The differential diagnosis of pontine angle meningioma and acoustic neuroma with computed tomography

Vertigo as the sole presenting symptom of cerebellopontine angle meningioma

We report a rare case of cerebellopontine angle (CPA) meningioma whose sole symptom was severe vertigo. A 39-year-old woman with right CPA meningioma was referred for surgery. She experienced severe vertigo for 2 years without any other symptoms. Caloric test indicated right canal paresis of 90%. Her audiogram was normal. After surgery, vertigo symptoms disappeared dramatically. The mechanisms of restoration from vertigo are discussed.

Surgical management of posterior petrous meningiomas

Posterior petrous meningiomas (commonly termed posterior pyramid meningiomas and/or meningiomas of the posterior surface of the petrous pyramid) are the most common meningiomas of the posterior cranial fossa. They are located along the posterior surface of the temporal bone in the region of the cerebellopontine angle. They often mimic vestibular schwannomas, both clinically and on neuroimaging studies. Common clinical symptoms include hearing loss, cerebellar ataxia, and trigeminal neuropathy. The site of dural origin determines the direction of cranial nerve displacement. Total resection can be achieved in most cases with a low morbidity rate and an excellent prognosis. The authors review the surgical management of posterior petrous meningiomas.

Preoperative differentiation between meningioma of the cerebellopontine angle and acoustic neuroma using MRI

Preoperative differentiation between acoustic neuroma (AN) and meningioma of the cerebellopontine angle (CPA) is important in selection of the surgical approach, successful tumor removal, and preservation of hearing and facial nerve. We retrospectively reviewed the magnetic resonance imaging (MRI) findings associated with 30 meningiomas involving the CPA (MCPA) encountered between 1987 to 1991 at the University of California, San Francisco. Magnetic resonance imaging was critical in differentiating meningioma from AN in the CPA. Typical findings on MRI associated with MCPA, differentiating them from ANs, include: meningiomas are sessile, possessing a broad base against the petrous face, whereas ANs are globular; they are often extrinsic and eccentric to the internal auditory canal (IAC); when involving the IAC, they usually do not erode the IAC; MCPAs demonstrate hyperostosis of the subjacent bone and possess intratumoral calcification; they involve adjacent intracranial spaces and structures; and meningiomas are characterized by a distinctive dural "tail" extending away from the tumor surface. While any one finding may not be diagnostic by itself, taken together the constellation of these findings is strongly indicative of meningioma. In our experience, MRI with gadolinium enhancement was able to distinguish MCPA from AN in nearly every case.

"Dural tail" adjacent to acoustic neuroma on MRI: a case report

A "dural tail" on Gd-DTPA-enhanced MRI has been often observed adjacent to meningiomas and considered to be useful in distinguishing meningioma of the cerebellopontine angle from acoustic neuroma. However, demonstration of a dural tail adjacent to an acoustic neuroma indicates that this sign is not specific.

Non-acoustic tumors of the cerebellopontine angle

52 patients with non-acoustic neurinoma tumors of the cerebellopontine angle undergoing surgery over a 16 year period (1974-1989) are analyzed with regard to epidemiologic factors, presenting symptoms, neurological findings, diagnostic procedures, surgical approaches, recurrences, and longterm survival rates. Meningiomas (20 cases) and epidermoid tumors (16 cases) outnumber the rare tumors which exhibit wide histological variation. Trigeminal neuralgia was found as a significantly frequent sign of epidermoids. Total removal was possible in nine meningiomas (45%), fourteen epidermoid tumors (87.5%) and 11 (69%) mostly malignant rare tumors. There were many longterm survivors in meningioma and epidermoid groups with a median follow-up period of 4.1 years. The results are compared to those reported in the literature and a brief review of reported rare tumors of the angle is presented.

Petrous meningiomas: a review of seventeen cases

Seventeen patients with petrous meningiomas managed at St. Michael's Hospital, during the years 1973-1987, were retrospectively reviewed. There were 15 females and 2 males; their ages ranged from 42 to 68 years (mean age: 53 years). The clinical presentation most commonly included headache and eighth cranial nerve dysfunction; the average duration of symptoms was 6 years (3 month-27 years). Computed tomography was performed in 15 cases. The mean tumour size was 2.5 centimeters (0.5-4 cm). The most common site of tumour origin was at or medial to the porus acousticus. Meningioma was suspected preoperatively in 10 of the 15 patients who had preoperative CT scans. Complete excision was obtained in 12 cases. There were no operative deaths after initial resections. Postoperative morbidity included worsening of pre-existing hearing loss in six patients, transient facial nerve palsies in six, permanent facial nerve palsies in four and new facial or corneal hypesthesia in three. Two patients developed cerebrospinal fluid fistulae. Tumour recurrence occurred into two patients in whom a complete resection was anticipated. Also, in two patients with incompletely resected tumours second operations were required. Fourteen patients are alive, 13 of whom care for themselves independently. The average follow-up was 5 years (6 months-9 years). It seems appropriate to recommend initial radical surgical excision of these benign tumours, where possible, in order to prevent tumour recurrence.

Acoustic neurinoma and posterior fossa meningioma. Clinical and CT radiologic findings

Clinical and computed tomography (CT) findings of twenty-three patients with acoustic neurinoma (AN) and eleven patients with posterior fossa meningioma (PFM) are described. AN frequently (94%) presents with the complaint of hearing loss, while PFM often (60%) presents with non-specific pains in the head or neck. The CT characteristics of AN and PFM in this series were similar to those found in most previous publications. The maximal measured mean diameter of PFM (40.2 mm) was significantly larger than that of AN (26.4 mm). Hydrocephalus was apparently influenced by tumor location rather than by its size. It is concluded that diagnostic ability has been improved in cases of CPA tumors, but not in those of non-CPA PFM, probably because of the earlier clinical presentation of the former. Clinical efforts are still necessary to detect the smaller tumors.

Meningiomas of the clivus and apical petrous bone. Report of 35 cases

Between March, 1966, and June, 1985, 23 women and 12 men underwent partial or total resection of apical petrous or clivus meningiomas at The National Hospital for Nervous Diseases. Presenting symptoms were typically of long duration (mean 29 months) and consisted primarily of gait disturbance, headache, hearing loss, and facial pain. Cranial nerve deficits, especially affecting the fifth, seventh, and eighth nerves. were observed in nearly every patient. Tumor size, but not location, was generally associated with degree of preoperative disability. Plain skull films were usually unremarkable, but computerized tomography (CT) proved highly accurate in determining tumor location and size. A characteristic pattern of vascular displacement was seen on vertebral angiograms, although blood supply to the tumors was derived primarily from branches of the internal and external carotid arteries. Subtotal or total resection was undertaken in all cases; nine patients required adjunctive cerebrospinal fluid shunting procedures. Although surgical techniques evolved during the course of the 20-year study, a combined supra- and infratentorial approach proved a relatively safe and effective means of surgical treatment. New or worsened postoperative deficits, especially cranial nerve palsies, and complications in the immediate postoperative period frequently resulted in temporary deterioration of the clinical status during this period; the total operative mortality rate was 9%. Follow-up periods ranged up to 9 years; 70% of patients resumed an independent existence, and none is known to have required subsequent tumor surgery. The size of the lesion was the only significant factor in determining outcome. These data suggest that meningiomas of the clivus and apical petrous bone can be accurately diagnosed by CT and three-vessel angiography, and effectively treated by microsurgical resection.

Postoperative CT findings in acoustic neurinomas operated upon by a translabyrinthine approach

The findings at CT examinations, performed on 46 patients with acoustic neurinomas about 6 months after translabyrinthine surgery, were analyzed and compared with preoperative findings. Direct as well as indirect signs of expansion had disappeared postoperatively. Bulging of cerebellar tissue towards the operative defect in the petrous bone, a finding not connected with local adhesions, was notable. Hypodensity in the vicinity of the removed tumor occurred either due to local widening of the subarachnoid space or due to changes within the cerebellar parenchyma. Local and general widening of the fourth ventricle as a sign of atrophy was a frequent finding.

Meningiomas of the cerebellopontine angle

The majority of cerebellopontine angle tumors are acoustic neurinomas; however, 10% to 15% are meningiomas. Meningiomas are benign lesions that must be removed but may require surgical approaches different from those used for acoustic neurinomas. To determine if meningiomas could be distinguished from acoustic neurinomas clinically, findings in 20 patients who underwent removal of a meningioma were compared to those in 131 patients who had an acoustic neurinoma removed during the same period. We found that in patients with meningiomas the tumors frequently are large at presentation, the otologic symptoms and audiometric findings are less dramatic, and roentgenograms of the skull and tomograms of the petrous apex rarely show erosion of the internal auditory canal. Computerized tomography is the most useful method for differentiating a meningioma from a neurinoma: when a meningioma is present the characteristic finding is a broad-based mass aligned with the petrous ridge, not centered over the internal auditory canal.

Cerebellopontine angle meningiomas. Microsurgical excision and follow-up results

During the years 1974 through 1981, 22 patients with cerebellopontine angle meningiomas underwent surgery: 14 tumors were excised completely, and eight subtotally. A retromastoid approach was used in 19 cases and a subtemporal approach in three cases. There was no operative mortality and the quality of survival was good. Five patients suffered new cranial nerve deficits as a result of the operation. The average follow-up period was 5 years. One tumor thought to be completely removed has recurred, but has not required another operation so far. One subtotally excised tumor required reoperation. Computerized tomography and arteriography were important in preoperative evaluation. Good neuroanesthesia, the use of the surgical microscope and microtechnique, and an understanding of the pathological relationships were factors contributing to good results.

Meningiomas of the posterior fossa

Clinical and surgical results in 38 cases of posterior fossa meningiomas are presented. All cases have been diagnosed and operated upon during the last 12 years in this department. We have identified five locations for these tumors: cerebellopontine angle, cerebellar convexity, tentorium, peritorcular, and clivus. Clinical features of these tumors and their surgical management are described. Sixty-eight percent of the cases presented have been diagnosed by computed tomography scan. All cases were operated upon with a 15.78% postoperative mortality; 36.85% of the patients remained symptom-free; 26.32% suffered mild neurological deficits; and 21.05% suffered severe neurological deficits. Total resection had been accomplished in 84.22% of the cases. Computed tomography scans allow earlier and more accurate diagnosis of these tumors, which in our opinion has modified the surgical results for the better. We discuss our findings and compare them with other published articles.

CT of meningiomas on the Posterior surface of the petrous bone

A detailed analysis of the CT findings in 16 surgically verified cases of meningioma of the posterior surface of the petrous bone is presented. The results indicate that a correct preoperative diagnosis is possible in almost every case. Frequently occurring specific CT criteria for meningioma of the posterior surface of the petrous bone include: hyperdense, homogeneously enhancing, extra-axial, CPA mass; inverse relationship between precontrast attenuation value and degree of contrast enhancement of the tumor; oval shape; obtuse angle between lateral tumor border and posterior surface of petrous bone, and evidence of transcisternal supratentorial tumor extension. Infrequently occurring specific CT criteria include: tumor calcification; hyperostosis or exostosis of the posterior surface of the petrous bone; a comma-shaped tumor configuration in cases with transcisternal tumor extension and evidence of transtentorial tumor extension. Oxygen CT cisternography is the most sensitive and reliable technique for detecting small tumors. The CT differential diagnosis of meningioma of the posterior surface of the petrous bone is discussed.

Diagnosis of cerebellopontine angle tumors with small quantities of air

Difficulty in detecting small acoustic neuromas has encouraged us to study patients suspected of having a tumor by air cisternography augmented with computed tomography. Ninety patients were examined without complication. Five cubic centimeter of air was introduced via lumbar puncture and manipulated into the cerebellopontine angle cisterns. Scanning is commenced immediately. Filling of both internal auditory canals and identification of the neurovascular bundle in the cerebellopontine angle cistern was possible in all patients except those with tumors. The diagnostic accuracy, speed, and lack of morbidity have made this procedure the initial radiologic examination at our institution for patients suspected of having acoustic neuroma.

Attenuation profiles of the petrous bone with acoustic neuroma

Attenuation profiles across the petrous bone covering the whole internal auditory meatus (IAM) were constructed from the printouts obtained by computed tomography (CT) with narrow collimation performed on 12 patients with 13 acoustic neuromas. In healthy patients the attenuation profiles of right and left petrous bone were very similar in shape. The attenuation values of the individual pixels in the pixel columns of the printout located at the site of the porus and the IAM reflected the demineralization of the petrous bone and the widening of the porus and the IAM caused by the acoustic neuroma. A widening deep in the meatus was demonstrated in a patient with an intracanalicular tumor, and therefore it seems possible to make this diagnosis by CT scanning combined with the construction of attenuation profiles across the petrous bone. In the presence of unilateral acoustic neuroma there was a significant and characteristic difference in shape between the attenuation profiles of the two sides with generally lower attenuation values on the tumor side together with signs of widening of the porus and the IAM. In cases of bilateral acoustic neuroma comparison of the attenuation profiles can be made with mean attenuation curves obtained from scanning normal petrous bones. The prevailing physical limitations for demonstrating a narrow bony canal like the IAM with CT was experimentally analyzed using bone-simulating plastic material.

Evaluation of the internal auditory meatus with acoustic neuromas using computed tomography

Forty-seven patients with 48 unoperated acoustic neuromas have been studied by computed tomography (CT) with respect to bone changes. CT and conventional X-ray examination of the skull were compared. The importance of using a small collimator, proper selection of the plane of the CT section and changing of the window level is stressed. CT detects porus changes as accurately as conventional X-ray methods.