Petrous apex cholesterol granuloma: maintenance of drainage pathway, the histopathology of surgical management and histopathologic evidence for the exposed marrow theory

Surgical Approaches to Petrous Apex Cholesterol Granulomas: A Systematic Review and Network Meta-analysis

OBJECTIVE

To compare the outcomes of different surgical approaches to petrous apex cholesterol granulomas (PACG).

DATA SOURCES

PubMed, Embase, Google Scholar, Cochrane, and Web of Science.

REVIEW METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses-Network Meta-analyses guidelines, databases were searched from inception to November 31, 2022. Studies comparing two or more approaches were included. Reviews and population studies were excluded. The main outcome measures were the resolution of symptoms, serviceable hearing, complication, and revision rates.

RESULTS

The search yielded 2132 studies. After applying inclusion and exclusion criteria, 15 studies remained, consisting of 214 patients treated with lateral approaches (n = 182) or anterior endonasal approaches (n = 32). The efficacy of lateral and anterior endonasal approaches in achieving symptom resolution was comparable (73% vs. 68%, p = 0.5). Both exhibited similar rates of complications (33% vs. 37%, p = 0.3), albeit with distinct profiles. Lateral approaches were associated with higher rates of facial palsy and sensorineural hearing loss (44% vs. 18%, p = 0.03). Anterior endonasal approaches demonstrated higher rates of epistaxis and cerebrospinal fluid leak (15% vs. 1%, p = 0.001). Anterior endonasal approaches exhibited lower revision rates (OR: 0.35, 95% CI: 0.14-0.88). The placement of a stent in both approaches was associated with higher symptom resolution (OR: 5.12, 95% CI: 1.05-9.97) and lower revision rates (OR: 0.71, 95% CI: 0.33-0.92).

CONCLUSIONS

Anterior endonasal approaches yield lower revision rates compared to lateral approaches for PACG. Both approaches demonstrate similar effectiveness in symptom resolution and comparable rates of complications, with distinct profiles. Facial nerve and hearing status are important factors that should be addressed when selecting the approach. Stenting is beneficial.

LEVEL OF EVIDENCE

NA Laryngoscope, 134:1540-1550, 2024.

Bilateral cholesterol granulomas of the maxillary sinus with review of the literature

Cholesterol granulomas are a common benign pathology classically found in the mastoid antrum and air cells of the temporal bone and less commonly found in the paranasal sinuses. We present a unique case of bilateral cholesterol granulomas of the maxillary sinus that is the second case to our knowledge reported in the literature. In an effort to provide an update about cholesterol granulomas of the paranasal sinuses, we examined the literature from January 2011 through 2021 in conjunction with a previous systematic review of the literature from 1970 to December 2010. This report reinforces that upon presentation, cholesterol granulomas can resemble multiple pathologies and histology is needed for diagnosis. This report should serve as an updated resource for otolaryngologists regarding cholesterol granulomas of the paranasal sinuses.

Surgical anatomy of the transcanal infracochlear approach

PURPOSE

The objective of this study is to describe the detailed surgical anatomy of the infracochlear approach to prevent complications and to compare the postauricular transcanal microscopic and endoscopic approaches to reach the petrous apex.

METHODS

Cadaver heads were dissected using a binocular surgical microscope, endoscopes, and an electric drill. The dimensions of the access field that could be reached and manipulated with surgical instruments and straight drill via postauricular transcanal microscopic and endoscopic approaches were evaluated.

RESULTS

Both postauricular microscopic and transcanal endoscopic approaches were considered to be inapplicable in cases with a tympanic cavity located jugular bulb closer than 3 mm to the cochlea. This relationship was seen in 3 (9%) sides of the cadavers. In 4 specimens (12%), a cochlear aqueduct with an open lumen was detected. Both postauricular microscopic and transcanal endoscopic approaches reached a nearly identic dissection area. Detailed anatomy of the approach and measurements about the topography of the third portion of the facial nerve from the tympanic cavity were presented.

CONCLUSION

Both traditional microscopic postauricular and endoscopic transcanal approaches provided comparable access areas to the inferior petrous apex with wide exposure, and radiologic measurements were compatible. A tympanic cavity located jugular bulb in close relation with cochlea was the only instance that restricted the applicability of this technique.

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.

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

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

Surgery of the lateral skull base: a 50-year endeavour

Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

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.

Petrous Apex Cholesterol Granulomas: Outcomes, Complications, and Hearing Results From Surgical and Wait-and-Scan Management

OBJECTIVE

1. To analyze the surgical outcomes in the management of petrous apex cholesterol granulomas (PACG) with a brief literature review.2. To evaluate the importance of wait-and-scan management option.

STUDY DESIGN

Retrospective review.

SETTING

Quaternary referral center for otology and skull base surgery.

SUBJECTS AND METHODS

Charts of 55 patients with at least 12 months of follow-up were analyzed for demographic, clinical, audiometric, and radiological features. Patients were divided into surgical group (SG) (n = 31) and wait-and-scan (n = 24) (WS) group. Surgical approach was chosen as per hearing status and PACG extension and relation to nearby neurovascular structures and included either drainage by transmastoid-infralabyrinthine approach (TM-IL)/transcanal-infracochlear approach (TC-IC) or resection by infratemporal fossa type B approach (ITF-B). The combination of ITF-B with trans-otic (TO) approach or TO approach solely was used in unserviceable hearing cases. Postoperative outcomes and complications were evaluated in SG.

RESULTS

Postoperative symptom relief was observed in 24 patients (77.4%). Diplopia and paresthesia recovered in each case and improvement in headache, dizziness, tinnitus, and hearing loss was observed in 87.1% cases. Serviceable hearing was preserved in 24 of 26 cases. Postoperative complication rate was 32.2% including incidences of profound hearing loss, facial nerve paresis, carotid artery injury and intraoperative CSF leaks. Revision surgery was required in 3 (9.6%) cases, after TM-IL approach.

CONCLUSION

Surgical drainage is preferable to more aggressive resection procedures, with the latter reserved for recurrent lesions or lesions with severe hearing loss/involvement of critical neurovascular structures. ITF-B approach provides adequate cyst and neurovascular control for resection, while avoiding brain retraction. An initial wait-and-scan approach can be used in most patients where symptoms and imaging justify so.

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.

Large Cholesterol Granuloma of the Middle Ear Eroding into the Middle Cranial Fossa

Background

Cholesterol granuloma of the middle ear is extremely rare in comparison to cholesterol granuloma of the petrous apex but sometimes shows an aggressive course.

Case Report

We report herein a case involving a large, aggressive cholesterol granuloma of the middle ear that eroded the middle cranial fossa. A 64-year-old woman presented with pain in the left ear and hearing loss. Cholesterol granuloma was finally diagnosed from diffusion-weighted imaging, and cortical mastoidectomy was performed with canal wall down tympanoplasty type III. Recovery was uneventful recovery and the patient well at the 3-year follow-up.

Conclusion

This case demonstrates the rare but clinically important pathology of aggressive cholesterol granuloma of the middle ear.

Tympanomastoid cholesterol granulomas: Immunohistochemical evaluation of angiogenesis

OBJECTIVES/HYPOTHESIS

This study investigates the immunohistochemical expression of vascular endothelial growth factor (VEGF) and CD34 in patients treated for middle ear and mastoid cholesterol granulomas to evaluate the angiogenesis and vascularization of this type of lesion. A correlation between the immunohistochemical data and the radiological and intraoperative evidence of temporal bone marrow invasion and blood source connection was performed to validate this hypothesis.

STUDY DESIGN

Retrospective study.

METHODS

Immunohistochemical expression of VEGF and CD34 in a group of 16 patients surgically treated for cholesterol granuloma was examined. Middle ear cholesteatomas with normal middle ear mucosa and external auditory canal skin were used as the control groups. The radiological and intraoperative features of cholesterol granulomas were also examined.

RESULTS

In endothelial cells, there was an increased expression of angiogenetic growth factor receptors in all the cholesterol granulomas in this study. The quantitative analysis of VEGF showed a mean value of 37.5, whereas the CD34 quantitative analysis gave a mean value of 6.8. Seven patients presented radiological or intraoperative evidence of bone marrow invasion, hematopoietic potentialities, or blood source connections that might support the bleeding theory. In all of these cases there was computed tomography or intraoperative evidence of bone erosion of the middle ear and/or temporal bone structures. The mean values of VEGF and CD34 were 41.1 and 7.7, respectively.

CONCLUSIONS

High values of VEGF and CD34 are present in patients with cholesterol granulomas. Upregulation of VEGF and CD34 is indicative of a remarkable angiogenesis and a widespread vascular concentration in cholesterol granulomas.

LEVEL OF EVIDENCE

3b. Laryngoscope, 127:E283-E290, 2017.

Java brucea and Chinese herbal medicine for the treatment of cholesterol granuloma in the suprasellar and sellar regions: A case report and literature review

RATIONALE

A cholesterol granuloma (CG) is usually found in the middle ear, papilla, orbits, petrous apex, and choroid plexus, but is highly uncommon in the skull. In spite of benign clinicopathological lesions, bone erosion can be seen occasionally in the patient with CG. The optimal treatment strategy is radical surgery, but complete excision is usually impossible due to anatomical restrictions and a risk of injury to the key structures located nearby. Here, we report a patient with CGs in the suprasellar and sellar regions who was successfully treated with Java brucea and Chinese herbal medicine.

PATIENT CONCERNS

A 31-year-old man presenting with progressive decreased vision in both eyes was analyzed.

DIAGNOSES

A skull magnetic resonance imaging (MRI) scan showed a low-density tumor in the uprasellar and sellar regions and histopathological examination revealed a CG.

INTERVENTIONS

The patient was referred the surgery and radiotherapy. In the meantime, brucea soft capsules and herbal medicine combined were administered to him.

OUTCOMES

The related clinical symptoms and signs resolved significantly after several months, as his therapy progressed. The patient showed no sign of recurrence during the treatment period. Furthermore, he was still alive and disease-free at 37 months of follow-up visit.

LESSONS

Overall, brucea soft capsules and a Chinese herbal formula treatment combined could be beneficial in improving the patient's quality of life with CG in the skull.

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.

Upper Nasopharyngeal Corridor for Transnasal Endoscopic Drainage of Petroclival Cholesterol Granulomas: Alternative Access in Conchal Sphenoid Patients

Background Cholesterol granulomas arising at the petrous apex can be treated via traditional open surgical, endoscopic, and endoscopic-assisted approaches. Endoscopic approaches require access to the sphenoid sinus, which is technically challenging in patients with conchal sphenoidal anatomy.

Clinical Presentation A 55-year-old woman presented with intermittent headaches and tinnitus. Formal audiometry demonstrated moderately severe bilateral hearing loss. CT of the temporal bones and sella revealed a well-demarcated expansile lytic mass. MRI of the face, orbit, and neck showed a right petrous apex mass measuring 22 × 18 × 19 mm that was hyperintense on T1- and T2-weighted images without enhancement, consistent with a cholesterol granuloma. The patient had a conchal sphenoidal anatomy.

Operative Technique Herein, we present an illustrative case of a low-lying petroclival cholesterol granuloma in a patient with conchal sphenoidal anatomy to describe an alternative high nasopharyngeal corridor for endoscopic transnasal transclival access.

Postoperative Course Postoperatively, the patient's symptoms recovered and no complications occurred. Follow-up imaging demonstrated a patent drainage tract without evidence of recurrence.

Conclusion In patients with a conchal sphenoid sinus, endoscopic transnasal transclival access can be gained using a high nasopharyngeal approach. This corridor facilitates safe access to these lesions and others in this location.

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.

Image-guided percutaneous aspiration and gelfoam treatment of petrous apex cholesterol granuloma: a new theory and method for diagnosis and treatment

Although diagnosis of cholesterol granulomas of the skull base can be straightforward with computed tomography (CT) and magnetic resonance imaging (MRI) appearance, treatment is controversial with various skull base approaches described in the literature. This report describes a 35-year-old man who presented with a symptomatic, enlarging cystic lesion in the left petrous apex and clivus that had imaging features of a cholesterol granuloma (cholesterol cyst). Due to a prior history of treated mediastinal germ cell tumor, pathologic confirmation of the lesion was requested. A CT-guided percutaneous aspiration revealed dark used motor oil-like fluid. Continued aspiration yielded a change in the character of the fluid to marrow red. Injection of contrast revealed no communication with cerebrospinal fluid. Gelfoam (Pfizer, New York, New York, USA) was subsequently injected percutaneously into the residual cavity. Histopathology showed no evidence of malignancy and follow-up MRI at 1 month, 3 months, 6 months, and 1 year demonstrated continued decrease in size and signal of the lesion.

Development of cholesterol granuloma in a temporal bone petrous apex previously containing marrow exposed to air cells

OBJECTIVE

There is ongoing debate on the pathogenic mechanisms of cholesterol granuloma formation in the temporal bone. The purpose of this report is to provide evidence in support of the exposed marrow hypothesis in explaining the pathogenesis of petrous apex cholesterol granuloma.

STUDY DESIGN

Retrospective single case study.

MAIN OUTCOME MEASUREMENT

The primary outcome evaluated was the diagnosis of a new cholesterol granuloma in a petrous apex that previously demonstrated radiologic evidence of bone marrow exposed to petrous apex air cells.

RESULTS

A patient with a unilateral petrous apex cholesterol granuloma develops a new, contralateral cholesterol granuloma in a hyperpneumatized temporal bone petrous apex shown previously to have medullary bone exposed to air cells.

CONCLUSION

This report implicates the medullary-air cell interface in a hyperaerated temporal bone petrous apex in the development and growth of a petrous apex cholesterol granuloma.