Magnetic Resonance Imaging???Guided Biopsies of the Petrous Apex and Petroclival Region

Endoscopic Transnasal Approaches to Petrous Apex

Endoscopic extended transnasal approaches to the apex of the temporal bone pyramid are rapidly developing and are widely used in our time around the world. Despite this, the problem of choosing an approach remains relevant and open not only between the “open” and “endoscopic transnasal” access groups but also within the latter. In the article, we systematized all endoscopic approaches to the pyramid of the temporal bone and divided them into three large groups: medial, inferior, and superior—in accordance with the anatomical relationship with the internal carotid artery—and also presented their various, modern (later described), modifications that allow you to work more targeted, depending on the nature of the neoplasm and the goals of surgical intervention, which in turn allows you to complete the operation with minimal losses, and improve the quality of life of the patient in the early and late postoperative period. We described the indications and limitations for these accesses and the problems that arise in the way of their implementation, which in turn can theoretically allow us to obtain an algorithm for choosing access, as well as identify growth points.

Cholesterol Granulomas: A Comparative Meta-Analysis of Endonasal Endoscopic versus Open Approaches to the Petrous Apex

Petrous apex cholesterol granulomas (PACG) are rare disorders that can lead to patient morbidity and must, occasionally, be drained by either endoscopic endonasal (EN) or open procedures (OP). The objective of our study was to complete a review of the literature to compare the EN and OP approaches on multiple levels, notably on safety and effectiveness. Ovid MEDLINE and Embase were used to perform a thorough literature review of all cases of PACG treated by either EN or OP dating from January 1948 to August 2017. In total, 49 articles were selected including 23 for EN (n=76) and 26 for OP (n=210). Differences were found in the incidence of preoperative hearing loss (HL) (EN 18.4%, OP 57.3%; p<0.001), headache (EN 48.7%, OP 31.2%; p=0.007), and disequilibrium (EN: 14.5%, OP 26.1%; p=0.04). Differences in lesion proximity to the sphenoid sinus (EN 23.6%, OP: 1.0%; p<0.001), clivus (EN 11.8%, OP 4.7%; p=0.03), otic capsule (EN 0.0%, OP 5.2%; p=0.03), internal auditory canal (EN 2.6%, OP 10.9%; p=0.01), and internal carotid artery (ICA) (EN 9.2%, OP 2.8%; p=0.02) were found on preoperative imaging. The EN procedure had better hearing improvement rates (EN 85.7%, OP 23.4%; p<0.001), lower complication rates (EN 7.9%, OP 17.6%; p=0.04), shorter median follow-up (EN:13.5 months, OP:37.2 months; p<0.001), and shorter time to recurrence (EN 3 months, OP 22.6 months; p=0.002) than the known OP. No differences were found in age, preoperative size, recurrence rate, operative time, stent placement, or improvement of other symptoms. Endoscopic nasal approaches, when feasible, should be favored to open procedures for PACG drainage given their better hearing improvement and less complication rates.

Stereotactic biopsy approach to the upper clivus through the middle fossa floor that avoids pneumatised cavities and the intradural compartment

BACKGROUND

Biopsies of clival lesions are usually performed, under general anaesthesia, through an anterior endoscopic approach or, alternatively, through a trans-nasal or trans-oral stereotactic approach.

METHODS

A 57-year-old man with a symptomatic osteolytical lesion of the clivus, who refused general anaesthesia, underwent a sterotactically guided biopsy of the lesion by an antero-lateral approach through the temporal and sphenoid bones.

RESULTS

Biopsy was successfully performed and the resulting diagnosis was myeloma. The patient was comfortable during and after surgery and there were no complications.

CONCLUSIONS

The present stereotactic antero-lateral approach to the biopsy of the upper clivus can be considered an useful adjunct to the current trans-oral and transnasal approaches that often require general anaesthesia.

Recurrent petroclival meningiomas: clinical characteristics, management, and outcomes

This study seeks to elucidate the prognostic predictors and outcomes of recurrent/progressive petroclival meningiomas (PCMs). We reviewed our cohort of 39 recurrent/progressive PCMs (27 females, 69.2%) and analyzed the results from the literature. Twenty-three patients underwent reoperations, 2 received radiotherapy alone, and 14 declined any treatment. During a follow-up of 70.4 months, 7 patients experienced a 2nd recurrence/progression (R/P) and 18 patients died. In the 23 patients, gross total resection (GTR), subtotal resection (STR), and partial resection (PR) were achieved in 8, 8, and 7 patients, respectively. The percentage of the 2nd R/P-free survival of GTR, STR, and PR was 88%, 67%, and 40%, respectively. The overall survival following the 1st R/P of GTR, STR, and PR was 88%, 63%, and 33%, respectively. Patients rejecting treatment suffered from significantly poor overall survival (7%; p = 0.001) and short survival duration (42.0 months; p = 0.016) compared with that of the patients receiving treatment (67% and 86.9 months). The GTR was the only independent favorable predictor. In the 21 included studies with 98 recurrent/progressive PCM patients, 17 patients presented with a 2nd R/P and 10 died of a 2nd R/P; patients undergoing observation had a significantly poor tumor regrowth control rate compared with patients undergoing surgery (p = 0.004) or radiotherapy alone (p < 0.001). Proactive treatment should be performed for patients with recurrent/progressive PCMs. Observation can lead to relentless outcome. GTR as a preferential therapeutic strategy should be pursued as far as possible on the condition of minimal functional impairment.

Surgical approaches to central skull base and postsurgical imaging

The close proximity to or intricate involvement of critical neurovascular structures in the central skull base region or both present unique surgical challenges. Varied surgical approaches may be used to remove tumors in this region, including open craniotomies and minimally invasive transnasal or transfacial endoscopic approaches. The ideal surgical technique is chosen based on multiple factors including the aggressiveness, histopathology, and location of the tumor with respect to regional neurovascular elements. Postsurgical image analysis of the central skull base requires an intimate understanding of preoperative and expected postoperative appearance in relation to the nature of the excision and surgical materials used.

Lesions of the petrous apex: classification and findings at CT and MR imaging

The petrous apex is a complex region of the central skull base that is surrounded by a number of important vascular and neural structures and can be home to a wide range of disease processes. Lesions arising in or spreading to the petrous apex cause varied and occasionally severe clinical sequelae, which typically result from mass effect or direct invasion of the cranial nerves, brainstem, or internal carotid artery. Because the petrous apex is not amenable to direct examination, cross-sectional imaging with computed tomography and magnetic resonance (MR) imaging plays an important role in diagnosis and characterization of lesions occurring there. Petrous apex lesions can be classified on the basis of their origin into the following categories: developmental lesions, inflammatory lesions, benign tumors, malignant tumors, vascular lesions, and osseous dysplasias. The most common lesions arising in the petrous apex are cholesterol granulomas, which can be reliably diagnosed with MR imaging due to their high signal intensity on both T1-weighted images and T2-weighted images. In addition, one should also be familiar with anatomic variants or pseudolesions in the petrous apex that can be mistaken for pathologic conditions.

Endoscopic endonasal approach to cholesterol granulomas of the petrous apex: a series of 17 patients

Object

The aim of this study was to report the results in a consecutive series of patients who had undergone an endoscopic endonasal approach (EEA) for drainage of a petrous apex cholesterol granuloma (CG).

Methods

Seventeen cases with a confirmed diagnosis of petrous apex CG were identified from a database of more than 1600 patients who had undergone an EEA to skull base lesions at the authors' institution in the period from 1998 to 2011. Clinical outcomes were reviewed and compared with those in previous studies of open approaches.

Results

Nine patients underwent a transclival approach and 8 patients underwent a combined transclival and infrapetrous approach. A Silastic stent was used in 11 patients (65%), a miniflap in 4 (24%), and a simple marsupialization of the cyst in 3 (18%). All symptomatic patients had partial or complete improvement of their symptoms postoperatively and at the follow-up (mean follow-up 20 months, range 3–67 months). Complications developed in 3 patients (18%) including epistaxis, chronic serous otitis media, eye dryness, and a transient sixth cranial nerve palsy. Two patients (12%) had a symptomatic recurrence of the cyst requiring repeat endoscopic endonasal drainage. There were no instances of internal carotid artery injuries, CSF leaks, or new hearing loss. The mean postoperative hospital stay was 2 days (range 0.7–4.6 days). These results were comparable with those in previous studies of open approaches to petrous apex CGs.

There was a strong correlation between the size of the cyst and the type of approach chosen (Rpb [point biserial correlation coefficient] = +0.67, p = 0.003359) and a very strong correlation between the degree of medial extension (defined by the V-angle) and the choice of approach (Rpb = +0.81, p < 0.0001). Based on these observations, the authors developed an algorithm for guiding the choice of the most appropriate route of drainage.

Conclusions

The EEA is a safe and effective alternative to traditional open approaches to petrous apex CGs.

[New developments in computer-assisted surgery (CAS). From intraoperative imaging to ultrasound-based navigation]

Ever faster processor capacity is having an impact on computer-assisted or computer-aided surgery (CAS). The fusion of different imaging modalities enables functional data such as PET-CT, for example, to be available in image-guided surgery. Referencing of image data is the key to precise navigation. Intraoperative data acquisition is a new approach to improving accuracy. Thus, intraoperative CT conducted under navigational support enables automatic referencing of up-to-date image data. Alternatively, intraoperative magnetic resonance imaging or intraoperative sonography can be performed. Ultrasound systems have already been successfully integrated in existing navigational systems to compensate for intraoperative tissue shifting. Ultrasound systems may play a role in the future as a single modality in image-guided surgery in soft tissue of the neck and skull bone.

Endoscopic endonasal surgery for petrous apex lesions

BACKGROUND

Endoscopic endonasal approaches to the ventral skull base are categorized based on their orientation in coronal and sagittal planes. For all of these approaches, the sphenoid sinus is the starting point, and provides orientation to important vascular and neural structures. Surgical approaches to the petrous apex include 1) a medial approach, 2) a medial approach with internal carotid artery (ICA) lateralization, and 3) a transpterygoid infrapetrous approach (inferior to the petrous internal carotid artery). The choice of a surgical approach depends on the relationship of the lesion to the internal carotid artery (medial or inferior), degree of medial expansion, and pathology. The purpose of this paper is to discuss the anatomic and technical features of endoscopic surgical approaches to the petrous apex, provide a new classification for approaches that focuses on the relationship of the lesion to the petrous internal carotid artery, and provide outcomes data on our first 20 endoscopic petrous apex approaches.

METHODS

A retrospective clinical outcome study of endoscopic petrous apex surgeries was performed at the University of Pittsburgh Medical Center. The medical records from patients with endoscopic endonasal approaches to isolated petrous apex lesions were reviewed for demographics, diagnoses, presentation, endoscopic approach, and clinical outcomes. Patients with lesions that extended into the petrous apex but were not isolated to the petrous apex were excluded (e.g., clival chordoma with extension into the petrous apex).

RESULTS

Twenty patients were included in the analysis: 13 inflammatory cystic lesions (9 cholesterol granulomas and four petrous apicitis) and 7 solid lesions. Chondrosarcoma was the most common solid petrous apex lesion in our series. Twelve of 13 cystic lesions were drained endoscopically (one surgery was aborted early in the series). All drained patients had resolution of presenting symptoms. One patient had closure of the outflow tract without return of symptoms and one patient had revision endoscopic drainage due to scarring and neo-osteogenesis and return of unilateral headache. No carotid injuries and no new cranial neuropathies occurred perioperatively. The advantages and limitations of the medial transsphenoidal approaches (with and without carotid mobilization) and the transpterygoid infrapetrous approach are discussed.

CONCLUSIONS

The endoscopic endonasal approach to petrous apex lesions is safe and effective for appropriately selected patients in the hands of experienced endoscopic skull base surgeons. If offers advantages of removing the hearing and facial nerve risks from the transtemporal/transcranial approaches and allows for a larger and more natural drainage pathway into the sinuses.

[Computer-aided surgery of the paranasal sinuses and the anterior skull base]

Endoscopic or microscopic surgery for chronic rhinosinusitis with or without nasal polyps is a routine intervention in daily practice. It is often a delicate and difficult minimally invasive intervention in a narrow space, with a tunnel view of 4 mm in the case of endoscopy and frequent bleeding in chronically inflamed tissue. Therefore, orientation in such a "labyrinth" is often difficult. In the case of polyp recurrence or tumors, the normal anatomical landmarks are often missing, which renders orientation even more difficult. In such cases, computer-aided navigation together with images such as those from computed tomography or magnetic resonance imaging can support the surgeon to make the operation more accurate and, in some cases, faster. Computer-aided surgery also has great potential for education.

Tumor-biology and current treatment of skull-base chordomas

Chordomas are rare, slow growing tumors of the axial skeleton, which derive from the remnants of the fetal notochord. They can be encountered anywhere along the axial skeleton, most commonly in the sacral area, skull base and less commonly in the spine. Chordomas have a benign histopathology but exhibit malignant clinical behavior with invasive, destructive and metastatic potential. Genetic and molecular pathology studies on oncogenesis of chordomas are very limited and there is little known on mechanisms governing the disease. Chordomas most commonly present with headaches and diplopia and can be readily diagnosed by current neuroradiological methods. There are 3 pathological subtypes of chordomas: classic, chondroid and dedifferentiated chordomas. Differential diagnosis from chondrosarcomas by radiology or pathology may at times be difficult. Skull base chordomas are very challenging to treat. Clinically there are at least two subsets of chordoma patients with distinct behaviors: some with a benign course and another group with an aggressive and rapidly progressive disease. There is no standard treatment for chordomas. Surgical resection and high dose radiation treatment are the mainstays of current treatment. Nevertheless, a significant percentage of skull base chordomas recur despite treatment. The outcome is dictated primarily by the intrinsic biology of the tumor and treatment seems only to have a secondary impact. To date we only have a limited understanding this biology; however better understanding is likely to improve treatment outcome. Hereby we present a review of the current knowledge and experience on the tumor biology, diagnosis and treatment of chordomas.

A novel treatment approach to cholesterol granulomas

✓ The authors report a novel technique for the treatment of cholesterol granulomas. An extradural middle fossa approach was used to access the granuloma, with drainage through silastic tubes into the sphenoid sinus via the anteromedial triangle between V1 and V2.

Cholesterol granulomas occur when the normal aeration and drainage of temporal bone air cells is occluded, resulting in vacuum formation and transudation of blood into the air cells. This process results in anaerobic breakdown of the blood with resulting cholesterol crystal formation and an inflammatory reaction. Traditional treatment of this lesion involves extensive drilling of the temporal bone to drain the granuloma cyst and establish a drainage tract into the middle ear. Such drainage procedures can be time consuming and difficult, and potentially involve structural damage to the inner ear and facial nerve. An extradural middle fossa approach provides easy access to the granuloma and anterior petrous bone entry into the granuloma for resection. Granuloma drainage is then achieved using shunt tubing in the sphenoid sinus via a small hole in the anteromedial triangle between V1 and V2.

Five patients with symptomatic cholesterol granuloma were treated without complication using this novel extradural middle fossa approach. One patient required reoperation 1-year postoperatively for cyst regrowth and occlusion of the drainage tube. At the 5-year follow-up examination, no patient reported recurrent symptoms.

Extradural middle fossa craniotomy and silastic tube drainage into the sphenoid sinus is a viable alternative method for treatment of cholesterol granuloma.

Pediatric MR-guided interventions

MRI guided interventions are a relatively new but steadily growing field within surgery in pediatric age. Besides the advantages of MRI, such as multiplanar capability and excellent soft tissue contrast and spatial resolution, particularly relevant for the pediatric population is the lack of ionizing radiation. There is meanwhile a group of well defined diagnostic or therapeutic indications for applying MR imaging during pediatric interventions. Aim of this review is to give an overview about indications of MR-guided procedures in children as well as the advantages and disadvantages of MR-guided interventions. We also briefly discuss interventional MR-systems and MR-compatible devices. It is our opinion that MR-guidance for pediatric interventions is a promising technique at the beginning of its development.

Interventional and intraoperative MR: review and update of techniques and clinical experience

The concept of interventional magnetic resonance imaging (MRI) is based on the integration of diagnostic and therapeutic procedures, favored by the combination of the excellent morphological and functional imaging characteristics of MRI. The spectrum of MRI-assisted interventions ranges from biopsies and intraoperative guidance to thermal ablation modalities and vascular interventions. The most relevant recently published experimental and clinical results are discussed. In the future, interventional MRI is expected to play an important role in interventional radiology, minimal invasive therapy and guidance of surgical procedures. However, the associated high costs require a careful evaluation of its potentials in order to ensure cost-effective medical care.