Microsurgery of residual or recurrent complex intracranial aneurysms after coil embolization - a quest for the ultimate therapy.

The long-term stability of coil embolization (CE) of complex intracranial aneurysms (CIAs) is fraught with high rates of recanalization. Surgery of precoiled CIAs, however, deviates from a common straightforward procedure, demanding sophisticated strategies. To shed light on the scope and limitations of microsurgical re-treatment, we present our experiences with precoiled CIAs. We retrospectively analysed a consecutive series of 12 patients with precoiled CIAs treated microsurgically over a 5-year period, and provide a critical juxtaposition with the literature. Five aneurysms were located in the posterior circulation, 8 were large-giant sized, 5 were calcified/thrombosed. One presented as a dissecting-fusiform aneurysm, 9 ranked among wide neck aneurysms. Eight lesions were excluded by neck clipping (5 necessitating coil extraction); 1 requiring adjunct CE. The dissecting-fusiform aneurysm was resected with reconstruction of the parent artery using a radial artery graft. Three lesions were treated with flow alteration (parent artery occlusion under bypass protection). Mean interval coiling-surgery was 4.6 years (range 0.5-12 years). Overall, 10 aneurysms were successfully excluded; 2 lesions treated with flow alteration displayed partial thrombosis, progressing over time. Outcome was good in 8 and poor in 4 patients (2 experiencing delayed neurological morbidity), and mean follow-up was 24.3 months. No mortality was encountered. Microsurgery as a last resort for precoiled CIAs can provide-in a majority of cases-a definitive therapy with good outcome. Since repeat coiling increases the complexity of later surgical treatment, we recommend for this subgroup of aneurysms a critical evaluation of CE as an option for re-treatment.

Predictor of Visual Impairment Following Paraclinoid Aneurysm Surgery: Special Consideration of Surgical Microanatomy Related to Paraclinoid Structures.

BACKGROUND: Microsurgical clipping with extradural anterior clinoidectomy (EDAC) for paraclinoid aneurysm is an established technique with good angiographic outcomes, although postoperative worsening of visual acuity remains a concern. Multiple reports show visual acuity deteriorating after clipping, yet the cause remains unclear. OBJECTIVE: To analyze results of asymptomatic paraclinoid aneurysm surgeries treated with EDACs, specifically focusing on the microanatomy of paraclinoid structure dissection. This determined the causes of delayed visual impairment and microsurgical indications. METHODS: Results of the treatment with EDAC of 94 patients with cerebral aneurysm and normal preoperative visual acuity but also full visual fields were retrospectively analyzed. RESULTS: The mean aneurysm size was 6.2 (±3.3) mm. Clipping was performed in 87 cases and trapping in 7 cases. Complete angiographic occlusion was observed in 91 patients. In 26 cases, a postoperative visual deficit occurred. A total of 20 cases exhibited partial visual field deficits, including 5 who were asymptomatic. Visual deficits were only detectable by postoperative ophthalmologic testing. Six showed light perception impairment or blinding. Of the 15 patients with symptomatic partial visual field deficits, 5 showed improvement at follow-up. Visual deficits persisted in 22 patients at the last follow-up. Multivariate logistic regression analysis revealed that medial projecting aneurysm (adjusted odds ratio [OR]: 10.43) and the opening of the carotidoculomotor membrane (adjusted OR: 5.19) were significantly related to visual impairment. CONCLUSION: Excess dissection of carotidoculomotor membranes causes postoperative delayed visual worsening. For treating small, asymptomatic paraclinoid aneurysms, carotidoculomotor membranes should not be opened, and microsurgical clipping should not be performed for preoperative asymptomatic medial projecting aneurysms.

Complex Bypass Surgery for Multiple Fusiform Aneurysms, Including a Thrombosed Giant Aneurysm of the Middle Cerebral Artery.

Treatment of complex middle cerebral artery (MCA) aneurysms are challenging; however, an appropriate surgical strategy can ensure favorable outcomes. Notably, a protective bypass strategy is essential to treat complex aneurysms and involves the creation of a bypass channel distal to the aneurysm before repairing it. A protective bypass enables the surgeon to establish adequate distal blood flow during the approach to the aneurysm, as well as during additional revascularization. This Video 1 describes complex bypass surgery that successfully treated multiple fusiform aneurysms, including a thrombosed giant aneurysm of the MCA. A 12-year-old girl presented with a history of chronic headache and incidentally diagnosed multiple fusiform aneurysms along the course of the right internal carotid artery to the MCA, including a thrombosed giant aneurysm of the M2 segment of the MCA (M2) superior trunk. The aneurysms were treated by trapping and excision along with a superficial temporal artery to MCA triple bypass, and an M2-radial artery graft-M2 bypass. The patient developed mild left hemiparesis postoperatively but recovered well and was discharged with a modified Rankin Scale score of 0. The pathophysiology of this patient should be different from common saccular aneurysm because of young age and multiple fusiform shape. Hence continuous follow-up is essential. The next surgical strategy should be reconsidered according to the situation if the recurrence is occurred. This surgical video shows the surgical strategy and stepwise procedure to treat complex aneurysms and will be useful to vascular neurosurgeons to devise a surgical approach utilizing a "protective bypass strategy."

The sellar and suprasellar region: A "hideaway" of rare lesions. Clinical aspects, imaging findings, surgical outcome and comparative analysis.

OBJECTIVE: Apart from the "common" lesions (e.g. pituitary adenomas, Rathke's cleft cysts, meningiomas and craniopharyngiomas), there is a plethora of rare tumors or tumor-mimicking lesions in the sellar and suprasellar region (SSR). Due to a lack of characteristic imaging features, there is a dilemma in distinguishing these rare lesions from the more "common" ones preoperatively. Consequently, both diagnosis and definition of surgical goals, as well as further treatment strategies continue to be challenging for all attending physicians. To replenish the scarce data on this issue, we analysed all patients with infrequent non-adenomatous pathologies in the SSR treated in our clinic, providing a database for further studies. METHODS: A retrospective study was performed including 223 patients who were operated on lesions within the SSR at the Department of Neurosurgery, Hannover Medical School, between 2006 and 2014. The patients' charts were analysed with regard to the results of pre-/postoperative endocrinological and neuroophthalmological examinations. Preoperative T2WI were analysed with special focus on distinct growth patterns within four quadrants constituting the (supra-)sellar region. In this way, a comparative analysis between the diverse lesions regarding their clinical features, resectability and the final outcome was possible. RESULTS: After exclusion of cases with "common" lesions, a collective of 20 patients with rare lesions within the SSR was obtained. The histopathological diagnosis revealed xanthogranulomas (n=6), metastatic tumors (n=5), colloid/epidermal cysts (n=3), pilocytic astrocytomas (n=2), and one case each of gangliocytoma, lymphocytic hypophysitis or concomitant germ cell tumor/rhabdomyosarcoma. In comparison to non-infiltrative lesions, those of infiltrative nature caused more frequently diplopia and deterioration of visual acuity (4 cases; p<0,05) that were less prone to improve postoperatively. Regarding growth pattern, metastatic tumors demonstrated main growth within the third quadrant with destructive remodelling of the dorsum sellae (p<0,05). While patients harbouring large lesions (>20mm) showed a significantly worse outcome regarding hormonal deficits (p=0,0313), the overall prognosis was heavily linked to the histopathological diagnosis. CONCLUSION: The correlation of the subtle radiological findings demonstrated with the specific clinical features may facilitate the differential diagnosis of rare lesions of the SSR and aid in establishing an interdisciplinary diagnostic and therapeutic procedure for these lesions.

Petroclival meningiomas: Magnetic resonance imaging factors predict tumor resectability and clinical outcome.

OBJECTIVE: Despite advances in skull base surgery, surgical removal of petroclival meningiomas (PCM) still poses a considerable neurosurgical challenge with regard to postoperative morbidity and the patients' long-term outcome. Knowledge of imaging features for PCM that might help to predict common risk factors encountered with tumor resection preoperatively is limited. The aim of this study was to clarify whether MRI features of PCM might predict tumor resectability and clinical outcome. METHODS: A retrospective analysis of 18 cases of PCM treated surgically in our department between 2007 and 2013 was performed. Following radiological tumor features were compared to the extent of tumor resection and the patients' outcome: a) tumor diameter, b) calcification, c) tumor margin towards the brainstem, d) presence of an arachnoidal cleavage plane, e) brainstem edema, f) brainstem compression and g) tumor signal intensity on T2WI. RESULTS: There was an excellent correlation between tumor resectability and preoperative findings with regard to the presence or absence of an arachnoidal cleavage plane and an irregular tumor margin towards the brainstem. Additionally, the presence of brainstem edema was significantly related to surgical morbidity, whereas a high tumor intensity on T2WI correlated significantly with soft tumor consistency and/or vascularity encountered during surgery. CONCLUSION: As demonstrated in our series, PCM with an irregular tumor margin and absence of an arachnoidal plane towards the brainstem should be considered a high-risk group. In these cases, especially when additional brainstem edema is present, limited resection of tumor may be aspired to avoid postoperative morbidity.

Electromagnetic navigation-guided surgery in the semi-sitting position for posterior fossa tumours: a safety and feasibility study.

BACKGROUND: Electromagnetic (EM)-guided neuronavigation is an innovative technique and a viable alternative to opto-electric navigation. We have performed a safety and feasibility study using EM-guided neuronavigation for posterior fossa surgery in the semi-sitting position in a selected subset of patients. METHODS: Out of 284 patients with posterior fossa tumours operated upon over a period of 40 months, a subset of 15 patients was thought to possibly benefit from EM navigational guidance and was included in this study. There were six children and nine adults (aged between 8 and 84 years; mean age, 34.6 years) with different neoplasms in the brainstem or close to the midline. All patients had contrast-enhanced three-dimensional (3D) magnetic resonance imaging (MRI) of the head preoperatively. EM-guided navigation was used to identify and preserve the venous sinuses during craniotomy and to determine the trajectory to the lesion using various approaches. Neuronavigation accuracy was repeatedly checked for deviations measured in millimetres on screen shots during surgery before and after dural opening in the coronal (z = vertical), axial (x = mediolateral) and sagittal (y = anteroposterior) plane. RESULTS: Referencing of the patient in the supine position was fast and easy. There was no loss of navigation accuracy after repositioning of the patient in the semi-sitting position (mean, 2.5 mm ± 0.92 mm). Identification of the pathological structure using EM navigation was achieved in all instances. Optimal angulation of the neck was selected individually to permit a comfortable position for the surgeon with full access to the lesion avoiding over-flexion. Deviation of accuracy at the surface of the target lesion ranged between 2.5 and 5.8 mm (mean, 3.9 mm ± 1.1 mm). CONCLUSIONS: EM-guided neuronavigation in the semi-sitting position was safe and technically feasible. It enabled fast and accurate referencing without loss of navigation accuracy despite repositioning of the patient. In contrast to conventional opto-electric neuronavigation there were no line of sight problems.

Surgical treatment of distal anterior cerebral artery aneurysms aided by electromagnetic navigation CT angiography.

The surgical treatment of distal anterior cerebral artery (DACA) aneurysms still presents a challenge for neurosurgeons because of their small size and their location in the depth of the narrow frontal interhemispheric fissure. This study aimed to investigate feasibility, safety, accuracy, and usefulness of electromagnetic (EM) navigation to aid clipping of DACA aneurysms. Eight patients (age between 2 and 68 years, mean age 49.8 years) with a DACA aneurysm underwent EM-guided neuronavigated microsurgery for clipping of the aneurysm. All patients underwent craniocervical 3D-CT angiography preoperatively. After planning the optimal approach and surgical trajectory avoiding opening of the frontal sinus, the head was fixed. Intraoperative screenshots were correlated with the microscopical view of the DACA aneurysms before clipping. EM-guided neuronavigation using CT angiography for DACA aneurysms enabled fast and accurate referencing of the patient and planning of a tailored craniotomy without opening of the frontal sinus. Intraoperative accuracy was highly reliable except in one instance due to dislocation of the dynamic reference frame (DRF). There was a good correlation between the 3D-CT angiography-based navigation data sets and the intraoperative vascular anatomy. In all patients, bridging veins were spared. The aid of EM neuronavigation was considered useful in all instances. EM-guided neuronavigation using CT angiography for surgery of DACA aneurysms is a useful tool optimizing the surgical approach directly to the aneurysm minimizing additional damage to the surrounding tissue during preparation of the aneurysm and the parent vessel.