Intracranial dural arteriovenous fistulae (DAVF) are rare vascular malformations. They are generally considered to be acquired lesions, often attributed to dural sinus thrombosis and intracranial venous hypertension. The authors encountered a case of DAVF associated with an octreotide-positive vestibular schwannoma. A 46-year-old female had symptoms of right ear congestion accompanied by pulsatile tinnitus and mild hearing loss. Magnetic resonance imaging (MRI) identified a lobulated mass centered at the cerebellopontine angle. Preoperatively, on cerebral angiography, there was an incidental discovery of a DAVF in the right posterior fossa. The decision was made to proceed with resection of the tumor in a staged fashion. Her latest follow-up MRI showed no evidence of recurrent tumor. This is the second reported case of DAVF associated with an intracranial schwannoma. Findings are discussed along with a thorough review of the literature. This case, combined with the data from the literature review, led us to believe that tumor-related angiogenesis might contribute to DAVF formation.
Intracranial dural arteriovenous fistulae (DAVF) are abnormal direct shunts between dural arteries and dural venous sinuses, meningeal veins or cortical veins. They are located within or near the wall of the dural sinus and account for 10%-15% of all intracranial arteriovenous malformations . DAVF primarily occur in adult patients and are most commonly located in the transverse-sigmoid sinus region followed by the cavernous sinus; however, any intracranial venous sinus may be involved . They are widely considered to be acquired lesions. Their acquired nature is further supported by their association with dural sinus thrombosis, head trauma, intracranial or spinal tumors [3-4], localized infection, previous neurosurgical procedures [1-2], and hypercoagulation states .
We encountered a rare case of a transverse-sigmoid sinus DAVF associated with the presence of a vestibular schwannoma, which occluded the right transverse and sigmoid sinuses. The pre-operative diagnosis of this lesion was confounded by the fact that the tumor was positive on octreotide nuclear scintigraphy.
A 46-year-old female had symptoms of right ear congestion accompanied by pulsatile tinnitus and mild hearing loss. Neurological examination revealed weakness of cranial nerves X and XII. Magnetic resonance imaging (MRI) identified a 4.2 x 4.7 x 4.1 cm lobulated mass centered at the cerebellopontine angle that was hypointense on T1-weighted, heterogeneous on T2-weighted, and avidly enhancing on post-contrast images (Figure 1A). No significant component was noted within the internal auditory canal. An Octreoscan was performed, which showed intense increased tracer uptake in the mass centered in the region of the right jugular foramen, thereby supporting the suspected diagnosis of paraganglioma (Figure 1B).
Digital subtraction angiography (DSA) demonstrated a surprising lack of vascularity associated with the tumor. However, there was an incidental discovery of a Cognard IIa+b dural arteriovenous fistula in the right posterior fossa associated with an occluded right sigmoid sinus (Figure 2A-2D).
Due to the extensive volume of tumor, the patient underwent a staged surgical resection. The first surgery included a modified radical right neck dissection, right superficial parotidectomy with facial nerve dissection, as well as the initial approach to the tumor and partial extradural resection. One week later, the patient underwent the second stage surgery where the tumor was radically resected using a right transcochlear approach. The right sigmoid sinus was ligated. The facial nerve was mobilized and transposed. Postoperative MRI confirmed complete resection of the tumor (Figure 1C). Histological analysis of samples from both surgeries confirmed the tumor not to be a paraganglioma, but instead a schwannoma (Figure 3).
She had a long recovery from the surgery due to the lower cranial nerve palsies but has shown gradual improvement. Her latest follow-up MRI (48 months from surgery) (Figure 1D) showed no evidence of recurrent tumor; however, there was some residual posterior fossa DAVF. At that time, she also reported bothersome pulsatile tinnitus that she perceives on the right despite a complete hearing loss on the right side. DSA revealed new large feeders from the right middle meningeal artery (MMA) and occipital arteries into the residual DAVF (figure 2E), which were not present on initial presentation (Figure 2D). The DAVF was embolized utilizing Onyx in the right MMA. Final right common carotid artery (CCA) angiogram demonstrated resolution in arteriovenous shunting (Figure 2F). Vertebral artery injection after embolization demonstrated minimal residual shunting via the right anterior inferior cerebellar artery (AICA) (Figure 2G). A further intervention was declined by the patient and angiographic follow-up in one year has been scheduled.
In our patient, we encountered a transverse-sigmoid sinus DAVF associated with a schwannoma of the right skull base. Although angiography was not available prior to diagnosis of the large skull base mass, one could hypothesize that the schwannoma led to the venous sinus obstruction, and subsequently the formation of the DAVF. DAVF formation attributed to a tumor has been described, but it is rare. A detailed PubMed query was performed, which identified 26 previously reported cases (Table 1) [3-17]. Analysis of the previously reported cases exhibited a slight female predominance (61.5%) and a mean age of 60.26 years (range 25-78). This is only the second case associated with an intracranial schwannoma. In the vast majority of cases (78%), the tumor was a meningioma. Although there are exceptions, most cases of DAVF associated with tumor are also associated with sinus obstruction, underlining the importance of venous outflow obstruction in DAVF pathophysiology. Specifically, the most common location of occlusion was the sigmoid sinus, which was occluded in 38.5% of cases. Interestingly, 23% of cases were not related to sinus occlusion. The most common location for a DAVF associated with a tumor was the transverse-sigmoid sinus (48% of cases). Some investigators hypothesize that meningiomas are the most likely tumor type to be associated with DAVF due to their highly vascular nature, which in turn accentuates venous hypertension, especially when the sinus is occluded .
Another unique characteristic in our case was the positive 111In-octreotide scintigraphy (Octreoscan), which is used to evaluate the presence of somatostatin receptors in intracranial tumors in vivo. Expression of somatostatin receptors has been linked with increased angiogenic activity in meningiomas and other neoplasias . This is only the second reported case of an intracranial schwannoma with positive octreotide scintigraphy . Past studies have shown that somatostatin receptors are expressed in most meningiomas, paragangliomas and hemangiopericytomas, but not in schwannomas, with some investigators using octreotide scintigraphy for the differential diagnosis of meningioma versus schwannoma [19-20]. Our case further supports the conclusion by Dupuch et al. that no investigation is able to establish a definitive preoperative differential diagnosis between schwannoma and meningioma . Taking into consideration the case we encountered, we hypothesize that aberrant angiogenesis through somatostatin receptor pathways may play a role in the pathogenesis of DAVF associated with intracranial tumors. Even though there is currently no evidence showing a direct connection between somatostatin pathways and DAVF formation, studies have shown that the presence of somatostatin receptors correlates with aberrant angiogenesis in various tumor settings . Our hypothesis aims at opening new avenues of investigation that will help in better understanding DAVF pathophysiology.
In summary, we present an unusual case of DAVF associated with an octreotide positive vestibular schwannoma. This case demonstrates that lesions in the cerebellopontine angle could affect local vasculature, possibly by both causing local venous hypertension and somatostatin receptor-related angiogenesis, to the extent it may lead to a DAVF formation.
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Dural Arteriovenous Fistula Associated With a Vestibular Tumor: An Unusual Case and Review of the Literature
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Cite this article as:
Kritikos M E, Oselkin M, Sharma N, et al. (June 27, 2018) Dural Arteriovenous Fistula Associated With a Vestibular Tumor: An Unusual Case and Review of the Literature. Cureus 10(6): e2890. doi:10.7759/cureus.2890
Received by Cureus: June 05, 2018
Peer review began: June 11, 2018
Peer review concluded: June 25, 2018
Published: June 27, 2018
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Kritikos et al. This is an open access article distributed under the terms of the Creative Commons Attribution License CC-BY 3.0., which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.