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

[Tumors of the posterior cranial fossa]

Various types of brain tumor can occur in the region of the posterior fossa. Brain metastases in adults are the most common malignancies at this localization. Ependymomas, medulloblastomas and pilocytic astrocytomas occur mostly in children and only rarely in adults. Other tumors that occur in the posterior fossa are meningiomas, schwannomas, hemangioblastomas, brain stem gliomas and epidermoid tumors. Due to the fact that the various tumors of the posterior fossa have different treatment approaches and prognoses, an accurate and specific diagnosis is mandatory. This review discusses the imaging aspects by computed tomography (CT) and magnetic resonance imaging (MRI) of the most frequent tumors of the posterior fossa.

Prevalence and Surgical Implications of Dural Enhancement at the Porus Acusticus in Vestibular Schwannomas

OBJECTIVE

Demonstrate the association of radiographic dural enhancement with increased tumor adherence at the porus acusticus, which may influence completeness of resection and facial nerve outcome.

STUDY DESIGN

Case series with chart review.

SETTING

Academic referral center.

SUBJECTS AND METHODS

A total of 205 consecutive patients with histopathologically confirmed vestibular schwannoma (VS) were evaluated. Patients with tumors exhibiting dural enhancement on postgadolinium T1-weighted magnetic resonance imaging were identified and compared with matched controls. Completeness of resection, intraoperative details, and facial nerve outcomes were analyzed.

RESULTS

Excluding strictly intracanalicular tumors (n = 32, 16%) and those with NF2 (n = 10, 4.9%), the presence of dural enhancement was radiographically confirmed in 16 (9.8%) cases. Paired analysis did not reveal significant baseline differences between cases and controls. Subtotal resection was performed in 5 (31%) of the 16 patients with tumors exhibiting dural enhancement, in contrast to 1 (3%) of the matched controls (P = .01). Four (25%) demonstrated increased tumor adherence at the porus acusticus intraoperatively, compared with 1 control (3%, P = .04). Long-term facial nerve function was similar between cases and controls (81% vs 84% House-Brackmann I-II function, P = 1.00).

CONCLUSION

Dural enhancement is present in approximately 10% of extracanalicular VS. Dural enhancement at the porus acusticus may represent hypervascularity, dural reaction, or infiltration, and portends increased tumor adherence and greater likelihood of subtotal resection to preserve facial nerve function. To our knowledge, this is the first series that reports the prevalence of this phenomenon in VS and the potential surgical implications. Recognition preoperatively may be valuable toward patient counseling.

Non-schwannomatosis lesions of the internal acoustic meatus-a diagnostic challenge and management: a series report of nine cases

Vestibular schwannomas (VS) are the most common lesions of cerebellopontine angle (CPA) corresponding to 76-91 % of the cases. Usually, these lesions present typical CT and MRI findings. Non-schwannomatous tumors restricted to the internal auditory meatus (IAM) are rare and their preoperative radiological diagnosis may be difficult. This article describes nine surgically treated intrameatal non-schwannomatous lesions (NSL) and reviews the literature. In the last 16 years, a total of 471 patients with diagnosis of VS were operated on in our department. Preoperatively, 42 patients had diagnosis of intrameatal schwannomas, but surgery revealed in nine cases NSL (3 meningiomas, 3 arachnoiditis/neuritis, 1 cavernoma, 1 vascular loop, and 1 arachnoid cyst). Most frequent symptoms presented by patients with NSL were hearing loss 89 % (8/9) of patients, tinnitus 78 % (7/9), and vertigo 33 % (3/9). Almost all lesions (8/9) presented MRI findings of isointense signal in T1W with contrast enhancement. The only exception was the arachnoid cyst with intracystic bleeding, which was hyperintense in T1W that is not enhanced with contrast. This series shows an occurrence of 21.4 % of non-schwannomatous tumors in 42 cases of lesions restricted to the IAM. Whenever a solely intrameatal enhanced tumor is detected, it is necessary to think about other diagnostic possibilities rather than VS. Therapeutic management may be changed, specially if radiosurgical treatment is considered.

[Extra-axial brain tumors]

Neuroradiology plays a key role in the diagnosis of patients with brain tumors. Computed tomography (CT) and especially magnetic resonance imaging (MRI) allow accurate anatomic depiction of intracerebral lesions. The implementation of native and contrast studies allows the characterization of the various lesions. This review discusses the imaging aspects with CT and MRI of the most common primary extra-axial brain tumors.

Simultaneously occurring tumours within the same cerebello-pontine angle: refining literature definitions and proposal for classification

We report on an unusual case of a patient, not affected by neurofibromatosis, harbouring two radiologically spatially contiguous tumours within the same cerebello-pontine angle. Pathological findings were consistent with the diagnosis of two spatially distinct primary tumours, namely a meningioma and a schwannoma. We proposed a classification of tumours occurring at the same location consistent with the different spatial arrangement and histological nature of these conditions. The correct classification of these nosological entities will allow further more accurate evaluations of these cases in order to clarify the pathogenesis, prognosis and best treatment of each one.

A review on dural tail sign

“Dural tail sign” (DTS) which is a thickening of the dura adjacent to an intracranial pathology on contrast-enhanced T1 MR Images, was first thought to be pathognomonic of meningioma, however, many subsequent studies demonstrated this sign adjacent to various intra- and extra-cranial pathologies and in spinal lesions. In this paper we outline the history, accompanying pathologies and the differentiation and probable pathophysiology of DTS. We also discuss whether we can predict tumoral involvement of the dural tail before surgery and whether the dural tail adjacent to a tumor should be resected.

Meningiomas involving the internal auditory canal: a diagnostic and surgical challenge

Meningiomas are the second most common lesion encountered within the cerebello-pontine angle (CPA) and rarely project into or originate from the internal auditory meatus (IAM). It is important to distinguish between meningiomas and acoustic neuromas preoperatively as the choice of surgical approach may differ depending on the tumour type. Fortunately, most lesions can be accurately diagnosed with gadolinium-enhanced magnetic resonunce imaging (MRI). We report six cases of meningioma involving the IAM, often leading to an incorrect preoperative MRI diagnosis. We highlight the challenges these tumors present to radiologists and surgeons.

The dural tail sign--beyond meningioma

There have been somewhat conflicting reports published about the significance of linear meningeal thickening and enhancement adjacent to peripherally located cranial mass lesions on contrast-enhanced magnetic resonance (MR) images. Most of the authors consider this so-called "dural tail sign" or "flare sign" almost specific for meningioma. This review illustrates the MR imaging findings of a wide spectrum of disorders that show this dural sign. Causes include other extra-axial lesions and also peripherally located intra-axial lesions such as neuromas, chloromas, metastases, lymphoma, gliomas, pituitary diseases, granulomatous disorders, and also cerebral Erdheim-Chester disease. The dural tail sign is not specific to a particular pathological process. Nevertheless, useful conclusions can be drawn from the morphology of the lesion, its enhancement pattern, and its solitary or multifocal presentation. The final diagnosis must be based on cerebrospinal fluid studies or histological studies after biopsy.

Extra-axial brain tumors

Meningiomas, schwannomas, metastases, maldevelopmental cysts, epidermoids, dermoids and bone tumors represent the vast majority of extra-axial brain tumors. The location of extra-axial brain tumors affects treatment planning and predicts their prognosis. Computed tomography and particularly magnetic resonance imaging are used for diagnosis and localization. In this article, the imaging findings of the extra-axial brain tumors are discussed.

Meningiomas of the internal auditory canal

OBJECTIVE

Meningiomas arising primarily within the internal auditory canal (IAC) are notably rare. By far the most common tumors that are encountered in this region are neuromas. We report a series of eight patients with meningiomas of the IAC, analyzing the clinical presentations, surgical management strategies, and clinical outcomes.

METHODS

The charts of the patients, including histories and audiograms, imaging studies, surgical records, discharge letters, histological records, and follow-up records, were reviewed.

RESULTS

One thousand eight hundred meningiomas were operated on between 1978 and 2002 at the Neurosurgical Department of Nordstadt Hospital. Among them, there were 421 cerebellopontine angle meningiomas; 7 of these (1.7% of cerebellopontine angle meningiomas) were limited to the IAC. One additional patient underwent surgery at the Neurosurgical Department of the International Neuroscience Institute, where a total of 21 cerebellopontine angle meningiomas were treated surgically from 2001 to 2003. As a comparison, the incidence of intrameatal vestibular schwannomas during the same period, 1978 to 2002, was 168 of 2400 (7%). There were five women and three men, and the mean age was 49.3 years (range, 27-59 yr). Most patients had signs and symptoms of vestibulocochlear nerve disturbance at presentation. One patient had sought treatment previously for total hearing loss before surgery. No patient had a facial paresis at presentation. The neuroradiological workup revealed a homogeneously contrast-enhancing tumor on magnetic resonance imaging in all patients with hypointense or isointense signal intensity on T1- and T2-weighted images. Some intrameatal meningiomas showed broad attachment, and some showed a dural tail at the porus. In all patients, the tumor was removed through the lateral suboccipital retrosigmoid approach with drilling of the posterior wall of the IAC. Total removal was achieved in all cases. Severe infiltration of the facial and vestibulocochlear nerve was encountered in two patients. There was no operative mortality. Hearing was preserved in five of seven patients; one patient was deaf before surgery. Postoperative facial weakness was encountered temporarily in one patient.

CONCLUSION

Although intrameatal meningiomas are quite rare, they must be considered in the differential diagnosis of intrameatal mass lesions. The clinical symptoms are very similar to those of vestibular schwannomas. A radiological differentiation from vestibular schwannomas is not always possible. Surgical removal of intrameatal meningiomas should aim at wide excision, including involved dura and bone, to prevent recurrences. The variation in the anatomy of the faciocochlear nerve bundle in relation to the tumor has to be kept in mind, and preservation of these structures should be the goal in every case.

Schwannoma arising from the tentorium at an unusual location: case report

OBJECTIVE AND IMPORTANCE

We present a case of schwannoma attached to the tentorium.

CLINICAL PRESENTATION

A 41-year-old woman without evidence of neurofibromatosis presented with a 3-month history of headache, positional vertigo, and truncal ataxia. Magnetic resonance imaging revealed an extra-axial cystic mass lesion in the left anteromedial cerebellar region with a dural tail sign.

INTERVENTION

The tumor was removed completely by retrosigmoid craniotomy. Dense adhesion of the tumor to the inferior surface of the tentorium was confirmed during surgery. On light microscopic study, this neoplasm was composed of spindle cells and showed palisaded structures. Immunohistochemically, the tumor cells stained positive for S-100 protein and vimentin. Reticulin staining revealed a pericellular pattern of distribution of reticulin fibers. Electron microscopy confirmed the presence of a basement membrane encompassing the tumor cells. From these findings, the tumor was diagnosed as a schwannoma arising from the tentorium.

CONCLUSION

To our knowledge, this case report is the first to describe a schwannoma arising from the tentorium. Our case report indicates that schwannoma is a possible pathology in the differential diagnosis of dura-based tumors.

Vestibular schwannoma showing a dural tail on contrast-enhanced magnetic resonance images

The dural tail on contrast-enhanced magnetic resonance (MR) images, frequently observed in meningiomas, has been used to distinguish between cerebellopontine angle meningiomas and vestibular schwannomas. We report on a 66-year-old female with vestibular schwannoma showing the dural tail on contrast-enhanced MR images. Histological examination revealed that the dural tail corresponded to the thickened dura mater comprising of collagen fibres and scattered hyalinization with no tumoral invasion.