P.I. Nikitin, O.A. Pavlov, A.I. Nikitin, S.K. Sergienko
Mariinsky hospital, Saint Petersburg, Russia
Reports on aneurysms of distal branches of cerebral vessels and their endovasal exclusion from blood circulation, are scanty, to say nothing of information on successful treatment of aneurysms of the superior cerebellar artery (SCA). Aneurysms of the SCA distal branches are extremely rare. We have not come across any description of one-stage embolization of multiple aneurysms of the SCA branches in an acute hemorrhagic period. According to medical literature, aneurysms of such localization were diagnosed only in 6 (0.3%) out of 2349 cases with aneurysmal subarachnoid hemorrhages (SAH) . Gacs G. et al.  reported 6 cases of the SCA distal aneurysms (0.7%) in a series of 910 aneurysms of vertebrobasilar localization. Lubics B. et al.  informed, that only 8 (0.55%) out of 1450 aneurysms had been localized in a peripheral segment of cerebellar arteries. Thus, multiple aneurysms of distal segments of the SCA seem to be a unique phenomenon.
As for pathogenesis of aneurysms of the SCA distal segments, discussed in medical literature, it includes both hereditary factors and some specific causes. In comparison with cerebral aneurysms of typical localization, distal ones are more often mycotic (bacterial) [2, 3]. Bacterial aneurysms are embolic by their nature. It is an explanation of their peripheral localization and frequent multiplicity. Though an embolic lesion is more typical of the middle cerebral artery region, it can be watched in a vertebrobasilar area too. The main diagnostic criteria of mycotic aneurysm are presence of bacterial endocarditis with positive blood cultures, a dynamic change of aneurysm morphology (its shape, size), a multiple character, stenosis in close vicinity to aneurysm and development of ischemic complications .
As a rule, traumatic false aneurysms develop in distal segments of cerebral vessels; however, a posterior region of circulation is involved only in 10% of cases .
Some authors note a frequent combination of distal aneurysms of cerebellar arteries with arteriovenous malformations (AVM), which is supposed to be a sign of congenital pathology [2, 6]. For example, distal cerebellar aneurysms were combined with AVM in 6 out of 16 cases; all of them were located on a feeding artery . According to the authors, it is a situation, when increased blood flow can be a cause of aneurysm.
Cerebral vasculitis, watched in systemic diseases of connective tissue, is considered to be one of the rare causes of distal aneurysms . Transmural angiitis or fibrinoid necrosis lead to local debility of a vascular wall and aneurysm appearance. Referring to other reports, the authors note, that aneurysms of such genesis are usually multiple and fusiform.
One should mention a neoplastic cause of distal aneurysms, being embolic by their nature .
Taking into account diverse pathogenesis of distal aneurysms, it is necessary to emphasize importance of thorough examination of a patient. A revealed cause of aneurysm can demand carrying out specific treatment, for example antibacterial or steroid therapy in septic endocarditis and systemic lupus erythematosus respectively.
Distal aneurysms of the SCA have some peculiarities. Gacs G. et al.  note, that they tend to rupture, when their size is smaller (less than 5 mm) than that of aneurysms with typical localization. It happens because of a thin wall of a vessel’s distal segment. CT examination demonstrates predominance of SAH in perimesencephalic and superior cerebellar cisterns . According to Gacs et al. , vasospasm develops less frequently due to distal localization of aneurysm.
Performing open interventions on aneurysms of vessels of a vertebrobasilar region is connected with technical difficulties and characterized by high rates of mortality and disability . There are several recent reports, discussing successful treatment of the SCA distal aneurysms with an endovasal method. Some authors describe aneurysm exclusion from blood flow by occluding the SCA distal segment at the aneurysm level with the help of detachable microcoils or histoacryl [4, 10-13]. Good tolerance of such occlusion, conditioned by adequate collateral blood flow and an ischemic lesion of the cerebellum cortex only, is emphasized [4, 13]. Nevertheless, selective embolization of aneurysm with the vessel preservation is considered to be optimum [7, 9].
Now we would like to dwell on our case. Female patient S., aged 52, was admitted on the fourth day of the disease onset with verified SAH. He complained of severe headache and dizziness. A state severity was estimated on the basis of the Hunt-Hess scale (the score of 2). CT demonstrated SAH (Fisher III). Angiographic examination revealed two aneurysms of the left superior cerebellar artery. They involved the area of branching of the main trunk and the SCA cortical branch. Their size was 6´6 mm and 8´5 mm respectively (Fig.1A). Superselective catheterization of the left SCA trunk was made with subsequent superselective angiographic examination (Fig.1B). The first aneurysm was embolized with Trufill Orbit Complex Fill 6´15 (Fig.1C). Then a microcatheter was moved forward in a distal direction up to the second aneurysm and its embolization with Trufill Orbit Complex Fill 6´15 was performed. The aneurysms were excluded from blood circulation totally (Fig.1D).
There were no clinical and laboratory signs of the above pathologic states. Thus, the SCA aneurysms were supposed to be congenital. A postoperative period was characterized by development of constrictive-stenotic angiopathy and normal pressure hydrocephalus, treated conventionally. The patient was discharged on the 53rd day for further outpatient treatment (GOS III).
Thus, the above example of excluding the SCA aneurysms from blood circulation is indicative of possible endovascular treatment of cases with this pathology.