Stereotactic Radiosurgery of Intracranial Dural Arteriovenous Fistulas

A Practical Grading Scale for Predicting Outcomes of Radiosurgery for Dural Arteriovenous Fistulas: JLGK 1802 Study

Background and Purpose

To assess the long-term outcomes of intracranial dural arteriovenous fistula (DAVF) treated with stereotactic radiosurgery (SRS) alone or embolization and SRS (Emb-SRS) and to develop a grading system for predicting DAVF obliteration.

Methods

This multi-institutional retrospective study included 200 patients with DAVF treated with SRS or Emb-SRS. We investigated the long-term obliteration rate and obliteration-associated factors. We developed a new grading system to estimate the obliteration rate. Additionally, we compared the outcomes of SRS and Emb-SRS by using propensity score matching.

Results

The 3- and 4-year obliteration rates were 66.3% and 78.8%, respectively. The post-SRS hemorrhage rate was 2%. In the matched cohort, the SRS and Emb-SRS groups did not differ in the rates of obliteration (P=0.54) or post-SRS hemorrhage (P=0.50). In multivariable analysis, DAVF location and cortical venous reflux (CVR) were independently associated with obliteration. The new grading system assigned 2, 1, and 0 points to DAVFs in the anterior skull base or middle fossa, DAVFs with CVR or DAVFs in the superior sagittal sinus or tentorium, and DAVFs without these factors, respectively. Using the total points, patients were stratified into the highest (0 points), intermediate (1 point), or lowest (≥2 points) obliteration rate groups that exhibited 4-year obliteration rates of 94.4%, 71.3%, and 60.4%, respectively (P<0.01).

Conclusions

SRS-based therapy achieved DAVF obliteration in more than three-quarters of the patients at 4 years of age. Our grading system can stratify the obliteration rate and may guide physicians in treatment selection.

An analysis of the anatomic route of the hypoglossal nerve within the hypoglossal canal using dynamic computed tomography angiography in patients with anterior condylar arteriovenous fistulas

OBJECTIVE

The venous outlet of anterior condylar arteriovenous fistulas (AC-AVFs) often empties into the anterior condylar vein (ACV). Hypoglossal nerve palsy is one of the major complications after transvenous embolization (TVE) for the AC-AVF within the hypoglossal canal. However, no studies have investigated the route of the hypoglossal nerve within the hypoglossal canal in AC-AVF. The aim of the current study is to retrospectively verify the anatomical route of the hypoglossal nerve within its canal using dynamic computed tomography angiography (CTA) in order to facilitate the safe TVE for AC-AVF.

PATIENTS AND METHODS

We included five patients with AC-AVF from 2011 to 2017. Dynamic CTA was performed on all patients. When the ACV was well-visualized by dynamic CTA, the hypoglossal nerve could be recognized as a less-intense structure within the surrounding enhanced vasculatures and the nerve route within the canal was analyzed. We also analyzed the location of the fistulas by digital subtraction angiography and cone-beam computed tomography.

RESULTS

In all five patients, the filling defect of the hypoglossal nerve ran through the most caudal portion of the hypoglossal canal. The fistulous pouches were located in the hypoglossal canal in three cases, and in the jugular tubercle venous complex in two cases. In all three cases with AC-AVF in the hypoglossal canal, the fistulous pouches were located in the superior wall of the hypoglossal canal, which means superior to the ACV. We performed TVE in four patients and none developed post-therapeutic hypoglossal nerve palsy.

CONCLUSION

In the current study, dynamic CTA is useful for detecting the hypoglossal nerve within the hypoglossal canal. The hypoglossal nerve usually ran the bottom of its canal and the fistulous pouches were usually located at the superior aspect of the canal opposite side to the hypoglossal nerve. Accordingly, the selective embolization within the fistulous pouch located in the superior aspect of the ACV including jugular tubercle venous complex can reduce the risk of hypoglossal nerve palsy.

Progress in research on intracranial multiple dural arteriovenous fistulas

Intracranial multiple dural arteriovenous fistulas (MDAVFs) are rare lesions that are difficult to treat. The key factors involved in the development of MDAVFs remain unknown. At present, the majority of reports on intracranial MDAVFs are confined to case reports and small case series, and thus understanding of MDAVFs is limited. The current review assesses the available literature to date with the aim of reviewing the progress in research on intracranial MDAVFs. Intracranial MDAVFs may be divided into two types: Synchronous and metachronous. While the exact pathogenesis of MDAVFs is unknown, a number of possible mechanisms are considered relevant. The first is that MDAVFs develop following recanalization of a large sinus thrombosis that involves several sinuses. The second possibility is that a pre-existing DAVF may induce sinus thrombosis or venous hypertension, resulting in a new MDAVF. The third is that MDAVFs are caused by increased angiogenic activity, which may induce the development of MDAVFs. Intracranial MDAVFs have a malignant clinical course, and their symptoms generally rapidly progress following onset. It is therefore important to identify intracranial MDAVFs at an early stage. A number of imaging technologies, including computed tomography (CT), magnetic resonance imaging (MRI), digital subtraction angiography (DSA) and single-photon emission computed tomography (SPECT), may be used to detect MDAVFs. Of these, CT and MRI provide information on brain morphology, SPECT provides brain blood flow information, and DSA is the gold standard that may be used to identify angioarchitecture and hemodynamics. MDAVFs require timely and aggressive treatment, which may include endovascular embolization, surgical resection, radiosurgery and conservative treatment, and in some cases, combined treatments are required. Appropriate and aggressive treatment regimens can markedly improve neurological deficits and cognitive function in patients with MDAVFs.