Intermittent isometric exposure prevents brain retraction injury under venous circulatory impairment

Interhemispheric Precuneus Retrosplenial Transfalcine Approach for Falcotentorial Meningiomas: Anatomic Study and Clinical Series

BACKGROUND

Falcotentorial meningiomas are surgically challenging. Currently accepted approaches include occipital interhemispheric and supracerebellar infratentorial approaches, which have documented drawbacks.

OBJECTIVE

To propose an alternative approach to the posterior tentorial incisural space, the interhemispheric precuneus retrosplenial transfalcine approach (IPRTA).

METHODS

A total of 6 colored-silicone-injected adult cadaveric heads were dissected. We measured the interval between bridging veins and studied computed tomography venography scans of 20 subjects to confirm the feasibility of the IPRTA. Bony landmarks, the region's bridging veins, and the anterior and posterior borders of the approach were identified. The surgical corridor widths (veins' interval) and lengths were compared between alternative midline approaches. We also reviewed 4 consecutive clinical cases using this approach.

RESULTS

The IPRTA provides the shortest distance to the anterior and posterior limits of the posterior tentorial incisura. Moreover, it is the only approach that provides direct visualization of the anterior and posterior limits of falcotentorial junction meningiomas. In all specimens and patients, a minimum 30-mm interval between the anterior and posterior parietal veins was found in at least one of the hemispheres. Tumor removal was successful in all 4 patients but resulted in mild paresthesia in the lower extremities of 2 patients and temporary foot drop in 1 patient.

CONCLUSION

The IPRTA offers the shortest and most direct corridor for falcotentorial meningiomas and provides excellent visualization of most of the critical structures in the region. Detailed preoperative evaluation of the deep and superficial venous structures is recommended.

Evaluation of Venous Drainage Patterns for Skull Base Meningioma Surgery

The evaluation of venous drainage patterns prior to surgery for skull base meningioma is important owing to their deep location and the vulnerability of surrounding vascular structures. In recent years, the microsurgical skull base approach has matured as a surgical technique, making it an important option for reducing complications related to skull base meningioma surgery. In addition, knowledge of the venous anatomy can prevent venous drainage route disturbance and potentially life-threatening complications. Hence, this topic review aimed to provide an overview of normal venous anatomy as it relates to the microsurgical skull base approach, discuss known changes in venous drainage routes that are associated with the progression of skull base meningioma and the selection of an appropriate operative approach with the highest likelihood of preserving venous drainage structures.

Retractorless Surgery for Anterior Circulation Aneurysms via a Pterional Keyhole Approach

Brain retraction is required during many intracranial procedures to provide more working space. However, it is difficult to avoid brain retraction injury. Here, we report on retractorless surgery for anterior circulation aneurysms via a pterional keyhole approach. All patients undergoing a minimally invasive pterional keyhole approach within 3 days after hemorrhage by the same surgeon were included in the study. Patients were randomly assigned into group I (with the retractorless technique) and group II (with fixed retractors). Data on adequate clipping level, intraoperative ischemia induced by retraction, operation time, brain retraction injury, intraoperative blood loss, intraoperative aneurysm rupture, and modified Rankin Scale were collected for the 2 groups. A consecutive series of 47 patients (21 patients in group I, 26 patients in group II) successfully underwent a minimally invasive pterional keyhole approach. Statistical analysis revealed no significant between-group differences with regard to sex, age, Hunt-Hess grade, adequate clipping level, operation time, intraoperative blood loss, and aneurysm rupture (P > 0.05). However, no intraoperative ischemia was detected in group I, whereas 23.1% (6 of 26) of patients in group II had reversible ischemia. Furthermore, the proportion of brain retraction injuries in group I (5.3%) was lower than that in group II (34.6%). In addition, a better prognosis was obtained in patients who underwent retractorless surgery. With the careful and accurate use of a handheld suction device and operating instruments, the retractorless technique can replace fixed retraction, reduce brain retraction injury, and is applicable to surgeries on anterior circulation aneurysms via pterional keyhole approaches.

Re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms

BACKGROUND

Unplanned re-exploration of the craniotomy after surgical treatment of unruptured intracranial aneurysms (UIAs) is sometimes required, but the underlying causes and rates of these procedures are seldom reported. This study retrospectively analyzed the causes of such re-explorations to identify methods for decreasing their necessity.

METHOD

From January 2000 to December 2011, 1,720 patients with a total of 1,938 UIAs underwent surgical treatment at our institution. From this cohort, 26 patients (1.5 %) with 38 UIAs required re-exploration. Clinical data, aneurysm characteristics, treatment methods, and the incidence and causes of re-exploration of the craniotomy were analyzed for these 26 patients.

RESULTS

Several causes of re-exploration were identified: compromised distal blood flow (eight patients, 0.47 %), hemorrhagic venous infarction (four patients, 0.23 %), brain retraction injury (three patients, 0.17 %), newly identified aneurysms (three patients, 0.17 %), bleeding from an incompletely clipped aneurysm (two patients, 0.12 %), epidural hematoma (two patients, 0.12 %), failed aneurysm clipping (two patients, 0.12 %) and other causes (two patients, 0.12 %). Annual re-exploration incidence rates ranged from 0 to 3.1 %. Annual incidence rates gradually decreased following the introduction of several intraoperative monitoring systems.

CONCLUSIONS

Precise surgical planning and careful operative techniques can reduce the incidence of unplanned re-exploration of the craniotomy. The introduction of various intraoperative monitoring systems can also contribute to a reduction in this incidence.

Sequential and spatial profiles of apoptosis in ischemic penumbra after two-vein occlusion in rats

Object

The two-vein occlusion model is known to be useful for ischemic penumbra studies in vivo. It was applied here to examine sequential changes in the expression of Bax and Bcl-2 proteins and in apoptotic cells to assess the relationship between penumbra and apoptosis.

Methods

Two cortical veins were occluded photochemically by using rose bengal dye in 27 Wistar rats. The animals were killed with perfusion fixation at the following intervals: 4, 12, 24, 48, 96, and 168 hours after vein occlusion (four at each interval; three additional rats were sham-treated). Immunohistochemical analysis for the Bcl-2 family of proteins was performed along with the terminal deoxynucleotidyl transferase–mediated deoxyuridine triphosphate nick-end labeling (TUNEL) assay to examine the relationship to single-cell death.

Cells positive for antiapoptotic proteins began to appear in the TUNEL assay for animals killed 24 hours after vein occlusion, with a peak at 48 hours. These cells were localized in the core of infarction. Immunohistochemical staining for Bax protein showed an increased presence around ischemic lesions at 4 hours after vein occlusion, and the amounts continued to rise until 24 hours, when the localization was diffuse around the core of infarction. Negative findings on immunohistochemical studies for Bcl-2 protein were seen at the early phase after two-vein occlusion.

Conclusions

After vein occlusion, apoptosis appeared sequentially and widely in cortical lesions considered to be the penumbra. Therefore, control of apoptosis would be expected to offer a therapeutic window for treatment of venous infarction.