Petrous apex cholesterol granuloma: pictorial review of radiological considerations in diagnosis and surgical histopathology

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.

Radiological Classification and Management Algorithm of Petrous Apex Cholesterol Granuloma

Background: Petrous apex cholesterol granulomas (PACGs) are benign inflammatory cystic lesions of the temporal bone. Usually, asymptomatic patients may develop symptoms as the lesions expand. The diagnosis is based on both CT and MRI scans and the management relies on "wait and scan" or surgery. This paper aims at evaluating surgical outcomes and proposing a CT-based classification and a management algorithm. Methods: Patients with PACGs who were surgically treated between 2014 and 2024 were included. Symptoms, imaging, approach type and complications were considered. CT scans were classified as Type A (preserved apex cellularity), Type B (erosion of the apex cellularity), and Type C (involvement of the noble structures bone boundaries). The possible connection of the lesion with the infracochlear, perilabyrinthine and sphenoidal cellularity was assessed. Results: Nineteen patients with symptoms like diplopia, headache and sensorineural hearing loss were included. According to our classification, 1/19 patients was Type A, 4/19 were Type B and 14/19 were Type C. Five patients underwent a total resection, seven a subtotal and seven a surgical drainage. Only two complications were recorded, and 17/19 patients showed symptom regression and stability during follow-up. Conclusions: While the management of PACGs is still controversial, according to our classification and surgical outcomes, Type A, being mostly asymptomatic, should be managed with "wait and scan", Type B should undergo surgery when symptoms are present, while Type C should always undergo surgery because of their invasiveness and potential complications. When possible, a drainage should be attempted; otherwise, a surgical resection is chosen, and its completeness depends on the preoperative general and hearing status.

Imaging of Pathologies of the Temporal Bone and Middle Ear: Inflammatory Diseases, Their Mimics and Potential Complications-Pictorial Review

Imaging of the temporal bone and middle ear is challenging for radiologists due to the abundance of distinct anatomical structures and the plethora of possible pathologies. The basis for a precise diagnosis is knowledge of the underlying anatomy as well as the clinical presentation and the individual patient's otological status. In this article, we aimed to summarize the most common inflammatory lesions of the temporal bone and middle ear, describe their specific imaging characteristics, and highlight their differential diagnoses. First, we introduce anatomical and imaging fundamentals. Additionally, a point-to-point comparison of the radiological and histological features of the wide spectrum of inflammatory diseases of the temporal bone and middle ear in context with a review of the current literature and current trends is given.

Orbital cholesterol granuloma: Case report and literature review

Cholesterol granuloma is a chronic foreign-body inflammatory response that is often seen in the middle ear, mastoid antrum, and petrous apex. However, it can also occur in other anatomical locations, including the orbit. A 34-year-old male presented with painless nonaxial proptosis of the left eye, and imaging revealed a well-defined intraorbital extraconal lesion consistent with an orbital cholesterol granuloma. The pathogenesis of this rare cystic condition is unknown, but trauma and inadequate airflow through pneumatized temporal bone air cells have been proposed as potential triggers. Treatment involves total excision of the granuloma with careful removal of residual tissue adherent to the bone and the periosteum to minimize the risk of recurrence. Cholesterol granulomas usually have a good prognosis.

Fat in the brain: Facts and features

The presence of fat within a lesion in the brain is not only easy to identify on both CT/MRI but also can help narrow the differential. The purpose of this paper is to illustrate the spectrum of common and rare fat-containing lesions in the brain that are encountered in clinical practice. This paper intends to discuss 15 such lesions which are confirmed by MRI findings and histopathological correlation. We divided the spectrum of fat-containing lesions into lesions with adipose cells, lesions with cholesterol-rich content and tumours with lipomatous differentiation/transformation. Knowledge of these common and rare fat-containing lesions is essential for making the right diagnosis or narrowing the differential diagnosis.

Malignant Brain and Spinal Tumors Originating from Bone or Cartilage

Malignant bone tumors affecting the brain and spine are a rare and exceedingly difficult-to-treat group of diseases. Most commonly consisting of chordoma and chondrosarcoma, these tumors also include giant-cell tumors and osteosarcomas. This chapter will cover the background, epidemiology, genetics, molecular biology, histopathology, radiographic features, clinical manifestations, therapeutic approaches, and clinical management of each entity.

Typical and Atypical Symptoms of Petrous Apex Cholesterol Granuloma: Association with Radiological Findings

Objective: Petrous apex cholesterol granuloma (PACG) is a lesion that can give rise to different symptoms, and correlations with etiopathology are ambiguous. The aim of this study is to analyze the association between PACG symptoms and radiological findings at presentation, in order to establish a reproduceable pre-operative radiological evaluation and guide the surgical indication. Methods: PACG patients were collected in two tertiary care hospitals. All cases underwent CT/MRI to evaluate the cyst localization and erosion of surrounding structures. Typical and atypical symptoms were then analyzed and compared to radiologic findings established in accordance with the literature. Results: Twenty-nine patients were recruited; the most common symptoms were headache (69%), diplopia (20.7%) and fainting (24.1%), an atypical clinical manifestation related to jugular tubercle involvement. Significant associations between symptoms and radiologic findings were noted in terms of headache and temporal lobe compression (p = 0.04), fainting and jugular tubercle erosion (p < 0.001), vestibular symptoms and internal auditory canal erosion (p = 0.02), facial paresthesia and Meckel’s cave compression (p = 0.03), diplopia and Dorello canal involvement (p = 0.001), and tinnitus and cochlear basal turn erosion (p < 0.001). All patients were treated via an endoscopic−endonasal approach, in which extension was tailored to each case. At a median follow-up of 46 months, 93.1% of patients experienced resolution of symptoms. Conclusions: This clinico-radiological series demonstrates associations between symptoms and anatomical subsites involved with PACG. Hence, it may guide the surgeon at the time of surgical decision, since it asserts that typical and atypical symptoms are actually related to PACG.

Incidental Findings in Head and Brain MRI of Military Pilots and Applicants: Consequences for Medical Flight Fitness

INTRODUCTION: With improved imaging technology, the number of incidental findings detected in cerebral MRI is increasing. This is a challenge that the German Air Force has to deal with in the context of standardized MRI examinations of young pilot candidates and pilots.METHODS: The German Air Force Centre of Aerospace Medicine hosted a 2-d conference to develop recommendations and procedures for the handling of some of the most frequently encountered cerebral incidental findings.RESULTS: Radiological MRI findings from a total of 2724 routine examinations of the skull of pilots and pilot applicants (26.8 ± 10.6 yr old; range from 16 to 62; over 80% range from 17 to 33; 96% men) revealed that in 28.1% of the examinations, one or more incidental findings were discovered. For seven of the following categories of incidental findings, decision guidelines could be established: white matter hyperintensities (N = 393; prevalence 14.4%; 95% CI 13.11-15.75), pinealis cysts (317; 11.6%; 10.43-12.84), developmental venous anomalies (64; 2.3%; 1.78-2.92), cavernomas (15; 0.6%; 0.27-0.83), aneurysms (14; 0.5%; 0.25-0.78), cholesterol granulomas (22; 0.8%; 0.47-1.14), and heterotopias of the gray matter (6; 0.2%; 0.04-0.4).CONCLUSION: Considering pilots health and aviation safety, a waiver decision is often possible after thorough discussion, depending on the specific criteria of the incidental finding and of the type of license.Kühn S, Sönksen S-E, Noble H-J, Knopf H, Frischmuth J, Waldeck S, Müller-Forell W, Weber F, Bressem L. Incidental findings in head and brain MRI of military pilots and applicants: consequences for medical flight fitness. Aerosp Med Hum Perform. 2022; 93(5):450-457.

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.

Clivus pathologies from diagnosis to surgical multidisciplinary treatment. Review of the literature

The Clivus is a bone that lies in a central position of the skull base, and it is a crucial point that splits and connects different anatomical compartments at the same time. There is significant variability of diseases involving the clivus, from neoplasms to non-neoplastic, inflammatory or traumatic lesions. Each of these is rare in frequency, and this heterogeneity contributes to yield the management even more challenging. Clival pathologies can be asymptomatic or have manifestations ranging from aspecific headache to cranial nerves palsies, till life-threatening complications as cerebrospinal fluid rhinorrhoea, meningitis or brain abscess. There isn’t an univocal endorsement among experts with regard to the best approaches to manage the clivus. The paths described are many, the main division is between the transclival and transcranial lateral approaches. We performed a review of the literature, thus highlighting how authors seem to suggest that the surgical approach shouldn’t be chosen aprioristically, but based on a patient centred analysis, considering the combination of multiple surgical corridors. From diagnosis to surgery and medical therapy, clival pathologies require a team of multidisciplinary experts to ensure the best standard of treatment and higher survival rate.

[Pathology of the apex of the temporal bone pyramid: cholesterol granuloma and congenital cholesteatoma]

The report presents modern views on the origin and pathomorphological characteristics of the cholesterol granuloma of the petrous apex of temporal bone, its clinical comparison with congenital cholesteatoma of the same localization. The differential diagnostic features in CT and MRI scans are analyzed in detail, and the principles of surgical treatment, indications and contraindications are discussed. Also the case of atypical course of cholesterol granuloma is presented, which was difficult in the diagnostics but with a successful treatment result.

Gradenigo's Syndrome and Bacterial Meningitis in a Patient with a Petrous Apex Cholesterol Granuloma

Gradenigo's syndrome (GS) classically involves a triad of ear pain due to acute or chronic otitis media (OM), facial or retro-orbital pain in the distribution of the trigeminal nerve, and an abducens nerve palsy. The simultaneous presentation of all three components has become less common in cases of GS reported in the literature, particularly in the era of antibiotics effective against typical organisms attributed to OM and petrous apicitis. In addition to infectious petrous apicitis arising directly from OM, more recent cases of GS are attributed to the compression of the same traversing cranial nerves in the presence of various expansile petrous apex (PA) lesions, both benign and malignant. We report a case of a 24-year-old male who presented initially with nausea, fever, photophobia, left-sided retro-orbital pain, and headache. He was diagnosed with bacterial meningitis by lumbar puncture and treated with empiric antibiotics, with CSF eventually revealing nontypeable Haemophilus influenzae. Several days into his course, he developed diplopia with leftward gaze. Brain imaging revealed an expansile, erosive PA cholesterol granuloma with associated contiguous dural and leptomeningeal enhancement. The patient improved with antibiotics and eventually underwent surgical intervention. This atypical presentation of GS with a rare complication of meningitis in the setting of a PA granuloma demonstrates the importance of early recognition of this syndrome, as well as consideration of added surgical intervention in patients with pre-existing petrous lesions at potentially higher risk of dangerous complications of GS.

Endoscopic Endonasal Transpterygoid Approach Using Pedicled Nasoseptal Flap for Petrous Apex Cholesterol Granuloma With Intraoperative Video

With the development of minimally invasive endoscopic surgery and image-guided navigation systems, the endoscopic endonasal approach to petrous apex lesions has become more favorable. In this case, a petrous apex cholesterol granuloma was successfully treated with an endoscopic endonasal transpterygoid approach. A navigation system was used, and a contralateral nasoseptal flap and silicone tube stent were applied to maintain the cholesterol granuloma drainage pathway. The authors describe the endoscopic endonasal transpterygoid approach using a pedicled nasoseptal flap for petrous apex cholesterol granuloma and provide an intraoperative video and a literature review.

Indications and endonasal treatment of petrous apex cholesterol granulomas

PURPOSE OF REVIEW

Lesions of the petrous apex of the temporal bone can be challenging to access and approaches laterally through the mastoid as well as medially through an endonasal approach are utilized to access this region while preserving function of adjacent structures. Cholesterol granulomas of the petrous apex requiring surgery are marsupialized to prevent expansion of the inflamed cyst and relieve associated clinical symptoms. The endonasal approach to the petrous apex has in the past been limited to lesions medial to the internal carotid artery.

RECENT FINDINGS

Endoscopic approaches have been developed to expand the range of petrous apex lesions that are accessible endonasally. These endonasal corridors include a nasopharyngeal/transclival corridor, lateralization of the internal carotid artery to create an expanded medial window, a pterygopalatine infrapetrosal approach, and a contralateral maxillary approach, which allow improved access to the inferior and lateral petrous apex. Nasoseptal flaps may reduce the risk of postoperative stenosis of the drainage tract.

SUMMARY

Endoscopic endonasal approaches can be used safely to address both medial and lateral/inferior petrous apex lesions. Morbidity of these procedures is low and use of a nasoseptal flap may limit restenosis of the drainage pathway.

T1-Weighted Dynamic Contrast-Enhanced Magnetic Resonance Imaging (DCE-MRI) to Distinguish Between Concurrent Cholesterol Granuloma and Invasive Ductal Carcinoma of the Breast: A Case Report

Patient: Female, 52

Final Diagnosis: Cholesterol granuloma of the breast

Symptoms: Follow up

Medication: —

Clinical Procedure: Surgical excision

Specialty: Radiology

Long-term Symptom-specific Outcomes for Patients With Petrous Apex Cholesterol Granulomas: Surgery Versus Observation

OBJECTIVE

Review long-term symptom-specific outcomes for petrous apex cholesterol granulomas (PACG).

STUDY DESIGN

Retrospective review.

SETTING

Tertiary center.

PATIENTS

Adults with PACG were assessed from 1998 to 2015.

INTERVENTION(S)

Symptomatic patients were stratified into surgical and observation subgroups.

MAIN OUTCOME MEASURE(S)

Resolution rates of individual symptoms and chief complaints were assessed as was the impact of surgical approach and stent usage on symptom-specific outcomes. Symptom recurrence rates were tabulated.

RESULTS

Twenty-seven patients were included whose mean age was 44.8 ± 3.3 years. Fourteen and 13 patients stratified into the surgical and observation subgroups respectively. The surgical subgroup trended toward a longer follow-up period (mean 68.5 vs. 33.8 mo; p = 0.06). Overall, the most frequent symptoms encountered were headache (52%), aural fullness, tinnitus, and vestibular complaints (41% each). Visual complaints, retro-orbital pain, and cranial neuropathies were less common (18%, 15%, 11%). The overall symptom resolution rate was significantly higher in the surgical subgroup (48% vs. 26%, p = 0.03). In both subgroups, headache, retro-orbital pain, and visual complaints had the highest resolution rates. Vestibular complaints and tinnitus were very unlikely to resolve. Significantly more patients in the surgical group resolved their chief complaints (70% vs. 25%, p = 0.02). While approach type and stent usage did not significantly influence symptom outcomes, all patients with symptom recurrence (11%) were initially managed without stents.

CONCLUSION

Symptom-specific outcomes were better in patients managed surgically for PACG. Individual symptom resolution rates were highly variable. Some symptoms were refractory regardless of management strategy. Surgical approach and stent usage did not significantly influence symptom outcomes.

A novel drainage approach in patients with cholesterol granuloma: From petrous apex to mastoid air cell

Background:

Cholesterol granulomas (CG) of the petrous apex (CGPA) are benign lesions that have high recurrence rates after surgical intervention. We describe the use of a robust silicon drain between the petrous apex and mastoid air cells to allow constant aeration of the lesion for preventing recurrence.

Case Description:

A retrospective analysis was performed using the data of four patients treated at the Maastricht University Medical Centre between 2014 and 2016. Using the middle fossa approach, the petrous apex was reached, the cyst was opened, and the content aspirated. Subsequently, a robust silicon drain was placed between the cyst and mastoid air cell system. The outcome measures were clinical improvement of the symptoms and radiological parameters. The patients were female (n = 2) and male (n = 2) with an age range between 33 and 53 years at the time of the operation. Computed tomography and magnetic resonance imaging scans were used to confirm CG diagnosis. The most common presenting symptoms in our population were diplopia and headaches. The symptoms improved after surgery and there were no complications. Thus far, no recurrence has been observed and imaging shows aeration in the lesion area.

Conclusion:

The use of a robust drain seems to be an effective, safe, and feasible option to prevent recurrences in patients with CG.

Spontaneous resolution of a petrous apex cholesterol granuloma

Cholesterol granuloma is the most common primary lesion of the petrous apex. Management of petrous apex cholesterol granuloma has evolved in recent years from primary surgical treatment to conservative observation. In this article, a case of spontaneous resolution of a petrous apex cholesterol granuloma is described. To the authors' knowledge, this is the first known report of spontaneous involution of a petrous apex cholesterol granuloma. Radiographic differential diagnosis of petrous apex lesions and the natural history of cholesterol granulomas are discussed.

The Natural History and Management of Petrous Apex Cholesterol Granulomas

OBJECTIVE

To evaluate the clinical and radiographic characteristics of cholesterol granulomas of the petrous apex, as well as the outcomes of operative and conservative management.

STUDY DESIGN

Retrospective chart review.

SETTING

Two independent tertiary academic referral centers.

PATIENTS

Adult and pediatric patients with cholesterol granulomas of the petrous apex were identified from the experience of two separate centers. Patients were included after radiographic diagnosis and clinical evaluation. All patients with less than 6 months of follow-up and those with iatrogenic postoperative cholesterol granulomas were excluded.

INTERVENTION

Demographic information, presenting symptoms, imaging characteristics, treatment strategies, and outcomes were recorded.

MAIN OUTCOME MEASURES

Patients were evaluated on the basis of symptom and radiographic evolution during time, with or without operative intervention.

RESULTS

Ninety petrous apex cholesterol granulomas were analyzed (57.8% females, 55.6% right-sided). The average age at presentation was 43.1 years (median 42.0, range 8.0-77.0 years). The most common presenting symptom was headache (56.7%), and the average lesion size in the greatest dimension was 2.1 cm (median 1.7, range 0.7-5.0 cm). During a mean follow-up of 46.0 months, no cases of spontaneous rupture or carotid injury occurred. Twenty-three patients (25.6%) ultimately underwent surgical management, most commonly for intractable headache, and only 47.8% of these patients experienced durable symptom improvement by their last postoperative follow-up.

CONCLUSION

Many cholesterol granulomas of the petrous apex remain stable during time and can be safely managed with primary observation. Surgery should be reserved for lesions that are causing, or threatening, neurologic dysfunction because of mass effect or erosion of critical structures such as the otic capsule. Cranial neuropathy associated with cholesterol granuloma may improve after operative management; however, symptoms such as headache and dizziness are less likely to benefit from surgery. As a general guideline, in the presence of a radiologically stable cholesterol granuloma in the petrous apex, alternative etiologies for headache and dizziness should be considered and treated before offering surgical intervention.

Cholesterol Granuloma Development following Temporal Bone Surgery

OBJECTIVE

To describe the clinical presentation and management of patients with cholesterol granulomas (CGs) that develop following temporal bone surgery.

STUDY DESIGN

Case series with chart review.

SETTING

Two independent tertiary academic referral centers.

SUBJECTS AND METHODS

A multicenter retrospective review was performed to identify all patients between 2001 and 2014 who were diagnosed with a CG that developed following temporal bone surgery. Patients with a history of idiopathic petrous apex CGs were excluded, as were those with <6 months of follow-up after diagnosis. Demographic and clinical data were recorded at presentation, and the main outcome measure was symptom evolution over time.

RESULTS

A total of 20 patients met inclusion criteria (median age, 55.0 years; 70.0% female), and their cases were analyzed. Diagnosis was made, on average, 149.5 months (median, 94.5; range, 13.0-480.0) following a temporal bone operation, which was for chronic ear disease in 75.0% of cases. The most common presenting symptoms were otalgia (55.0%) and otorrhea (40.0%). In patients initially managed with observation, 71.4% required no surgical intervention through a mean of 56.8 months (median, 30; range, 12.0-178.0) of follow-up. For those who initially underwent surgical excision, durable symptom relief was achieved in 66.7% of cases.

CONCLUSION

Postoperative CG formation in the temporal bone is a rare occurrence that can be encountered years following surgery. The present study suggests that conservative management can be appropriate for many cases in which patients are relatively asymptomatic.

Tympanomastoid cholesterol granuloma: radiological and intraoperative findings of blood source connection

The hypothesis that the close contiguity between the cholesterol granulomas and some rich blood sources provided the trigger to the aggressive nature of tympanomastoid cholesterol granulomas has been recently reported. To corroborate this new etiopathogenetic theory we retrospectively reviewed a series of 14 patients with primary middle ear and mastoid cholesterol granulomas and investigated the temporal bone marrow invasion and its hematopoietic potentialities and a possible cholesterol granulomas contiguity with relevant vascular structures such as the carotid artery, sigmoid jugular system, mastoid or dural vein. Eight cases did not show radiological sign of bone marrow invasion or hematopoietic potentialities visible in MRI. Besides no intraoperative vascular connections that could explain an initial bleeding source were found. Cholesterol granulomas bone marrow invasion was present in six patients. A bone marrow hematopoietic potentiality was showed in four of these patients, whereas, an evident anatomical contiguity of the cholesterol granuloma with some important temporal bone vascular structures was visible in five cases. Analysis of cardiovascular risk factors showed that four patients presented one or more of the risk factors analysed.

Imaging of skull base pathologies: Role of advanced magnetic resonance imaging techniques

Imaging plays a vital role in evaluation of skull base pathologies as this region is not directly accessible for clinical evaluation. Computerized tomography (CT) and magnetic resonance imaging (MRI) have played complementary roles in the diagnosis of the various neoplastic and non-neoplastic lesions of the skull base. However, CT and conventional MRI may at times be insufficient to correctly pinpoint the accurate diagnosis. Advanced MRI techniques, though difficult to apply in the skull base region, in conjunction with CT and conventional MRI can however help in improving the diagnostic accuracy. This article aims to highlight the importance of advanced MRI techniques like diffusion-weighted imaging, susceptibility-weighted imaging, perfusion-weighted imaging, and MR spectroscopy in differentiation of various lesions involving the skull base.

Endoscopic Transnasal Approach for Cholesterol Granuloma of the Petrous Apex

Cholesterol granulomas are rare round or ovoid cysts. They contain cholesterol crystals surrounded by foreign bodies of giant cells and are characterized by chronic inflammation. Large cholesterol granuloma can compress surrounding tissue especially cranial nerves. There are several types of surgery for the resection of cholesterol granuloma. We describe 4 cases of cholesterol granuloma operated on via transnasal endoscopic approach. In this report, we describe radiologic and pathologic features of this lesion and explain the advantages and disadvantages of transsphenoidal endoscopic approach for these rare lesions.

Atypical radiographic features of skull base cholesterol granuloma

Cholesterol granulomas (CGs) are the most common benign lesions of the petrous apex (PA) and have distinct computed tomography (CT) and magnetic resonance imaging (MRI) characteristics. On CT, CGs of the PA (PACG) present as expansile lesions with erosion of bony trabeculae. MRI shows a hyperintense lesion on T1-and T2-weighted images and do not enhance with gadolinium. The objective is to describe the radiographic features of CGs of the skull base that do not arise from the PA. This study is a retrospective review. Three patients were operated on for suspected recurrent endolymphatic sac tumor, intracranial cholesteatoma, and recurrent sphenoid wing meningioma based on CT and MRI findings. Pathology results were consistent with CG in all three cases. All patients had bone erosion on CT. These skull base CGs did not demonstrate similar MRI features. These lesions were hyperintense, iso-to-hyperintense, and hypointense on T1-weighted MRI, respectively. These CGs were hyperintense in two cases and iso-to-hyperintense in one case on T2-weighted MRI. These lesions either demonstrated central or rim enhancement after gadolinium administration. Skull base CGs that do not arise from the PA demonstrate a broad spectrum of radiographic characteristics on MRI that are not typical of PACG.

Cholesterol Granuloma of the Petrous Apex: A 5-Year Review of Radiology Reports with Follow-Up of Progression and Treatment

Objectives To assess the stability and outcomes of patients with cholesterol granulomas at Brigham and Women's Hospital. Design A retrospective review of neuroradiology magnetic resonance imaging (MRI) studies was performed. The number of newly diagnosed cases of cholesterol granuloma per year was determined. Additional data included age and gender, clinical presentation if applicable, growth on imaging follow-up, and recurrence on postoperative follow-up if applicable. Participants Inclusion criteria included patients who underwent MRI studies between January 1, 2009 and July 1, 2013. Upon review of imaging of these patients, 18 patients had findings compatible with cholesterol granuloma. Results During the study period, an average of three cases of cholesterol granuloma were diagnosed on MRI per year. Three of 18 patients underwent treatment. Two underwent surgery, both of whom demonstrated recurrence on postoperative follow-up imaging. One patient who underwent computed tomography-guided percutaneous aspiration and Gelfoam (Pfizer, New York, United States) embolization had no recurrence on imaging follow-up of up to 23 months. Among the patients who were observed without intervention, growth was identified in only one patient. Conclusions Cholesterol granulomas are a rare entity; however, their appearance on imaging may be greater than previously reported. Most of the lesions demonstrate stability and can be observed.