34 Right-sided Occipital Dural Arteriovenous Fistula

Right-sided Occipital Dural Arteriovenous Fistula

Clinical Presentation

A 20-year-old woman was admitted with a right-sided parietooccipital headache. Three years earlier, she had a cerebral venous thrombosis (CVT) in the right transverse (TS) and sigmoid sinus (SiS). The CVT was likely the combined result of a heterozygote plasminogen activator inhibitor type 1 deficiency (PAI-1), a prothrombin mutation, and oral contraceptives. She was administered oral anticoagulation for 12 months. The current headaches seemed similar to those described 3 years before and she feared a relapse. She also reported a right-sided pulsatile tinnitus which started roughly 6–9 months after CVT. Despite its unremitting daily persistence, she had adapted to the noise. An outpatient otorhinolaryngology consultation revealed nothing remarkable and no accompanying symptoms were reported. Her neurologic status was within normal limits. The right occipital artery (OccA) was easily palpable and digital compression led to mild amelioration of her tinnitus. Clinically, we suspected that an occipital dural arteriovenous fistula (DAVF) had formed as a sequel to her CVT.

Initial Neuroradiologic Findings

Cerebral MRI showed no old or acute parenchymal lesions (not shown). Source data of the 3D time-of-flight MR angiography (TOF-MRA) revealed irregular signal appearance in the right SiS which was assumed to present arterialized venous vessels. The distal SiS seemed occluded (Fig. B34.1) and the right OccA and middle meningeal arteries (MMA) were prominent (Fig. B34.2). Finally, 3D TOF-MRA showed arterialized right proximal SiS and TS as well as prominent right OccA and MMA (Fig. B34.3 and Fig. B34.4).

Suspected Diagnosis

Occipital right-sided DAVF fed by the right MMA and OccA based on a former CVT.

Questions to Answer by Ultrasound Techniques

Could the feeding arteries be identified by ultrasound?
Could the draining veins be identified?
What was the shunt volume?
Could the fistula state be estimated according to Cognard?

Initial Neurosonologic Findings

Extracranial Duplex Sonography

Because we suspected DAVF, blood volume flow (BVF) measurements were performed in addition to the standard flow velocity assessment. Comparison of the right and left sides revealed increased flow velocity and BVF in the right common carotid artery (CCA) and right external carotid artery (ECA) compared with the left-side vessels. Pulsatility was accordingly reduced in the right CCA and ECA, and the right ECA had an increased diameter (5.4 versus 3.6 mm) (Figs. B34.5– B34.11). A marked hyperperfusion was also detected in the right-sided OccA, again with concomitantly reduced pulsatility index (PI) (Fig. B34.12 and Fig. B34.13). Assessment of both internal carotid arteries (ICAs) and vertebral arteries (VAs) was normal.

The examination of the venous drainage revealed a mild left-sided flow dominance via the internal jugular veins (IJVs) (Fig. B34.14 and Fig. B34.15). A left-sided dominance was also observed in the vertebral veins (VVs) (Fig. B34.16 and Fig. B34.17). Compression of the right OccA led to a reduced flow in the left IJV. Also, the previous monophasic flow changed to a biphasic flow pattern (Fig. B34.18). Global cerebral circulation time measured between the left CCA and left IJV after echo contrast agent injection was ~2 seconds).

Transcranial Duplex Sonography

Normal blood flow parameters were seen in all basal cerebral arteries on both sides. The MMA was detectable on both sides and revealed an internalized flow signal with increased flow velocity and decreased pulsatility on the right side and a normal signal contralateral (Fig. B34.19 and Fig. B34.20). Venous analysis showed normal flow signals in the basal vein of Rosenthal (BVR) on both sides as well as in the vein of Galen and straight sinus (StS) revealing peak systolic flow velocities of ~10 cm/s. However, we observed a prominent antegrade flow at the left TS. The main finding was a marked retrograde flow in the right TS with a peak systolic flow velocity of 25 cm/s (Fig. B34.21 and Fig. B34.22).

Fig. B34.1 (A,B) Source images of a 3D ce-MRA, axial plane, showing signal irregularities of the right sigmoid sinus (arrows) considered to be partial recanalization or arterialization.

Fig. B34.2 (A) Raw-data TOF-MRA, axial plane, showing enlarged OccA on the right side (arrow). (B) Ce-MRA, axial plane, revealing a prominent middle meningeal artery (arrow). No corresponding artery is seen on the contralateral side.

Fig. B34.3 3D TOF-MRA, axial maximal intensity projection (MIP), suggestive of a DAVF, showing a prominent flow signal in the right TS indicating arterialization (arrowhead) and marked signals of the assumed middle meningeal artery (arrow) and its branches (white arrows).

Fig. B34.4 3D TOF-MRA, coronal MIP, suggestive of a DAVF, showing a prominent flow signal in the right TS indicating arterialization (small arrowhead) and marked signals of the OccA (arrow) and branches of the middle meningeal artery (white arrows). The center of the DAVF is marked by the large arrowhead.

Fig. B34.5 Extracranial duplex, longitudinal plane. Right CCA with increased BVF and reduced pulsatility in comparison to the contralateral side (BVF 500 mL/min, PI = 1.5).

Fig. B34.6 Extracranial duplex, longitudinal plane. Left CCA with normal BVF and pulsatility (BVF 380 mL/min, PI = 2.19).

Fig. B34.7 Extracranial duplex, longitudinal plane. Right ICA with normal BVF (210 mL/min).

Fig. B34.8 Extracranial duplex, longitudinal plane. Left ICA with normal BVF (250 mL/min).

Fig. B34.9 Extracranial duplex, longitudinal plane. Right ECA with BVF increase and low PI in comparison to the contralateral side (BVF 350 mL/min, PI = 1.36).

Fig. B34.10 Extracranial duplex, longitudinal plane. Left ECA with normal BVF and pulsatility (BVF 130 mL/min, PI = 2.56).

Fig. B34.11 Extracranial duplex, color-mode image, axial plane. (A) Note that the diameter of the right ECA exceeds the diameter of the ICA. (B) Normal and physiologic relation of larger ICA and smaller ECA diameter on the left side.

Fig. B34.12 Extracranial duplex, axial plane. Right OccA with increased BVF and decreased PI (BVF 210 mL/min, PI = 1.34).

Fig. B34.13 Extracranial duplex, axial plane. Left OccA with normal ultrasound parameters (BVF 20 mL/min, PI = 3.17).

Fig. B34.14 Extracranial duplex, longitudinal plane. Right IJV with normal BVF (430 mL/min).

Fig. B34.15 Extracranial duplex, longitudinal plane. Left IJV with normal BVF (490 mL/min).

Fig. B34.16 Extracranial duplex, longitudinal plane. Right VV with BVF in the normal range (10 mL/min).

Fig. B34.17 Extracranial duplex, longitudinal plane. Left VV with BVF in the normal range (40 mL/min).

Fig. B34.18 Extracranial duplex, longitudinal plane. During compression of the right OccA (white dotted line) the flow spectrum changes from monophasic to biphasic. Also, the diastolic flow markedly decreases, which indicates reduced fistula flow from the right OccA into the left IJV during compression.

Fig. B34.19 TCCS (transtemporal approach), right-sided insonation, axial lower pontine plane. Right MMA with internalized flow signal comprising high diastolic flow (flow velocity 48/19 cm/s, PI = 0.9).

Fig. B34.20 TCCS (transtemporal approach), left-sided insonation, axial lower pontine plane. Left MMA with normal flow signal and lower velocities compared with the right MMA (flow velocity 26/5 cm/s, PI = 1.75).

Fig. B34.21 TCCS (transtemporal approach), left-sided insonation, oblique midbrain plane. The right TS revealed a marked retrograde flow signal with increased pulsatility (flow velocity 25/16 cm/s).

Fig. B34.22 TCCS (transtemporal approach), left-sided insonation, oblique midbrain plane. The left TS revealed a marked antegrade flow signal (flow velocity 20/14 cm/s).