Transverse sinus stenting for treatment of papilloedema secondary to a large brain herniation into a dural venous sinus with associated tectal plate lesion: Case report and literature review

Abstract

Brain herniation into a dural venous sinus is a rare entity of unknown clinical significance without a clear relationship to raised intracranial pressure. There are yet to be detailed reports of interventional neuroradiology procedures involving sinus stenting across brain herniations. The authors of this paper present the first case of a stent placed across a large brain herniation into the transverse sinus in a patient with a tectal plate lesion and features of chronically raised intracranial pressure. This case demonstrates objective resolution of papilloedema and venous sinus pressure gradient at six months without complication.

Introduction

Brain herniation into a dural venous sinus (BHDVS) remains a rare entity despite improved high-resolution magnetic resonance imaging (MRI) availability.^1–5 The prevalence and clinical significance of BHDVS has not been fully characterised. It is unclear if BHDVS represents a symptomatic lesion or has an association with raised intracranial pressure (ICP).^1,2,4,6 Transverse sinus stenting (TSS) is safe and effective in the management of idiopathic intracranial hypertension (IIH). ⁷ The role of endovascular intervention in BHDVS has only recently been reported. ⁸ The authors of this paper present management of a clinically significant brain herniation (BH) into the transverse sinus (TS) with a concurrent tectal plate lesion and presumed chronically raised ICP. This is presented as one of the first descriptions of this clinical combination of pathology and treatment, with a supporting literature review.

Case report

A 52-year-old male with a background of diabetes mellitus, hypertension, obesity and obstructive sleep apnoea attended routine retinopathy screening with his optometrist. Asymptomatic papilloedema was observed bilaterally without associated headaches, vomiting or subjective visual disturbance. On initial examination, visual acuity (VA) was 6/4.8-2 right eye (RE) and 6/4.8 left eye (LE), peripapillary retinal nerve fibre length (RNFL, in µm) RE 116 and LE 79.

The patient underwent an MRI of the brain which demonstrated chronic hydrocephalus with enlargement of the lateral and third ventricles as well as a non-enhancing tectal plate lesion constricting the lower sylvian aqueduct, presumed a low-grade glioma. There was fullness of the sella and mild flattening of the pituitary gland. There was mild right optic sheath hydrops, scleral flattening and prominence of the optic papilla (Figure 1).

Figure 1.

(a) Axial T1 post-Gd MPRAGE demonstrating right optic sheath distension, scleral flattening and prominent papilla (red asterisk). Note peri-aqueductal hypointense non-enhancing lesion (red arrow). Note unremarkable left optic sheath; (b) sagittal FLAIR shows tectal lesion (red arrow) narrowing the aqueduct causing supratentorial hydrocephalus. Note flattened pituitary in mildly enlarged sella (red asterisk); (c) 3D MRV demonstrates filling defect in dominant right sigmoid sinus (red arrow), with prominent transdiploic collateral veins (red asterisk); (d) oblique sagittal CT venogram shows finger-like filling defect in right sigmoid sinus (red asterisk).

An elongated filling defect within the dominant right sigmoid sinus and anterior aspect of the TS, measuring 37 mm long and 8 mm in width, was also noted, with signal intensities matching that of brain parenchyma and CSF. This represented a large BH of the temporal lobe, including the temporal horn of the right lateral ventricle and arachnoid mater (Figure 2).

Figure 2.

Coronal post-Gd T1 MPRAGE demonstrating elongated right temporal brain herniation, with a right lateral ventricular component, filling the lumen of the sigmoid sinus.

Given the patient was asymptomatic, management was expectant. Six-month repeat assessment demonstrated bilaterally reduced VA RE 6/6 – 1 and LE 6/6 + 2, RNFL RE 246, LE 93 without change after a trial of acetazolamide. Given progressive clinical findings, a decision was made to perform DVS manometry with a view to establish the role of TSS.

Retrograde venography demonstrated an elongated scalloped filling defect in the dominate right TS with extensive transdiploic collateral drainage. Venous sinus manometry performed under local anaesthetic demonstrated a gradient greater than 15 mmHg across bilateral TS. In light of this, and the threat to vision, a decision was made to proceed to TSS. Dual anti-aggregant therapy with aspirin 100 mg and 75 mg clopidogrel daily was commenced seven days prior to intervention, and continued until three most post-procedure when aspirin was continued as a single agent. Under general anaesthetic, a 65 cm 8 F guide sheath (Destination®, Terumo Interventional Systems) was placed in the right internal jugular vein following right sapheno-femoral junction access. A co-axial 100 cm 6 F long-sheath (Neuron MAX™ 088, Penumbra Inc) was advanced to the torcula and used to deliver a 10 × 80 mm self-expanding stent (Protégé™ GPS™, Medtronic) across the lesion, effectively jailing the intrasinus BH and restoring the native lumen. Balloon angioplasty was not required. Completion venography demonstrated near complete reversal of the filling defect and reduction in collateral opacification. The patient had an uneventful recovery (Figure 3).

Figure 3.

Pre- (a,c) and post- (b,d) stenting venography, demonstrates (a,c) venogram demonstrating scalloped intra-sinus filling defects (white arrow), collateral venous opacification (thin white arrows) and contralateral reflux (white asterisk) (b,d). Post-stenting venogram demonstrates restoration of sinus lumen and diminished collateral filling.

Follow-up ophthalmological assessment demonstrated restoration of RE RNFL to 99, LE 77. Three-month follow-up MR confirmed stent patency with no change in ventricular girth and no adverse changes in the adjacent parenchyma. Six-month follow-up venography demonstrated considerable improvement in venous outflow enabled by the stent with complete resolution of collateral venous opacification. The pressure gradient across the right TS had returned to 5 mmHg and the pressure in the proximal TS dropped from 32 mm Hg to 12 mm Hg (Figure 4).

Figure 4.

(a) Six month post-stent (white asterisk) follow-up venogram shows normalised dominant right transverse/sigmoid sinus filling and regression of collateral veins; (b) oblique sagittal CT venogram demonstrating restoration of sigmoid sinus lumen.

Discussion

Brain herniations into a dural venous sinus are rare with few case reports^8–11 and case series^1–5,12 making up the literature. The description and pathophysiological mechanism is debated but may result from BH through established arachnoid granulations (AG) in the DVS. Although a pathogenesis associated with raised ICP has been proposed,^6,12 it remains uncommon to identify this relationship.^1,2,4 Brain herniations have been reported as incidental findings and occasionally as clinically significant or symptomatic lesions.^1,2,8,12 To our knowledge, this is the first clinically significant BHDVS with a concurrent lesional cause for chronic raised ICP that has undergone TSS. In this discussion the authors focus on BHDVS alone as these represent a potential target for interventional neuroradiology and decision-making may benefit from an understanding of the literature surrounding this rare combination of pathologies.

Approximately 100 cases of BHDVS can be found in literature.^1–5,8–13 Brain herniations into the DVS and/or calvarium have an incidence of 0.32% in an adult population ¹ and 0.65% in a paediatric population, ³ estimates based on screening of 6160 and 2320 MRIs, respectively. Brain herniations have been reported in ages ranged from 5 weeks ³ to 91 years. ¹³ Hernia size has been reported from 2.5 to 28 mm.^1,5 The most common DVS location is the TS.^1–3,5 Temporal lobe and cerebellar herniation is most common.^1,2 It is unclear if multiplicity is a common feature or not, as the largest case series have conflicting reports.^1,2,5 A female predominance also seems to have been established.^1–5,8–13The reported case in this paper does not have any biometric details of significance, aside from the unusually large volume herniation encountered.

The description of BH has varied, including; BH into AG, ¹⁰ DVS and calvarium, ¹² acquired ² or occult ¹¹ encephalocele. Early description of autopsy specimens in patients with raised ICP report herniations into arachnoid villi. ⁶ The modern description in literature postulates a relationship with giant AG. This theory has been supported by a temporal ¹⁰ and spatial^1,2,4 relationship.

Arachnoid granulations invaginate the dura to project into the DVS^2,12 and may enlarge with age, pulsatile CSF flow or increased CSF pressure. ¹² It has been proposed that BHDVS is facilitated by sinus wall compromise caused by AG or nearby protruding veins.^1,2 It has also been suggested that BH into AG is further enabled by pia-arachnoid bridges formed during AG development. ² It is possible that the same factors producing AG perpetuates BHDVS and may be accentuated by increases in ICP.

The challenge in establishing this temporal sequence is that typically patients do not have prior images for comparison, as in our case. Chan et al. ¹⁰ reported a case in which an initial CT was thought to show an AG without herniation, only to find the BH into the same location one month later on MRI, in the setting of raised ICP following trauma. This may have established a sequential event, although CT may not be sensitive to the BH which often requires high-resolution MRI.^1,4 It has been suggested that the frequent co-location of both AG and BHDVS supports the pathophysiological mechanism.^1,2

A relationship with raised ICP is a controversial aspect of BHDVS. Although cases have been reported with concurrent lesional (e.g. tumour, trauma) and non-lesional (e.g. IIH) causes of chronic raised ICP, this is not typical.^1–4 The incidence of IIH in a population found to have BHDVS has been reported as higher than the incidence in the general population, suggesting a potential association with raised ICP. ² However, this may in part be attributable to selection bias as there is no current study screening high-resolution MRIs for BHDVS in the general population, and patients with symptoms of IIH would reasonably be more likely to have an MRI.

The evolution of raised ICP and concurrent BHDVS over time is unclear. It has been shown that BHDVS have been variable, and remained stable, on serial imaging in the setting of current or previously raised ICP. ⁴ Liebo et al. ⁴ reported growth of a cerebellar tumour with concurrent increasing BH, although a case in the same series did not show similar effects under similar conditions. In addition it has been reported that BHDVS have remained unchanged after relieving mass effect by surgical resection of a tumour responsible for raised ICP. ¹ It has also been reported that patients with IIH have evolved favourably with medical management independent of the potential contribution of BHDVS to TS stenosis. ² In IIH populations, venous sinus stenosis can be described as intrinsic (e.g. related to AG) or extrinsic (e.g. related to venous wall collapse under raised ICP), leading to discussions around VS stenosis as a cause or effect of raised ICP. ¹⁴ Ahmed et al. ¹⁴ suggests intrinsic stenosis as a primary sinus obstructive cause, citing Kollar et al.’s ⁹ description of a BH, while recognising extrinsic compression as a perpetuating cause. It is likely that the sinus stenosis in the presented case was a mixed stenosis, particularly given the size of the BHDVS and the tectal plate lesion as a potential, but unproven, independent cause of raised ICP. It has not been established if the degree of stenosis inherent to BHDVS causes, exacerbates, or has no effect on the clinical or radiological findings of raised ICP. The possibility of a “vicious cycle” is also raised.

So far, documented reports have failed to demonstrate consistency or specificity when trying to associate ICP and BHDVS. It does however remain a biologically plausible explanation that raised ICP could either be responsible for inciting or exacerbating BHDVS. In this reported case it remains unclear if the aqueductal stenosis is truly a cause of raised ICP as the lesion was not found in isolation and there has not been a direct measure of the patient’s CSF pressure.

Another controversial aspect of BHDVS is their clinical significance. They are often an incidental radiological finding, although symptomatic and clinically significant BHDVS have been reported.^1,2,4 An element of their clinical significance would be differentiating them from other causes of filling defects in the DVS, such as normal anatomy (AG) or pathology (thrombus, neoplasm).^1,2 Headaches, vertigo, tinnitus and CSF leak have all been reported. The lack of differentiating symptoms may reflect the lack of eloquent BH, typically cerebellum and temporal lobe.^1,2,4

The reported case provides clinical significance given progressive visual disturbance with demonstrated severe RNFL thickening prior to intervention, with resolution after TSS. Unilateral papilloedema is uncommon but has been described in the setting of IIH. ¹⁵ The significance in this case is unclear. The clinical significance of BHDVS and concurrent IIH may become more relevant with improved detection of BHDVS, the potential contribution of BHDVS to TS stenosis and raised ICP, and the efficacy of TSS for IIH. ⁷

Most reported interventions have been directed at concurrent lesions without focus on the BHDVS, including resection of meningiomas and an astrocytoma. ¹ It is unclear the role BHDVS played in those cases. Kollar et al. ⁹ reported resection of a dural arteriovenous fistula which included the TS. This was noted to have a filling defect prior that may have potentially contributed to formation of the fistula.

Recently, endovascular intervention for BHDVS has been described. Drocton et al. ⁸ reported three cases of TSS in patients with IIH that were noted to have BHDVS. Interestingly, only in one case was a TSS place ipsilateral to a BHDVS. Drocton et al. ⁸ described TSS placement lateralised to the dominant sinus, irrespective of the BHDVS. Outcomes were reported as positive, with resolution of raised pressure in the two cases followed-up.

The foundation to this intervention is the well-published use of TSS in IIH patients. It has been shown that TS stenosis plays a contributing role and the pressure gradient across this stenosis contributes to raised ICP. ⁷ BHDVS may compound TS stenosis and pressure gradients in IIH patients. The procedure has been undertaken in the setting of giant AGs thought to be responsible for stenosis. ¹⁶ It is conceivable to think that some of these cases may have involved undetected BHDVS given the frequency BHDVS occur in AG and the failure to detect BHDVS without high-resolution MRI. ²

The decision-making in the current case was challenging. The rationale to proceed to treatment was as follows: firstly, the clinically significant finding of papilloedema, albeit unilateral; secondly, the patient demonstrated objective progression of the papilloedema; and thirdly, venous sinus manometry demonstrated objective evidence of a pressure gradient across the BHDVS, with precarious transdiploic collateral venous outflow. After establishing an intent to treat there was equipoise in targeting the TS stenosis with TSS or the aqueduct stenosis with CSF diversion. The reported case did not fit purely in the IIH population given a tectal plate lesion with chronic hydrocephalus, nor did it fit in the isolated chronic hydrocephalus population given a brain herniation and mixed sinus stenosis. Targeting TS stenosis outside the IIH population has been reported with positive outcomes in patients yet to have CSF diversion. ¹⁷ The authors elected to target the TS stenosis as a novel approach that may have similar risk and upfront cost but lower revision and complication rate, as is the trend in IIH population.^17,18

Limitations of this approach are yet to manifest. Stenting may cause compression of viable brain with clinical effects unknown. Herniated brain has previously been identified in a state of disorganisation at autopsy ⁶ and atrophy and gliosis on MRI.^2,5 This indicates that herniated brain may not be functional. The sustained clinical benefit may also be questioned given the suspected contributing cause, a tectal plate lesion leading to chronically raised ICP, remains untreated. It would be reasonable to expect that this may impact sustained outcomes. Close clinical and radiological monitoring is warranted. Applicability of the technique described also warrants further consideration. As mentioned this is the first description of this combination of pathology and selection for intervention.

Conclusion

Brain herniation into a dural venous sinus remains a rare and incompletely characterised entity. The presented case provides insight into the potential role of interventional neuroradiology in improving objective clinical outcomes, independent of CSF diversion in a patient with evidence of chronically raised ICP. It may serve as a test case to establish the safety and efficacy when managing these lesions in future practice.