Basilar Complex Research Articles

A modified anterior temporal approach for low-position aneurysms of the upper basilar complex.

Background:Although surgery for aneurysms of the upper basilar complex is generally accomplished by a pterional or subtemporal approach, both techniques have disadvantages. Therefore, attempts have been made to combine both the approaches, such as an anterior temporal approach, which exposes the anterior aspect of the temporal lobe during standard fronto-temporal craniotomy. However, in all these techniques, the temporal vein is sacrificed to allow posterior retraction of the temporal lobe, which may cause venous infarction in the temporal lobe.Methods:Our institutional review board approved this prospective study. We modified the anterior temporal approach for low-position aneurysms of the upper basilar complex by performing posterior clinoidectomy as necessary, thereby preventing the sacrifice of all vessels.Results:From 2007 to 2014, seven patients were operated on using this modified approach, and four patients underwent additional posterior clinoidectomy. Complete clip ligation was performed for all aneurysms without sacrificing any vessels, and there were no permanent complications attributable to manipulation for clipping or posterior clinoidectomy.Conclusions:The modified anterior temporal approach allows a wider operating field within the retro-carotid space, without sacrificing any vessels, and permits safer posterior clinoidectomy and aneurysm clipping in patients with low-position aneurysms of the basilar complex.

PTERION: A SITE FOR NEUROSURGICAL APPROACH

Pterion is defined as point of sutural confluence seen in the normal ateralis of the skull where frontal, parietal, temporal and sphenoid bones meet. It is a commonly used neurosurgical landmark. The anatomic location of the pterion is important in surgical interventions following surgical approaches to the anterior and middle cranial fossae, following extradural hemorrhage as well as tumors involving inferior aspects of the frontal lobe, such as olfactory meningioma, used in operations on the Broca's motor speech area and in repairing aneurysms of the middle cerebral artery as well as those of the upper basilar complex and also the anatomical varieties of the pterion, is of interest mainly to anthropologists and forensic pathologists, for assessing the location of the pterion in incomplete archeological remains or forensic materials. The pterion exhibits population-based variations. The aim of the study is to determine the position of the pterion using the midpoint of the zygoma (MPZ) and the frontozygomatic suture (FZS) as palpable points.In the present study seventy dry skulls (34 male and 36 female) were used. The dry skulls were obtained from the department of anatomy, K M C Mangalore, Manipal University. Only the intact skulls were included in the study. The sexing was done on the morphological basis. The Distance between pterion to FZS and pterion to MPZ of right and left side of the male skull bones when compared with the right and left side of female skull bones showed statistically significant side difference among male and female bones.

Role of Uncal Resection in Optimizing Transsylvian Access to the Basilar Apex: Cadaveric Investigation and Preliminary Clinical Experience in Eight Patients

The pretemporal approach has gained popularity for the treatment of basilar apex aneurysms. However, it requires the sacrifice of anterior temporal bridging veins to allow posterior temporal lobe retraction and, for patients with dominant pretemporal venous drainage, has the attendant risk of venous hypertension, hemorrhagic venous infarction, or seizures postoperatively. Alternatively, we have found that splitting the sylvian fissure, resecting the uncus, and applying posterolateral retraction to the medial temporal lobe provides a similar exposure to the basilar apex while preserving the anterior temporal bridging veins. To evaluate the transsylvian, trans-uncal approach to the basilar apex, we report our initial clinical results using this exposure in eight consecutive patients. A morphometric cadaveric analysis comparing this approach with the pretemporal approach was also performed. For the clinical study, all hospital charts and imaging studies were retrospectively reviewed for patients undergoing the transsylvian, trans-uncal approach for the treatment of an upper basilar trunk aneurysm between July 2000 and July 2002. In the anatomic study, six formalin-fixed cadaver specimens were used. Two sequential exposures of the basilar apex were performed on each specimen side. First, the pretemporal exposure was performed with anteroposterior temporal lobe retraction. Next, after the temporal lobe had been allowed to return to normal anatomic position, the retractor was repositioned on the medial aspect of the temporal lobe superficial to the uncus, and a 10 x 10 x 15-mm volume of uncus was removed. Morphometric measurements were performed for each exposure. Four basilar bifurcation and four superior cerebellar segment aneurysms in eight consecutive patients were successfully clip-ligated by use of the transsylvian, trans-uncal approach. All patients had temporal bridging veins that were preserved, as documented by angiography and operative reports. No patient developed a venous infarction or new postoperative seizures, with a mean follow-up of 9.75 months (range, 0.5-28 mo). The cadaveric analysis revealed that in addition to providing a similar exposure of the upper basilar complex, the transsylvian, trans-uncal approach provided additional exposure of the ipsilateral posterior cerebral and superior cerebellar arteries compared with the pretemporal approach. When approaching the basilar bifurcation, the transsylvian, trans-uncal approach provides superior exposure of the ipsilateral superior cerebellar and posterior cerebral arteries compared with the pretemporal approach, while preserving the anterior temporal bridging veins. This approach is most valuable in patients with dominant temporal venous drainage or when additional exposure of the ipsilateral posterior cerebral or superior cerebellar arteries is required.

Microsurgical and Endoscopic Approaches to the Basilar Bifurcation: Quantitative Comparison of Combined Pterional/Anterior Temporal and Orbitozygomatic Extended Approaches

To determine the most effective route to the upper third of the basilar artery, 10 cadaver dissections were performed comparing the exposure gained using the combined pterional/anterior temporal approach and the orbitozygomatic extended approach. Endoscopic evaluation through an eyebrow incision in each dissection helped determine whether any advantage was conferred by the cranial base approach. This also served to assess the benefit of using the endoscope as an adjunct to open procedures in evaluating the opticocarotid and retrocarotid routes to the basilar artery. The results of cadaveric dissections suggest that compared with the exposure afforded by the combined pterional/anterior temporal approach, the orbitozygomatic extended approach yields an increase of 8 cm in the anteroposterior axis and 10 cm in the superoinferior axis. Furthermore, as expected, the increases in visibility were directed anteriorly and posteriorly. When employed through the craniotomy site during aneurysm clipping, endoscopy was found to be potentially useful in assessing the contralateral elements of the upper basilar complex.

The effect of orbitozygomatic access for ruptured basilar and related aneurysms on management outcome

Despite increasing use of craniofacial access for complex intracranial and skull base pathology, there have been no reports detailing the impact of improved access on clinical outcome. Orbitozygomatic access was used in 32 patients with an aneurysm of the basilar bifurcation, superior cerebellar, or posterior cerebral arteries over a 9-year period. Operative mortality was 0%, overall management mortality 9% and management morbidity was 9%. This approach was selected for these patients because of the anatomy of the aneurysm and its relationship to the terminal basilar complex and the dorsum sellae/posterior clinoid process. The flexibility achieved by the access allowed intraoperative use of multiple corridors of access. Morbidity directly attributable to the use of orbitozygomatic access was minimal. While management outcome after aneurysmal subarachnoid hemorrhage relates directly to the severity of the initial hemorrhage, rather than the surgical approach chosen, in selected patients we recommend the use of this approach as a valuable adjunct to the armamentarium of the vascular neurosurgeon.

The Combined Pterional/Anterior Temporal Approach for Aneurysms of the Upper Basilar Complex

A technique for achieving a combined pterional (subfrontal) and anterior temporal exposure for aneurysms of the upper basilar complex is described. The technique is not new, but it does involve several modifications not previously described. A standard pterional skin incision that extends below the zygoma just anterior to the tragus is used. The skin flap is separated from the temporal fascia down to the fat pad over the zygoma; at this point, the superficial layer of the temporalis fascia is incorporated and retracted with the skin flap to expose the zygomaticofrontal process and the zygomatic arch. The muscle is cut anteriorly and inferiorly and is retracted posteriorly over the ear. The bone flap includes the anterior temporal squama down to the temporal floor anteriorly. The pterion and the sphenoidal wings are drilled so as to expose completely the dura over the anterior temporal pole. After opening the dura on a flap centered on the sylvian fissure, the medial cisterns are opened widely and the fissure is opened all the way to the middle cerebral bifurcation. Posterolateral temporal retraction and, when necessary, subpial resection of the anteromedial portion of the uncus enhance the exposure posterolateral to the oculomotor nerve. The advantages of this combined approach are as follows: it combines the more anterior angle of vision offered by the pterional approach with the lateral line of vision offered by the subtemporal approach; it eliminates the need for temporal lobe elevation and it allows simultaneous clipping of other aneurysms of the ipsilateral anterior circle of Willis; and it also reduces the frequency and severity of oculomotor palsy, when compared with the subtemporal approach.

The Combined Pterional/Anterior Temporal Approach for Aneurysms of the Upper Basilar Complex

The Combined Pterional/Anterior Temporal Approach for Aneurysms of the Upper Basilar Complex