Clinical History
A 33-year-old male patient, heroin-addicted, with a clinical history of infective endocarditis and recurrent bacteraemia (culture isolation of S.mitis, S.sanguis and E.faecalis) treated with antimicrobial-therapy, was admitted to emergency-department with fever, confusion, balance disorder, headache persisting despite analgesic administration, cervicalgia and rigor nucalis. Patient came to our attention for emergency Computed Tomography (CT) evaluation.
Imaging Findings
Emergency-CT showed a left temporo-occipital haemorrhage, with compression of occipital horn of left lateral ventricle; bleeding was depicted in all components of ventricular system(Fig.1a-c).
Contrast-enhanced CT demonstrated an aneurysm in atypical location, next to bleeding site (Fig.2a-c).
10 days later CT demonstrated reduction of hyperdensity and blood flooding in lateral ventricles, which however remained increased in size (Fig.3a-b).
Selective Digital-Subtraction-Angiography (DSA) of left-internal carotid artery showed a temporo-occipital parenchimographic-gap (Fig.4); DSA of left vertebral artery demonstrated a centimetric aneurysmatic-dilatation of temporal postero-inferior branch of the lateral occipital branch of left posterior cerebral artery (Fig.5a-b).
Superselective catheterisation of aneurysm afferent vessel confirmed the presence of an unregularly sacciform aneurysm, with irregular external profile and not well-defined collar (Fig.6a-c).
A 1.5F microcatheter(Magic 1.5F) was then advanced over a microwire(Hybrid 0.008'') proximally to the aneurysm; cyanoacrylate(Glubran2) embolisation with Lipiodol-Ultrafluid (LUF) was performed until the aneurysm was no longer filling with contrast-medium(Fig.7a-b).
Post-procedural CT and DSA demonstrated the complete aneurysm exclusion from circulation (Fig.8-9).
Discussion
Microbial aneurysm(MA) is a rare type of intracranial aneurysm, differing from saccular aneurysm (in the anterior circulation in 85-95%of cases)for its infectious aetiology, occurrence in relatively young people, multifocality, and peripherical location.Pathogens frequently involved are bacteria, but mycobacterial, viral and fungal origin might be demonstrated [1].
Common clinical manifestation includes fever, headache, seizures, haemiparesis, or altered sensorium; however, the commonest MA presentation is intracranial bleeding. MA risk of rupture and fatal bleeding is higher if compared to other aneurysms [1].
Imaging is essential to MA diagnosis. CT easily detects intracranial bleeding by depicting an area of hyperdensity, but might not provide sufficient details of MA: therefore a CT-Angiography(CTA) is commonly performed.CTA might have to be repeated 2–3days after the first scan, even if it is negative, since MA might evolve faster then other aneurysms [1].
Despite its invasiveness, DSA is considered as gold standard for cerebral aneurysms.Angiographic features that allow distinguishing MA from other aneurysms are peripheral location, poorly defined neck, fusiform shape, irregular outline and multiplicity[1].
Therapeutic approach differs conventional berry aneurysms. Antimicrobial-therapy is performed in all patients;further available treatments include surgery and endovascular-therapy(EVT).
If MA enlarges, fails to resolve or ruptures during medical treatment, it should be considered for surgery or EVT.Although successful surgical treatment rates have been reported, the friability of inflamed tissue or the risk of occlusion of the parent artery during clip application are limiting factors.As an attractive alternative, EV management offers a safer and less invasive method to exclude aneurysm from blood flow than open craniotomy with surgical clipping, maintaining at the same time distal parent artery flow[2].
Surgery is reserved if intraparenchymal haemorrhage and increasing intracranial pressure are reported, or if clot evacuation is required[3].
EVT with Guglielmi detachable coils (GDCs) is preferred for proximal aneurysms treatment, while distal aneurysms are preferably managed with glue because they need a flow-dependent catheter to be reached, not easily passed through by coils.Glue determines a more complete exclusion of the aneurysmal sac from bloodstream than coils, even if major risk of embolization of the parent vessel is present.
Aneurysm embolisation is typically performed using fluoroscopic-guidance, which involves gaining access to common femoral artery and navigating a 5-7F guide-catheter into the internal carotid or vertebral arteries.A 1.5-2.3F microcatheter is then advanced over a microwire into the aneurysm.Coils or glue are deployed and detached through the microcatheter until the aneurysm is no longer filling with contrast-medium [4].
A post-procedural DSA is commonly required in order to detect promptly any procedural complication.
Differential Diagnosis List
Intraparenchymal haemorrhage in the left temporal ruptured intracranial microbic aneurysm.
Congenital arteriovenous malformation (MAV) in the brain
Bleeding neoplasm
Stroke
Final Diagnosis
Intraparenchymal haemorrhage in the left temporal ruptured intracranial microbic aneurysm.