Cerebral angiography (figure 3) revealed a 11 mm aneurysm in the distal right middle cerebral artery (figure 3a) and a smaller one in the distal left posterior cerebral artery (figure 3b). The next day the aneurysm at the right hemisphere was obliterated by selective coiling and the smaller aneurysm at the left hemisphere was glued. CT of the thorax and abdomen showed an aneurysm in the distal superior mesenteric artery and signs of bilateral renal infarction with preserved renal function. His neurological state did not show any improvement. After three days patient was transferred to a university hospital for cardiac surgery. A mitral bioprosthesis was implanted. Three days after surgery the patient was discharged from the ICU to the CCU and after that to surgical ward and one month after his first admission in our hospital and one month after his first admission to our hospital he was discharged to a rehabilitation clinic. His neurological state further improved to nearly his previous condition and continues to improve.

Discussion

Neurological events as a complication of endocarditis are seen in about a quarter to one third of patients.[1,2] The majority are ischaemic events (56%) due to septic embolisms. Mycotic aneurysms occur in 1-10% of patients with endocarditis.[1,2] Only 0.5% of all patients with infectious endocarditis will develop subarachnoid or intracerebral bleeding due to ruptured mycotic aneurysms.[1] Endocarditis is an infection of the endothelium of the heart. Its incidence is about 3-10 per 100,000 people;[3] 25-30% of the cases of endocarditis are healthcare-associated infections, due to for example intravascular catheters and haemodialysis. The remaining cases are community-acquired infections often caused by bacteria entering the circulation via the oral cavity or the skin.[3,4] By far the most common micro-organisms associated with infective endocarditis of native valves are Gram-positive cocci, such as Staphylococcus, Streptococcus and Enterococcus species.[3,5] The term mycotic aneurysm was first described by William Osler in 1885 as a consequence of fungal vegetations.[6] However, nowadays it is used as a more general description for all aneurysms caused by infectious embolisms originating from the heart. Mycotic aneurysms or intracranial infectious aneurysms are quite uncommon phenomena. Of all intracranial aneurysms, 0.7-5.4% are mycotic aneurysms.[7] These are typically seen in patients with endocarditis and less often in patients with intracranial infections such as meningitis or post-surgery infections.[8] Neurological events due to infectious endocarditis are associated with poorer outcomes; mortality risk is about 45%, which is nearly twofold higher than in patients without neurological events.[1] Mycotic aneurysms can occur in any cerebral vessel, but more often in the distal branches of the middle cerebral artery.[9,10] Mycotic aneurysms are caused by either primarily microembolisms from the vaso vasorum or secondary as embolisms as a result of fragmentation of cardiac septic embolisms. Embolisms cause an inflammatory reaction which destroys the adventitia. It spreads through the tunica media where it causes a rupture between the internal elastic layer and endothelium of the vessel. This leads to weakness of the vessel wall and aneurysm formation.[11] Besides the systemic symptoms of endocarditis (such as general malaise and fever) patients with a ruptured aneurysm may have headache due to high intracranial pressure, confusion, seizures or paresis.[11,12]

The administration of antibiotics to avoid neurological complications is important. The 2019 Dutch Working Party on Antibiotic Policy (SWAB) guidelines for the antimicrobial treatment of infective endocarditis advise amoxicillin 12 g/day in six doses and ceftriaxone 4 g/day in two doses as empirical therapy in a patient with a native valve and subacute presentation.[13] When Streptococcus mitis is cultured as the causative agent, antibiotics are switched to penicillin 12 million units/day in six doses. One observational study described an absolute reduction in neurological complications of 4% in all patients with endocarditis.[1] However, antibiotics only is associated with significantly higher mortality than antibiotics combined with surgery (clipping) or endovascular repair (coiling). A systematic review described a significantly higher mortality in patients treated only by antibiotics (27.8%, 95% CI 24.3-31.7) compared with antibiotics and neurosurgical clipping surgery (12.0% 95% CI 8.1-16.9, p< 0.001) or embolisation (1.0, 95% CI 0.1-3.4, p< 0.001).[14] What was unusual in this case was the young age of the patient. While the peak incidence of subarachnoid haemorrhage is around 50 years, our patient was quite young.[15] Subarachnoid haemorrhage heralding endocarditis is a known, but rare complication with a high risk of poor outcome or mortality. In young patients presenting with subarachnoid haemorrhage, based on more than one aneurysm in the distal branches of the main cerebral arteries, and fever and general malaise, we should be aware of more than ‘just an aneurysm’ and consider endocarditis as the underlying cause.