with a clear surgical margin using skull base surgical techniques may offer a good prognosis.

Pediatric Skull Base Surgery

In the second of these two articles, we will discuss our clinical experience with skull base surgery in the pediatric population. We present a retrospective analysis of 55 patients less than 16 years of age who underwent skull base surgical approaches at the Primary Children’s Medical Center or the University of Utah Medical Center between January 1992 and April 1999. There were 30 boys and 25 girls (mean age 9.8 years). Patient follow-up averaged 58 months. Most patients had pathology that required either an anterior or anterolateral approach; 6 patients underwent a far-lateral or a transpetrosal exposure. Thirty-five procedures were performed by a neurosurgeon, a pediatric otolaryngologist performed 11 procedures, and 10 procedures were performed by both services together. Ninety-six percent of patients (n = 53) had a Glasgow Outcome Score of 4 or 5. Complications included 4 sustained cranial nerve palsies and 2 hemipareses. There were no CSF leaks, infections or deaths. Patients with sellar region pathology had a disproportionately higher incidence of postoperative morbidity. We conclude that in selected pediatric cases, skull base surgical techniques can be performed effectively and safely with the use of multidisciplinary teams. To implement these techniques, knowledge of their limitations and of the anatomical differences between the adult and pediatric cranial base is essential.

Lateral skull base malignancies

Historically poor outcomes have been characteristic in patients with lateral skull base malignancies. As advances in skull base surgical techniques have been made, complete resection has increasingly been achieved. This has resulted in improved survival rates and local tumor control. The authors performed a retrospective review of 95 patients treated for lateral skull base malignancies. The mean age of the patients was 49.4 years. There were 44 females and 51 males. The mean follow-up period was 50 months. Resection was performed in all patients, and postoperative radiotherapy was undertaken in 54% of the cases. Local disease control was maintained in 73% of the patients. Tumor involvement of the facial nerve and intracranial tumor extension did not jeopardize the rate of local control. Despite the fact that technical advances in skull base surgery have resulted in a higher incidence of complete tumor resection and improved survival rates, a respect for the poor prognosis historically associated with lateral skull base malignancies should be maintained and treatment should be appropriately aggressive.

Jugulotympanic paragangliomas

Jugulotympanic paragangliomas are the most common tumors of the middle ear and temporal bone. Although these larger tumors can prove to be formidable, the advent of microscopic and skull base surgical techniques has greatly enhanced the ability to treat and manage these tumors.

Skull base chordomas: overview of disease, management options, and outcome

Cranial base chordomas are locally invasive tumors that, from a midline, clival location, extend in different directions and display various patterns of skull base invasion. Although histologically benign, their invasive nature makes true "oncological" resection virtually impossible to achieve in most cases, despite modern skull base surgical techniques. Moreover, because of the tumor's location and proximity to critical neural and vascular structures, surgery-related morbidity can be significant when an aggressive resection is undertaken. Cytoreductive surgery assumes a critical role in the management of these lesions. The choice of surgical approach and the extent of resection are dependent on several factors: location and extension of the tumor, the surgeon's philosophy and familiarity with a specific approach, and the patient's preexisting clinical status. Proton-beam radiotherapy seems to be effective as an adjunct to surgery in achieving local tumor control. The timing of radiation therapy, however, remains controversial. Gamma knife surgery has been proposed as an adjunctive therapy, but the limited experience and short follow-up periods do not permit formulation of meaningful conclusions at this time. Recurrences are common, although in a subset of patients prolonged disease-free survival is demonstrated.

Cranial chordomas: results of radical excision

The authors analyze their experience with the treatment of 29 patients who underwent radical excision of skull base chordomas. Modern skull base surgical techniques were used in all patients who were treated between August 1991 and July 2000. The degree of tumor resection was gauged according to intraoperative inspection and postoperative high-resolution imaging findings. There were 21 patients with primary disease and eight with recurrent disease. Total resection was accomplished in 18 patients. Five patients had undergone radiotherapy prior to the present surgery, and an additional eight patients underwent postoperative radiotherapy. There were no surgery-related deaths. In five patients who died of the disease, surgery and radiotherapy had failed to effect a cure. Two of the remaining patients are alive with recurrent disease, and there is questionable evidence of recurrence in another patient. All 24 patients are functioning independently. Cranial nerve impairment was the most common postoperative deficit, followed by cerebrospinal fluid (CSF) leakage and infection. The use of skull base techniques in radical surgery provides an opportunity to excise the tumor and the involved bone. In most cases the procedure-related cranial nerve deficits improve over time. The complications of CSF leakage and infection can be minimized and are preventable. Proton beam irradiation is an excellent adjuvant treatment but is reserved for patients with definite tumor recurrence or residual tumor that can be identified on the imaging studies.