ABSTRACT
INTRODUCTION: The multimodal approach to treatment of arteriovenous malformations yields good results. However, small and deep malformations still pose a big problem for surgeons. Transvenous embolization was designed as an alternative for the cases when endovascular treatment is required and conventional transarterial embolization is not available. CASE STUDY: A 41-year-old patient with binodal malformation in the subcortical nuclei of the left hemisphere of the brain, which had previously become a source of massive parenchymal ventricular hemorrhage, was operated on using the transarterial and, for the first time in our clinic, transvenous approaches. Transarterial embolization of the thalamic node of malformation was performed as the first step. After 6 months, transvenous embolization of the hypothalamic node of malformations was performed as the second step. Successful operation was ensured by using a stable coaxial guiding catheter system with the maximum distal approach and intranidal positioning of a microcatheter with detachable distal portion upon temporary occlusion of afferent vessels of the malformations using a balloon catheter. The operation resulted in total thrombosis of the malformation. No perioperative complications were observed. Control examination in 6 months did not reveal recanalization of the malformation. CONCLUSION: The transvenous approach can be successfully used in endovascular treatment of small and deep arteriovenous malformations with a single drainage vein, which are inaccessible to direct surgery. It can also be used when radiosurgery is associated with a high risk in cases where transarterial embolization is infeasible.
Subject(s)
Embolization, Therapeutic , Intracranial Arteriovenous Malformations/therapy , Adult , Humans , MaleABSTRACT
1. Limnaea stagnalis neurones have been used to study the functioning of membrane receptor-channel complexes. The experiments were performed using a fixed membrane potential (E) and the intracellular perfusion technique. The cells employed responded to acetylcholine (ACh) by changing only their Cl- conductance. 2. ACh-induced currents, their fluctuations and relaxations resulting from a jump of E were studied. 3. The following facts have been established based on analysis of ACh currents, their fluctuations and relaxations: (1) the characteristic time of the exponential decay of the autocorrelation function, tau N, is in the range of 15-20 ms; (2) the characteristic relaxation time, tau R, equals 50-60 ms (ACh concentration = 0.25 microM, desensitization is not observed); (3) E does not exert any functionally significant effect upon tau N or tau R which could have governed the non-linearity of the membrane voltage-current characteristic; (4) variation of ACh concentration from 0.25 to 1 microM has a significant effect on tau R but not on tau N; (5) lowering of the ACh solution temperature from 22 to 8.5 degrees C results in a 20% increase of the ACh current, a 3- to 4-fold decrease of the single-channel conductance (gamma), a 20% increase in tau N and a 3- to 4-fold increase in tau R. 4. The suberylcholine (SCh)-induced membrane current has approximately the same value as the ACh-induced current at equal concentrations of ACh and SCh (0.25 microM); the tau N and gamma values were also quite close, but tau R was 2.3 times lower for SCh than for ACh. 5. An essentially two-stage scheme of functioning of membrane receptor-channel complexes is proposed. The scheme has two distinguishable and measurable stages and involves five closed states and one open state; it offers an explanation for our experimental data as well as the results of other workers.
