Beyond the otoscope: an imaging review of congenital cholesteatoma

Congenital cholesteatoma (CC) is a non-neoplastic lesion of keratin debris lined by epithelium found in the temporal bone. It is the lesser-known sibling of the acquired cholesteatoma and may be classified as congenital middle ear cholesteatoma and congenital petrous bone cholesteatoma. The incidence is rising, probably owing to increased recognition and advances in imaging modalities. Cone beam CT provides detailed anatomical information, highlighting quadrant location, ossicular involvement, and mastoid extension. MRI aids in lesion characterization and detection of complications. The classification systems for congenital middle ear and petrous bone cholesteatoma are helpful in the preoperative workup and have a role in predicting postoperative recurrence rates. Management almost invariably involves surgical intervention aimed at preserving middle and inner ear function. Follow-up of CC is mainly based on MRI together with otoscopic examination. Non-echo planar diffusion-weighted imaging, especially, has proven essential for detecting residual disease. This review article emphasizes the significance of imaging in the timely diagnosis and management of CCs. CLINICAL RELEVANCE STATEMENT: This article underscores the crucial role of imaging for prompt detection, preoperative assessment, and postoperative follow-up of CCs, a condition with rising incidence associated with potentially severe complications. KEY POINTS: Timely diagnosis of CCs is imperative for avoiding complications. Imaging is key in detection, preoperative evaluation, and postoperative management. Cone Beam CT and non-echo planar DWI represent state-of-the-art imaging techniques.

A Rare Case of Abducens Nerve Palsy Caused by Primary Squamous Cell Carcinoma of the Middle Ear

Abducens nerve palsy is the most common ocular motor nerve palsy, and its possible aetiologies are numerous and diverse. Primary malignancy rarely occurs in the middle ear, with most cases associated with long-standing ear discharge and peak age of presentation in the sixties. We report a rare case of a 64-year-old male who presented with right abducens nerve palsy, which led to the diagnosis of primary squamous cell carcinoma of the right middle ear, and to our knowledge, this has not been reported previously in English literature.

Multicompartmental cystic trigeminal schwannoma as an uncommon differential diagnosis of cerebellopontine angle tumors

Trigeminal schwannoma is the second most common intracranial schwannoma yet accounts for less than 0.5% intracranial tumors [1]. Cystic degeneration is uncommon. We would like to report a pathologically proven multicompartmental cystic trigeminal schwannoma in a young adult presenting with chronic headache. A literature review on the imaging features of trigeminal schwannoma is performed to assist radiologists in accurate disease localization and prioritizing differential diagnosis in challenging cases. Confident preoperative radiological diagnosis would directly affect management strategies.

Imaging findings in otitis media and resulting secondary lesions in dogs and cats - an image essay

Over the past 2 decades, the increasing availability of computed tomography (CT) and magnetic resonance imaging (MRI) as well as the growing professional expertise have significantly improved the diagnostics of middle and inner ear diseases in dogs and cats. In answering some of the diagnostic questions, CT and MRT demonstrate equivalent performance. For most questions, however, there are differences in the diagnostic performance due to the physical imaging properties of the 2 modalities.CT is more sensitive in demonstrating involvement of the bulla wall and is more effective for detecting abnormal content within the tympanic bulla. In addition, with CT it is often easier to guide tissue samplings. On the other hand, structural changes of the soft tissues of the skull, head, meninges, brain, and nerves are not or only insufficiently detectable on CT images. MRI is clearly superior here. Therefore, MRI is essential for the characterization of materials inside the bulla cavity and for demonstrating the extent of any central spread of otitis media (OM).In this image essay, CT and MRI features of OM and resulting secondary lesions described in the literature are analyzed and summarized. Own image examples are used for illustration. Information on the etiology, pathogenesis, pathomorphology, and clinical signs important for understanding these changes are presented in concise descriptions.

Common Neck and Otomastoid Infections in Children

Neck infections are common in children, though the clinical presentation is often vague and nonspecific. Therefore, imaging plays a key role in identifying the site and extent of infections, evaluating for potentially drainable collections, and assessing for airway and vascular complications. This review focuses on imaging features associated with common and characteristic neck infections in children to include tonsillar, retropharyngeal, and otomastoid infections; suppurative adenopathy; superimposed inflammation or infection of congenital cystic lesions; and Lemierre syndrome.

Imaging of Temporal Bone Mass Lesions: A Pictorial Review

Tumoral lesions of the temporal bone include benign or malignant tumors and congenital or inflammatory lesions. Temporal bone lesions are difficult to approach. Therefore, making a preoperative diagnosis and considering whether the lesions require treatment are necessary; if they require treatment, then the type of treatment requires consideration. These tumors cannot be observed directly and must be diagnosed based on symptoms and imaging findings. However, the differentiation of temporal bone lesions is difficult because they are rare and large in variety. In this pictorial review, we divided temporal bone lesions by location such as along the facial nerve, along the internal jugular vein, around the endolymphatic sac, in the internal auditory canal/cerebellopontine angle, petrous apex, middle ear, and mastoid, focusing on the imaging findings of temporal bone lesions. Then, we created a diagnostic flowchart that suggested that the systematic separation of imaging findings is useful for differentiation. Although it is necessary to make comprehensive judgments based on the clinical symptoms, patient background, and imaging findings to diagnose temporal bone mass lesions, capturing imaging features can be a useful differentiation method.

Imaging of Skull Base Tumors

The skull base provides a platform for supporting the brain while serving as a conduit for major neurovascular structures. In addition to malignant lesions originating in the skull base, there are many benign entities and developmental variants that may simulate disease. Therefore, a basic understanding of the relevant embryology is essential. Lesions centered in the skull base can extend to the adjacent intracranial and extracranial compartments; conversely, the skull base can be secondarily involved by primary extracranial and intracranial disease. CT and MRI are the mainstay imaging methods and are complementary in the evaluation of skull base lesions. Advances in cross-sectional imaging have been crucial in the management of patients with skull base pathology, as this represents a complex anatomical area that is hidden from direct clinical exam. Furthermore, the clinician must rely on imaging studies for therapy planning and to monitor treatment response. It is crucial to have a thorough understanding of skull base anatomy and its various pathologies, as well as to recognize the appearance of treatment-related changes. In this review, we aim to describe skull base tumors and tumor-like lesions in an anatomical compartmental approach and present imaging methods that aid in diagnosis, management, and follow-up.

Anatomy and Pathology of the Skull Base: Malignant and Nonmalignant Lesions

The skull base (SB) is the osseous foundation of the cranial vault. It contains many openings that allow communication between the extracranial and intracranial structures. This communication is crucial in normal physiologic processes yet may also arrow spread of disease. This article provides a comprehensive review of SB anatomy including important landmarks and anatomic variants relevant to SB surgery. We also illustrate the diverse pathologies affecting the SB.

"Leave me alone": anatomical structures and variations seen on computed tomography of the temporal bone

The anatomical structure of the temporal bone is quite complex. There are a great number of anatomical variations that are often confused with temporal bone pathologies, especially fractures. It is important that radiologists and surgeons be able to recognize such variations.

Surgical management of petrous apex cholesteatomas in the pediatric population: A systematic review

Background:

Cholesteatomas are growths of squamous epithelium that can form inside the middle ear and mastoid cavity and damage nearby structures causing hearing loss when located at the petrous apex. The primary goal of petrous apex cholesteatoma resection is gross total removal with tympanoplasty and canal-wall up or canal-wall down tympanomastoidectomy. At present, there is no definitive surgical approach supported by greater than level 4 evidence in the literature to date.

Methods:

A systematic review was conducted utilizing PubMed, Embase, and Scopus databases. Articles were screened and selected to be reviewed in full text. The articles that met inclusion criteria were reviewed for relevant data. Data analysis, means, and standard deviations were calculated using Microsoft Excel.

Results:

After screening, five articles were included in the systematic review. There were a total of eight pediatric patients with nine total cholesteatomas removed. Conductive hearing loss was the most common (77%) presenting symptom. Perforations were noted in seven ears (86%). Recurrence was noted in 50% of patients with an average recurrence rate of 3.5 years (SD = 1.73). Average length of follow-up was 32.6 months (SD = 21.7). Canal-wall up was the most utilized technique (60%) and there were zero noted surgical complications. Five of the seven (71%) patients that experienced hearing loss from perforation noted improved hearing.

Conclusion:

Due to its rarity, diagnostic evaluation and treatment can vary. Further, multi-institutional investigation is necessary to develop population-level management protocols for pediatric patients affected by petrous apex cholesteatomas.

Trans-cortical vessels in the mouse temporal bulla bone are a means to recruit myeloid cells in chronic otitis media and limit peripheral leukogram changes

Chronic otitis media, inflammation of the middle ear, is a sequel to acute otitis media in ∼8% of children. Chronic otitis media with effusion is the most common cause of childhood deafness and is characterised by effusion of white blood cells into the auditory bulla cavity. Skull flat bones have trans-cortical vessels which are responsible for the majority of blood flow in and out of the bone. In experimental models of stroke and aseptic meningitis there is preferential recruitment of myeloid cells (neutrophils and monocytes) from the marrow in skull flat bones. We report trans-cortical vessels in the mouse temporal bone connect to the bulla mucosal vasculature and potentially represent a means to recruit myeloid cells directly into the inflamed bulla. The mutant mouse strains Junbo (Mecom^Jbo/+) and Jeff (Fbxo11^Jf/+) develop chronic otitis spontaneously; Mecom^Jbo/+ mice have highly cellular neutrophil (90%) rich bulla exudates whereas Fbxo11^Jf/+ mice have low cellularity serous effusions (5% neutrophils) indicating differing demand for neutrophil recruitment. However we found peripheral leukograms of Mecom^Jbo/+ and Fbxo11^Jf/+ mice are similar to their respective wild-type littermate controls with healthy bullae and infer preferential mobilization of myeloid cells from temporal bulla bone marrow may mitigate the need for a systemic inflammatory reaction. The cytokines, chemokines and haematopoietic factors found in the inflamed bulla represent candidate signalling molecules for myeloid cell mobilization from temporal bone marrow. The density of white blood cells in the bulla cavity is positively correlated with extent of mucosal thickening in Mecom^Jbo/+, Fbxo11^Jf/+, and Eda^Ta mice and is accompanied by changes in epithelial populations and bone remodelling. In Mecom^Jbo/+ mice there was a positive correlation between bulla cavity WBC numbers and total bacterial load. The degree of inflammation varies between contralateral bullae and between mutant mice of different ages suggesting inflammation may wax and wane and may be re-initiated by a new wave of bacterial infection. Clearance of white blood cells and inflammatory stimuli from the bulla cavity is impaired and this may create a pro-inflammatory feedback loop which further exacerbates otitis media and delays its resolution.

Magnetic Resonance Imaging of Head and Neck Emergencies, a Symptom-Based Review, Part 2: Ear Pain, Face Pain, and Fever

The use of magnetic resonance (MR) imaging in the emergency department continues to increase. Although computed tomography is the first-line imaging modality for most head and neck emergencies, MR is superior in some situations and imparts no ionizing radiation. This article provides a symptom-based approach to nontraumatic head and neck pathologic conditions most relevant to emergency head and neck MR imaging, emphasizing relevant anatomy, "do not miss" findings affecting clinical management, and features that may aid differentiation from potential mimics. Essential MR sequences and strategies for obtaining high-quality images when faced with patient motion and other technical challenges are also discussed.

Giant cholesterol granuloma of petrous apex

Cholesterol granulomas are chronic inflammatory lesions located primarily in the apex of the petrous part of the temporal bone. They are benign, tumor-like lesions, consisting of a cystic cavity filled with a chocolate-brown fluid and present as hyperintense masses on T1 and T2 sequences on MRI. The most common causes of cholesterol granulomas are chronic middle ear infections and traumas, explaining their prevalence in young to middle aged patients. Due to their progressively expanding nature, clinical presentation include vertigo, diplopia, tinnitus, hearing loss and seizures. Treatment of cholesterol granulomas consists of two different approaches: watch and wait or radical surgery to remove the granulomatous tissue. We present the case of a 38-year-old male patient who was admitted to the Neurology Clinic with complaints of loss of consciousness, headache, pain on the left side of the face and tinnitus in the left ear. These symptoms had been present for some time and gradually worsened in intensity and frequency. Initially after an EEG was performed, the patient showed signs of focal epilepsy and began treatment accordingly. Subsequently, a CT and an MRI of the head and neck were performed, which showed a large, well demarcated expansile mass within the left petrous apex, which was hyperintense on T1 and T2. Based on his clinical presentation and radiologic findings, a diagnosis of cholesterol granuloma was established. Through this case report we hope to emphasize the role imaging modalities play in the diagnosis and appropriate management of cholesterol granulomas.

Pediatric Petrous Apex Lesions: A Radiological Classification and Diagnostic Algorithm

The petrous apex (PA) is involved in a myriad of pathological conditions, some of which are exclusive in children. Diagnosis may be difficult due to vague clinical presentation, and local examination is challenging owing to its inaccessible location. This is further complicated by multiple unfused sutures and ongoing PA pneumatization in children. Cross-sectional imaging is vital for the evaluation of the PA lesions, due to their precarious location and proximity to the major neurovascular structures. Several classification systems have been proposed for these lesions based on their site of origin, solid or cystic appearance, surgical or non-surgical (no touch lesions) management, and benign or malignant nature. In this article, we emphasize the distinctive role of different cross-sectional imaging modalities in the diagnosis of pediatric PA lesions, with special attention to normal variants that should not be mistaken for pathology. We also propose a radiological classification and algorithmic approach to aid in the precise diagnosis and facilitate appropriate management of the various PA lesions in children.

An unusual case of acute otitis media resulting in Gradenigo syndrome: CT and MRI findings

With the widespread use of antibiotics, Gradenigo syndrome is a rare complication of acute otitis media (AOM) and acute mastoiditis. It is an uncommon form of petrous apicitis and can be life-threatening. We report the case of a 14-year-old female with unresolved AOM, who developed otorrhea, ipsilateral headaches, diplopia and raised inflammatory markers. Magnetic Resonance Imaging (MRI) demonstrated features of petrous apicitis and confirmed the suspicion of Gradenigo syndrome. The objective of this clinical case report is to highlight this unusual syndrome together with its radiological appearance to improve its diagnosis and management.

Imaging of Petrous Apex Lesions

The petrous apex may be affected by a range of lesions, commonly encountered as incidental and asymptomatic findings on imaging performed for other clinical reasons. Symptoms associated with petrous apex lesions commonly relate to mass effect and/or direct involvement of closely adjacent structures. Petrous apex lesions are optimally assessed using a combination of high-resolution CT and MRI of the skull base. Management of petrous apex lesions varies widely, reflecting the range of possible pathologies, with imaging playing a key role, including lesion characterization, surveillance, surgical planning, and oncological contouring.

Petrous apex lesion following meningitis: management and discussion

A 9-year-old male with history of mixed hearing loss presented with petrous apex lesion following episode of meningitis. Serial imaging revealed persistence of the lesion necessitating biopsy to rule out malignancy. Biopsy revealed inflammatory changes. The management of petrous apex lesions following meningitis can be conservative but repeat imaging is necessary to rule out progression and to rule out neoplastic process.

Cavum trigeminale cephalocele associated with intracranial hypertension in an 18-month-old child: illustrative case

BACKGROUND

Cavum trigeminale cephaloceles (CTCs) are characterized by a cystic appearance and extension of the posterolateral aspect of Meckel’s cave into the superomedial portion of the petrous apex. A possible mechanism is a transient or sustained increase of intracranial pressure transmitted to Meckel’s cave, leading to its secondary herniation, in the presence of predisposing local factors. The majority of CTCs are incidental findings. Among symptomatic cases, headache, trigeminal neuralgia, cerebrospinal fluid leak, vertigo, ataxia, facial numbness, hearing loss, diplopia, and other visual disturbances have been described.

OBSERVATIONS

The authors describe a case of an 18-month-old male patient referred to their hospital with drowsiness, vomiting, left cranial nerve VI palsy, and papilledema. Neuroradiological investigation revealed the presence of a CTC with a swollen aspect of the left pontine hemisection and indirect signs of intracranial hypertension. The patient was managed with implantation of a ventriculoperitoneal shunt.

LESSONS

CTCs are rare lesions that are difficult to recognize on neuroimaging, in which they can be mistaken for tumoral or inflammatory lesions. The most frequent asymptomatic forms should be considered as “leave-me-alone” lesions. In cases of intracranial hypertension, according to a supposed theory on the origin of CTCs, the authors recommend treating only the intracranial hypertension instead of performing more invasive surgical procedures, especially in pediatric patients.

Posterior Skull Base Anatomy and Pathology

A posterior skull base lesion is an uncommon radiological finding that may be noted incidentally or during targeted imaging of patients with clinical symptoms attributable to the lesion. It may be inflammatory or neoplastic in etiology, or may simply be an anatomic variant or a "don't-touch" lesion that should not be misinterpreted as something more ominous. A systematic approach to the evaluation of the posterior skull base is therefore required in order to differentiate lesions requiring immediate attention from those requiring a less urgent course of action or none at all. This review will focus on the imaging features of pathologic conditions that are more commonly encountered in posterior skull base CT and MR examinations.

Rare case of bilateral petrous apex cephalocele

The petrous apex is a pyramidal-shaped structure which is difficult to examine due to difficult anatomical location. Lesions in the petrous apex can be managed surgically or they can be incidental lesions, which are managed conservatively. Petrous apex cephaloceles (PAC) are the cystic lesion due to herniation in the Meckel's cave of temporal bone. Bilateral PAC is a very rare phenomenon with only 21 cases reported in the literature so far. We present here a case of bilateral PAC, who presented with headache and was managed conservatively.

Beyond Tympanomastoidectomy: A Review of Less Common Postoperative Temporal Bone CT Findings

Postoperative temporal bone imaging after surgical procedures such as ossiculoplasty, tympanomastoidectomy, cochlear implantation, and vestibular schwannoma resection is often encountered in clinical neuroradiology practice. Less common otologic procedures can present diagnostic dilemmas, particularly if access to prior operative reports is not possible. Lack of familiarity with the less common surgical procedures and expected postoperative changes may render radiologic interpretation challenging. This review illustrates key imaging findings after surgery for Ménière disease, superior semicircular canal dehiscence, temporal encephalocele repairs, internal auditory canal decompression, active middle ear implants, jugular bulb and sigmoid sinus dehiscence repair, and petrous apicectomy.

Carotid petrous segment aneurysm presenting as hypoglossal nerve palsy

Aneurysm in the petrous segment of the internal carotid artery is extremely rare, and symptoms are usually derived from compression of neighbor structures such as nerve palsies. Clinical symptoms can be nonspecific and imaging findings are complex, making the diagnosis of this kind of aneurysms extremely challenging. CT angiography is the best diagnostic tool, and treatment options include surgical and endovascular approaches, the latest being preferred. We report an extremely rare case of an aneurysm in the petrous apex presenting with hypoglossal nerve palsy. We document the aneurysm through CT and confirm it using angiography. We also describe the satisfactory management of this rare case. To the best of our knowledge this an extremely rare aneurism presenting with hypoglossal nerve palsy, in which successful interventional management was achieved through a specific and prompt diagnosis.

Petrous apex pneumatisation in children: a radiological study

OBJECTIVE

This study aimed to investigate petrous apex pneumatisation in children, as an understanding of petrous apex pneumatisation is useful in the diagnosis and surgical management of middle-ear disease.

METHODS

Computed tomography head scans from 1700 patients aged 0-16 years were assessed. Petrous apex bone and air cell volumes were calculated to determine the degree of petrous apex pneumatisation. Scans were analysed for communicating tracts between the middle ear and petrous apex.

RESULTS

Petrous apex pneumatisation was found in 21.0 per cent of patients. Positive relationships were found between age and petrous apex pneumatisation prevalence (rs = 0.990, p < 0.001), and between age and degree of petrous apex pneumatisation (rs = 0.319, p < 0.001). Petrous apex pneumatisation prevalence did not significantly differ by sex or ethnicity. Communicating tracts were identified in 84.3 per cent of patients with petrous apex pneumatisation, most commonly anterior to the otic capsule.

CONCLUSION

In children, the prevalence and degree of petrous apex pneumatisation increases with age, but prevalence is not affected by sex or ethnicity.

Bilateral petrous apex cephaloceles: Is surgical intervention indicated?

INTRODCUTION

Petrous apex cephaloceles are characterized by herniation of Meckel's cave into the petrous apex. An extensive review of the literature reveals 20 cases of bilateral petrous apex cephaloceles. This article reports an additional case of bilateral petrous apex cephaloceles and reviews the pertinent literature.

PRESENTATION OF CASE

A 64-year-old female was referred from a primary care clinic due to longstanding headache. A non-enhanced CT scan of the brain revealed osteolytic bony lesions at the petrous apices and an empty sella. A brain MRI with contrast showed CSF-containing lesions in the petrous apices, communicating with Meckel's cave bilaterally. The patient was managed conservatively and is currently followed up in the neurosurgery clinic.

DISCUSSION

While the exact etiology remains uncertain, petrous apex cephaloceles are postulated to originate from sustained, chronic elevation of intracranial pressure. On MRI, petrous apex cephaloceles display signal intensities resembling CSF throughout all sequences. They demonstrate well-defined margins continuous with Meckel's cave. CT scans allow further characterization, i.e. invasive erosions, of the osseous structures in patients with petrous apex cephaloceles.

CONCLUSION

A thorough understanding of the petrous apex anatomy and its pathological lesions is paramount. A brain MRI remains the diagnostic imaging of choice to characterize petrous apex cephaloceles.

ICAR: endoscopic skull-base surgery

BACKGROUND

Endoscopic skull-base surgery (ESBS) is employed in the management of diverse skull-base pathologies. Paralleling the increased utilization of ESBS, the literature in this field has expanded rapidly. However, the rarity of these diseases, the inherent challenges of surgical studies, and the continued learning curve in ESBS have resulted in significant variability in the quality of the literature. To consolidate and critically appraise the available literature, experts in skull-base surgery have produced the International Consensus Statement on Endoscopic Skull-Base Surgery (ICAR:ESBS).

METHODS

Using previously described methodology, topics spanning the breadth of ESBS were identified and assigned a literature review, evidence-based review or evidence-based review with recommendations format. Subsequently, each topic was written and then reviewed by skull-base surgeons in both neurosurgery and otolaryngology. Following this iterative review process, the ICAR:ESBS document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:ESBS document addresses the role of ESBS in primary cerebrospinal fluid (CSF) rhinorrhea, intradural tumors, benign skull-base and orbital pathology, sinonasal malignancies, and clival lesions. Additionally, specific challenges in ESBS including endoscopic reconstruction and complication management were evaluated.

CONCLUSION

A critical review of the literature in ESBS demonstrates at least the equivalency of ESBS with alternative approaches in pathologies such as CSF rhinorrhea and pituitary adenoma as well as improved reconstructive techniques in reducing CSF leaks. Evidence-based recommendations are limited in other pathologies and these significant knowledge gaps call upon the skull-base community to embrace these opportunities and collaboratively address these shortcomings.

Headache in Petrous Apicitis: A Case Report of Chronic Migraine-like Headache Due to Peripheral Pathology

OBJECTIVE

To report a case of petrous apicitis that manifested as chronic migraine without aura and to discuss the pathophysiological mechanisms behind this presentation.

BACKGROUND

Petrous apicitis is a rare complication of acute otitis media with varied clinical presentations that stem from the close proximity of the petrous apex to numerous neurovascular structures. Headache is among the common symptoms of petrous apicitis.

METHODS

A case of new onset headache in the setting of petrous apicitis with symptomatic response to antibiotic therapy was reported. We provided a brief review of peripheral pathophysiological mechanisms of migraine and correlated to mechanism of headache in petrous apicitis.

RESULTS

A 65-year-old man with chronic otitis externa/media presented with ongoing headache fulfilling International Classification of Headache Disorders 3rd edition (ICHD-3) criteria for chronic migraine without aura that persisted despite undergoing right mastoidectomy and tympanoplasty with multiple courses of oral antibiotic therapy for his chronic otitis. MRI brain revealed petrous apicitis, otomastoiditis, and clival osteomyelitis. His imaging findings improved and his migraine-like headache completely resolved after treatment with a prolonged course of antibiotics.

CONCLUSIONS

Petrous apicitis can present as a headache with features of migraine, and in this case in particular, as chronic migraine without aura. The pathophysiological mechanisms that may underlie the generation of migraine-like headache in petrous apicitis may include the activation of nociceptive fibers within the periosteum of the petrous apex and clivus whose cell bodies originate in the trigeminal ganglion and upper cervical dorsal root ganglia. By treating the peripheral pathology, resolution of the headache may be achieved.

Immunophenotypic features of dedifferentiated skull base chordoma: An insight into the intratumoural heterogeneity

Chordomas are rare and low-grade malignant solid tumours, despite their histologically benign appearance, that arise in the bone from embryonic notochordal vestiges of the axial skeleton, a mesoderm-derived structure that is involved in the process of neurulation and embryonic development. Chordomas occurring in the skull base tend to arise in the basiocciput along the clivus. Three major morphological variants have been described (classical, chondroid, and atypical/dedifferentiated). The pathogenesis and molecular mechanisms involved in chordoma development remain uncertain. From a pathological standpoint, the microenvironment of a chordoma is heterogeneous, showing a dual epithelial-mesenchymal differentiation. These tumours are characterised by slow modality of biologic growth, local recurrence, low incidence of metastasis rates, and cancer stem cell (CSC) phenotype. The main molecular findings are connected with brachyury immunoexpression and activation of the downstream Akt and mTOR signalling pathways. The differentiation between typical and atypical chordomas is relevant because the tumoural microenvironment and prognosis are partially different. This review provides an insight into the recent and relevant concepts and histochemical markers expressed in chordomas, with special emphasis on dedifferentiated chordomas and their prognostic implications.

Development of a snake-like dexterous manipulator for skull base surgery

Petrous apex lesions constitute considerable surgical challenges due to their location in the skull base and close relationship with critical structures such as inner ear, carotid arteries, facial nerves and jugular bulb. These lesions often cannot be treated completely with rigid tools due to the limited accessibility. We are aiming to develop a snake-like manipulator to assist surgeons with the infralabyrinthine treatment of petrous apex lesions with increased dexterity. This snake-like dexterous manipulator (SDM) with 3.3 mm outer diameter and 40 mm working length was designed including a tool channel with a diameter of 1.8 mm and an endoscope channel with a diameter of 0.7 mm. The SDM can be actuated in one plane and two directions enabling the C- and S-shaped bends and rotated around its longitudinal axis. The constant curvature modeling was implemented to predict the deflection in one direction. Experiments were carried out with optical microscope to find out different bending modes. Experimental bending modes were in a good agreement with the theoretical ones in terms of the bending behavior. However tip position prediction showed discrepancies up to 1 mm in X and 2 mm in Z axes.

Extra-axial brain tumors

Extra-axial brain tumors are the most common adult intracranial neoplasms and encompass a broad spectrum of pathologic subtypes. Meningiomas are the most common extra-axial brain tumor (approximately one-third of all intracranial neoplasms) and typically present as slowly growing dural-based masses. Benign meningiomas are very common, and may occasionally be difficult to differentiate from more aggressive subtypes (i.e., atypical or malignant varieties) or other dural-based masses with more aggressive biologic behavior (e.g., hemangiopericytoma or dural-based metastases). Many neoplasms that typically affect the brain parenchyma (intra-axial), such as gliomas, may also present with primary or secondary extra-axial involvement. This chapter provides a general and concise overview of the common types of extra-axial tumors and their typical imaging features.

Anatomical Factors Influencing Pneumatization of the Petrous Apex

Objectives

Aim of the present study was to define the relationship between petrous apex pneumatization and the nearby major anatomical landmarks using temporal bone computed tomography (CT) images.

Methods

This retrospective, Institutional Review Board-approved study analyzed CT images of 84 patients that showed normal findings bilaterally. Pneumatization of the petrous apex was classified using two methods. Eight parameters were as follows: angle between the posterior cranial fossa and internal auditory canal, Morimitsu classification of anterior epitympanic space, distance between the carotid canal and jugular bulb, distance between the cochlear modiolus and carotid canal, distance between the tympanic segment and jugular bulb, high jugular bulb, distance between the vertical segment and jugular bulb, and distance between the lateral semicircular canals and middle cranial fossa.

Results

There was a significant difference in Morimitsu classification of the anterior epitympanic space between the two classification methods. Poorly pneumatic upper petrous apices were distributed uniformly in three types of Morimitsu classification, but more pneumatic upper petrous apices were found more often in anterior type. Lower petrous apex was well pneumatized regardless of the types of anterior epitympanic space, but the largest amount of pneumatization was found more frequently in the anterior type of anterior epitympanic space.

Conclusion

This study showed that there was no reliable anatomic marker to estimate petrous apex pneumatization and suggests that the pneumatization of the petrous apex may be an independent process from other part of the temporal bone, and may not be influenced by the nearby major anatomical structures in the temporal bone. In this study, the anterior type of anterior epitympanic space was found to be closely related to more well-pneumatized petrous apices, which implies that the anterior saccule of the saccus medius may be the main factor influencing pneumatization of the petrous apex.

Metastatic Prostate Cancer to the Left Temporal Bone: A Case Report and Review of the Literature

Breast, lung, and prostate cancers are the three most common malignancies to metastasize to the temporal bone. Still, metastatic prostate cancer of the temporal bone is a rare finding, with approximately 21 cases reported in the literature and only 2 cases discovered more than 10 years after initial treatment of the primary. This disease may be asymptomatic and discovered incidentally; however, hearing loss, otalgia, cranial nerve palsies, and visual changes can all be presenting symptoms. We present the case of a 95-year-old man with history of primary prostate cancer treated 12 years earlier that was seen for new-onset asymmetric hearing loss and otalgia. The tympanic membranes and middle ears were normal; however, based on radiologic findings and eventual biopsy, the patient was diagnosed with extensive metastatic prostate cancer to the left temporal bone. This case (1) demonstrates that a high index of suspicion for unusual etiologies of seemingly benign symptoms must be maintained in elderly patients having prior history of cancer and (2) substantiates the value of temporal bone imaging when diagnosis may be unclear from history and physical exam.

Excavating Meckel's cave: Cavum-trigeminale-cephaloceles (CTCs)

BACKGROUND AND PURPOSE

Cavum-trigeminale-cephaloceles (CTCs) are rare lesions of Meckel's cave and the petrous apex. Despite distinctive imaging features, they are frequently mistaken for other petrous apex lesions. In contrast to many of these entities, CTCs do--when asymptomatic--not require any invasive work-up or even surgical excision. Since correct diagnosis has profound impact on clinical decision-making, we report on a series of CTCs with distinct imaging features and their important differential diagnoses.

MATERIAL AND METHODS

We report a retrospective series of 5 patients with CTCs and the associated imaging features including the absence of diffusion restriction and solid contrast enhancement as well as their size, anatomical location with regard to adjacent structures and the remodeling or erosion of surrounding bony structures.

RESULTS

Our series contains the largest CTC that has, to the best of our knowledge, been reported so far. It revealed a deep cervical extension and was initially mistaken for a branchial cleft cyst. Furthermore, we show that CTCs can erode or remodel important structures such as canalis nervi hypoglossi, canalis Vidiani, foramen rotundum, ovale, lacerum and spinosum without causing clinical symptoms.

CONCLUSION

In contrast to previous reports in which asymptomatic CTC did not include critical structures such as the foramina rotundum, ovale, lacerum or spinosum or the hypoglossal or Vidian canal, we show that CTCs can be asymptomatic even when eroding or remodeling such clinically important structures. When extending below the skull base, CTCs are a rare differential diagnosis to cystic cervical lesions such as type II branchial cleft cysts.

[Anatomy of the petrous portion of the temporal bone]

The petrous portion of the temporal bone is an important location of traumatic injuries as well as inflammatory and neoplastic diseases in the clinical daily routine. In addition to the articles in this issue that focus on these diseases, this article provides a short overview of the clinically relevant anatomy of the petrous portion of the temporal bone.

Vascular lesions of the central skull base region

The arterial and venous structures of the central skull base region form complex anatomical relationships with each other and with adjacent osseous and neural structures. Vascular structures including the cavernous sinuses and internal carotid arteries can be displaced, encased, or invaded by neoplastic, inflammatory, or infectious lesions of the central skull base. Consequently, the vascular structures have a unique role in determining the imaging appearance, clinical significance, and therapeutic options of lesions occurring in the central skull base. This article briefly reviews the basic anatomy of the cavernous sinus and the relationship of the internal carotid artery to the cavernous sinus and central skull base. The major imaging features of some common vascular lesions, including skull base aneurysm, carotid-cavernous fistula, and cavernous sinus thrombosis are presented.

Petrous apex lesions in the pediatric population

A variety of abnormal imaging findings of the petrous apex are encountered in children. Many petrous apex lesions are identified incidentally while images of the brain or head and neck are being obtained for indications unrelated to the temporal bone. Differential considerations of petrous apex lesions in children include "leave me alone" lesions, infectious or inflammatory lesions, fibro-osseous lesions, neoplasms and neoplasm-like lesions, as well as a few rare miscellaneous conditions. Some lesions are similar to those encountered in adults, and some are unique to children. Langerhans cell histiocytosis (LCH) and primary and metastatic pediatric malignancies such as neuroblastoma, rhabomyosarcoma and Ewing sarcoma are more likely to be encountered in children. Lesions such as petrous apex cholesterol granuloma, cholesteatoma and chondrosarcoma are more common in adults and are rarely a diagnostic consideration in children. We present a comprehensive pictorial review of CT and MRI appearances of pediatric petrous apex lesions.

Anatomical variations of the sphenoid sinus and its adjacent structures: a review of existing literature

The sphenoid sinus, one of the posterior groups of sinuses, has long been regarded as a 'neglected sinus' due to the anatomical location, poor understanding and poor accessibility, till the advent of endoscopes and modern imaging techniques. Increasing knowledge and greater understanding of this sinus has permitted an evolution in surgical practices and boundaries. Various literatures of the past report a great variety of rates of pneumatization, rates of optic nerve protrusion and dehiscence, as well as internal carotid artery (ICA) protrusion and dehiscence. One similarity noted among these studies is that the rates vary according to the ethnicity of the patients. Recommendations have also been made along the way with regard to modified surgical techniques. This review aims to describe the pneumatization of sphenoid sinus and the topographical relation of the optic nerve and ICA in different populations.

Fibromyxoma of the lateral skull base in a child: case report

Purpose Fibromyxomas and myxomas are benign tumors of mesenchymal origin usually found outside the nervous system, most commonly in the atrium of the heart. They can also arise in the mandible or maxilla, but it is exceedingly rare to find them within the skull base. The history, histologic features, and the literature, with emphasis on other pediatric cases, are reviewed for this uncommon skull base neoplasm. Methods We describe the case of a 13-year-old girl who presented with a 1-year history of facial weakness, numbness, and hearing loss. A large locally destructive tumor centered in the petrous bone was found on magnetic resonance imaging. Results A mastoidectomy combined with a middle fossa craniotomy was performed for gross total resection. The child is disease free 12 months after surgery. Conclusion Diagnosis could not be made solely on radiographic studies because of the lack of pathognomonic imaging features. Radical resection provided the patient the best chance of cure. Long-term surveillance is necessary to monitor for tumor recurrence.