Key-words: Dural arteriovenous fistula - surgical approach - transcranial embolization
Introduction
Dural arteriovenous fistula (DAVF) is an acquired vascular malformation of dural venous
sinuses. DAVFs are associated with features of cerebral venous congestion, raised
intracranial pressure (ICP), and increased risk of intracerebral hemorrhage.[[1 ]] Acute raise in ICP secondary to DAVF has been rarely described in the literature.[[2 ]] Treatment of DAVF by direct transcranial embolization of the fistula through craniotomy
has been described uncommonly in the literature.[[3 ]],[[4 ]],[[5 ]],[[6 ]],[[7 ]],[[8 ]] We describe the clinical features and management of a patient who presented with
acute raise in ICP secondary to transverse sinus DAVF.
Case Report
A 58-year-old female presented with sudden onset of giddiness and multiple episodes
of vomiting. On presentation, she was conscious, obeying commands, and had a Glasgow
Coma Scale (GCS) of 15. Computed tomography (CT) of the brain revealed hemorrhages
in the left posterior temporal lobe and left cerebellar hemisphere with mildly dilated
bilateral lateral ventricles. In view of atypical pattern of hemorrhage, a CT cerebral
angiography was performed, which showed multiple subarachnoid curvilinear vascular
channels over the bilateral cerebellar hemispheres and left temporal lobe [[Figure 1 ]]. A digital subtraction angiography (DSA) was done, which revealed a DAVF in relation
to isolated left transverse sinus with extensive cortical venous reflux suggesting
Cognard Type IIa + b fistula. It was showing meningeal arterial feeders from temporal
squamous branch of the left middle meningeal artery, left posterior auricular artery
and left occipital artery, and cortical venous reflux. The DSA venographic phase image
showed that the left transverse sinus was isolated from the venous circulation, and
it was not used by the brain for normal drainage [[Figure 2 ]]. The imaging features suggested extensive venous congestion in the posterior fossa
due to arterialized flow in the cortical veins secondary to DAVF. The patient was
planned for definitive treatment of the DAVF by endovascular embolization through
transarterial (femoral) approach. However, on day 2 of admission, her neurological
condition deteriorated and her GCS became 8. After the protection of the airway, a
repeat CT scan of the brain was performed, which showed interval increase in hydrocephalus
and effacement of perimesencephalic and prepontine cisterns suggesting raised ICP
[[Figure 3 ]]. After informed consent, the patient was taken up for emergency occipital decompressive
craniectomy, and simultaneous intraoperative direct embolization of DAVF of the left
transverse sinus was planned.{Figure 1}{Figure 2}{Figure 3}
Figure 1: (a-c) Axial sections of computed tomography of the brain at the time of presentation
demonstrating hemorrhage in the left temporal lobe (thick arrow) and cerebellum (thin
arrow). (d) Axial maximum intensity projection image of computed tomography angiogram
demonstrating multiple curvilinear tortuous channels (thin curved arrows) in the cerebellum
Figure 2: (a-c) Digital subtraction angiography images of selective left external carotid injections
showed early opacification of the left transverse sinus (dotted arrows), which is
isolated and having cortical venous reflux (arrowheads). (d-f) Delayed venous phase
images of selective left vertebral, left internal carotid artery, and right internal
carotid artery injections, respectively, showing no drainage into the left transverse
sinus
Figure 3: (a-c) Axial sections of computed tomography of brain on day 2 of admission showing
effaced basal cisterns with dilated lateral ventricles. (d) Sagittal section of computed
tomography of the brain showing crowded posterior fossa components
Operative technique
The patient was placed in a prone position. A 6 cm posterior midline incision was
made and deepened till the bone. The underlying bleeding vessels were cauterized,
and self-retracting clips were applied. Suboccipital craniotomy was done, and bone
was nibbled up to C1 vertebra. The foramen magnum was decompressed. The dura covering
the cerebellum was opened. After the decompressive craniectomy, the upper margin of
craniotomy was drilled to expose the posterior aspect of the left transverse sinus.
It was punctured directly using a 21-G micropuncture needle (Cook, Bloomington, Indiana,
USA). Once backflow of blood is confirmed through the needle, a 0.018” wire was then
advanced through the needle into the isolated segment of the left transverse sinus
under C-arm fluoroscopic guidance. The needle was exchanged for a micropuncture sheath
(4F radial sheath) (Avanti+, Cordis, Santa Clara, USA). An Echelon-10 (ev3, Toledo
Way, Irvine, USA) and Synchro 0.014 (Stryker neurovascular) guidewire assembly was
introduced through the micropuncture sheath into the left transverse sinus. The microcatheter
was primed with dimethyl sulfoxide. Under fluoroscopic guidance, embolization of isolated
left transverse sinus was done using graded injections of liquid embolic agent ethyl
vinyl alcohol polymer Onyx-18 (ev3, Toledo Way, Irvine, USA). The injection of Onyx-18
was done till complete cast is formed in the isolated sinus, and reflux was allowed
into foothills of feeding arteries and draining veins [[Figure 4 ]]. The micropuncture sheath was removed from the transverse sinus, and bleeding was
controlled by electrocautery. After the completion of the operative procedure, the
patient was shifted to neuroangiosuite for a DSA. Selective injection of the carotid
arteries and vertebral arteries revealed no residual AVF or cortical venous reflux
[[Figure 5 ]] and [[Figure 6 ]]. CT scan of the brain done on postoperative day 4 revealed spacious basal cisterns
and decreased dilatation of lateral ventricles as compared to preoperative CT scan
[[Figure 6 ]]. Postprocedure, the patient was monitored in neurointensive care. The patient gradually
improved and was extubated on postoperative day 3. The patient was discharged in a
neurologically stable condition on day 9. At 1-year follow-up, her neurological condition
was stable with no recurrence of symptoms.{Figure 4}{Figure 5}{Figure 6}
Figure 4: (a) Intraoperative photograph showing suboccipital craniotomy and exposed left transverse
sinus (thin arrows) (b-e). Intraoperative fluoroscopic image demonstrating micropuncture
needle and guidewire placement (thick arrows), microcatheter positioning (dotted arrows),
and Onyx cast in the isolated left transverse sinus (curved arrows)
Figure 5: (a-f) Postoperative digital subtraction angiography of left VA injection demonstrating
no residual dural arteriovenous fistula with no significant stasis in the posterior
fossa venous circulation
Figure 6: (a-c) Postoperative digital subtraction angiography of left internal carotid artery
injection demonstrating no residual dural arteriovenous fistula. (d-f) Axial sections
of computed tomography of brain demonstrating occipital craniotomy postoperative changes
with Onyx cast artifacts and decreased lateral ventricular dilatation
Discussion
DAVFs comprise about 10%–15% of intracranial vascular malformations.[[9 ]] Transverse-sigmoid sinus DAVF is one of the most common types of DAVFs.[[10 ]] DAVFs signify an abnormal connection between dural or meningeal arteries and venous
system of the brain, with arterialization of veins and resulting in venous hypertension.
Demonstration of surplus of leptomeningeal vessels on cross-sectional imaging is an
imaging marker of venous congestion in DAVFs.[[11 ]]
The raise in ICP in the index case can be attributed to hydrocephalus, cerebellar
venous congestion, and edema. Any pathophysiological process impeding cerebrospinal
fluid (CSF) or venous outflow would result in hydrocephalus. Nonobstructive hydrocephalus
in DAVF is explained by venous hypertension causing increased dural sinus pressure,
which results in decreased CSF absorption as higher CSF pressure is necessary to drive
bulk flow of CSF across the meninges.[[2 ]],[[12 ]] The drainage of CSF to mitigate the raised ICP is contraindicated in such cases
and in fact may exacerbate the clinical worsening, as it may increase the venous sinus
and CSF pressure gradient further. The other important cause of cerebellar edema and
hemorrhages in posterior fossa is arterialization of cerebellar cortical veins causing
significant impediment of blood flow from capillaries to the venous circulation, resulting
in significant interstitial edema and cerebellar hemorrhage.[[12 ]] In DAVF with venous hypertension, the raise in ICP is usually insidious in onset;
however, an acute raise in ICP as in the index case is very unusual. It can be probably
explained by breakthrough of venous hypertension contributed by extensive arterialized
cerebellar cortical veins in the posterior fossa that is too much to compensate for
the volume of CSF and brain.[[2 ]]
The clinical signs, symptoms, and imaging features of DAVF are reversible if recognized
and treated early. Treatment of DAVFs is aimed at obliterating the arteriovenous shunting
that is leading to venous hypertension. Treatment options in the index case include
endovascular embolization (transarterial/venous) and microsurgery. For the treatment
of DAVF, endovascular transarterial or transvenous embolization is usually the first-line
option.[[9 ]] In the index case, the endovascular option was chosen over microsurgical excision,
as microsurgery option would have required more extensive exposure and ligation of
multiple arterialized cortical veins. Several reports have been published previously
using the transcranial route for venous access.[[3 ]],[[4 ]],[[5 ]],[[6 ]],[[7 ]],[[8 ]],[[9 ]] In the index case, transarterial approach using Onyx Liquid Embolic System was
considered initially; however, due to acute neurological deterioration, the patient
was taken up for emergency decompressive craniectomy, and in the same sitting, intraoperative
transcranial embolization of DAVF was performed. Single-stage craniectomy and embolization
in the setting of acutely raised ICP in DAVF have not been described before. As a
rule, DAVF embolization with liquid embolics such as Onyx is done under roadmap guidance.
Transcranial venous embolization under C-arm guidance in the usual neurosurgical operating
room should be done with caution, as nontarget embolization of the liquid embolic
agent may not be detected on simple fluoroscopy without a roadmap. In the index case,
percolation of Onyx into isolated transverse sinus, draining cortical venous foothills,
and arterial feeders was considered to be a finishing point. The targeted venous pouch
was isolated, and it was in communication with only the cortical veins, and it was
angiographically demonstrated to be isolated from the rest of the dural venous sinuses,
so the chance of nontarget embolization to normal venous circulation was very minimal.
Percolation of Onyx into the foothills of draining cortical veins was acceptable as
they had flow reversal secondary to arterialization, and they had no contribution
to normal brain venous drainage.
Conclusion
DAVF presenting as acute raise in ICP is very rare. Emergency management by transcranial
embolization in the same stage after the decompressive craniectomy may be safe and
effective in this specific clinical setting.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form, the legal guardian has given his consent for images and other clinical
information to be reported in the journal. The guardian understands that names and
initials will not be published and due efforts will be made to conceal identity, but
anonymity cannot be guaranteed.
