1 INTRODUCTION

Although the leading causes of subarachnoid hemorrhage (SAH) are aneurysm rupture and arteriovenous malformations, cerebral venous sinus thrombosis (CVST) can, in rare cases, be associated with SAH.¹ This phenomenon is an uncommon presentation, with less than a hundred cases reported based on our review of the literature. CVST itself typically presents with headache, nausea, vomiting, weakness, loss of vision, and seizure.² Because of its rarity, a high index of suspicion is important in making the diagnosis.³

CVST accounts for 1% of all strokes^{4, 5} and has a mortality as high as 30% with the annual incidence ranging from 0.22 to 1.57 per 100,000. It is more common in women than men.^{6, 7} Multiple reversible and irreversible factors are associated with CVST and include surgery, thrombophilia, antiphospholipid syndrome, cancer, inflammatory bowel disease, use of the oral contraceptive pill, infection, and pregnancy.⁸

The reason why SAH might occur together with CVST is still debated. In some cases, they could be coincidental. However, there are many hypotheses with regards a causal relationship between the two entities; hence, there is a need to review all the cases in the existing literature to see the similarities and differences across these rare cases and presentations. The purpose of this review is to highlight what is known regarding these cases, how they are managed and to highlight the need for further studies that will serve as a basis for the development of a standard management guideline across board. In this article, we systematically reviewed all such published cases of CVST and SAH occurring concurrently, noting their common characteristics, imaging findings, treatment, and outcomes.

2 METHOD AND MATERIALS

2.3 Selection of sources of evidence

Three reviewers working independently evaluated the titles, abstracts, and then full text of all cases identified by our searches for relevant papers. We resolved disagreements on study selection and data extraction by consensus where necessary. The process is summarized in Figure 1.

3 DISCUSSION

Subarachnoid hemorrhage should be considered in the event of a sudden worsening headache.⁹ The diagnostic modality of choice for subarachnoid hemorrhage in the initial stages is a non-contrast CT scan.^{9, 10} With an equivocal result, a lumbar puncture is advised; however, given the increased sensitivity of a non-contrast CT scan within the six-hour timeframe, the choice to undertake a lumbar puncture should be through a shared decision-making process.⁹ As aneurysms are a common cause of SAH, CTA scans are important in demonstrating a causative aneurysm.⁹ A non-contrast CT scan is also a useful diagnostic modality for diagnosing a CVST as it can show findings that include, but are not limited to, venous sinus or deep vein hyper-density.^{11, 12} CT venography and/or MR venography are recommended diagnostic modalities of choice, as recommended by the European Stroke Organization.¹³

Transverse sinuses, superior sagittal sinuses, and the sigmoid sinus are the most common sites of CVSTs, and in most cases, multiple sinuses are affected.^14-16 This is consistent with the findings of our review study, which showed that multiple sinuses were frequently affected with the superior sagittal sinus and the transverse sinus being the commonest sites. In cases with a coexisting cerebral venous sinus thrombosis, the perimesencephalic region is a common location for non-aneurysmal SAH.^{17, 18} The most common locations for aneurysms are in the circle of Willis, particularly the anterior communicating artery and the internal carotid artery.^{19, 20}

A third of CVST cases might present with intracerebral hemorrhage.²¹ However, there is a paucity of literature on how common it is for CVST to occur with subarachnoid hemorrhage. One hypothesis of ‌why SAH may occur simultaneously with CVST is that the blood from the ensuing hemorrhagic infarct (resulting from the venous thrombosis) may extend into the subarachnoid space.²² This may certainly be the case in some of our findings where there was parenchymal hemorrhage besides the presence of CVST and SAH; however, its absence (also seen in many of the cases identified) may suggest a more direct causal relationship. A leading hypothesis supporting this stipulates that when CVST occurs, the ensuing secondary venous hypertension could be transmitted to the cortical veins, leading to the dilation and rupture of the fragile thin-walled cortical veins in the subarachnoid space.^{17, 23} Sometimes, the occurrence of both entities together could be coincidental, as seen in instances with an aneurysmal cause of the SAH, like in some of the identified cases.

Regardless of etiology, the treatment of a patient with SAH and CVST occurring concurrently can pose a dilemma. The risk of rebleeding in SAH is high, and in the absence of immediate surgical intervention for aneurysmal SAH, antifibrinolytics have been advised.²⁴ This is in sharp contrast to the standard treatment of CVSTs, which involves rapid anticoagulation and the stoppage of any prothrombotic medications.¹¹ Using systemic anticoagulation where simultaneous subarachnoid hemorrhage exists might worsen the hemorrhage. In cases of simultaneous CVST and ICH, endovascular interventional therapy has been ‌ beneficial.²⁵ There is a possibility that such interventions may also yield positive results when used in cases of CVST occurring with SAH. Interestingly, in our study, despite the SAH, most of the patients were treated with anticoagulant therapy with good outcomes reported. Despite our comprehensive review, this study was not without limitations. Because we excluded articles that were not in the English Language, we could have potentially missed relevant literature. There was also heterogeneity in the way the case reports were reported which meant some relevant data could have been missed. Regardless, this review will contribute to the growing body of work on this occurrence.

4 CONCLUSION

We have performed a comprehensive review of cases that had the simultaneous occurrence of SAH and CVST and have identified their peculiarities and the challenges to management. Further research is needed in order to identify a causal relationship and to serve as a basis for the development of a standard management guideline across the board.

AUTHOR CONTRIBUTIONS

D.J involved in conceptualization, methodology, software, validation, formal analysis, investigation, resources, data collection, data curation, writing—original draft, writing—review and editing, project administration, supervision, submission, and correspondence. O.O and T.M involved in conceptualization, methodology, software, validation, formal analysis, investigation, resources, data collection, data curation, writing—original draft, writing—review and editing.

CONFLICT OF INTEREST

The authors hereby declare that there are no competing interests.

CONSENT

As this was a review of cases in already literature, no individual consent was required. Consent was however obtained by the individual case reports used in this review in accordance with the journal's patient consent policy.