Peripetrosal arachnoid cysts

PURPOSE OF REVIEW: The present review summarizes the current theories on arachnoid cyst formation, the common presentations of cysts surrounding or eroding the temporal bone from the middle and posterior cranial fossae, the diagnostic strategies and the management considerations and options. RECENT FINDINGS: Arachnoid cysts are most common in the middle cranial fossa and rarely present in association with the petrous apex. They are frequently found incidentally on imaging studies performed in the workup for unrelated symptoms. When they do cause symptoms, these are usually nonspecific. Thus it is important to establish the relationship between the two. Peripetrosal arachnoid cysts may cause cranial nerve deficits in addition to symptoms related to intracranial hypertension. Small asymptomatic cysts are managed conservatively with serial imaging. Large symptomatic cysts are often managed surgically with shunting, open excision or open or neuroendoscopic fenestration or marsupialization. The management of large asymptomatic cysts depends on the patient and cyst characteristics. SUMMARY: Peripetrosal arachnoid cysts are often incidental findings. Careful selection of surgical candidates is of utmost importance. Multiple surgical options with similar success rates are available. The rates and profile of their complications may differ. Overall, approximately 70% of patients experience improvement in their symptoms with surgery.     

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.     

Large cholesterol granuloma of the petrous apex treated via subcochlear drainage.

This is a case report of a patient with bilateral cholesterol granuloma of the petrous apex, who presented with unilateral symptoms. Initially suspected as having a dermoid cyst, he underwent posterior fossa exploration, drainage and biopsy. Symptoms recurred one year later and subcochlear drainage of the petrous apex cyst was successfully performed. Follow-up for over 18 months shows no clinical nor imaging signs of recurrence. A MEDLINE literature search was carried out and relevant paper publications reviewed. Case presentation including initial, pre- and post-operative imaging is presented. This is followed by discussion of current concepts on the presentation and management of large cholesterol cysts of the petrous apex.     

Transcochlear transtentorial approach for removal of large cerebellopontine angle meningiomas.

Meningiomas of the cerebellopontine angle (CPA) most often arise from the posterior surface of the petrous pyramid and may extend along the dura to involve the tentorium. Petroclival meningiomas often involve Meckel's cavity and the tentorium. It is impossible to completely remove these large lesions with extension to the supratentorial region by conventional surgical approaches to the CPA such as the suboccipital, middle fossa, or translabyrinthine routes. If total tumor resection is not accomplished, recurrence inevitably follows. A transcochlear approach and actual excision of a large portion of the tentorium allows wide exposure to these large CPA and petroclival meningiomas with supratentorial extension. Thirty-three CPA meningiomas were reviewed from 1976 to 1991. Fourteen patients had tumor extension not only into Meckel's cavity but to the supratentorial region. Ten patients had complete tumor removal, whereas subtotal removal was associated with cavernous sinus invasion. The surgical technique is described in detail with accompanying illustrations. Preoperative symptoms, medical imaging scans, results, and complications are discussed.     

Neurotologic management of intracranial epidermoid tumors

OBJECTIVES: Epidermoid cysts are the most common intracranial embryonal tumor, although they account for only 1% of all intracranial tumors. Epidermoids often spread into several intracranial compartments. Thorough preoperative surgical planning is imperative for safe epidermoid removal. This paper discusses the neurotologic management of intracranial epidermoid cysts STUDY DESIGN: Retrospective chart review. METHODS: A database search revealed 10 patients with diagnosis of intracranial epidermoid cysts between January 1, 1971 and December 31, 2003 at our institution. RESULTS: Six males and four females with ages ranging from 18 to 54 years of age underwent surgery between September 1, 1971 and November 4, 2003. The average tumor size was 3.9 cm; six originated in the cerebellopontine angle and four in the petrous apex. Six patients had a translabyrinthine approach to the tumor, two with additional transcochlear exposure. Two patients had tumors removed by way of the middle fossa approach and one through the suboccipital approach. Multiple cranial nerves were involved by tumor in all patients, including nerves III through XI. The internal carotid artery was involved by tumor in four patients. Multiple cranial nerve deficits were seen preoperatively, and facial weakness was the most common new deficit postoperatively. Eight patients required intradural access for complete tumor removal. Seven had complete tumor removal. Headaches were the most common complication. One patient had seizures postoperatively, and another had a malignant epidermoid, which resulted in death. CONCLUSIONS: Intracranial epidermoid cysts require complex surgical planning. They involve multiple cranial nerves and vascular structures. Complete resection is frequently possible with minimal new cranial nerve deficits.     

Petrous apicitis: surgical anatomy

Various surgical approaches to the petrous apex for exposure and drainage of suppurative processes are available to the otologist. The petrous apex may be conveniently divided into anterior and posterior portions by a line in the coronal plane through the internal auditory canal. The approach to the posterior petrous apex follows fistulous tracts in the sinodural angle, the subarcuate fossa, and the infralabyrinthine tract. The anterior petrous apex may be entered by means of a radical mastoidectomy. Fistulous tracts into an infected anterior petrous apex may be found through the hypotympanum, below the cochlea, through a triangle anterior to the cochlea, below the middle fossa dura, and above the carotid artery. In this approach to the petrous tip, one must have a thorough knowledge of the anatomical relationships around the carotid artery and cochlea: the carotid artery lies within 1.69 +/- 0.70 mm of the cochlea anteriorly, and the carotid artery may be exposed within the middle ear.     

Radiographic diagnosis, surgical treatment, and long-term follow-up of cholesterol granulomas of the petrous apex

Cholesterol granuloma is an unusual lesion of the petrous apex. Accurate preoperative differentiation of the various lesions of the petrous apex by computed tomography scanning only has been difficult. We reviewed the clinical findings, computed tomography and magnetic resonance imaging scans, surgical approaches, and long-term follow-up in 10 patients with cholesterol granuloma of the petrous apex who were seen between 1971 and 1988. Headache and deficits of the 5th, 6th, 7th, and 8th cranial nerves were common presenting symptoms. Magnetic resonance imaging with special imaging techniques was accurate in diagnosing cholesterol granuloma in four patients preoperatively and three patients prior to revision surgery. The optimal surgical approach was chosen on the basis of clinical and radiographic findings and included the transsphenoidal, infralabyrinthine, transcochlear, and suboccipital routes. Our review reveals that magnetic resonance imaging is more specific than computed tomography in establishing a preoperative diagnosis and is also the technique of choice in follow-up. The long-term results are discussed.     

Petrous anatomy for middle fossa approach

OBJECTIVE: The objective was to describe the relationship of anatomical landmarks required for the middle fossa approach to lesions of the petrous apex and internal auditory canal (IAC). Landmarks for safe identification of the IAC are defined, as are two zones (safe zones I and II) anterior and posterior to the IAC. STUDY DESIGN: Temporal bone anatomical study. METHODS: Ten temporal bones underwent high-resolution computed tomography followed by wet bench dissection. A set of 39 different distances between vital structures was measured, where possible, from both radiology films and under the microscope. Mean, median, minimum, and maximum measurements of all distances were determined. Angular measurements were made using a specially designed instrument. RESULTS: Measurements were made in an anatomical position to mimic the middle fossa surgical technique. Measurements are presented for the superior surface of the temporal bone from the sigmoid sinus and inner table to vital structures, from the anterior and posterior petrous apex, and from the IAC. CONCLUSIONS: Petrous apex anatomical knowledge is required for the safe middle fossa approach to the IAC and petrous apex. Two safe zones are defined that should prevent damage to the cochlea and the superior semicircular canal.     

Extended middle fossa approach to the petroclival junction and anterior cerebellopontine angle.

OBJECTIVES: This article seeks to demonstrate the use of the extended middle cranial fossa approach in the treatment of tumors arising in the anterior cerebellopontine angle and petroclival region. STUDY DESIGN: We conducted a retrospective chart review. SETTING: Tertiary referral center. PATIENTS:: Ten-year retrospective chart review of over 800 skull base surgical cases demonstrated 16 cases in which the senior author used the extended middle cranial fossa as the sole approach to access the posterior cranial fossa, petroclival junction, or the anterior cerebellopontine angle. There were five males and 11 females, 13 meningiomas, 2 trigeminal schwannomas, and 1 brainstem glioma. Presenting symptoms were dependent on extent of brainstem compression and involvement of surrounding cranial nerves. The symptoms are broken down as follows: hydrocephalus, one; balance disturbance, three; diplopia, five; trigeminal neuralgia, two; hemifacial numbness, one; seizures, one; expressive aphasia, one; and hearing loss, two. RESULTS: Of the 16 patients in this study, one patient needed postoperative care in a skilled nursing facility. Postoperative facial nerve weakness was not experienced in any patient. One patient developed a transient cerebrospinal fluid leak that resolved spontaneously. One patient developed a pseudomeningocele secondary to postoperative hydrocephalus. This was corrected with wound exploration and placement of a ventricular peritoneal shunt. Hearing was not maintained in one patient. Two patients developed new fourth nerve paresis and two patients developed new sixth nerve palsies. There were no postoperative infections and no deaths. CONCLUSIONS: The extended middle cranial fossa approach provides excellent access and exposure to tumors in the anterior cerebellopontine angle and petroclival junction. The approach allows more direct access to the area anterior to the internal auditory canal. The key to the approach is adequate bone removal of the petrous apex to provide exposure down to the inferior petrosal sinus and anteriorly to Meckel's cave and the petroclival junction. Extradural elevation of the temporal lobe with suitable brain relaxation minimizes postoperative complications.     

Cholesterol granulomas

PURPOSE OF REVIEW: This paper reviews the literature relating to the pathogenesis, diagnosis and management of petrous apex cholesterol granulomas. RECENT DEVELOPMENTS: Diagnosis of cholesterol granulomas can be challenging due to the rarity of this surgical condition and similarities to other petrous apex pathology. Recent literature reports novel locations of cholesterol granulomas, provides support for a new theory of pathogenesis, describes additional cases of endoscopic approaches to excision, and evaluates the efficacy of stenting to prevent recurrence of the lesion. SUMMARY: Cholesterol granulomas of the petrous apex are significant due to their similarity to other petrous apex lesions, their adverse effect on cranial nerves and their challenging surgical location. These lesions are now believed to be an inflammatory reaction to the by-products of eroded marrow cavities in the temporal bone. The ideal surgical approach takes into account the hearing status of the patient and lesion location and may include the endoscopic transsphenoid, transmastoid, infralabyrinthine, middle fossa, and transotic approaches. Lesions should be excised, drained, and stented with the largest diameter silicone stent possible.     

Posterior fossa arachnoid cyst presenting with isolated sensorineural hearing loss

Arachnoid cysts are benign cysts occurring in the intra-arachnoid space and containing cerebrospinal fluid. They constitute approximately 1 per cent of all intracranial masses. They are uncommon in the posterior cranial fossa. Common presenting symptoms include headaches, seizures, focal neurologic signs and vague dizziness. Magnetic resonance imaging is the preferred method of investigation, and the treatment for symptomatic cysts is generally surgical drainage. We report the unusual presentation of a young patient with a posterior fossa arachnoid cyst that manifested in the form of isolated unilateral sensorineural hearing loss. The patient underwent posterior fossa craniotomy and marsupialization of the cyst. To our knowledge, posterior fossa arachnoid cyst presenting with isolated hearing loss alone has not been reported in the English literature. A review of the literature pertaining to posterior fossa arachnoid cysts, including the clinical features, diagnosis and management, is also presented.     

Endonasal endoscopic approach to the petrous apex: an image-guided quantitative anatomical study.

BACKGROUND: The petrous apex is a relatively inaccessible region, deeply situated within the skull base. Removal of lesions from this area, traditionally accomplished via lateral approaches, can cause significant morbidity. We undertook an anatomical study to investigate the surgical anatomy of the petrous apex through an endonasal endoscopic approach, which has been sporadically described in the literature, to investigate its feasibility and to characterise clear and consistent surgical landmarks for access. METHODS: Cadaveric dissections were performed on five heads. Pre-dissection computed tomography scans were used, with the BrainLab navigation system, to verify entry into the petrous apex. Surgical landmarks were characterised in relation to fixed sphenoid sinus structures, and surgical access before and after drilling the sphenoid sinus rostrum was quantitatively compared. RESULTS: The landmark for entry into the petrous apex was the intersection of a vertical line halfway between the medial surface of the internal carotid artery and the midline, with a horizontal line one-third of the way up from the postero-inferior floor of the sphenoid sinus. The dimensions of the postero-superior sphenoid sinus were characterised by the inter-carotid distance, pituitary-to-sphenoid-floor distance and the width of the sphenoid sinus floor, which were 15 +/- 3 mm, 16 +/- 3 mm and 26 +/- 1.6 mm respectively. The surface area of surgical access was 193 +/- 28 mm(2), increasing to 316 +/- 39 mm(2) after drilling of the sphenoid rostrum (P < 0.001; paired t-test). CONCLUSIONS: Endoscopic approach to the petrous apex is anatomically feasible, and, aided by image navigation, could extend the scope of endonasal surgery to access highly-selected lesions in the middle cranial fossa.     

Intracranial Extension of Acquired Aural Cholesteatoma

Objective Cholesteatoma of the petrous bone extending into the intracranial region is an unusual occurrence. Most cases have been attributed to secondary extension of a primary epidermal blastomatous malformation of the temporal bone into the middle or posterior fossae. Within the past two and a half decades, intracranial extension of acquired aural cholesteatoma has been recognized as a likely alternative to this mechanism. Recent literature has rejoined this observation by considering both primary and secondary cholesteatoma of the petrous bone as a single group, petrosal cholesteatoma. The present study is presented to analyze the clinical presentation, imaging findings, and surgical treatment of six patients with acquired aural cholesteatoma extending into the intracranial region. Findings in this study are compared with the extant literature on congenital and acquired cholesteatoma of the petrous bone. This study proposes that petrosal cholesteatoma is a valid anatomical construct; however, the pathogenesis of petrosal cholesteatoma is still important in understanding the clinical presentation and management of cholesteatoma that extends beyond the usual confines of the middle ear and mastoid. Study Design Retrospective case review conducted at a tertiary referral center. Methods From 1985 to 1999, 477 patients were surgically treated for acquired aural cholesteatoma. Patients with intracranial extension of cholesteatoma were studied. Clinical presentation, imaging studies, operative findings, surgical treatment, and postoperative results were evaluated. Results Six cases in a series of 477 patients with acquired aural cholesteatoma had intracranial extension of disease. In this series, the most frequent pathway for intracranial extension was supralabyrinthine through the supratubal recess into the middle cranial fossa. A less frequent pathway was via the retrofacial air cells into the posterior cranial fossa. Surgical access for removal of intracranial cholesteatoma was accomplished through several approaches including translabyrinthine, transcochlear, retrolabyrinthine, and middle cranial fossa. In two patients who had reoperation for possible residual disease, one was free of residual disease and one was found to have residual cholesteatoma in the region of the horizontal facial nerve. Conclusion Acquired aural cholesteatoma can extend into either the middle or posterior cranial fossae. In this study, cholesteatoma extended into the middle fossa through the supratubal recess along the labyrinthine facial nerve and into or above the internal auditory canal. A less frequent path is through the retrofacial air cells into the posterior fossa. Intracranial acquired cholesteatoma is generally small and presents with complaints related to underlying otitis media rather than the neurological deficits that are often associated with primary petrous bone cholesteatoma. While computed tomography and magnetic resonance imaging are both required to differentiate congenital petrous cholesteatoma from other lesions of the petrous bone, computed tomography of the temporal bone is usually sufficient to diagnosis and define intracranial extension of acquired aural cholesteatoma. These lesions can be completely excised rather than exteriorized.     

Differential diagnosis of primary petrous apex lesions.

Accurate preoperative diagnosis of petrous apex lesions is critical because the surgical approaches used for this region are different depending upon the specific disease process involved. While CT and MRI have each improved the accuracy of preoperative diagnosis of petrous apex pathology, these imaging studies are most helpful when used in conjunction with one another. When systematically applied, the combination of CT with contrast and MRI (with and without gadolinium) permits accurate differential diagnosis of primary petrous apex lesions. This review presents the imaging approach employed at the House Ear Clinic for the differential diagnosis of primary lesions of the petrous apex.     

Neurotologic follow-up after radiation of posterior fossa tumors

OBJECTIVE: Stereotactic radiation treatment, also known as gamma knife surgery or radiosurgery, has come into acceptance as a treatment alternative to surgical removal for posterior fossa tumors. The purpose of this article is to describe the role of the neurotologist in the optimal management of neurotologic complications after stereotactic radiation, as illustrated by five patients. STUDY DESIGN: Retrospective chart review. PATIENTS: Five patients who underwent stereotactic radiation of posterior fossa tumors. MAIN OUTCOME MEASURES: Presence or absence of neurotologic complications (tumor growth, hearing loss, imbalance/ataxia, vertigo, and facial paralysis) or neurosurgical complaints (facial numbness, motor weakness, headache, hydrocephalus, and subarachnoid cysts). RESULTS: Postradiation neurotologic complaints included vertigo, imbalance/ataxia, and progressive hearing loss in four of the five patients. Continued tumor growth occurred in two patients; two patients had no growth; in one patient the tumor became smaller. The complications of facial nerve paralysis, facial numbness, motor weakness, headache, hydrocephalus, cerebellar edema, and posterior fossa arachnoid cyst formation occurred less frequently. CONCLUSIONS: Stereotactic radiation of posterior fossa tumors can produce significant neurotologic problems. It is imperative that neurotologists remain involved in the follow-up care of patients with posterior fossa tumors to offer optimal treatment alternatives for the neurotologic disorders.     

岩骨胆脂瘤的诊断与外科治疗

目的探讨岩骨胆脂瘤的病因和临床表现特点以及手术方式。方法对1986年12月～2003年4月收治的12例岩骨胆脂瘤患者(继发9例，原发3例)进行回顾性分析。结果原发岩骨胆脂瘤首发症状为面瘫及听力下降，鼓膜正常。继发岩骨胆脂瘤主要表现为耳流脓史，听力下降及面瘫，鼓膜通常有穿孔或不正常。慢性中耳炎病史及耳科手术史与继发性岩骨胆脂瘤的发生密切相关。颞骨CT可明确病变范围及与面神经的关系，能为确定手术方式提供直接的参考。继发及原发岩骨胆脂瘤的治疗原则相同：彻底清除胆脂瘤上皮。手术入路有4种：经迷路、中颅窝、迷路中颅窝联合入路、颅颈联合入路(迷路下)。1例继发胆脂瘤因反复复发而行4次手术外，其余11例随访4个月～15年无复发。吻合的3例面神经中，2例由House Brackmann分级V恢复到Ⅳ；减压及神经连续性完整的3例中2例由Ⅳ恢复到Ⅲ，1例无恢复。结论继发及原发胆脂瘤病因不相同，临床表现各具特点。手术进路的选择取决于病变部位、范围及听力状况，经迷路、中颅窝是主要入路。单纯中颅窝入路应采用术腔相对封闭的术式；其他人路应采取开放术腔式手术。     

Petrous apex cholesterol granuloma involving the sphenoid sinus

Petrous apex cholesterol granulomas are slowly expanding lesions that clinically present with a variety of cranial nerve deficits. We present a case of a 40-year-old man with a right-sided, sudden-onset hearing loss. Apart from a 60-dB high-frequency sensorineural hearing loss in the right ear, all other neurotologic examinations were normal. Computed tomography revealed partial destruction of the right carotid canal, petrous apex, and clivus. Surgical treatment was performed via an endoscopic transnasal, trans-sphenoid approach using an image-guidance system. Postoperative magnetic resonance imaging showed a significant reduction in the size of the cholesterol granuloma and a stable hearing threshold.     

Endoscopic anatomy of the pterygopalatine fossa and the transpterygoid approach: development of a surgical instruction model

INTRODUCTION: The pterygopalatine fossa (PPF) is a narrow space located between the posterior wall of the antrum and the pterygoid plates. Surgical access to the PPF is difficult because of its protected position and its complex neurovascular anatomy. Endonasal approaches using rod lens endoscopes, however, provide better visualization of this area and are associated with less morbidity than external approaches. Our aim was to develop a simple anatomical model using cadaveric specimens injected with intravascular colored silicone to demonstrate the endoscopic anatomy of the PPF. This model could be used for surgical instruction of the transpterygoid approach. METHODS: We dissected six PPF in three cadaveric specimens prepared with intravascular injection of colored material using two different injection techniques. An endoscopic endonasal approach, including a wide nasoantral window and removal of the posterior antrum wall, provided access to the PPF. RESULTS: We produced our best anatomical model injecting colored silicone via the common carotid artery. We found that, using an endoscopic approach, a retrograde dissection of the sphenopalatine artery helped to identify the internal maxillary artery (IMA) and its branches. Neural structures were identified deeper to the vascular elements. Notable anatomical landmarks for the endoscopic surgeon are the vidian nerve and its canal that leads to the petrous portion of the internal carotid artery (ICA), and the foramen rotundum, and V2 that leads to Meckel's cave in the middle cranial fossa. These two nerves, vidian and V2, are separated by a pyramidal shaped bone and its apex marks the ICA. CONCLUSION: Our anatomical model provides the means to learn the endoscopic anatomy of the PPF and may be used for the simulation of surgical techniques. An endoscopic endonasal approach provides adequate exposure to all anatomical structures within the PPF. These structures may be used as landmarks to identify and control deeper neurovascular structures. The significance is that an anatomical model facilitates learning the surgical anatomy and the acquisition of surgical skills. A dissection superficial to the vascular structures preserves the neural elements. These nerves and their bony foramina, such as the vidian nerve and V2, are critical anatomical landmarks to identify and control the ICA at the skull base.     

Surgical management of petrous apex meningioma

When centered in the petrous apex, meninglomas behave like other neoplasms occurring in that region. The petrous apex can be approached by several routes: posterior craniectomy; middle fossa craniectomy; translabyrinthine, transcochlear, and transeth-moidosphenoid approaches. A patient harboring a malignant meningioma in her petrous apex is presented. A middle fossa craniectomy, coupled with posterior displacement of the facial nerve, allowed access to the entire temporal bone from above. The patient received postoperative irradiation.     

Anatomical landmarks for transnasal endoscopic skull base surgery

Resection of midline skull base lesions involve approaches needing extensive neurovascular manipulation. Transnasal endoscopic approach (TEA) is minimally invasive and ideal for certain selected lesions of the anterior skull base. A thorough knowledge of endonasal endoscopic anatomy is essential to be well versed with its surgical applications and this is possible only by dedicated cadaveric dissections. The goal in this study was to understand endoscopic anatomy of the orbital apex, petrous apex and the pterygopalatine fossa. Six cadaveric heads (3 injected and 3 non injected) and 12 sides, were dissected using a TEA outlining systematically, the steps of surgical dissection and the landmarks encountered. Dissection done by the “2 nostril, 4 hands” technique, allows better transnasal instrumentation with two surgeons working in unison with each other. The main surgical landmarks for the orbital apex are the carotid artery protuberance in the lateral sphenoid wall, optic nerve canal, lateral optico-carotid recess, optic strut and the V2 nerve. Orbital apex includes structures passing through the superior and inferior orbital fissure and the optic nerve canal. Vidian nerve canal and the V2 are important landmarks for the petrous apex. Identification of the sphenopalatine artery, V2 and foramen rotundum are important during dissection of the pterygopalatine fossa. In conclusion, the major potential advantage of TEA to the skull base is that it provides a direct anatomical route to the lesion without traversing any major neurovascular structures, as against the open transcranial approaches which involve more neurovascular manipulation and brain retraction. Obviously, these approaches require close cooperation and collaboration between otorhinolaryngologists and neurosurgeons.