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Abstract
A woman in her mid-50s who had undergone a subtotal resection of a peritorcular meningioma 3 years earlier presented with symptoms suggestive of increased intracranial pressure. A delayed diagnosis of a torcular dural arteriovenous fistula (dAVF) diagnosis was made on MRI. Digital subtraction angiography confirmed a torcular dAVF (Borden type II). Staged 3 rounds of transarterial (TA) embolisation were performed using n-butyl cyanoacrylate, ethylene vinyl alcohol copolymer and coils of the complex torcular dAVF, which significantly reduced the flow and corresponded with improved symptoms of pulsatile tinnitus, vision and headache. We reviewed previously reported cases of dAVFs that developed after craniotomy for meningioma resection. Despite its rarity, a torcular dAVF can develop after craniotomy and progress from low to high grade due to its location. Diagnosis requires a thorough understanding of subtle imaging findings, which may be present in follow-up studies obtained for tumour surveillance.
- Neuroimaging
- Interventional radiology
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Background
Tentorial middle region dural arteriovenous fistula (dAVF) is extremely rare to develop after craniotomy. Acquired progressive torcular dAVF (Lawton type 3) after craniotomy has not been reported in the literature. Cranial dAVFs are arteriovenous shunts between dural arteries and dural venous sinuses, dural veins or leptomeningeal veins.1 In a meta-analysis of 1077 patients with cerebral dAVFs reported before 2017, torcular dAVF represents only 4.7% (51/1077) of all cerebral dAVFs.1 Although the majority are thought to be idiopathic, a subset has been associated with trauma, infection, venous sinus thrombosis and previous craniotomy.2 Yajima et al, have reported 25 cases of dAVFs developing after craniotomy in the literature.3 Here, we report the first case of an acquired progressive torcular dAVF after subtotal resection of a peritorcular meningioma as well as a review of the relevant literature.
Case presentation
A woman in her mid-50s presented with a change in her long-standing headache pattern, experiencing increased frequency and constant pressure in the posterior head. MRI with gadolinium showed a 1.8 cm meningioma in the right paramedian aspect of the torcula (figure 1(A–C)). The patient underwent posterior fossa craniotomy for resection due to interval growth on follow-up imaging and worsening of the headache, leaving part of the meningioma adjacent to the torcula. The histopathological diagnosis was meningothelial meningioma (WHO grade I).
Preoperative and postoperative MRIs (A–F). Axial T2WI (a) and post-gadolinium enhanced axial T1WI (B) and coronal T1WI (C) show an enhancing extra-axial tumour in the posterior fossa near the torcula on the right (white arrow). Postoperative baseline MR imaging at 4 months (D–F). Axial T2WI (D), post-gadolinium axial T1WI (E), and coronal T1WI (F) show a small residual extra-axial tumour in the posterior fossa near the torcula on the right (white arrow).
9 months postoperative, she developed a multitude of symptoms suggestive of increased intracranial pressure. The symptoms included a pressure-like headache, bilateral optic disc oedema, transient visual obscuration, concentration and memory deficits, and bilateral pulsatile tinnitus. The initial working diagnosis was idiopathic intracranial hypertension (IIH) due to mechanical obstruction of the right transverse sinus (TS) by the residual meningioma.
An MRI scan at that time demonstrated the stability of the residual peritorcular meningioma (figure 1(D–F)). Contrast-enhanced magnetic resonance venography revealed moderate stenosis at the proximal right TS and non-flow limiting focal narrowing at the distal left TS. The torcula and bilateral sigmoid sinuses (SS) were patent (figure 2A). There were no imaging findings to suspect a dAVF.
Postoperative MRVs with Gadolinium enhancement (A–C). At 9 months MRV (A) shows focal moderate stenosis at the proximal right transverse sinus (long arrow) and a mild focal narrowing at the distal left transverse sinus (short arrow) with normal distal flow. At 36 months MRV (B) shows interval increased stenoses of the proximal right (long arrows) and distal left transverse sinuses (short arrows). Also noted were markedly progressed dilated cortical veins bilaterally (arrowheads). Follow-up post dural arteriovenous fistula embolization MRV (C) demonstrates complete occlusion of the bilateral transverse sinuses (long and short arrows) and persistent prominent cortical veins bilaterally (arrowheads). MRV, magnetic resonance venography.
At 21 months postoperatively, a follow-up MRI demonstrated interval increased prominence of the supratentorial and infratentorial cortical vessels concerning a dural AVF (figure 3B and figure 4(B, E and H)), and a CT angiography and venography was recommended. Unfortunately, this follow-up imaging was read as normal. Her symptoms continued to worsen during the follow-up. Extensive blood work, CSF analysis and opening pressures were normal.
Postoperative follow-up MRIs at 9 month (A), 21 month (B) and 36 month (C). The follow-up images show progressive development of numerous dilated vessels on the bilateral inferolateral occipital regions on axial T2WI, which was prominent occipital arteries (arrow heads).
Postoperative follow-up MRIs at 9 month (A,D,G), 21 month (B,E,H) and 36 month (C,F,I). Axial T2WI mages show prominent and progressive development of numerous dilated vessels of the bilateral superior orbital vein (arrowheads), along the tentorium (thin arrows), Sylvian fissure (thick arrows) and overlying the cerebral hemispheres (black arrows).
At 36 months postoperatively, follow-up MRI showed marked interval progression of the abnormally dilated vessels overlying the cerebral hemispheres and tentorium, with bilateral prominent occipital arteries suspicious for a dAVF. There was also further occlusion of the right transverse sinus (figure 3C, figure 4(C, F and I)). The residual peritorcular meningioma remained stable in size.
An immediate diagnostic cerebral angiogram (DSA) was performed, demonstrating a Borden II and Cognard type a+b fistula at the torcula. The fistula was supplied by multiple feeders, including an occipital meningeal branch of the right vertebral artery (VA), right posterior inferior cerebellar artery (PICA), tentorial branches of the superior cerebellar arteries, bilateral occipital arteries (OA), a posterior branch of the right middle meningeal artery (MMA) and the right marginal tentorial artery (MTA) of Bernasconi and Cassinari (figure 5A–F). There was reflux into dilated, tortuous deep and cortical veins, completely altered and rerouted bilaterally, with the presence of a pseudophlebitic cortical venous pattern secondary to bilateral TS occlusions (figure 5(G, H and I)).
Postoperative DSA imaging at 36 month shows a torcular dAVF (A–J). DSA images show dAVF (red oval) with multiple feeding arteries and drainage into torcula (black arrow). Main feeders are the occipital meningeal branch of the right vertebral artery (white arrowheads), right posterior inferior cerebellar artery (black arrowheads), tentorial branches of the bilateral SCA (blue arrows), bilateral occipital arteries (yellow arrows), posterior branch of the right middle meningeal artery (green arrows) and Bernasconi and Cassinari artery (short white arrows). The venous phase images (G–I) show occlusions at the proximal right transverse sinus (long arrows) and distal left transverse sinus (short arrows). The late venous phase shows the presence of pseudophlebitic cortical venous pattern (arrow heads). dAVF, dural arteriovenous fistula; DSA, digital subtraction angiography.
Four rounds of staged transarterial embolisation were performed. During the initial treatment, the PMA of the right VA and the distal branch of the right PICA were targeted using 20% diluted n-butyl cyanoacrylate with Lipiodol. 11 weeks following the initial embolisation, a second embolisation was performed targeting the posterior branch of the right MMA and the right occipital artery using ethylene vinyl alcohol (EVOH) copolymer and gel foam torpedoes. A third TA embolisation was performed 6 weeks later targeting the left occipital artery using EVOH copolymer for the superior branch and coils for the inferior branch of the left occipital artery and the distal branch of the right PICA. At the end of this procedure, there was residual dAVF supply from tiny right PICA branches. Along the course, a thrombus formed within the superior sagittal sinus, which improved partially with direct oral anticoagulants (DOACs). She has been on a variety of DOACs. Angioplasty and stenting of the left TS were discussed, but we deemed that the risk of losing the outflow of the vein of Labbe, along with the 15.4% potential risk of in-stent occlusion rate, was too high.4 Additionally, she has a nickel allergy and was refractory to DOAC. During the last transarterial embolisation, the right occipital artery was targeted using EVOH copolymer. This resulted in a complete angiographic cure with no residual filling of the fistula.
Outcome and follow-up
The patient has not been able to return to work. She still has quite a few challenges, including exhaustion, gastrointestinal issues, loud tinnitus, some visual issues and issues with focusing, retention and memory.
Discussion
dAVFs represent 10%–15% of all intracranial vascular malformations with an incidence between 0.16 and 0.51 per 100 000 adults per year.5 6 They are most commonly idiopathic, acquired lesions that usually develop in response to venous sinus thrombosis, occlusion, increased sinus pressure, previous neurosurgical procedures, trauma or hypercoagulability states.2 The pathogenesis of dAVFs is still unclear.2 7 8
A torcular dAVF is an extremely rare and complex vascular lesion.1 8–10 According to Lawton et al, the tentorial middle region dAVF includes six types (type 1: Galenic, type 2: straight sinus, type 3: torcular, type 4: tentorial sinus, type 5: superior petrosal and type 6: incisura) from their attachment to the clinoid processes and petrous ridges anteriorly to the torcula posteriorly.8 11 Tentorial dAVFs are less common than TS–SS and cavernous sinus dAVFs account for 12%–15%.1 2 8 12 The torcular dAVF (Lawton type 3) accounts for only 3%–4.7% of all tentorial dAVFs.1 2 8 The majority of torcular dAVFs are Borden type II and III.2
Clinical symptoms of tentorial dAVFs can vary depending on their location and haemodynamic status.8 11 13 Intracranial haemorrhage is one of the most feared and fatal complications of any dAVFs. However, it does not specifically correlate with the type of tentorial dAVF.1 14 The reported progression rate of low- to high-grade dAVFs is 1.4%.2 15
dAVFs are dynamic lesions that may either progress or spontaneously regress. Therefore, close attention to any change in subtle imaging findings is important because this may significantly alter the type of venous drainage pattern and pose a risk factor for the development of dAVFs.14 16
Flow voids from large, arterialised draining veins and varices can be visualised on T2-weighted MRI.17 MRI may also show indirect signs of venous hypertension or cortical venous reflux, such as pial vein engorgement, dilated venous pouch or abnormal vascular enhancement.10 Hetts et al, reported that 19 (3.2%) of 579 patients had progressive dAVFs, and the presence of the pseudiphelibitic cortical venous pattern was more common in this group.18 The main feeding arteries of the torcular herophili dAVF include posterior meningeal artery (PMA), MMA, MTA and artery of Davidoff and Schechter. They drain supratentorially into the medial and inferior occipital veins along the sagittal and TSs or the basal vein of Rosenthal.17 All torcular dAVFs are associated with sinus thrombosis and show bidirectional drainage relative to the tentorium.17 19 Therefore, abnormally prominent flow voids and interval progression of the dilated cortical veins on T2WI are the suspicious imaging findings of the development of dAVFs on follow-ups.
Although several cases of dAVFs have been reported secondary to craniotomy due to sinus occlusion,3 we did not find the torcular dAVF after craniotomy in the literature. We conducted a literature review and found 11 cases of dAVF developing after craniotomy for meningioma resection (table 1),3 16 19–25 not including our case. The mean patient age was 57 (46–67 years old) with a slight female predilection 7:4 (female:male ratio). The median interval development of dAVF after craniotomy was 37 months (6–90 months). There were 7 cases of developed postoperative sinus stenosis or occlusion. 10 out of 11 cases were directly related to the site of craniotomy. Only one case was developed at a different site. The TS/SS junction was the most common location of dAVFs after craniotomy, representing 9 of the 11 cases. A total of nine cases presented with non-haemorrhagic symptoms, and only one case with haemorrhage. The main clinical presentation was tinnitus, bruit, visual obscuration and headache in nine cases and two cases were asymptomatic in these studies. A total of six cases were developed after suboccipital craniotomy. Four cases were Borden II or III dAVFs, and three cases were Borden I; the rest were not mentioned in these studies. Six dAVFs were treated with endovascular embolisation, and four of them started with TA embolisation as an initial treatment. Two dAVF cases were surgically resected; one case did not require any treatment because the patient was asymptomatic. Four cases achieved good or complete resolution of the dAVFs after endovascular treatment, and one case showed partial regression. There was one recurrence that occurred after 6 months following combined endovascular and surgical treatments. Despite many treatment options, transarterial embolisation is the most common and the first-line treatment for tentorial middle region dAVF.8 11
Clinical characteristics of dAVFs reported after craniotomy for meningioma resection
Patient’s perspective
Reflecting on my medical journey over the past 8 years, I am struck by how much persistence was required to get answers. Initially, my symptoms were dismissed as menopause until I insisted on an MRI, which led to the discovery of a brain tumour. After my craniotomy and tumour resection, my symptoms worsened; whooshing sounds, pressure, vision issues and severe fatigue became daily hurdles. It was my physiotherapist who I went to for back pain who urged me to see a neuro-ophthalmologist, leading to an IIH diagnosis. My neurosurgeon and neuro-ophthalmologist worked together but despite a lumbar puncture and various medications with difficult side effects, I continued experiencing whooshing, pressure, nerve pain and muscle spasms that made sleep and even sitting difficult.
Researching my own condition, I advocated for a stent, believing compromised blood flow caused my symptoms, though my scans did not reflect this. Eventually, I was sent to a vascular neurosurgeon and an interventional neuroradiologist who confirmed an AV fistula that nearly took my life. This was the beginning of challenging treatments during Covid, with multiple surgeries and extended hospital stays, yet for the first time, I felt heard and part of the team. My fourth brain surgery appears to have cured the AV fistula, although I still have the brain tumour and face lingering effects like exhaustion, severe tinnitus, visual issues, and GI problems. Despite it all, I’m grateful to be here, and that is everything.
Learning points
First case of delayed postoperative progressive torcular dural arteriovenous fistula (dAVF) after craniotomy for a meningioma resection.
Although torcular dAVF is extremely rare, it can develop after craniotomy and can progress from low to high grade due to its location and multiple feeders.
Diagnosis requires a good understanding of subtle imaging findings that could potentially be present in follow-up imaging studies obtained for tumour surveillance.
Ethics statements
Patient consent for publication
References
Footnotes
Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: UE-E, DV is the guarantor of the manuscript. The following authors gave final approval of the manuscript: AW, SW, DV.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.