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Cerebral mycotic aneurysms (MAs) also called infective aneurysms, are uncommon and are usually encountered in patients with infective endocarditis. These aneurysms often present with intracranial hemorrhage. MAs may resolve on treatment with antibiotics alone. However prognosis with medical management alone is unpredictable. Good prognosis with surgery has been reported for single accessible ruptured MAs. However surgery is associated with significant morbidity. Endovascular treatment of MAs along with appropriate antibiotics is emerging as an acceptable option for these patients.
We describe two cases of infective endocarditis complicated by ruptured MA treated successfully by liquid embolic glue material.
Intracranial mycotic aneurysms (MAs) also called infective aneurysms are rare compared to 'berry' aneurysms, comprising two to six per cent of all intracranial aneurysms 1,2. The most common presentation of MA is intracranial bleed 3. Usually MAs are multiple and distally located i.e. they arise from secondary or tertiary branches of the major cerebral arteries3,4. These aneurysms need to be treated urgently because rebleed and neurological deterioration are common, with a high mortality rate of up to 83%5. MAs may be treated with antibiotics alone6,7. However prognosis with conservative management is unpredictable and this prompts towards an active management in the form of Endovascular treatment (EVT) or surgery1,7. Surgery is associated with high risk in these patients. The traditional surgical therapy for a MA consists of parent artery occlusion and aneurysmal resection. Therefore, endovascular parent artery occlusion appears to be an acceptable alternative for MAs4. Embolization with glue, Guglielmi detachable coils or autologous clots are some of the modalities described for management of such aneurysms8,9. We describe two cases of ruptured distal MAs treated by parent artery occlusion using liquid embolic material.
A 17-year-old male, a known case of rheumatic heart disease (RHD), presented with on and off high grade fever and sudden onset of right sided hemiparesis. Blood investigations showed leucocytosis and a negative blood culture. 2D-Echocardiography revealed severe aortic regurgitation and mild aortic stenosis with large vegetations seen on the aortic valve. Plain computed tomography (CT) of the brain revealed an intraparenchymal hematoma in left parieto-occipital region. Cranial digital subtraction angiography (DSA) showed an irregular aneurysm arising from the parieto-occipital branch of left posterior cerebral artery (Figure (Figure1A1A,,B).B). The patient was started on broad spectrum antibiotics. Twelve weeks later the patient showed improvement in hemiparesis. Follow-up angiography, however, showed an increase in size of the aneurysm and therefore endovascular embolization was planned.
Selective catheterization of the left posterior cerebral artery aneurysm was done using Spinnacker 1.5F and Transcend 10 microguidewire (Boston Scientific, Natick, MA, USA) and embolization was performed with N-butyl-cyano-acrylate/lipiodol (glue) mixture (25%). Check angiograms showed complete occlusion of a short stem of the parent vessel and the aneurysm (Figure (Figure1C1C,,D).D). The patient showed no additional neurological deficits and is currently doing well.
A 27-year-old female, a known case of RHD, presented with headache and fever along with weakness of right lower limb and aphasia. Magnetic resonance imaging of the head showed an intraparenchymal hematoma in the left perisylvian region (Figure (Figure2A).2A). 2D Echocardiography revealed severe mitral regurgitation with trivial aortic regurgitation with a large vegetation on the anterior mitral leaflet. Blood cultures were positive for streptococcus viridians. Cranial DSA showed an irregular aneurysm arising from frontal branch of left middle cerebral artery (Figure (Figure2B).2B). Under general anesthesia superselective catheterization of the branch was carried out by Ultraflow microcatheter and Mirage guidewire (ev3, MTI, Irvine, CA, USA). Fluoroscopically (IDF (GE) subtraction fluoroscopy) monitored controlled injection of glue was performed to occlude the stem of the parent vessel leading to the aneurysm and the aneurysm itself (Figure (Figure2C).2C). Delayed imaging showed retrograde filling of the distal branch through collaterals, but no filling of the aneurysm (Figure (Figure2D).2D). The patient was managed conservatively for the hematoma and treated with appropriate antibiotics. At discharge the patient was conscious, oriented and following commands with no motor or sensory deficits except aphasia.
The formation of a mycotic aneurysm (MA) starts with the lodgment of a septic embolus in the vascular tree followed by necrosis and inflammation of the vessel wall that becomes fragile leading to a pseudoaneurysm formation 5. Most MAs occur in patients with infective endocarditis1 and are seen in 2-10% of these patients10. Other causes include contiguous extension of infection from meningitis, osteomyelitis, sinusitis and cavernous sinus infection. Streptococcus is the most common causative organism followed by staphylococci, enterococci, pneumococcus and haemophilus species 1. When endocarditis is associated with a distal aneurysm, the diagnosis of a MA is usually clear 7.
The management of MAs complicating infective endocarditis is controversial. Conservative treatment with antibiotics is effective in many patients 6 and shows healing of the aneurysm over a period of time. Medical treatment is necessary for the underlying endocarditis and reduces the MA-related hemorrhagic risk. However, the outcome of MAs with antibiotic treatment alone is highly variable. The aneurysms may resolve, reduce in size, reduce in size initially and later enlarge, rupture and then enlarge or persist1,7.
Some authors advocate a repeat angiography schedule under antibiotic cover to follow the aneurysms (especially in case of unruptured aneurysms) and recommend invasive treatment only if the aneurysms rebleed, persist or grow in size 1. Nonetheless there is a danger of aneurysmal rupture in the waiting period and the risk is further accentuated due to anticoagulation treatment often necessitated by the underlying cardiac condition. Endovascular treatment (EVT) of mycotic cerebral aneurysms before cardiac surgery is an evolving solution for these patients 8.
Good prognosis with surgical treatment has been reported in cases of single accessible ruptured MAs 4. However, surgical treatment is associated with significant morbidity due to the procedure itself and due to the underlying cardiac condition in these patients. Besides, surgical localization is not easy due to the peripheral location of these aneurysms and due to the associated hematoma 11. The risks of surgery are greater for patients with large, multiple or ruptured MAs and for patients with MAs located in highly functional areas 7.
EVT is less invasive than surgery. Unlike the results of surgery, the results of EVT are not influenced by the timing of the procedure, by previous rupture, or by the number and location of MAs. Multiple EVT procedures are feasible for multiple aneurysms or newly occurring aneurysms in these patients 7. If the aneurysm can be reached with a microcatheter, glue embolization is the logical choice because it permits simultaneous sealing of the aneurysm and the parent vessel 12,13. It is usually well tolerated and is unlikely to induce a stroke, because a stroke would either have already occurred or would have been avoided by the presence of collateral vessels 14. Parent vessel occlusion with coils may lead to distal refilling of the MA through collateral vessels 5.
In the first case we followed the convention of a trial of conservative treatment with antibiotics and treated the aneurysm when it showed no regression on follow-up angiography. In the second case we undertook a more aggressive management with embolization when the patient first presented with bleed.
Although safe enough, endovascular procedures are associated with a small risk. The technique usually involves microwire-based catheterization and dissection or perforation of distal vessels especially at bends is an endangering event15.
The timing of the EVT may be a debatable issue. Considering the greater risks associated with surgery, the variability of outcomes with antibiotic treatment and the good results of EVT, some authors have recommended that EVT be considered at the time of diagnosis for all patients with cerebral MAs 7. We tend to agree that mycotic aneurysms presenting with bleed should be treated with EVT. Peripherally located intracerebral mycotic aneurysms appear to be suitable and can be effectively treated with parent vessel occlusion using glue. However, incidentally found and unbled mycotic aneurysms may deserve a trial of antibiotic therapy and may be followed-up by serial angiographies. Active intervention in the form of EVT or surgery may be undertaken in such cases if there is an increase in the size of the aneurysm or a bleed occurs.