Santiago Vargas-Arango1, Santiago Nova-Escobar1, Sergio Alberto Vargas-Velez1,2Patient
49 years, male
A 49 year-old male with infective endocarditis by Streptococcus Sanguinis is scheduled for mitral valve replacement due to a 14x4mm vegetation. Two days before surgery, the patient presents with severe headache, loss of consciousness and right hemiparesis. Septic embolism with associated intracerebral bleeding is suspected and is immediately taken for urgent brain CT and surgery. Craniotomy and clipping were performed in the distal branch of the left middle cerebral artery. Digital subtraction angiography was not performed.
Figure 1A. Axial Brain Non-enhanced CT: Depicts well defined area of hyperattenuation with peripheral vasogenic edema, epicenter in the left parietal lobe and 7mm midline deviation. Findings are consistent with Intraparenchymal acute hemorrhage.
Figure 1B. Brain Axial CTA shows a well defined, round, hyperenhancing nodule within the area of intraparenchymal hemorrhage, suggesting mycotic aneurysm inside the intraparenchymal hemorrhage
Figure 2. Brain Axial CTA-MIP reveals a nodular enhancing lesion, arising from a cortical artery, consistent with a mycotic aneurysm in a distal branch of the left middle cerebral artery.
Figure 3A. Signs of craniectomy in the temporooccipital region with residual subdural hemorrhage; in the surgical site there are clips, pneumocephalus and residual intraparenchymal hematoma.
Figure 3B. Despite the evacuation of the hematoma, there are signs of vasogenic edema in the peri atrial area with compression of the occipital horn of the left lateral ventricle and signs of subfalcine shift of 10.4mm.
The term mycotic aneurysm(MA) refers to the inflammation of an artery due to bacterial or mycotic infection; in descending order of frequency, the aorta, peripheral arteries, cerebral arteries, and mesenteric arteries are the most commonly involved. Nowadays, the most common cause of MA is intravenous drugs use[2,3] but for intracranial MA(ICMA) is infective endocarditis(IE)[4,5], due to septic embolization of vegetations, infiltrating the intima and going outward through the vessel wall[2,4]. Although it is an uncommon complication of IE, the overall mortality of ICMA is 60%.
Most ICMA are asymptomatic unless they rupture causing headache, seizures or focal neurologic symptoms[2,4,5]. Imaging is necessary to establish the diagnosis, being intra-arterial cerebral angiography the “gold standard”; CT angiography(CTA) and MR angiography(MRA) have low sensitivity for detecting MA(42.9% and 33.3% respectably), however they are useful due to the high negative predictive value for intracranial hemorrhage. The images help to localize, characterize, assess the number of aneurisms, detect other complications and map the vascular anatomy for treatment planning and following. The most available technic is the CTA, where it is possible to assess the key characteristics of the ICMA: predilection for the anterior circulation, usually peripheral, from segment 2 and beyond, and fusiform in appearance. 20-33% can be proximal to the first bifurcation of the circle of Willis and tend to be similar to berry aneurism. Features that may help to differentiate the two are stenosis or occlusion close to the aneurism, rapid change in morphology, or the presence of other MA. When there’s a ruptured aneurism the image findings are intracranial, intraventricular, or subarachnoid hemorrhages[5,6].
The antimicrobial treatment varies according to the etiology of IE, Staphylococcus and streptococcus are the most common organism[2,4,5]. Streptococcus sanguinis MA, although rare, is usually treated with ceftriaxone + vancomycin empirically, then, after blood culture’s results, an 8-week treatment with ceftriaxone IV, followed by a 6 weeks course of oral penicillin is accepted. A conservative approach with antibiotics guided by blood cultures with serial CTA follow-up may be a reasonable option[2,4,5]; if the aneurism is growing or fails to reduce in size, surgical or endovascular approach may be considered; when the aneurism is ruptured it must be immediately secured.
MA associated with IE is an uncommon but highly mortal complication, hence, the clinician should be alert if any of the symptoms develops and choose the ideal diagnostic image for early treatment.
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