The skull base: tumoral lesions

Non-chordomatous clival bony tumors: A rare experience and systematic literature review

BACKGROUND

Non-chordomatous bony tumors of the clivus are extremely rare. Site, extent, and aggressiveness of tumor limits the extent of resection. It poses challenge to the neurosurgeons due to the complexity of anatomy. There is paucity of literature exclusively on non-chordomatous bone tumors of the clivus in young adults.

OBJECTIVES

To analyze the clinical presentation, imaging findings, surgical approach, complications, and outcome of primary clival bony tumors in young adults.

METHODS

We retrospectively reviewed children and young adults with primary clival bony tumors excluding chordoma who underwent surgical resection between years 2010 and 2023 in our center. We analyzed the demographic details, imaging findings, operative variables, perioperative complications, length of stay, complications, and outcome at latest follow-up.

RESULTS

The mean age was 17.5 ± 1.73 years (range 16 to 19 years). Headache was the presenting complaint in all four patients (100%). The mean duration of symptom was 7.25 ± 3.2 months (range 5 to 12 months). The tumor was localized in clivus in all four patients (100%). The mean length of stay in hospital was 30.5 ± 13.48 days (range 11 to 40 days). All patients underwent surgical treatment. Surgical approaches used were anterior approach in four patients (100%). Gross total excision was performed in one patient (25%), sub-total excision was performed in two patients (50%), and tumor decompression was performed in one patient (25%). Of these, three were designated as having benign tumors and one had a malignant tumor. There was no perioperative mortality. There was one mortality (25%) on 2 months follow-up due to tumor progression. Three patients (75%) had improved symptomatically at latest follow-up. Two patients (50%) received adjuvant chemoradiotherapy. The mean follow-up was 38 ± 39.29 months (range 2 to 72 months).

CONCLUSION

Non-chordomatous bony tumors of the clivus are rare and often underestimated. Surgery is the treatment of choice. Tumor consistency and adhesion to critical neurovascular structures precludes gross total resection. Various approaches are in the armamentarium. Approach to be decided based on the expertise of the neurosurgeon to achieve safe maximal resection. Multidisciplinary approach is mandatory for streamlined management. Adjuvant therapy is decided based on the residual tumor following surgery.

Imaging of Acute and Chronic Skull Base Infection

Skull base infections are uncommon but can be life threatening without timely recognition. Imaging plays a crucial role because symptoms can be vague and nonlocalizing. Necrotizing otitis externa in diabetic or immunocompromised patients is the commonest cause of skull base osteomyelitis (SBO), followed by sinogenic infections and idiopathic central SBO. Multiparametric magnetic resonance (MR) and high-resolution CT are the mainstays for establishing a diagnosis and estimating disease extent, with MR being superior in ascertaining marrow and soft tissue involvement. Monitoring treatment response, of which imaging is a fundamental part, is challenging, with emerging promising imaging tools.

The Treatment Strategy for Skull Base Reconstruction for Anterior Cranial Fossa Intra- and Extracranial Tumors

ABSTRACT

Anterior cranial fossa intra- and extracranial tumors arise from the anterior cranial fossa and invade the orbit and nose. Anterior cranial fossa tumor resection and skull base reconstruction are challenging for neurosurgeons due to the complex anatomy, leakage of cerebrospinal fluid, and critical neurovasculature involvement. The authors report a case series of cranio-orbital communicating tumors and cranionasal-orbital communicating tumors. All patients underwent a modified Derome approach or transfrontal basal approach, and all tumor resections were satisfactory. Skull base reconstruction for small defects (<1.5 cm) can be performed with autogenous fascia, muscle, and fat. Large defects (≥1.5 cm) require autogenous fascia, muscle, and fat combined with osseous reconstruction (autogenous bone, titanium mesh, and polyetheretherketone). The techniques and treatments were successful, and only 1 patient experienced mild cerebrospinal fluid leak but no intracranial infection, pneumocrania or intracranial hemorrhage. Additionally, long-term follow-up demonstrated that the outcomes remain favorable. According to a literature review, this technique might be an alternative strategy for treating anterior cranial fossa intra- and extracranial tumors, and better skull base reconstruction can prevent many postoperative complications.

CT Evaluation of Variations in the Middle Cranial Fossa Foramina: A Potential Guide for Skull Base Surgery

OBJECTIVES

To evaluate and classify the variations of foramen ovale (FO), foramen spinosum (FS).

METHODS

Six hundred fifty-eight computed tomographies (CTs) were evaluated by 2 observers. Foramen ovale was classified as oval, almond, round, and slit-like. Duplication, absence, and confluence for FS were noted. Bony outgrowths were categorized as tubercule, bony plate, and spine.

RESULTS

Oval shaped FO was the most common subgroup. Most common FS variation was the confluence with FO. Of bony outgrowths, tubercule-shaped were the most common type and spine-shaped ones were the least. Substantial agreement for bony plate and tubercule, almost excellent agreement for all the other parameters were found between 2 observers.

CONCLUSIONS

Foramen ovale called lobulated and had not classified previously was described in this study. Computed tomography is a reliable tool for anatomical evaluation of FO and FS, which would effect the methods of middle cranial fossa surgery. Thus, radiologists should be a pathfinder about the variations of these structures.

Proton MR spectroscopic features of the cisternal segment of the trigeminal nerve in patients with trigeminal neuralgia: A pilot study

PURPOSE

To investigate normal quantitative proton magnetic resonance spectroscopy (MRS) features of the cisternal segment of the trigeminal nerve and evaluate possible metabolite concentration differences in the affected and unaffected nerves of trigeminal neuralgia patients.

MATERIAL AND METHODS

A total of 33 consecutive patients who underwent a MR study of the internal auditory canal/posterior fossa and dedicated trigeminal nerve multivoxel MRS were enrolled. Measurements of N-acetyl aspartate (NAA), creatine (Cr), choline (Cho), myoinositol (mI), glutamate-glutamine (Glx) concentrations, and ratios of NAA-to-Cr, Cho-to-Cr, and Cho-to-NAA were automatically calculated by the dedicated software. Vascular conflicts were also recorded.

RESULTS

The mean Cr concentration was significantly higher on the affected sides in all parts of the nerve (p < 0.05), while the mean NAA concentration was significantly higher in only the distal portion (p = 0.04). Mean mI concentration was significantly higher in the middle and distal parts (p < 0.05). NAA-to-Cr ratio was significantly higher in the proximal and middle parts (p < 0.05), while Cho-to-Cr ratio was significantly higher only in the middle portion (p = 0.028). Finally, the Cho-to-NAA ratio was significantly higher only in the distal portion (p = 0.04). Vascular conflicts were observed in 24 patients (72.7%), and in 20 of them (60.6%) the conflict was on the same side as the neuralgia symptoms.

CONCLUSION

Although the detected statistical relationships were variable in the spectroscopic measurements, metabolite concentrations and ratios were successfully exhibited in all patients. Features of a normal trigeminal nerve were able to determine by MRS. All calculated metabolite concentrations were higher in the affected nerves; however, only some of them were statistically significant. No statistically significant relationships were found between the MRS measurements and nerves with and without vascular compression.

Ophthalmic and orbital considerations in the evaluation of skull base malignancies

INTRODUCTION

The orbital contents, afferent and efferent visual pathways, and the cranial nerves involved in eye movement, corneal sensation and eyelid closure traverse the skull base, a region bounded by the intracranial cavity, the paranasal sinuses, and the deep spaces of the face and head. As such, tumors from above or below have potential to affect some aspect of the visual system.

METHODS

We discuss here the clinical ophthalmologic and orbital considerations in the evaluation of patients with these tumors, as well as the ophthalmic sequelae of treatment with radiation or surgery (or both). And for the surgeon, we discuss the ophthalmic and orbital considerations in surgical planning, the role of the orbital surgeon in skull base surgery, and briefly discuss transorbital approaches to the skull base.

RESULTS AND CONCLUSION

Ophthalmic and orbital dysfunction may be the main source of disability in patients with skull base malignancy; it is thus incumbent on those who manage patients with tumors of this region to be aware of the ophthalmic, neuro-ophthalmic and orbital manifestations, so as to best tailor therapy and monitor treatment outcomes.

Neuro-endoscope for skull base tumors

The endoscope has traditionally been used in neurosurgery to access a lesion within a natural body cavity. The challenge has been to access and resect deep-seated intraparenchymal lesions using a minimally invasive endoscopic technique. Endoscopic endonasal trans-sphenoidal surgery has gained increasing acceptance by otolaryngologists and neurosurgeons. Surgical procedures of the skull base include exposure, resection, and base reconstruction. These approaches start at the sphenoid sinus, which provides a reference point to important vascular and neural structures. The endoscopic endonasal approach is optimal in paramedian ventral skull base tumors, allowing wide access to the ventral skull base regions and allowing early devascularization of the tumor without retraction of the brain. Limited exposure results in limited "injury" to surrounding tissue and consequently reduced post-operative pain, a shorter length of hospital stay, a reduction in the time to return to work, and decreased overall cost.

Skull Base Tumors and Tumor-Like Lesions: A Pictorial Review

A number of tumors and tumor-like non-neoplastic lesions with different cell types on histology occur in the skull base. A wide variety in disease and lesion appearance often complicates the process of radiological diagnosis. The main role of radiographic imaging is the detection and characterization of skull base lesions, with evaluation of the extent of invasion or preservation of adjacent critical organs. Evaluation of the skull base anatomy and surgical planning by using image guidance are also important for surgeons. Computed tomography (CT) and magnetic resonance (MR) imaging are the preferred modalities for the evaluation of skull base lesions. CT and MR are used for lesion detection, tissue characterization and assessment of neurovascular and bone involvement by the lesions. Both modalities provide useful information, one sometimes of greater value than the other. T1-weighted MR imaging is useful in detecting skull base lesions, typically surrounded by abundant fatty bone marrow. T2-weighted MR imaging is generally useful for tumor tissue characterization. CT surpasses MR imaging in evaluating intratumoral calcification and bone destruction or hyperostosis. To date, imaging features have been well-reported in individual skull base tumors; however, correct diagnosis by imaging alone still presents a challenge. Knowledge of clinical issues and awareness of variants of skull base tumors are of help in making a diagnosis. The purpose of this article is to review pertinent clinical issues, typical imaging appearances and certain imaging variations of common skull base lesions.

A Clinical and Radiological Approach to the Management of Benign Mesenchymal Sinonasal Tumors

PURPOSE

Benign mesenchymal sinonasal neoplasms (BMSN) are rare and histologically heterogeneous. Differential diagnosis, appropriate management, and outcome are still a matter of debate. The aim of this study is to provide evidence for further refinement of assessment and treatment in the future.

PROCEDURES

We retrospectively reviewed data on 93 patients with neuroradiologically verified BMSN treated at our university reference center during the past 22 years.

RESULTS

The most frequent BMSN recorded in our cohort was osteoma of the frontal sinus. Only one-third of the patients affected were symptomatic at initial presentation. The 2 other common fibro-osseous tumor entities, fibrous dysplasia and ossifying fibroma, were confirmed in 12 and 6 patients, respectively. Patients with soft tissue tumor entities such as hemangioma, glomangiopericytoma, angiofibroma, and hamartoma were all symptomatic and underwent surgical resection.

CONCLUSION

Understanding and recognizing the spectrum of appearances of benign mesenchymal sinonasal tumors will improve patient assessment and clinical management. The pathognomonic neuroradiological signs of a particular tumor entity should be actively sought as the neuroradiological features may be the diagnostic clues. Computed tomography and magnetic resonance imaging play complementary roles in identifying the morphological details and locoregional staging of benign mesenchymal sinonasal tumors.

Imaging of skull base tumours

The skull base is a highly complex and difficult to access anatomical region, which constitutes a relatively common site for neoplasms. Imaging plays a central role in establishing the differential diagnosis, to determine the anatomic tumour spread and for operative planning. All skull base imaging should be performed using thin-section multiplanar imaging, whereby CT and MRI can be considered complimentary. An interdisciplinary team approach is central to improve the outcome of these challenging tumours.

Optimized imaging of the midface and orbits

A variety of imaging techniques are available for imaging the midface and orbits. This review article describes the different imaging techniques based on the recent literature and discusses their impact on clinical routine imaging. Imaging protocols are presented for different diseases and the different imaging modalities.

Diagnostic efficiency of multidetector computed tomography versus magnetic resonance imaging in differentiation of head and neck paragangliomas from other mimicking vascular lesions: comparison with histopathologic examination

The purpose of this study was to determine the efficiency of Multidetector Computed Tomography (MDCT) versus MRI in detection and characterization of paragangliomas and differentiating them from other vascular mimicking conditions in the neck and skull base in comparison with histo-pathological results as a gold standard. A prospective study included 30 patients with vascular neck lesions. They were susceptible for MDCT and MRI for characterization of the nature of the lesions. Histo-pathological evaluation was performed in all lesions for confirmation. As a result of this study included 30 patients: 22 males and 8 females. Paragangliomas were the commonest detectable lesions; 12/30 patient had glomus tumor (1 glomus tympanicum, 2 glomus vegale, 4 glomus jugulo-tempanicum, and 5 glomus jugular), 6 carotid body tumor, 2 hemangiopericytoma, 3 vegal Schwanoma, 4 lymphadenopathy, 2 juvenile angiofibroma, and one neurofibroma. The sensitivity of MDCT was higher than MRI in differentiation of paragangliomas from other mimicking lesions, where MDCT sensitivity was 83.33 % and the NPV was 80 % while that of MRI was 77.7 % and the NPV 75 %, but both techniques have moderate agreement between them in differentiating paragangliomas from other mimicking vascular lesion. MDCT with its new utilities has near degree of accuracy in detection and localization of paragangliomas as the same that of MRI. Both techniques have moderate agreement between them in differentiating paragangliomas from other mimicking vascular lesions. So, it is better to use both of them as complementary techniques for accurate diagnosis and grading of paraganglioma.

Imaging of sinonasal tumours

More than 70 benign and malignant sinonasal tumours and tumour-like conditions have been described. However, sinonasal tumours are rare, and sinonasal cancers comprise only 3% of all head and neck cancers and 1% of all malignancies, with a peak incidence in the 5th to 7th decades and with a male preponderance. The early symptoms and imaging findings of sinonasal tumours are similar to rhinosinusitis with runny and stuffy nose, lacrimation and epistaxis and therefore neglected both by the patients and doctors. When late symptoms such as anosmia, visual disturbances, cranial neuropathy (Cn II, IV, V, VI) or facial swelling appear, the patient is referred to sinonasal endoscopy or imaging. At the time of correct diagnosis more than half of the tumours have reached an advanced stage with a poor prognostic outcome. Even if imaging is performed in the early stages, a radiologist inexperienced with sinonasal anatomy and tumour features may easily interpret early signs of a malignant tumour as rhinosinusitis or a lesion that does not require follow-up. This article presents the imaging findings in some of the most common benign and malignant sinonasal tumours, and the TNM classification and staging of sinonasal carcinomas.

Different imaging techniques in the head and neck: Assets and drawbacks

In this review, the gold standard imaging techniques for the head and neck and the latest upcoming techniques are presented, by comparing computed tomography (CT), magnetic resonance imaging and positron emission tomography-CT, as well as ultrasound, depending on the examined area. The advantages and disadvantages of each examination protocol are presented. This article illustrates the connection between the imaging technique and the examined area. Therefore, the head and neck area is divided into different sections such as bony structures, nervous system, mucous membranes and squamous epithelium, glandular tissue, and lymphatic tissue and vessels. Finally, the latest techniques in the field of head and neck imaging such as multidetector CT, dual-energy CT, flash CT, magnetic resonance angiography, spectroscopy, and diffusion tensor tractography using 3 tesla magnetic resonance are discussed.

Imaging of the central skull base

The central skull base (CSB) constitutes a frontier between the extracranial head and neck and the middle cranial fossa. The anatomy of this region is complex, containing most of the bony foramina and canals of the skull base traversed by several neurovascular structures that can act as routes of spread for pathologic processes. Lesions affecting the CSB can be intrinsic to its bony-cartilaginous components; can arise from above, within the intracranial compartment; or can arise from below, within the extracranial head and neck. Crosssectional imaging is indispensable in the diagnosis, treatment planning, and follow-up of patients with CSB lesions. This review focuses on a systematic approach to this region based on an anatomic division that takes into account the major tissue constituents of the CSB.

Imaging of the anterior skull base

This article briefly discusses the imaging approach to lesions of the anterior skull base. A brief review of normal anatomy and imaging techniques is followed by a discussion about common neoplastic and non-neoplastic pathologies involving this region.

[Anatomy of the skull base and the cranial nerves in slice imaging]

Computed tomography (CT) and magnetic resonance imaging (MRI) are suitable methods for examination of the skull base. Whereas CT is used to evaluate mainly bone destruction e.g. for planning surgical therapy, MRI is used to show pathologies in the soft tissue and bone invasion. High resolution and thin slice thickness are indispensible for both modalities of skull base imaging. Detailed anatomical knowledge is necessary even for correct planning of the examination procedures. This knowledge is a requirement to be able to recognize and interpret pathologies. MRI is the method of choice for examining the cranial nerves. The total path of a cranial nerve can be visualized by choosing different sequences taking into account the tissue surrounding this cranial nerve. This article summarizes examination methods of the skull base in CT and MRI, gives a detailed description of the anatomy and illustrates it with image examples.

Skull base tumours Part II. Central skull base tumours and intrinsic tumours of the bony skull base

With the advances of cross-sectional imaging radiologists gained an increasing responsibility in the management of patients with skull base pathology. As this anatomic area is hidden to clinical exam, surgeons and radiation oncologists have to rely on imaging studies to plan the most adequate treatment. To fulfil these endeavour radiologists need to be knowledgeable about skull base anatomy, about the main treatment options available, their indications and contra-indications and needs to be aware of the wide gamut of pathologies seen in this anatomic region. This article will provide a radiologists' friendly approach to the central skull base and will review the most common central skull base tumours and tumours intrinsic to the bony skull base.

Skull base tumours part I: imaging technique, anatomy and anterior skull base tumours

Advances in cross-sectional imaging, surgical technique and adjuvant treatment have largely contributed to ameliorate the prognosis, lessen the morbidity and mortality of patients with skull base tumours and to the growing medical investment in the management of these patients. Because clinical assessment of the skull base is limited, cross-sectional imaging became indispensable in the diagnosis, treatment planning and follow-up of patients with suspected skull base pathology and the radiologist is increasingly responsible for the fate of these patients. This review will focus on the advances in imaging technique; contribution to patient's management and on the imaging features of the most common tumours affecting the anterior skull base. Emphasis is given to a systematic approach to skull base pathology based upon an anatomic division taking into account the major tissue constituents in each skull base compartment. The most relevant information that should be conveyed to surgeons and radiation oncologists involved in patient's management will be discussed.

Pathology of the trigeminal nerve

Imaging of the trigeminal nerve requires a thorough understanding of its anatomy and function, clinical symptoms related to malfunction, and its key pathologies. Because of the nerve's long course from the brainstem nuclei to the peripheral branches, MR imaging and CT studies have to cover a large anatomic area while providing high-resolution images. Although MR imaging has almost completely replaced CT as the diagnostic modality of choice for investigating trigeminal neuropathy, CT still plays a role in the assessment of skull base foramina and facial skeleton. In this article, the clinical, radiologic, and pathologic features of the most common conditions causing trigeminal nerve dysfunction at each specific anatomic level are discussed.

[Metastasis to the lateral skull base]

BACKGROUND

Tumours and metastases of the lateral skull base are rare findings. Clinically, the progressive involvement of ipsilateral cranial nerves is important.

CASE REPORT

A 69-year-old man presented with headache and palsies of the facial nerve and nerve VI. Furthermore, he had hearing loss and hypaesthesia of the trigeminal nerve (V3). Four months previously, laser therapy for carcinoma of the trachea (cT4 cN3 cM0) had been done. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed an intrapetrosal mass with destruction of the lateral skull base. The findings suggested a metastasis of the tracheal carcinoma. We performed a mastoidectomy with specimen collection, and the pathological analysis revealed infiltration of a squamous cell carcinoma. The patient died within 3 weeks after radiotherapy with palliative intention despite malignant progression.

CONCLUSION

The diagnosis and therapy of metastases to the lateral skull base is an interdisciplinary challenge. CT and MRI scans are essential for planning further procedures. In cases of headache and cranial nerve palsies, a metastasis to the lateral skull base must be considered in the differential diagnosis.

[Tumors and tumor-like lesions]

Tumors and tumor-like lesions are rare diseases in the paranasal sinuses. There is a great variety of histological types, but only a small number of morphological patterns on imaging. Histology is an important point in therapeutic planning. In most cases it is obtained by sampling, which is not as difficult in the sinonasal area as in other regions of the body. The main task of imaging is an exact estimation of the extent and spread of a lesion. This article discusses the possibilities and limitations of CT and MRI in the assessment of the dignity and spread of paranasal tumors and tumor-like lesions in consideration of necessary therapeutic information. Additionally, an overview of features on imaging of different paranasal tumors and tumor-like lesions is given.

CT–MR image data fusion for computer assisted navigated neurosurgery of temporal bone tumors

PURPOSE

To demonstrate the value of multi detector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the preoperative work up of temporal bone tumors and to present, especially, CT and MR image fusion for surgical planning and performance in computer assisted navigated neurosurgery of temporal bone tumors.

MATERIALS AND METHODS

Fifteen patients with temporal bone tumors underwent MDCT and MRI. MDCT was performed in high-resolution bone window level setting in axial plane. The reconstructed MDCT slice thickness was 0.8 mm. MRI was performed in axial and coronal plane with T2-weighted fast spin-echo (FSE) sequences, un-enhanced and contrast-enhanced T1-weighted spin-echo (SE) sequences, and coronal T1-weighted SE sequences with fat suppression and with 3D T1-weighted gradient-echo (GE) contrast-enhanced sequences in axial plane. The 3D T1-weighted GE sequence had a slice thickness of 1mm. Image data sets of CT and 3D T1-weighted GE sequences were merged utilizing a workstation to create CT-MR fusion images. MDCT and MR images were separately used to depict and characterize lesions. The fusion images were utilized for interventional planning and intraoperative image guidance. The intraoperative accuracy of the navigation unit was measured, defined as the deviation between the same landmark in the navigation image and the patient.

RESULTS

Tumorous lesions of bone and soft tissue were well delineated and characterized by CT and MR images. The images played a crucial role in the differentiation of benign and malignant pathologies, which consisted of 13 benign and 2 malignant tumors. The CT-MR fusion images supported the surgeon in preoperative planning and improved surgical performance. The mean intraoperative accuracy of the navigation system was 1.25 mm.

CONCLUSION

CT and MRI are essential in the preoperative work up of temporal bone tumors. CT-MR image data fusion presents an accurate tool for planning the correct surgical procedure and is a benefit for the operational results in computer assisted navigated neurosurgery of temporal bone tumors.

[Skull base tumors]

Modern imaging techniques have great importance in the diagnosis and therapy of skull-base pathologies. Many of these lesions, especially in relation to their specific location, can be evaluated using CT and MR imaging. Tumors commonly found in the anterior skull base include carcinoma, rhabdomyosarcoma, esthesioneuroblastoma and meningioma. In the central cranial fossa, nasopharyngeal carcinoma, metastases, meningioma, pituitary adenoma and neurinoma have to be considered. The most common neoplasms of the posterior skull base, including the CP angle, are neurinoma, meningioma, nasopharyngeal carcinoma, chordoma and paraganglioma. One major task of imaging is the evaluation of the exact tumor extent as well as its relationship to the neighboring neurovascular structures. The purpose of this review is to recapitulate the most important anatomical landmarks of the skull base. The typical imaging findings of the most common tumors involving the skull base are also presented.

[Benign and malignant lesions in the region of the inner ear and cerebellopontine angle]

Tumorous lesions in the region of the inner ear and cerebellopontine angle are very rare and can be classified into benign and malignant disease forms. This contribution presents and explains the CT and MRI characteristics of these tumors.High-resolution computed tomography (HRCT) in the axial projection is applied for evaluation in the high-resolution bone window. The coronary slices can be reconstructed from the axial datasets or in individual cases examined in the coronary plane.HRCT excellently demonstrates osseous lesions and in individual cases - e.g., exostoses - it can simply suffice to perform HRCT of the temporal bone, while HRCT is also excellent for detecting osseous lesions to determine whether the tumor is benign or malignant.MRI, on the other hand, excellently shows the extent of tumor spread because of its superb soft tissue contrast. Consequently, HRCT and MRI images of the inner ear and cerebellopontine angle provide meaningful information for visualization and classification of tumorous lesions. The two methods should not be considered as competing but rather as complementary and among other aspects exert considerable influence on the therapeutic approach.