This case report describes a fatal case of non-aneurysmal subarachnoid haemorrhage caused by septic cavernous sinus thrombosis secondary to odontogenic maxillary sinusitis, with Streptococcus dysgalactiae subsp. equisimilis (Group C Streptococcus) isolated as the causative organism.
Key Findings
Background
Septic cavernous sinus thrombosis secondary to odontogenic maxillary sinusitis can cause non-aneurysmal subarachnoid haemorrhage.
The patient was a man in his 50s who presented with visual loss, altered consciousness and shock.
CT revealed SAH near the left Sylvian fissure without an aneurysm.
Thrombosis was identified in the cavernous sinuses, superior ophthalmic veins, and internal jugular veins.
Right maxillary sinusitis was identified as the primary infectious source with an odontogenic origin.
Results
Group C Streptococcus (Streptococcus dysgalactiae subsp. equisimilis) was identified as the causative pathogen.
The organism was isolated from both blood cultures and purulent material aspirated during tooth extraction.
Streptococcus dysgalactiae subsp. equisimilis is classified as Group C Streptococcus.
The case highlights 'the pathogenic potential of Group C Streptococcus' in causing severe intracranial complications.
Results
The patient died despite intensive multimodal treatment including antibiotics, anticoagulation, tooth extraction, and surgical sinus drainage.
Treatment included broad-spectrum antibiotics, anticoagulants, tooth extraction, and endoscopic sinus drainage.
The patient developed haemorrhagic venous infarction as a complication during treatment.
Death resulted from cerebral herniation due to progressive brain swelling.
The case demonstrates the potentially fatal trajectory of septic cerebral venous thrombosis even with aggressive intervention.
Conclusions
Septic cerebral venous thrombosis should be recognised as a cause of subarachnoid haemorrhage.
The authors emphasise 'the importance of recognising septic cerebral venous thrombosis as a cause of SAH.'
SAH in this case was non-aneurysmal, representing an atypical presentation that could delay diagnosis.
The infectious source was odontogenic, indicating that dental infections can propagate to cause life-threatening intracranial complications.
What This Means
This research describes a case report of a man in his 50s who developed a serious brain bleed (subarachnoid haemorrhage) as a result of an infected blood clot in a major vein at the base of the skull (cavernous sinus thrombosis), which itself originated from an infected tooth causing sinusitis. The bacteria responsible — a type called Group C Streptococcus — spread from his tooth and sinus to infect the venous blood vessels draining the brain. Despite receiving intensive treatment including strong antibiotics, blood thinners, tooth removal, and surgical drainage of the sinuses, the patient's condition worsened, leading to bleeding within the brain and ultimately death.
This case is notable because subarachnoid haemorrhage (bleeding around the brain) is most commonly associated with ruptured aneurysms, but this patient had no aneurysm — the bleeding was caused entirely by the infected clot blocking venous drainage. This highlights that infected venous clots in the brain can cause strokes and bleeding that mimic other, more familiar causes, and that the connection between a dental infection and a fatal brain bleed may not be immediately obvious to clinicians.
This research suggests that dental and sinus infections, even when they seem localised, can in rare cases spread to cause life-threatening brain complications. It also draws attention to Group C Streptococcus as a pathogen capable of causing severe disease. Clinicians evaluating patients with subarachnoid haemorrhage should consider septic venous thrombosis — potentially driven by dental or sinus infection — as a possible cause, particularly when no aneurysm is found.
Nagamine Y, Endo T, Iwashita M, Suzuki T. (2026). Subarachnoid haemorrhage associated with septic cavernous sinus thrombosis secondary to odontogenic maxillary sinusitis.. BMJ case reports. https://doi.org/10.1136/bcr-2026-271999