Imaging destructive lesions of the petrous apex

Unilateral Facial Paralysis in the Pediatric Patient

Unilateral facial paralysis (FP) in the pediatric population is a rare entity secondary to multiple etiologies including infectious, vascular, and neoplastic. In persistent or recurrent FP, imaging can demonstrate a peripheral facial nerve (FN) lesion. Given the rarity of FN lesions, however, there is limited literature regarding optimal management. In this case series, we describe the presentation, evaluation, and management of unilateral FP in three pediatric patients along with a review of the literature. All patients presented with complete FP due to a peripheral FN lesion or compression of the FN. A combined mastoid and middle cranial fossa approach was utilized for excision in two cases, and the other child underwent a translabyrinthine approach. The pathology of the lesions revealed a meningioma, an arachnoid cyst, and a hemangioma. Presentation, evaluation, post-operative outcomes, as well as final pathologies are discussed.

Surgical approaches to the petrous apex

The petrous apex is a difficult to reach surgical area due to its deep position in the skull base and many vital surrounding structures. Petrous apex pathology ranges from extradural cholesterol granulomas, cholesteatomas, asymmetric pneumatization, and osteomyelitis to intradural meningiomas and schwannomas. Certain lesions, such as cholesterol granulomas, can be managed with drainage while neoplastic lesions must be completely resected. Surgical options use open, endoscopic, and combined techniques and are categorized into anterior, lateral, and posterior approaches. The choice of approach is determined by the nature of the pathology and location relative to vital structures and extension into surrounding structures and requires thorough preoperative evaluation and discussion of surgical goals with the patient. The purpose of this state-of-the-art review is to discuss the most commonly used surgical approaches to the petrous apex, and the anatomy on which these approaches are based.

Cholesteatoma in a cat

Case summary

A 14-year-old neutered female Burmese cat was referred for investigation of a caudal oropharyngeal mass. CT showed a thin walled cyst-like structure filling and expanding from the right tympanic bulla. Histopathology showed fragments of mildly dysplastic squamous epithelium and aggregates of keratin. These findings were considered consistent with a diagnosis of cholesteatoma.

Relevance and novel information

To the best of our knowledge, this is the first reported case of a cholesteatoma in a cat. Cholesteatoma should be considered a differential diagnosis for cats presenting with a caudal oropharyngeal mass, a history of chronic ear disease or a history of previous, surgically managed middle ear disease. Advanced imaging and biopsies should be considered important in the diagnosis of these lesions.

Transsphenoidal and infralabyrinthine approach of the petrous apex cholesterol granuloma

Space-demanding or destructive changes in the petrous bone are often challenging differential diagnosis. Cholesterol granulomas of the petrous apex can clinically present in a combination of hearing loss, vertigo, tinnitus, chronic cephalgia, impairment of facial nerve function, neuralgic pain of the nervus trigeminus, or manifest diplopia by the nerve palsy of the nervus abducens. CT-morphologically cholesterol granulomas appear as soft-tissue density masses, which may display a discrete rim after intravenous administration of a contrast agent. The MRI, T1 as well as T2-weighted images show a strong signal in the area of the lesion. Depending on the individual anatomical conditions, the surgical access must be carefully chosen between transsphenoidal, transtemporal, infracochlear/-labyrinthine, or translabyrinthine. Here, we present the transsphenoidal and translabyrinthine access for the excision of cholesterol granulomas of the petrous apex. The different accesses are compared using a neuro-navigation-supported surgical technique with respect to its complications, drainage possibilities, outcomes, and recurrence of symptoms.

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.

Petrous apex cephalocoele: contribution of coexisting intracranial pathologies to the aetiopathogenesis

OBJECTIVE

The aim of this study was to show the MRI findings of petrous apex cephalocoele (PAC) and the other intracranial pathologies that coexist with PAC, and to discuss the contribution of the co-existing pathologies to aetiopathogenesis.

METHODS

A retrospective analysis of our imaging archive for the period from January 2012 to October 2013 revealed 13 patients with PAC (12 females and 1 male; age range, 26-69 years). 11 patients underwent MRI examination of the cranium, and 2 patients underwent MRI examination of the sellar region. We evaluated the lesions for content, signal intensity, enhancement, relation to petrous apex and Meckel's cave. Images were also evaluated for coexisting pathologies.

RESULTS

The presenting symptoms included headache, vertigo, cerebrospinal fluid (CSF) leak and trigeminal neuropathy. All patients had PAC. All lesions were located posterolateral to the Meckel's cave and were isointense with CSF signal on all pulse sequences. All lesions were continuous with Meckel's cave. Coexisting pathologies included intracranial aneurysmal dilatation, empty sella, mass in hypophysis, arachnoid cyst, inferior herniation of parahippocampal gyrus and optic nerve sheath CSF distension.

CONCLUSION

Coexistence with other intracranial pathologies supports the possibility of CSF imbalance and/or intracranial hypertension in the aetiopathogenesis of PAC.

ADVANCES IN KNOWLEDGE

This study examined the contribution of the co-existing intracranial pathologies to the aetiopathogenesis of PAC.

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

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

Intraosseous schwannoma of the petrous apex

Primary neoplasms of the petrous apex are rare and include eosinophilic granuloma, chondroma, chondrosarcoma, chordoma, and schwannoma. We report just the second published case of an intraosseous schwannoma of the petrous apex and are the first to describe the entity using magnetic resonance imaging. By studying the computed tomography and magnetic resonance imaging features of this rare tumor, it is possible to suggest the diagnosis preoperatively.

[Radiological diagnostic of the non-pathological conditions of the petrous apex]

Many patients with otological symptoms are remitted to the otolaryngology outpatient clinics every day. These patients commonly undergo imaging studies, generally magnetic resonance imaging (MRI). In some cases, a positive unilateral result is found in the form of a potentially pathological signal that can be observed in the petrous apex region. We present the cases of 6 patients (aged between 26 and 62 years) with asymmetric bone marrow distribution or trapped mucous fluid secretions in the petrous apex, collected over a 6-year period. Diagnosis was made with the use of CT scans and MRI. All of the patients were referred for skull base surgery. In all cases a non-pathologic asymmetry was diagnosed in the petrous apex. Certain non-pathologic conditions of the petrous apex must be treated expectantly without any surgery.

[CT and MRI features of arachnoid cyst of the petrous apex: report of 3 cases]

PURPOSE

To describe the CT and MRI features of 3 cases of arachnoid cyst of the petrous apex.

PATIENTS AND METHODS

Three patients with isolated trigeminal neuralgia, trigeminal hypoesthesia, and sinusitis. Axial and coronal CT images were obtained. T1W, FSE T2W, FLAIR, T2*W and diffusion-weighted MR sequences were obtained.

RESULTS

In all cases, both CT and MRI showed expansile lesions eroding the petrous apex. Lesions were hypodense on CT and isointense to CSF on MRI, without contrast enhancement. In one case, the lesion was contiguous with Meckel's cave with temporal fossa and sphenoid sinus extension. CT and MR imaging features are useful to distinguish arachnoid cysts of the petrous apex from other benign lesions of the petrous apex.

CONCLUSION

CT and MRI imaging features allow diagnosis of arachnoid cyst of the petrous apex because its imaging features, especially on DWI, are different from other cystic lesions of the petrous apex, namely cholesteatoma. It should be considered in patients with trigeminal involvement, especially trigeminal neuralgia.

Lesions of the petrous apex: diagnosis and management

Management of petrous apex pathology poses a unique challenge even to the most seasoned skull base surgeons. The central location in the skull base with adjacent critical neurovascular structures makes access to this region more than a trivial matter. Significant advances in diagnostic imaging have greatly facilitated the diagnosis of petrous apex lesions. The introduction of modern skull base surgery techniques also has provided skull base surgeons with numerous avenues to the petrous apex while significantly decreasing morbidity. The latest diagnostic and management strategies are discussed and an update of some of the more common pathologic entities is provided.

Petrous apex cephalocele and empty sella: Is there any relation?

OBJECTIVE

To document the presence of incidental petrous apex cephalocele (PAC) in association with empty sella in a group of patients and propose an etiologic/pathologic relation between the two lesions.

MATERIALS AND METHODS

Retrospective review of our imaging archive for the period from October 2001 to October 2006 revealed five patients with PAC (four females and one male; age range, 25-60 years; mean, 47 years). All patients underwent enhanced MR examination of the skull base and four of them underwent CT examination. Lesions were evaluated for size, content, signal intensity, enhancement, and relation to Meckel's cave and petrous apex. Images were also evaluated for the presence of empty sella.

RESULTS

The presenting symptoms in all patients were not attributable to PAC. None of the patients had symptoms related to the trigeminal nerve or history of CSF leak. Four patients had bilateral PAC and one had left PAC (total nine lesions). The lesions ranged from 6 mm to 15 mm (mean 9 mm) in the maximum diameter. All lesions were centered posterolateral to Meckel's cave and had low attenuation on CT with sharply demarcated margins. No lesion reached the inner ear structures, internal auditory canal, or mastoid air cells. On MR imaging, all lesions demonstrated CSF signal intensity that is continuous with that of the Meckel's cave. Only the periphery of the lesions demonstrated mild enhancement. All patients had empty sella. One patient had small arachnoid cysts in the middle cranial fossa, bilaterally.

CONCLUSION

PAC and empty sella are similar mechanically in terms of CSF extension and erosion into petrous apex and sella, respectively. Both conditions are seen predominantly in females and have been reported in association with CSF leak, which raises a possibility of etiologic/pathologic relation between the two.

Cholesterol granuloma surrounding the endolymphatic sac

We report a unique case of cholesterol granuloma (CG) surrounding the endolymphatic sac (ES). A 49-year-old man presented with the left side of sensorineural hearing loss, tinnitus, and vertigo. Magnetic resonance and computed tomography imaging revealed a CG surrounding the left ES. The patient initially underwent left transmastoid surgical resection of the tumor. At the time of surgery, brown fluid was aspirated from the tumor, but no other tumors were found. Histopathological examination revealed that the tumor contained cholesterol crystals, confirming the diagnosis of CG. At his 12-month postoperative follow-up, there was no evidence of recurrence. We discuss the radiology, pathology, and surgical removal of CGs surrounding ES.

Invasive Cerebrospinal Fluid Cysts and Cephaloceles of the Petrous Apex

OBJECTIVE

To describe the presentation, diagnostic evaluation, and surgical management of petrous apex cerebrospinal fluid (CSF) cysts and cephaloceles.

STUDY DESIGN

Retrospective case review.

SETTING

Tertiary referral center.

PATIENTS

Six patients with symptomatic CSF cysts or cephaloceles.

INTERVENTION(S)

All patients underwent operative intervention.

MAIN OUTCOME MEASURE(S)

Presentation, imaging characteristics, operative findings, surgical approach, resolution of symptoms, and complications.

RESULTS

Six patients presented with various neurotologic symptoms including vertigo, otalgia, diplopia, meningitis, hearing loss, and retroorbital headaches. Four lesions were centered within the anterior petrous apex and were classified as a cephalocele originating from Meckel's cave. The remaining two lesions were arachnoid cysts that involved the posterior petrous apex. Cysts and cephaloceles both demonstrated bone erosion on computed tomography and were hyperintense on T2-weighted magnetic resonance imaging and isointense or hypointense on T1-weighted magnetic resonance imaging. A variety of surgical approaches was used to treat these lesions. Preoperative symptoms were improved in five of six cases. One patient developed a postoperative CSF leak that resolved with conservative measures.

CONCLUSION

Petrous apex CSF cysts and cephaloceles may present with a variety of neurotologic symptoms. Imaging often helps narrow the differential diagnosis, but these lesions can still be confused with other erosive skull base lesions such as cholesterol granulomas, epidermoids, or tumors. Optimal treatment of symptomatic posterior petrous apex CSF cysts is marsupialization via a posterior fossa approach (i.e., retrosigmoid or retrolabyrinthine). A middle fossa approach with obliteration of the anterior petrous apex may be used to treat symptomatic CSF cephaloceles arising from Meckel's cave.

Petrous Apex Effusion: A Clinical Disorder

INTRODUCTION

Petrous apex fluid accumulations without evidence of acute infection are routinely managed as "leave alone lesions" without potential morbidity. Are petrous apex fluid accumulations (effusions) in the absence of acute infection always asymptomatic without the need for treatment? If petrous apex effusions can produce symptoms separate from acute infections, what are the clinical outcomes in these patients?

STUDY DESIGN

Retrospective clinical review.

METHODS

A retrospective record review of 31 patients presenting with petrous apex effusions was performed with recording of clinical characteristics, interventions, and outcomes.

RESULTS

Eighteen of the 31 patients had clinical symptoms referable to the petrous apex effusion with the following characteristics: indolent and previous infections (4), hearing loss (3), headache and pressure alone (8), facial spasms (1), and positional vertigo (2). Overall, 5 of 18 symptomatic patients resolved with antibiotics, steroids, or positioning maneuvers. Three of five infracochlear drainages produced symptom resolution. Three of four patients undergoing retrolabyrinthine drainage had symptom resolution, and four of seven middle fossa drainages yielded symptom resolution. In contrast, infratemporal fossa drainage procedures did not resolve the patients' symptoms.

CONCLUSIONS

Isolated petrous apex effusions are rare, but they can cause symptoms. If medical management fails, surgical drainage based on the location is appropriate. The surgical drainage approach selected (infracochlear, infralabyrinthine, middle fossa, and endoscopic transnasal) should be based on an anatomic consideration of the involved petrous apex air cells (superior vs. inferior) and the relative position of the carotid artery and jugular bulb.

Petrous apex arachnoid cyst extending into Meckel's cave

A rare case of arachnoid cyst involving the petrous apex with an unusual clinical presentation has been described with special emphasis in the imaging features and importance of accurate presurgical diagnosis. Differentiation from the other benign lesions involving the petrous apex and the role of newer MR techniques in the diagnosis of these lesions has been highlighted.

Management of cholesterol granulomas of the petrous apex based on clinical and radiologic evaluation

OBJECTIVE

The purpose of this study was to analyze the imaging characteristics of 12 cholesterol granulomas as a function of their clinical symptoms. The results of the different surgical approaches and the management of these lesions are discussed.

STUDY DESIGN

Retrospective case review.

SETTING

Five tertiary referral centers.

PATIENTS

Twelve patients managed for a cholesterol granuloma of the petrous apex.

INTERVENTIONS

All patients were evaluated via computed tomography and magnetic resonance imaging. Eight patients required surgical drainage: through a conservative approach in seven patients (infralabyrinthine, n = 5; infracochlear, n = 2) and a transotic approach in one patient. Clinical and radiologic follow-up without surgery was the mode of treatment for four patients. The mean follow-up period was 18 months for patients who underwent operations and ranged from 6 months to 10 years for patients without operations.

RESULTS

Four patterns of clinical symptoms were noted: retrocochlear signs by an involvement of the internal auditory meatus (n = 8), headaches by a traction of the dura (n = 4), serous otitis media by a compression of the eustachian tube (n = 2), and asymptomatic lesions with no involvement of the adjacent structures (n = 2). Hearing and facial functions were preserved in all the cases treated by a noninvasive procedure. No recurrence or complication was reported in the patients who underwent operations. None of the noninvasively treated patients with cholesterol granulomas showed significant enlargement on follow-up imaging.

CONCLUSION

Clinical manifestations of cholesterol granulomas depend on their anatomic location and the involvement of the adjacent structures. Aggressive lesions in patients with residual hearing can be drained via an infralabyrinthine or an infracochlear approach with minimal morbidity. Follow-up must be preferred for patients with nonaggressive lesions. Although magnetic resonance imaging provides a specific diagnosis tool for cholesterol granulomas, computed tomography is essential for an accurate evaluation of the location of the cyst and choice of the surgical procedure.

Congenital cholesteatoma and cholesterol granuloma of the temporal bone: role of magnetic resonance imaging

Magnetic resonance imaging (MRI) can be of significant benefit in characterizing expansile lesions of the petrous apex. MRI can be of particular help in distinguishing congenital cholesteatoma from cholesterol granuloma. Furthermore, with the advent of faster high-resolution scanning techniques, MRI can define precise spatial relationships of these masses with the middle and inner ear structures, internal carotid artery, jugular vein, and other structures of the skull base. MRI scanning is sensitive in detecting intracranial extension of these masses. MR angiography can provide additional information regarding the relationship of these masses with adjacent vascular structures and confirm patency of the adjacent vessels. In the postoperative period, MR scanning can help evaluate for complete removal, complication, recurrence, or formation of complicating granulation tissue.

Petrous apex cholesteatoma

Primary or secondary petrous apex cholesteatoma requires surgical management. We describe here live patients with cholesteatoma in the petrous apex on whom different surgical approaches to this region were used. Translabyrinthine transcochlear (transotic) approach with VII-XII anastomosis was used in four patients. In one patient middle fossa approach with otic capsule and facial canal leaving intact was used. All patients are without recurrence of cholesteatoma with improving of the facial nerve function in one case. We discuss specific pathologies of the petrous apex, the surgical approach to this region indicated according to the size and type of pathology diagnosed, hearing loss and facial nerve function. Possible complications of this surgical procedure and their management are also discussed.

Non-communicating arachnoid cyst of the temporal bone presenting as facial nerve paralysis in an infant

Non-communicating arachnoid cyst of the lateral temporal bone is a rare condition. We present a case of a non-communicating arachnoid cyst of the temporal bone in an infant who presented with a lower motor neuron facial nerve paralysis. The patient was treated by surgical excision of the cyst.