It is important to localize brain lesions and prevent damage to vital structures during operation of brain pathologies. Many techniques have been developed but a more accurate localizing technique is still needed. Neuronavigation is used for this proposes and its utilities are in: biopsy and resection of tumors, endoscopy, skull base surgery and functional neurosurgery. Reports of its use in aneurysmal surgery are scarce.
Schmid-Elsaesser et al. stated that Navigation-CT angiography is useful when performing surgery on unruptured aneurysms, especially middle cerebral artery (MCA) aneurysms. They reported that the deviation of the neck in navigation-CT angiography was less than 2.6 mm and that, with this instrument, MCA aneurysms were approached via minicraniotomy, avoiding detachment of the temporalis muscle. Also they stated that current navigation systems are not precise enough to allow "blind" aneurysm clipping by placing a real clip on the virtual aneurysm neck (8).
Lee and Bang reported a rare case of an unruptured non-traumatic dissecting aneurysm of the M4 segment of the MCA accompanied by total occlusion of the ipsilateral ICA. They used navigation-CT angiography and treated M4 aneurysm with proximal ligation. With the guidance of this instrument, they could precisely locate the aneurysm without corticotomy, and by approaching through sulci, further cortical injury was avoided (9).
Kim et al. reported on 12 patients with a distal anterior vertebral artery (DACA) aneurysm who were treated with direct clipping guided by the neuronavigation system. There were no technical problems or complications during application of the neuronavigation system. The registration precision ranged from 0.5 - 1.5 mm (mean: 0.88 mm). The neuronavigation system provided real-time presentation of DACAs and assisted in detection of the DACA aneurysms. They believe that DACA aneurysms are good candidates for neuronavigation and additional benefits of a small craniotomy and accurate intraoperative orientation during surgery result in a minimally invasive aneurysm procedure (10).
Carvalho et al. used a frameless stereotactic navigation system for the microsurgical resection of a distal infectious aneurysm. They used MRI scan with appropriate protocol and demonstrated the aneurysm on Fluid attenuated inversion recovery (FLAIR) sequence. They explained that these images increased aneurysm localization accuracy, allowed surgical planning and visualization of the infectious aneurysm during surgery, resulted in a simpler procedure with a smaller craniotomy, reduced the time for dissection and diminished the risk of vascular and parenchymal iatrogenic damage (11).
Kil et al. reported on 32 patients with unruptured intracranial aneurysms. They were treated by direct surgical neck clipping through the neuronavigation-guided keyhole approach. A 4 to 5 cm skin incision and a small 2.5 × 4 cm craniotomy was performed around the sylvian fissure. They stated that navigation-guided keyhole approach is helpful for the management of anterior circulation aneurysms in selected cases. It has the advantages of less operative time, fewer days of hospitalization, and cosmetic results (12).
We applied the neuronavigation system to guide identification of a ruptured right posterior communicating aneurysm. We used Gd enhanced MRI with appropriate protocol and detected the aneurysm in axial and coronal images. The aneurysm could be visualized virtually and we were able to confirm the location of the vascular pathology by this approach. MRI based neuronavigation results in precision of localization of the aneurysm, increases visualization of the lesion, decreases normal parenchymal and vascular injury and is useful for the treatment of cases of distal MCA and distal ACA aneurysms, while it can also be helpful for better localization of the neck of the aneurysm and results in less damage during aneurysm dissection in paraclinoid lesions.
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