Objective
Vertebrobasilar (VB) aneurysms remain considered as a significant challenge for both microneurosurgical and endovascular neurosurgeon/interventional neuroradiologists. The nature of the aneurysm formation and growth, as well as the tortuosity and geometry of the vessels in many cases, has reduced the efficacy of final clinical and radiological outcome of endovascular therapy. On the other hand, microsurgical treatment for VB aneurysms has also been reported to have a relatively high morbidity and mortality rate. The need to effectively treat the VB aneurysms was essentially based on the clinical fact that they have a higher rupture rate and worse prognosis than the anterior circulation group. Reducing the morbidity and mortality rate while increasing the aneurysm occlusion rate and its durability is the ultimate goal of aneurysm treatment. Our aim is to evaluate simple surgical techniques and their clinical and radiological results that have been used to treat VB aneurysms in department of neurosurgery of University of Helsinki and Helsinki University Hospital.
Patients and Methods
We analyzed surgical techniques that have been used in department of neurosurgery of University of Helsinki and Helsinki University Hospital during ten year period. The pre-operative clinical scale and final clinical and radiological outcomes were assessed to evaluate the efficacy of the surgical approaches. We used a defined subgroup of the surgical corridors into anterolateral, lateral, and posterolateral corridors to treat five levels of VB aneurysms. The five levels of VB aneurysms were divided based on their level to the clivus bone, which are above, upper, middle, lower, and lowermost.
Results
Above clivus level of VB aneurysm defined as more than 6 mm above the
posterior clinoid process (PCP) was effectively treated by LSO approach, a simple modification of pterional approach which has anterolateral surgical corridors.
Specifically for BB aneurysm, the wide P1 (first segment of PCA) angle was also a
determined factor for the selection to use LSO. Upper clivus level defined as within 6 mm above and 8 mm below the PCP was simply treated with a subtemporal approach,at a lateral corridor to reach the lesion. This approach was a workhorse to treat theupper clivus level aneurysm because of shorter distance, more “straight to the point,”and better visibility of posterior basilar perforators. Middle clivus level aneurysms,defined as more than 8 mm below the PCP to the level of internal acoustic meatus (IAM) were commonly treated with a simplified presigmoid approach. This posterolateral corridor offered a wider and better exposure of VB artery and its surrounding neural structures. VB aneurysm which is located at lower clivus level, defined as more than 10 mm above the foramen magnum to the level of IAM, was effectively treated with simple lateral suboccipital approach or tic craniotomy. If the aneurysm is located very low or defined as less than 10 mm above the foramen magnum, a modification called “enough-lateral” approach was recommended.
Conclusion
These five simple surgical approaches (LSO, subtemporal, presigmoid, lateral
suboccpital, and “enough-lateral”) were effective approaches to treat five different levels of VB aneurysm according to the clivus bone. The pre-operative clinical gradingscale and the large – giant size of aneurysm were the most consistent and determinant factors for unfavorable outcome in this study.Objective
Vertebrobasilar (VB) aneurysms remain considered as a significant challenge
for both microneurosurgical and endovascular neurosurgeon/interventional
neuroradiologists. The nature of the aneurysm formation and growth, as well as the tortuosity and geometry of the vessels in many cases, has reduced the efficacy of final clinical and radiological outcome of endovascular therapy. On the other hand, microsurgical treatment for VB aneurysms has also been reported to have a relatively high morbidity and mortality rate. The need to effectively treat the VB aneurysms was essentially based on the clinical fact that they have a higher rupture rate and worse prognosis than the anterior circulation group. Reducing the morbidity and mortality rate while increasing the aneurysm occlusion rate and its durability is the ultimate goal of aneurysm treatment. Our aim is to evaluate simple surgical techniques and their clinical and radiological results that have been used to treat VB aneurysms in department of neurosurgery of University of Helsinki and Helsinki University Hospital.
Patients and Methods
We analyzed surgical techniques that have been used in department of neurosurgery of University of Helsinki and Helsinki University Hospital during ten year period. The pre-operative clinical scale and final clinical and radiological outcomes were assessed to evaluate the efficacy of the surgical approaches. We used a defined subgroup of the surgical corridors into anterolateral, lateral, and posterolateral corridors to treat five levels of VB aneurysms. The five levels of VB aneurysms were divided based on their level to the clivus bone, which are above, upper, middle, lower, and lowermost.
Results
Above clivus level of VB aneurysm defined as more than 6 mm above the
posterior clinoid process (PCP) was effectively treated by LSO approach, a simple modification of pterional approach which has anterolateral surgical corridors.
Specifically for BB aneurysm, the wide P1 (first segment of PCA) angle was also a
determined factor for the selection to use LSO. Upper clivus level defined as within 6 mm above and 8 mm below the PCP was simply treated with a subtemporal approach,at a lateral corridor to reach the lesion. This approach was a workhorse to treat theupper clivus level aneurysm because of shorter distance, more “straight to the point,”and better visibility of posterior basilar perforators. Middle clivus level aneurysms,defined as more than 8 mm below the PCP to the level of internal acoustic meatus (IAM) were commonly treated with a simplified presigmoid approach. This posterolateral corridor offered a wider and better exposure of VB artery and its surrounding neural structures. VB aneurysm which is located at lower clivus level, defined as more than 10 mm above the foramen magnum to the level of IAM, was effectively treated with simple lateral suboccipital approach or tic craniotomy. If the aneurysm is located very low or defined as less than 10 mm above the foramen magnum, a modification called “enough-lateral” approach was recommended.
Conclusion
These five simple surgical approaches (LSO, subtemporal, presigmoid, lateral
suboccpital, and “enough-lateral”) were effective approaches to treat five different levels of VB aneurysm according to the clivus bone. The pre-operative clinical gradingscale and the large – giant size of aneurysm were the most consistent and determinant factors for unfavorable outcome in this study
