Skull Base, Petrous Apex, Tumors 

Updated: Jul 18, 2018
Author: Michael J Fucci, MD; Chief Editor: Arlen D Meyers, MD, MBA 

Overview

Background

The petrous apex lies at the anterior superior portion of the temporal bone.[1] Access to this region is difficult and often requires special surgical skills. The region is associated with severe life-threatening complications of otitis media. Improvements in antibiotic therapy, surgery for chronic otitis media, and the development of tympanostomy tubes have decreased incidence of suppurative petrous apicitis. Neoplastic and inflammatory lesions are the most common pathologic processes in the petrous apex. Imaging studies have greatly increased the ability to diagnose these lesions, especially in view of the often-vague symptomatology associated with these lesions. A number of the processes are diagnosed as incidental findings, and consultation is sought to determine the appropriate diagnosis and therapeutic plan. See the image below.

Petrous apicitis. An axial CT scan of the temporal Petrous apicitis. An axial CT scan of the temporal bone shows an air-fluid level within the right petrous apex and fluid within the middle ear space and mastoid.

Classic studies detailing the anatomy of the apex and development of improved surgical techniques, including the operating microscope and facial nerve monitor, permit access to the region while lowering the morbidity and mortality associated with surgery. Stereotactic radiation is a relatively new therapeutic tool that offers nonsurgical hope for treating some tumors. Diagnostic evaluation and treatment plan determination for the lesions are dynamic processes that have changed significantly over the past 20 years, and they should change significantly over the next 20 years.

For excellent patient education resources, visit eMedicineHealth's Ear, Nose, and Throat Center and Cholesterol Center. Also, see eMedicineHealth's patient education articles Earache, Hearing Loss, and Cholesterol FAQs.

History of the Procedure

Petrous apex lesions were primarily diagnosed as complications of chronic otitis media. Sophisticated imaging techniques, such as CT scanning and MRI, were not yet available, and the diagnosis was based on clinical findings, oftentimes correlating with a severe life-threatening scenario. Tympanostomy tubes, antibiotics, operating microscopes, drills, facial nerve monitors, and electroencephalography were not yet available. Pediatric wards were filled with children with intracranial complications secondary to chronic otitis media, including petrous apicitis. These lesions of the apex were evaluated by a careful history coupled with a thorough physical examination. Standard radiography, including Towne and Stenver views, coupled with polytomography permitted evaluation of the apex. Clinical suspicions were correlated with autopsy findings in fatal cases. The advent of improved imaging studies, such as CT scanning and MRI, allowed accurate diagnosis of lesions of the petrous apex.

Problem

Infectious lesions can cause meningitis, brain abscess, cranial nerve disorders, and other severe life-threatening problems. The infection must be treated promptly and aggressively to prevent adverse sequelae. In some cases, antimicrobial therapy alone is sufficient to resolve the infection. In most cases, however, surgical drainage of the abscess cavity facilitates recovery. Skull base osteomyelitis is a severe infection of the temporal bone that requires an extended course of antibiotics. Immunocompromised individuals are most susceptible to these severe infections, but these infections can occur in people with healthy immune systems.

Inflammatory lesions generally produce symptoms through the mass effect of the tumor. The apex hosts or borders several important structures discussed in Relevant Anatomy. If these lesions continue to expand, function is progressively sacrificed.

Neoplastic lesions, although rarely malignant, produce symptoms by mass effect and through direct invasion. The natural history of the disease must be thoroughly understood in order to make the correct clinical decisions. Vascular lesions produce symptoms by interrupting blood supply, by bleeding, or by producing a mass effect from the aneurysm or blood.

Lesions of the petrous apex are classified as infectious, inflammatory, neoplastic, and vascular abnormalities. The natural history of these disease processes can cause significant morbidity and mortality. The lesions most commonly observed in the petrous apex are listed below.

  • Inflammatory or congenital conditions

    • Cholesterol granuloma

    • Cholesteatoma

    • Mucocele

  • Infectious conditions

    • Petrous apicitis

    • Skull base osteomyelitis

  • Neoplastic conditions

    • Chordoma

    • Chondrosarcoma

    • Meningioma

    • Schwannoma (trigeminal acoustic, jugular foramen)

    • Metastasis

    • Glomus tumor

    • Nasopharyngeal carcinoma

  • Intrapetrous carotid artery aneurysm

  • Normal variants that may simulate pathologic conditions

    • Asymmetric bone marrow

    • Giant air cell

Epidemiology

Frequency

Lesions of the petrous apex remain relatively rare. Infectious causes are decreasing because of improved antibiotic therapy, improved techniques in chronic ear surgery, earlier and more frequent placement of tympanostomy tubes, and improved imaging studies leading to earlier diagnosis, ie, before the apex is affected. Inflammatory tumors remain infrequent, and major referral centers report few cases over several years. Neoplastic tumors of the apex also occur only rarely. Some neurootologists do not encounter a chordoma over the course of years of busy clinical practice. Skull base osteomyelitis secondary to otitis externa is common in elderly people who are immunocompromised, especially those with diabetes mellitus. Younger individuals who are immunocompromised also experience this disorder. Vascular tumors are extremely rare, with fewer than 50 cases reported in the literature.

However, incidental findings are becoming more common because the routine use of CT and MRI. The increased quality of these imaging studies and the ability to get details previously unavailable oftentimes finds abnormalities in the petrous apex. The etiology of the lesion requires a careful evaluation with occasional use of serial imaging studies to determine whether the lesion is growing.

Etiology

Infectious petrositis generally is secondary to eustachian tube dysfunction causing chronic otitis media, with or without cholesteatoma. Infectious petrositis is also secondary to acute otitis media with subsequent extension to an aerated petrous apex. The pathogens are assumed to be identical to those causing otitis media.

Cholesterol granulomas are believed to be secondary to chronic otitis media. A giant cell reaction ensues, and hemoglobin is broken down to form cholesterol debris.

Congenital cholesteatomas are secondary to trapped or misplaced ectoderm. Acquired cholesteatomas are secondary to eustachian tube dysfunction that cause retraction or to abnormal epithelial migration from tympanic membrane perforations or retractions.

Skull base osteomyelitis is secondary to a severe otitis externa, most commonly in patients who are immunocompromised.

The remaining disorders in the apex are idiopathic.

Pathophysiology

Petrous apicitis is a bacterial infection secondary to chronic otitis media, with or without cholesteatoma. This disease process is secondary to poor eustachian tube function. The process occurs after the air in the middle ear space is resorbed and a relative vacuum occurs. A bacteria-infected effusion follows and spreads to the apex through air cell tracts connecting the apex to the middle ear or mastoid.

With cholesteatomas, the tympanic membrane becomes retracted from the negative pressure. The retraction becomes deeper, squamous epithelium accumulates in the retraction pocket, and enzymes in the leading edge of the cholesteatoma erode bone. Bacteria through the middle ear colonize the pocket, and suppuration occurs. Skull base osteomyelitis is a severe complication of otitis externa in immunocompromised patients.

Inflammatory lesions are often secondary to eustachian tube dysfunction. Congenital cholesteatomas are from retained ectoderm.

The pathophysiology of neoplastic lesions is uncontrolled growth with invasion or pressure on the surrounding structures. The etiology of nasopharyngeal carcinoma is associated with the Epstein-Barr virus.

Presentation

The presenting symptoms of lesions of the petrous apex can be specific, readily directing attention to the apex, or these symptoms can be vague and nonspecific, not clearly calling attention to the skull base. Some lesions are diagnosed as incidental findings on imaging studies for nonrelated symptoms. Symptoms related to the apex are attributable to the mass effect of an expansile lesion.

In 1904, Gradenigo described a syndrome of abducens nerve palsy, pain secondary to gasserian ganglion inflammation, and facial nerve palsy from suppurative otitis media.[2] The abducens nerve is affected as it passes inferior to the petroclinoid ligament.

Facial pain or disturbance of the trigeminal nerve distribution occurs secondary to involvement of the trigeminal nerve at the Meckel cave. Facial paralysis is secondary to inflammation of the facial nerve in the temporal bone. Pain, usually around the eye, is an early symptom that is followed by the cranial neuropathies.

Several other symptoms from lesions of the petrous apex are common. Hearing loss occurs secondary to an effusion from eustachian tube dysfunction, ossicular erosion from chronic otitis media, or sensorineural hearing loss secondary to invasion of the otic capsule or the cochleovestibular nerve. Tinnitus and vertigo can also occur along with or independent of hearing loss. Facial paralysis occurs secondary to pressure on the facial nerve anywhere throughout its course in the temporal bone, especially near the geniculate ganglion. Headaches occur from distortion of the dura near the lesion. The headaches are primarily retro-orbital or at the vertex. Syncope, stroke, or amaurosis fugax occur secondary to carotid artery occlusion. Other cranial neuropathies occur with posterior lesions that affect cranial nerves VIII through XII or with anterior lesions that affect cranial nerves II-VI.

Indications

Interpreting indications for treating these lesions involves a careful risk and benefit analysis based on the symptoms, extent of disease, and natural history of the disease. Options for treating these lesions include observation, medical therapy, surgical therapy, and stereotactic radiation. Each disease process behaves differently, and specific treatment options for each lesion are discussed.

Relevant Anatomy

The 4 parts of the temporal bone are the petrous, squamous, tympanic, and mastoid portions. The petrous portion (ie, petrosa) is a 4-sided (ie, quadrilateral) pyramid with its apex anteromedial and its base posterolateral. The clivus anteromedially and the otic capsule posterolaterally border the apex.

The anterosuperior or cerebral portion of the apex forms the floor of the middle cranial fossa. Landmarks on the floor of the middle fossa are as follows:

  • Depression for the diverticulum of dura and arachnoid, known as the Meckel cave, which houses the gasserian ganglion of the trigeminal nerve

  • Facial hiatus where the greater superficial petrosal nerve carries preganglionic parasympathetic fibers to the sphenopalatine ganglion and afferent fibers to the lacrimal gland

  • Arcuate eminence formed by the arch of the superior semicircular canal

  • Tympanic canaliculus where the lesser superficial petrosal nerve carries preganglionic parasympathetic fibers to the otic ganglion

The posterosuperior surface or cerebellar aspect of the petrous bone is vertical and faces the posterior cranial fossa. It has bony landmarks as follows:

  • Internal meatus of the internal auditory canal

  • Orifice of the vestibular aqueduct

  • Groove for the superior petrosal sinus

  • Groove for the inferior petrosal sinus

The abducens, or sixth cranial nerve, travels with the inferior petrosal sinus and enters the cavernous sinus through a dural fold between the petroclival ligament and a notch in the petrosphenoid joint called the Dorello canal.

The posterior rim lies in a horizontal plane that articulates with the occipital bone to form the jugular foramen, near the opening of the cochlear aqueduct. The anterior rim articulates with the sphenoid bone and houses the anterior orifice of the carotid canal medially.

In the late 1930s and early 1940s, Lindsay performed several temporal bone studies examining the various tracts between the mastoid and petrous apex.[3, 4] He also examined the comparative anatomy of the apex. The petrous apex can be extensively pneumatized or unpneumatized, with bone marrow that fills the bone.[5] About 20-30% of apices are pneumatized. Most apices are relatively symmetric between the right and left side, essentially having the same amount of pneumatization or marrow formation. Asymmetric marrow formation can be mistaken for tumor.

The base of the apex contains the otic capsule or the inner ear. Air cells from the middle ear cleft invade the apex in varying degrees through tracts described by Lindsay. The pneumatization tracts from the mastoid and middle ear cleft to the apex are as follows:

  • The infralabyrinthine tract from the middle ear cleft inferior to the otic capsule to the apex[6]

  • The posteromedial tract of Lindsay extending along the posterior fossa anterior to the internal auditory canal to the apex

  • The subarcuate tract that follows the subarcuate artery through the arch of the superior semicircular canal to the apex

  • The anterior tract between the middle ear anterior to the cochlea and posterior to the carotid canal to the apex

  • The superior tract from the mastoid superior to the superior semicircular canal and superior to the internal auditory canal to the apex

An extensive 3-dimensional understanding of the anatomy of the temporal bone is absolutely necessary to surgically address disorders of the petrous apex. This region is filled with critical structures that are unforgiving to subtle mistakes in surgical technique or to those not intimately acquainted with the anatomy.

Contraindications

With the exception of petrous apicitis and skull base osteomyelitis, all lesions of the petrous apex are best treated surgically. Stereotactic radiation with increased dosage at the tumor and less to the surrounding brain promises a role in treating neoplastic lesions of the apex. Combined therapy with surgery followed by stereotactic radiation are undergoing several controlled studies to determine its efficacy in treating both primary and metastatic lesions.

 

Workup

Laboratory Studies

No specific laboratory evaluation is indicated in petrous apex lesions. Leukocytosis is often seen with infectious lesions, but, otherwise, laboratory findings are not helpful.

Imaging Studies

Imaging studies are the primary method used to diagnose these lesions. CT scanning is often the initial study used in evaluating the lesions. Contrast enhancement is helpful in the diagnosis, and its administration is recommended if no contraindications exist.

MRI provides valuable information in accurately diagnosing these lesions. The CT scan and MRI characteristics of each petrous apex lesion are outlined in Tables 1 and 2, respectively.

Table 1. Petrous Apex Lesion Characteristics on CT Scanning* (Open Table in a new window)

Lesion

Bone Erosion

Eroded Margin

Contralateral Apex

Contrast Enhancement

Cholesterol granuloma

+

Smooth

Highly pneumatized

-

Cholesteatoma

+

Smooth

Often not pneumatized

-

Petrous apicitis

+

Irregular

Variable

-

Effusion

-

-

Usually pneumatized

-

Bone marrow asymmetry

-

-

Variable

-

Carotid aneurysm

+

Smooth

Variable

+

Neoplasia

+

Variable

Variable

+

*From Jackler RK and Parker D: The radiographic differential diagnosis of petrous apex lesions. AJO 1992;13:561-574[7]

Table 2. Petrous Apex Lesion Characteristics on MRI Scanning (Intensity Compared with Adjacent Brain)* (Open Table in a new window)

Lesion

T1 Images

T2 Images

T1-Gadolinium

Cholesteatoma

Hypo

Hyper

No enhancement

Cholesterol granuloma

Hyper

Markedly hyper

No enhancement

Petrous apicitis

Hypo

Hyper

Rim enhancement

Effusion

Hypo

Hyper

Mucosal enhancement

Bone marrow asymmetry

Hyper

Hypo

No enhancement

Neoplasia

Hypo

Hyper

Enhancing

Carotid aneurysm

Hypo

Mixed

Rim enhancement

*From Jackler RK and Parker D: The radiographic differential diagnosis of petrous apex lesions. AJO 1992;13:561-574[7]

Preoperative angiography is required for suspected aneurysms. In rare cases, branches of the external carotid artery supply these lesions and preoperative embolization may be beneficial. The status of the internal carotid artery and vertebral-basilar systems are important in determining whether the carotid artery can be sacrificed. A balloon occlusion test is occasionally used to determine the neurologic status from a unilateral carotid occlusion.

Arteriography remains helpful in determining other lesions responsible for pulsatile tinnitus, such as glomus tumors.

MRI arteriography and venography determine dural sinus patency, although angiography remains the diagnostic criterion standard.

Diagnostic Procedures

See the list below:

  • Imaging studies, including CT scanning and MRI, usually narrow the differential diagnosis. MRI venography and angiography help in defining vascular lesions.

  • Preoperative histologic diagnosis is difficult because safe access to tissue is nearly impossible.

  • Cultures and sensitivities in bacterial disorders are helpful and are obtained from discharge within the ear canal or through a myringotomy.

Histologic Findings

Infectious lesions and inflammatory lesions

Petrous apicitis shows a white cell infiltrate consistent with an abscess.

Congenital and acquired cholesteatoma show sheets of stratified keratinizing squamous epithelium without evidence of abnormal mitosis. Granulation tissue and fibrosis often surround them.

Cholesterol granulomas represent a foreign body granulomatous response to cholesterol crystals arising secondary to hemorrhage. Poor ventilation facilitates accumulation of byproducts.

Mucoceles are cysts lined by pseudostratified ciliated columnar epithelium. Fibrosis, granulation tissue, hemorrhage, and squamous metaplasia are common.

Neoplastic lesions

Chordomas are malignant neoplasms arising from the embryonic remnants of the notochord. This pseudoencapsulated tumor contains cells that are epithelioid with vesicular nuclei and abundant cytoplasm that appears granular to vacuolated. Extensive vacuolization can appear as soap bubbles, compressing the nucleus and creating the classic physaliferous cells.

Chondrosarcomas are malignant tumors of cartilage with lobulated hypercellular areas characterized by hyperchromatic pleomorphic nuclei and prominent nucleoli.

Meningiomas are benign neoplasms arising from arachnoid cells. Four subgroups of meningiomas exist: syncytial or meningothelial, fibroblastic, transitional (both syncytial and fibroblastic), and angioblastic. The cells are whorled, and the nuclei have a punched out or empty appearance resulting from intranuclear cytoplasmic inclusions. Psammoma bodies are typical in meningothelial meningiomas.

Schwannomas are benign tumors arising from Schwann cells, typically on the eighth cranial nerve. Antoni A areas are composed of compact spindle cells, and Antoni B areas are composed of loose hypocellular areas. Most tumors have a mixture of both types. The nuclei are vesicular to hyperchromatic, elongated, and twisted with cells arranged in short interlacing fascicles. Whorling or palisading of nuclei is common.

Glomus tumors are benign and arise from the extra-adrenal neural crest paraganglia. Cell nests or zellballen patterns are characteristic of paragangliomas. Chief cells primarily compose the tumor, with uniform nuclei, dispersed chromatin, and abundant eosinophilic, granular, or vacuolated cytoplasm. Mitosis and necrosis are rare. The chief cells are argyrophilic, and reticulin staining delineates the cell nests.

Nasopharyngeal carcinoma arises from the surface epithelium of the nasopharynx. The World Health Organization subtypes these squamous cell tumors into 3 histologic variants: keratinizing, nonkeratinizing, and undifferentiated.

Keratinizing tumors represent 25% of all nasopharyngeal tumors. This is a classic squamous cell carcinoma often graded as well, moderately, and poorly differentiated.

Nonkeratinizing tumors represent 15% of all nasopharyngeal carcinomas. The growth pattern is similar to transitional cell carcinoma of the bladder. No desmoplastic response to tissue invasion occurs.

Undifferentiated tumors account for 60% of nasopharyngeal tumors. A syncytial growth pattern with oval or round vesicular nuclei, prominent eosinophilic nucleoli, scant cytoplasm, and increased mitosis is noted. Lymphoepithelioma is incorrectly diagnosed in some of these cases because of a significant nonneoplastic lymphoid composition.

Staging

No staging system currently exists for primary neoplasms of the petrous apex.

 

Treatment

Medical Therapy

Petrous apicitis (as seen in the CT scan images below) is an inflammatory process often secondary to suppurative otitis media. Medical therapy is aimed at eliminating bacterial infection and promoting drainage with aggressive antibiotic therapy. Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus are the primary pathogens responsible for petrositis. Steroids may help decrease inflammation, pain, and swelling. Early surgical intervention is critical because of the severe complications secondary to chronic otitis media and petrous apicitis.[8]

Petrous apicitis. An axial CT scan of the temporal Petrous apicitis. An axial CT scan of the temporal bone shows an air-fluid level within the right petrous apex and fluid within the middle ear space and mastoid.
Petrous apicitis. A coronal CT scan of the tempora Petrous apicitis. A coronal CT scan of the temporal bones shows an air-fluid level in the right petrous apex.

Skull base osteomyelitis is primarily a medical disease requiring long-term antimicrobial therapy directed against Pseudomonas aeruginosa. Severe otitis externa with granulation tissue in an immunosuppressed patient is the most common clinical setting. Often, the pain is described as deep and boring, with this symptom seeming out of proportion to physical findings. Aminoglycosides, coupled with an antipseudomonal penicillin derivative, are the antibiotics of choice. Quinolone antibiotics offer enteral therapy with encouraging results. Gallium-67 scanning is used to monitor the course of the disease. Technitium-99 scanning is more specific in the diagnosis, but findings remain positive after the course of the disease so they cannot be used to monitor therapy.

Surgical Therapy

With the exception of petrous apicitis and skull base osteomyelitis, all lesions of the petrous apex are best treated surgically. Preoperative histologic diagnosis or strong clinical suspicion is critical to making the proper surgical plan. The availability of an experienced and skilled neuroradiologist is critical in making a confident and accurate preoperative assessment. Ask to have the films read elsewhere if the preoperative imaging studies are inconclusive or vague. The diversity of apex lesions does not permit characterization of the surgical approach. The specific surgical techniques are discussed in Intraoperative details.

Preoperative Details

Careful preoperative evaluation is critical in minimizing intraoperative and postoperative complications. Neurologic examination allows a thorough understanding of preoperative deficits. Preoperative imaging studies define the exact size and location of the lesion. Angiography determines the vascular supply of the particular lesion and helps to narrow the differential diagnosis to assist in choosing the best treatment approach while avoiding complications. Autologous blood or donor-directed blood availability is addressed preoperatively. Often, central venous monitoring and arterial monitoring are helpful in the intraoperative and postoperative period.

One of the most significant decisions regarding surgery is the choice of approach. Factors influencing the approach choice include the location and size of lesion, suspected histopathology, facial nerve function, hearing level, vestibular function, trigeminal function, and surgical experience.

The main approaches currently used to access the petrous apex are systematically described below.

Transmastoid

This approach was initially developed to drain fluid in petrous apicitis. It includes the supralabyrinthine approach, the subarcuate approach, and the retrofacial approach. These approaches permit limited exposure of the apex. They preserve hearing and carry little risk to the facial nerve but do not allow sufficient exposure for tumor resection.

Middle fossa

William House popularized the middle fossa approach as a method of excising acoustic neuromas while preserving hearing. Others described this approach to access the petrous apex. Intracanalicular tumors smaller than 1.5 cm and serviceable hearing are approached through the middle fossa in some centers. The criterion for middle fossa approach in acoustic surgery has expanded to include larger tumors with some extension into the cerebellopontine angle. Facial neuromas, facial hemangiomas, trigeminal neuromas, cholesterol granulomas, congenital and acquired cholesteatomas, and some petroclival meningiomas can also be approached through the middle fossa subtemporal craniotomy.[9]

Transcochlear

The transcochlear approach described by House is essentially an anterior extension of the translabyrinthine approach. After a translabyrinthine approach is performed, the greater superficial petrosal nerve is cut anteriorly to the geniculate ganglion, and the nerve is taken out of its bony canal from the proximal internal auditory canal to the stylomastoid foramen. The facial nerve is reflected posteriorly, and the bony cochlea is removed with a drill. The anterior extent of the bony dissection is the petrous portion of the carotid artery. The procedure provides excellent exposure but leaves the patient with anacusis in the operated ear. Often, return of facial function is incomplete because of the extensive nerve manipulation. Meningiomas and cholesteatomas, especially when the hearing is already compromised, are often resected by this approach.

Infracochlear

The infracochlear approach is used primarily to drain petrous apex cholesterol granulomas. This approach is generally transcanal in the triangular space bordered anteriorly by the carotid artery, posteriorly by the jugular vein/bulb, and superiorly by the basal turn of the cochlea. Exposure is limited with this approach, and its usefulness is limited to draining cystic lesions of the apex.

Transethmoid-transsphenoid (open and endoscopic)

In 1977, Montgomery described the open approach through an incision near the medial canthus.[10] This approach is best for cystic lesions in contact with the posterior wall of the sphenoid sinus. The lesions are drained into the nose, and a silicone stent is often used to keep the tract open. The intranasal transsphenoidal endoscopic approach was first described by Fucci in 1994.[11] This method opens the sphenoid sinus and then opens the posterior wall of sphenoid sinus into the cyst. A stent is placed to keep the pathway open.

Other approaches

Fisch has used the infratemporal fossa type B for petrous apex exposure and the type C to obtain more medial access, even into the nasopharynx. These approaches need to be mentioned as viable options.

Various combinations of these approaches are useful and frequently used to access the apex. The size and nature of the mass and the potential morbidity with the acceptable exposure influence the approach.

A cadaveric study by Negm et al indicated that it is possible to reach the inferior medial petrous apex through an endoscopic endonasal corridor that does not cross the paranasal sinus cavities. According to the report, the sinuses need not be opened to identify three constant surgical landmarks for the petrous apex, specifically, the eustachian tubes, the Rosenmüller fossa, and the posterior end of the middle and inferior turbinates. The investigators observed that the petrous apex can be found on an extended straight line that lies between the upper end of the torus tubarius and, 9.875 mm away, the roof of the Rosenmüller fossa. The petrous apex is situated 9.75 mm from the roof of the Rosenmüller fossa.[12]

Newer available imaging techniques such as CT image-guided surgery and MRI-guided surgery afford the surgeon a real-time evaluation of the location and the progress of the dissection. This can allow the surgeon to immediately determine the exact location of the carotid artery, internal auditory canal, cochlea, and other pertinent structures in relationship to the probe. Image-guided surgery is extremely helpful in these difficult cases in which cranial nerves and vital blood vessels traverse the surgical field.

 

Intraoperative Details

Infectious lesions

See the list below:

  • Petrous apicitis: Petrous apicitis is most common in well-pneumatized temporal bones. These lesions are often drained successfully through the transmastoid approach. In 1985, Chole described the surgical anatomy of the petrous apex. The supralabyrinthine, retrofacial, and subarcuate approaches usually allow sufficient exposure to drain the purulent material from the apex.

  • Skull base osteomyelitis

    • Skull base osteomyelitis (ie, malignant otitis externa) is a severe osteogenic infection usually observed in elderly patients with diabetes mellitus or patients who are immunocompromised. The condition was first described by Chandler in 1968. Skull base osteomyelitis starts with severe otitis externa (swimmer's ear) with granulation tissue and purulent material in the external auditory canal. It is refractory to local treatment and is characterized by a severe, deep, and boring pain in the affected ear. Symptoms usually are out of proportion to the physical findings. CT scan and MRI findings are usually nondiagnostic.

    • Sometimes, the CT reveals bone destruction. Bone scans are the most helpful imaging modalities in diagnosing these disorders. In advanced cases, cranial neuropathies occur from extensive inflammation of the skull base.

    • P aeruginosa is the most common pathogen accounting for this disease. Bone scan using technitium-99 shows uptake in the region of the skull base. Findings on gallium scans are nonspecifically positive but are useful in monitoring patient response to treatment because bone scans remain positive after the clinical course of the disease. Treatment traditionally consisted of aminoglycosides and synthetic penicillin for 4-6 weeks. The use of oral quinolones has shown significant efficacy and is rapidly becoming the standard of care. The avoidance of aminoglycoside antibiotics reduces the incidence of ototoxicity and nephrotoxicity and the complications of long-term intravenous antibiotic delivery in treated patients. Some advocate use of adjunctive hyperbaric oxygen therapy. Surgical therapy is designed to remove abscess formation and necrotic bone in refractory cases.

Inflammatory lesions

See the list below:

  • Cholesterol granuloma

    • Cholesterol granuloma is the most common pathologic lesion of the petrous apex. These lesions are hyperintense on both T1- and T2-weighted MRI, as shown below. The imaging characteristics are shown in Table 2.

      Cholesterol cyst. A coronal T1-weighted image of t Cholesterol cyst. A coronal T1-weighted image of the temporal bone shows high-intensity signal in the left petrous apex.
      Cholesterol cyst. An axial T2-weighted image shows Cholesterol cyst. An axial T2-weighted image shows a lesion in the left petrous apex.
    • The terms cholesterol cyst or giant cholesterol cyst are used to describe the same or similar lesions. One study, however, suggests that cholesterol granulomas and giant cholesterol cysts are distinctly different entities. The term cholesterol granuloma describes a giant cell foreign body reaction in conjunction with fibrosis, vascular proliferation, hemosiderin-laden macrophages, and round cells.

    • These lesions occur elsewhere in the temporal bone, frequently secondary to surgery, chronic otitis media (with or without cholesteatoma), and chronic eustachian tube dysfunction. These granulomas develop from poor ventilation with a relative vacuum, resorption of air, mucosal hemorrhage, and hemoglobin breakdown leading to cholesterol formation.

    • Cholesterol granulomas have no cyst wall and do not require complete surgical excision. Treatment is drainage with establishment of a permanent ventilation system. Often, silicone tubing is used to stent the drainage system and prevent stenosis. The transcanal infracochlear approach described by Giddings provides hearing preservation with direct gravity-dependent access to the apex.[13] The transsphenoidal approach, either external or transnasal endoscopic, provides direct access to the lesions while preserving hearing. The situation is ideal if the lesion abuts the posterior wall of the sphenoid sinus. The intrapetrous carotid artery is immediately posterior to the sphenoid sinus, and great care is required to avoid injury when using a transsphenoidal approach. A plastic stent is placed to connect the cyst to the nasal cavity.

    • A systematic literature review by Eytan et al indicated that cholesterol granulomas of the petrous apex can be successfully treated with endoscopic endonasal management. Examining data from 53 patients treated in this way, the investigators found that, over a mean follow-up period of 20 months, cholesterol granuloma symptoms improved or resolved in 98.6% of cases. Complications (most commonly epistaxis) reportedly occurred in 13.2% of patients. Although restenosis was found in 9 out of 45 patients on follow-up endoscopic examination, only four patients had symptomatic cyst recurrence.[14]

    • Some authors advocate the middle fossa subtemporal extradural approach.[15] The cyst is opened and plastic is placed from the cyst to the eustachian tubes or epitympanum. The drainage is not gravity dependent, and stents have eroded into the dura, causing cerebrospinal fluid otorrhea and meningitis. The transcochlear approach is useful for large lesions in patients with hearing impairment. It is a technically challenging approach that requires relocating the facial nerve posteriorly, a procedure that not infrequently causes some residual facial dysfunction. The transcochlear approach is an aggressive approach that provides excellent exposure.

    • A study by Sweeney et al suggested that cholesterol granulomas of the petrous apex often remain stable and can therefore in many cases be managed via primary observation rather than surgery. The study included 90 petrous apex cholesterol granulomas, none of which during a mean 46-month follow-up spontaneously ruptured or caused carotid injury. The investigators stated that surgery normally should not be performed unless these granulomas are—through mass effect or erosion of the otic capsule or other critical structures—causing or likely to cause neurologic dysfunction.[16]

  • Cholesteatoma

    • Congenital cholesteatomas are nonmalignant epidermoid cysts derived from ectoderm trapped in the temporal bone. These expansile lesions are sterile unless they erode into the middle ear or external auditory canal. Acquired cholesteatomas occur from eustachian tube dysfunction causing retraction of the tympanic membrane or from epithelial migration through a tympanic membrane perforation. MRI shows low-intensity signal on T1-weighted images and high-intensity signal on T2-weighted studies.

    • Cholesteatomas are nonenhancing after administration of gadolinium. They are usually distinguished from cholesterol cysts by differences in the T1-weighted images, although cholesteatomas have variable intensity on T1-weighted imaging. CT scanning shows an expansile lesion in the apex that does not enhance with contrast administration. Acquired cholesteatomas usually show middle ear and mastoid disease with abnormal findings on otoscopic examination.

    • In both congenital and acquired cholesteatomas, the goals of surgery are complete removal of squamous epithelium, preservation or restoration of hearing, and maintenance of normal anatomy. Exteriorization of the cholesteatoma is a valuable technique that allows the cholesteatoma cavity to be cleaned through the ear canal.

    • The choice of surgical approach for petrous apex cholesteatomas requires the consideration of several important factors, including cranial nerve function, hearing status, carotid artery involvement, intracranial extension, size of lesion, bacterial contamination, spinal fluid otorrhea, and surgical experience. Congenital cholesteatomas in the apex have no contact with middle ear, mastoid, eustachian tube, or sphenoid sinus. Therefore, they are sterile, and the choice of approach depends on size and surrounding structures. Acquired cholesteatomas are contaminated with bacteria, and great care is required to avoid seeding the subarachnoid space and brain with pathogens. The presence of cerebrospinal fluid otorrhea or rhinorrhea requires repair of the defect, often by packing the defect with fat or muscle to obliterate the cavity. Recurrent disease is more difficult to detect with obliterative techniques, however.

    • Exteriorization is performed when complete excision cannot be safely executed without sacrificing vital structures such as the cochlea, facial nerve, or carotid artery. Cleaning the cavity or cholesteatoma bed is necessary to prevent accumulation of cholesteatoma with subsequent infection and bony erosion, possibly leading to intracranial complication.

    • Imaging studies are necessary because of the high rate of recurrent or residual disease. As in chronic ear surgery, some recommend a second stage operation at 6-12 months after the initial surgery to look for residual or recurrent cholesteatoma. Others recommend annual CT scanning or MRI to detect residual or recurrent disease. Exteriorized lesions are examined through the ear canal, looking for cholesteatoma, otorrhea, or an occluded drainage site.

  • Mucocele

    • Mucoceles are cystic structures most commonly found in the paranasal sinuses. These expansile lesions manifest secondary to obstruction of mucous glands. Bone destruction occurs through pressure necrosis. They are differentiated from cholesterol granulomas by CT scanning, where the fluid within the cyst is isodense with cerebrospinal fluid. The contralateral apex usually is well pneumatized. MRI shows a hypointense signal on T1-weighted images, and cholesterol granuloma is hyperintense on both T1- and T2-weighted images. It is differentiated from cholesteatoma by mucoceles enhancing on T1-weighted images with gadolinium.

    • If the mucocele is not expanding and symptoms are minimal, treatment is unnecessary. Consider surgery only with an expanding lesion or with significant symptoms. The goal of surgery is establishment of a permanent drainage route, often using a stent to prevent occlusion of the drainage pathway.

Neoplastic lesions

See the list below:

  • Meningiomas

    • Meningiomas arise from the arachnoid villi of the meninges. They are the most common benign tumor of the intracranial vault. Cerebellopontine angle meningiomas arise from the posterior surface of the petrous pyramid. Petroclival meningiomas arise from the clivus or the most medial aspect of the petrous apex. The tumors are often diagnosed by imaging studies prompted by cranial neuropathies and headache. Some meningiomas are locally invasive, while others exhibit little or no growth.

    • CT scanning shows a broad-based dural attachment, focal calcium deposits, hyperdensity to brain, and moderate homogenous contrast enhancement. Hyperostosis of the nearby calvaria can occur. MRI shows broad-based dural attachment, heterogeneous signal pattern, moderately intense homogenous enhancement, and surrounding brain edema. On T1-weighted images, 60% of the lesions are isointense, 30% are hypointense, and 10% are hyperintense. On T2-weighted images, 50% of the lesions are isointense, 40% are hyperintense, and 10% are hypointense. All intensities are in comparison to adjacent brain. Meningiomas frequently contain calcium deposits that cause signal voids. The most specific feature of a meningioma on MRI is an enhancing dural connection (ie, tail sign). These tumors have a rich vascular supply from dural vessels.

    • Numerous approaches are used to resect meningiomas, with the specific choice dependent on tumor size, tumor location, hearing status, facial nerve status, and surgeon experience. Recurrence rates for meningiomas are high, and complete resection is the goal in growing tumors. The effects of stereotactic radiation on meningiomas are unclear. Some suggest that growth is arrested and that stereotactic radiation should be used as the primary treatment. Others suggest that the role of radiation is only postoperative, to prevent or delay recurrence.

  • Schwannomas

    • Schwannomas originate from the Schwann cells lining the nerve. When found in the petrous apex, they usually originate from cranial nerves V, VII, and VIII. In rare cases, large schwannomas from the lower cranial nerves grow into the apex.[17] An MRI image of a trigeminal schwannoma is depicted in the image below.

      Trigeminal schwannoma. An axial T1-weighted MRI sh Trigeminal schwannoma. An axial T1-weighted MRI shows an enhanced lesion of the left petrous apex.
    • Cranial neuropathies and headaches are the most common presenting symptoms of schwannoma. CT scanning shows a smooth expansile lesion with postcontrast enhancement. MRI shows low-intensity signal on T1-weighted images and high-intensity signal on T2-weighted images. These lesions enhance with gadolinium administration.

  • Chordoma

    • Chordomas occur rarely and arise from notochord cells, primarily in the sphenoid and clivus. Tumors originating within the apex are rare, and spread is usually from the clivus. Patients with chordomas present with progressive cranial neuropathies and headache. They occasionally manifest with an invasive mass in the nasopharynx. Chondroid variants of chordoma account for 15% of all chordomas.

    • CT scanning shows an erosive and irregular mass that enhances with contrast administration. MRI reveals low intensity on T1-weighted images and increased signal on T2-weighted images. Contrast administration shows heterogeneous enhancement. Chondroid chordomas are more homogenous on MRI.

    • Surgery with postoperative radiation is the treatment plan of choice. Chordomas are difficult to completely excise and are only moderately radiosensitive. Average survival with aggressive treatment is only 4 years. Chondroid chordomas are less aggressive, with an average survival time of 15 years.

  • Chondrosarcoma

    • Chondrosarcomas account for only 0.15% of all intracranial neoplasms. Hearing loss, pulsatile tinnitus, vertigo/unsteadiness, VI palsy, and headaches are the presenting symptoms. CT scanning shows irregular bone destruction with contrast enhancement. MRI shows enhancement with gadolinium (greater than observed with chordomas). Complete surgical excision with postoperative radiation therapy is the treatment plan of choice. Chondrosarcomas are histologically graded, and survival depends on grade as well as symptoms, origin of lesion, and efficacy of surgical extirpation. An MRI image of a chondrosarcoma is depicted in the image below.

      Chondrosarcoma. An axial T1-weighted MRI image wit Chondrosarcoma. An axial T1-weighted MRI image with gadolinium shows an enhanced mass in the petrous apex.
  • Nasopharyngeal carcinoma

    • Advanced cases of nasopharyngeal carcinoma invade the clivus and infiltrate the petrous apex. Patients present with unilateral otitis media, headache, cranial nerve palsies, and neck mass. A careful inspection of the nasopharynx, often requiring directed biopsies, is indicated. Treatment involves radiation therapy with chemotherapy. CT scan images of nasopharyngeal carcinoma are seen in the images below.

      Nasopharyngeal carcinoma. An axial CT scan of the Nasopharyngeal carcinoma. An axial CT scan of the temporal bones shows a mass in the nasopharynx.
      Nasopharyngeal carcinoma. An axial CT scan of the Nasopharyngeal carcinoma. An axial CT scan of the temporal bones shows an erosive and invasive mass of the left petrous apex.
  • Metastasis: Breast carcinoma and prostate carcinoma metastasize to the temporal bone, especially to the petrous apex and the clivus. Kidney, lung, gastric, and thyroid carcinoma metastasize to the apex less commonly. When these lesions are discovered in the temporal bone, studies suggest the lesion has already metastasized elsewhere. CT scan and MRI characteristics are specific to the primary tumor and dependent on whether the tumor causes an osteogenic or osteoblastic reaction. The prognosis in patients with distant metastasis remains poor.

  • Direct extension from temporal bone

    • Squamous cell carcinomas and basal cell carcinomas (as seen in the MRI image below) of the temporal bone can directly invade the petrous apex. These tumors are usually easily detectable because the lesion is visible on the skin or in the ear canal.

      Basal cell carcinoma. An axial T1-weighted MRI sho Basal cell carcinoma. An axial T1-weighted MRI shows an isointense lesion of the left temporal bone that invaded the petrous apex.
    • The tumor seen in the above image obstructed flow through the sigmoid sinus. MRI venogram seen in the image below shows sigmoid sinus obstruction.

      Sigmoid sinus obstruction. An MRI venogram shows n Sigmoid sinus obstruction. An MRI venogram shows no flow in the left sigmoid sinus.

Intrapetrous carotid aneurysm

Aneurysms of the intrapetrous carotid artery are extremely rare, with fewer than 50 cases reported in the literature. Presenting symptoms are often hearing loss and neuropathies of cranial nerves IV, V, and VII. CT scanning shows a smooth expansile lesion of the carotid canal. Intravenous contrast shows enhancement in continuity with the carotid artery. MRI depends on the state of blood flow within the aneurysm. An acute thrombosis shows low signal intensity on T1-weighted images and high signal intensity on T2-weighted images.

Postoperative Details

Immediate postoperative examination is imperative. This allows assessment of neurologic status to determine postoperative deficits and to establish a baseline to monitor postoperative progression. Neurologic status, including facial nerve status, hearing condition, and trigeminal function, is critical in determining the success of the surgery and potential postoperative complications. A postoperative intracranial hematoma is suspected when the patient is extubated and has a change in mental status. Electrolyte and hematocrit surveillance along with radiographic imaging are standard in the postoperative care in these complex cases. Most patients who have undergone craniotomies receive a CT scan with no contrast on postoperative day one to evaluate the cranial vault for bleeding, brain compression, and hydrocephalus.

Follow-up

Care and thorough follow-up is imperative. In petrous apicitis, CT scanning is important to determine if suppuration recurred or is residual. Examination and imaging studies are necessary to determine if the drainage tract is open or closed. In skull base osteomyelitis, gallium scanning is often used to follow the course of the disease because technetium scan findings remain positive after treatment is no longer necessary. Cholesteatomas, both congenital and acquired, are monitored by clinical examination and imaging studies. The apex is difficult or impossible to visualize through the ear canal, and cholesteatomatous recurrences are common. Consequently, interval imaging studies are recommended. Cholesterol cysts are most commonly treated with drainage procedures, and the drainage tract can close. Efforts are made to keep the drainage tract open.

Reaccumulation of fluid and expansion of the cyst is possible, and imaging studies are necessary in the determination. Mucoceles behave similarly to cholesterol cysts with closure of the drainage tract with possible reaccumulation of mucus and expansion of the mucocele. Neoplastic lesions have a high risk of recurrence. Baseline postoperative imaging studies are necessary to establish residual disease and postoperative changes. These radiographs are then compared with new studies when looking for changes suspicious for residual or recurrent growing tumor. Of course, serial examinations are performed, with attention to the neurologic portion of the examination most closely related to structures at or near the apex.

Complications

Hearing loss (cranial nerve VIII)

Hearing loss is a common complication of surgery for lesions of the apex. Direct trauma to the cochlea or cochlear nerve accounts for profound hearing losses. Effusion, ossicular dislocation, ossicular drill trauma, encephaloceles, scar tissue, and other problems account for most conductive losses and partial hearing losses.

Facial paralysis (cranial nerve VII)

Facial paralysis is an unfortunate complication of petrous apex surgery. Facial nerve monitoring is considered the standard of care and provides useful intraoperative information. Immediately repair known surgical transection of the nerve. Use of a graft depends on the tension of the repair. Immediate implementation of eye care, including drops, ointment, and nighttime taping or patching, is critical in preventing exposure keratitis. A moisture chamber is also helpful in preventing dryness. If paralysis is permanent, other eye care and facial reanimation techniques are used to improve function and appearance.

Cerebrospinal fluid leak

Spinal fluid leak occurs through the wound, directly into the nose through the sphenoid sinus, or through the eustachian tube into the nasopharynx. The most critical factor needed to prevent CSF leak is meticulous intraoperative wound closure that addresses all possible routes of CSF drainage. Techniques to decrease the incidence of CSF leak include careful wound closure; packing of the eustachian tube, middle ear, and mastoid defect; packing of the nasopharynx and sphenoid sinus; and intraoperative lumbar drain placement. CSF leak can lead to meningitis, and aggressive therapy is indicated. Occasionally, the middle ear space is obliterated, the epithelium of the tympanic membrane and external auditory canal is removed, and the ear canal is oversewn closed. This measure has little consequence unless hearing is sacrificed.

Clinical determination of a CSF leak is usually quite clear. Occasionally, laboratory studies including glucose and beta-2 transferrin are used to verify CSF presence. Slow intermittent leaks are sometimes verified by localization studies. These slow leaks sometimes stop with lumbar drainage and supportive care. If the leak persists, surgical management is warranted.

Meningitis

Infection of the meninges is an uncommon complication of apex surgery. Acquired cholesteatomas account for the most severe intracranial infections because of middle ear and mastoid contamination. Meningitis is often associated with CSF leak. Clinical suspicion of meningitis is high, and diagnosis is rarely delayed. Treatment with antimicrobial therapy is started after proper cultures are obtained.

Recurrence/residual

Recurrent disease, whether infectious, inflammatory, or neoplastic, is a possible complication of petrous apex surgery. Careful history, thorough physical examination, and appropriate imaging studies are necessary to detect recurrences without undue delay.

Vertigo (cranial nerve VIII)

Damage to the labyrinth or the vestibular nerve usually causes a transient vertigo that resolves by central compensation. Incomplete labyrinthine insults and damage to the brain stem due to the pathologic condition or treatment can occasionally lead to severe intractable vertigo. Vestibular rehabilitation is the mainstay of therapy for fixed peripheral vestibular dysfunction. Only the most severe cases require an additional vestibuloablative procedure. Central vertigo requires long-term medical management.

Glossopharyngeal nerve and vagus nerve (cranial nerves IX and X)

Paralysis of these 2 nerves causes significant morbidity and occasional mortality. These nerves elevate the larynx and palate to protect the airway. They provide sensation to the base of tongue and supraglottic region to stimulate adduction of the vocal cords in order to prevent aspiration. Injuries to the glossopharyngeal and vagus nerves cause dysphagia, odynophagia, aspiration, decreased or ineffective cough, poor pharyngeal and esophageal motility, and inability to recognize food or secretions. Aspiration, pneumonia, and weight loss is common. Appropriate speech and swallowing therapy is critical, and additional surgical procedures, including thyroplasty, tracheostomy, feeding tube placement, gastrostomy, and others, are occasionally necessary to protect the airway, clear pneumonia, and provide nutrition.

Cerebral edema

Cerebral edema often occurs secondary to intraoperative retraction, interruption of venous drainage, and brain manipulation. It usually occurs several hours after surgery but can occur several days after surgery. Mental status change and a lateralizing or focal neurologic deficit are classic findings of cerebral edema. Some surgeons routinely obtain postoperative CT scans at certain intervals to screen for edema. Treatment is supportive and includes hyperventilation, mannitol, fluid restriction, and possibly corticosteroids.

Hematomas

Hematomas are potentially life-threatening complications that can cause pressure on the brain with subsequent change in mental status and respiratory depression. History, physical examination, imaging studies, and clinical suspicion permit early detection and prompt treatment. The hematoma must be evacuated and the cause of the bleed corrected. In intradural hematomas, the tumor itself or vessels that supplied the tumor are the culprits. In extradural hematomas, the middle meningeal artery is often the cause of bleeding. A small piece of surgical packing can be placed within the foramen spinosum to prevent hemorrhage. Dural edges are occasionally tacked to the bony margin of the craniotomy flap to eliminate dead space. Drains are sometimes used to prevent hematoma formation.

Fluid and metabolic disturbances

The pituitary-hypothalamic axis can be disturbed by surgery, especially if the operative site is near the pituitary gland itself, although any surgical manipulation or head trauma can cause difficulties. The syndrome of inappropriate antidiuretic hormone secretion (SIADH) and diabetes insipidus (DI) are the most common metabolic disorders from skull base surgery. Careful fluid management and occasional use of exogenous hormones is necessary to correct the electrolyte disorders. These abnormalities are usually transient with no long-term sequelae or treatment.

Seizures

Postoperative seizures can occur after any intracranial procedure, especially if the temporal lobe is manipulated. Prompt control of seizure activity is necessary to prevent increased intracranial pressure and bleeding. Laboratory studies and imaging studies are performed to identify possible causes.

Stroke and embolism

Postoperative strokes are potentially devastating complications of petrous apex surgery. Patients requiring carotid sacrifice should undergo preoperative vascular studies including a balloon occlusion test. If the patient passes the balloon occlusion test, some recommend xenon-enhanced CT scanning because 10-15% of those who pass the balloon test develop ischemia. Only 2% of those passing both the balloon occlusion test and the xenon CT scanning develop ischemia. Thrombosis of the anterior inferior cerebellar artery in the posterior fossa may cause stroke, while cerebral edema, increased intracranial pressure, and hematoma can cause decreased blood flow and stroke. Venous occlusion can cause vascular compromise and subsequent stroke. Cases of dural sinus thrombosis causing cerebral edema are reported. Vascular spasm from intracranial manipulation causes vascular compromise and loss of function.

Future and Controversies

Continual improvements in surgical techniques, imaging studies, intraoperative monitoring, and improved antimicrobials should decrease the morbidity and mortality of petrous apex surgery. Neurootologists and neurosurgeons have specialized training in treatment of these unusual disorders, so the operators are more experienced. Centers for skull base surgery are developing where petrous apex lesions could be sent. This will possibly allow pooling of these rare tumors, so that the centers would have increased experience and presumably increased expertise.

Cochlear implants now provide hearing in previously deaf individuals with an intact cochlea and cochlear nerve. Auditory brainstem implants to provide hearing in deaf individuals with no cochlear nerve by directly stimulating the cochlear nuclei are in development. An increased understanding of the vestibular system is possible through basic science research and through the space program, where scientists can study the effects of weightlessness on the vestibular system.

In 1968, the Karolinska Institute in Stockholm first used gamma stereotactic radiation to treat brain tumors. In 1987, the University of Pittsburgh School of Medicine became the first center in the United States to use gamma stereotactic radiation from cobalt-60 sources to treat brain tumors. Several published studies now suggest that certain intracranial neoplasms are best treated with stereotactic radiation rather than microsurgery. Recent studies have suggested that gamma stereotactic radiation prevents growth of acoustic neuromas in more than 90% of cases. Some studies suggest that, in selected populations, more than 70% of untreated acoustic neuromas do not grow. Nevertheless, gamma stereotactic radiation offers promise in treating petrous apex neoplasms. Studies are underway to determine whether stereotactic radiation is more therapeutically effective and economical than microsurgery. This controversy continues.

Medicolegal pitfalls

See the list below:

  • Obtain informed consent: Medicolegal issues often involve informed consent. The patient must be informed of all potential risks. A typewritten sheet that explains all risks and requires the patient's signature in addition to the standard hospital surgical consent form improves the patient's understanding of the potential consequences. Explain the risks with a family member present because the patient's understanding may be impaired due to emotional consequences.

  • Know and practice the standard of care: Standard of care issues are also significant medicolegal pitfalls. Use of a facial nerve monitor, an operating microscope, and the assistance of a neurosurgeon are often considered the standard of care. Close supervision of residents and fellows is critical to provide excellent education without sacrificing quality patient care.

  • Recognize limitations and obtain second opinions: Most attorneys scrutinize experience in treating these tumors. Do not risk performing these complicated operations without significant experience. Physicians are under ever-increasing pressure from insurance companies to perform operations that they would rather refer out because their more experienced colleague is not on the insurance panel. Avoid the pressure and refer out of network. Physicians rarely regret referring cases to more experienced colleagues. Realizing limitations and putting patient care at the pinnacle of the decision tree demonstrates excellent judgment.

  • Keep impeccable records: Carefully document all interactions with patients. Remember that if it was not recorded, it did not take place. Document follow-up recommendations, such as recommendation to return in 2 weeks if symptoms persist or patient refusal of tests such as MRI recommended for asymmetric hearing loss. Record missed appointments, cancellations, and phone conversations. Never, under any circumstances, alter a record. A case is indefensible if the record is altered.