Microsurgical clipping of intracranial aneurysms following unsuccessful endovascular treatment. Analysis of ten cases

A Cohesive Shear-Thinning Biomaterial for Catheter-Based Minimally Invasive Therapeutics

Shear-thinning hydrogels are suitable biomaterials for catheter-based minimally invasive therapies; however, the tradeoff between injectability and mechanical integrity has limited their applications, particularly at high external shear stress such as that during endovascular procedures. Extensive molecular crosslinking often results in stiff, hard-to-inject hydrogels that may block catheters, whereas weak crosslinking renders hydrogels mechanically weak and susceptible to shear-induced fragmentation. Thus, controlling molecular interactions is necessary to improve the cohesion of catheter-deployable hydrogels. To address this material design challenge, we have developed an easily injectable, nonhemolytic, and noncytotoxic shear-thinning hydrogel with significantly enhanced cohesion via controlling noncovalent interactions. We show that enhancing the electrostatic interactions between weakly bound biopolymers (gelatin) and nanoparticles (silicate nanoplatelets) using a highly charged polycation at an optimum concentration increases cohesion without compromising injectability, whereas introducing excessive charge to the system leads to phase separation and loss of function. The cohesive biomaterial is successfully injected with a neuroendovascular catheter and retained without fragmentation in patient-derived three-dimensionally printed cerebral aneurysm models under a physiologically relevant pulsatile fluid flow, which would otherwise be impossible using the noncohesive hydrogel counterpart. This work sheds light on how charge-driven molecular and colloidal interactions in shear-thinning physical hydrogels improve cohesion, enabling complex minimally invasive procedures under flow, which may open new opportunities for developing the next generation of injectable biomaterials.

Safety and efficacy of microsurgical treatment of previously coiled aneurysms: a systematic review and meta-analysis

BACKGROUND

We conducted a systematic review of the literature to evaluate the safety and efficacy of surgical treatment of previously coiled aneurysms.

METHODS

A comprehensive review of the literature for studies on surgical treatment of previously coiled aneurysms was conducted. For each study, the following data were extracted: patient demographics, initial clinical status, location and size of aneurysms, time interval between initial/last endovascular procedure and surgery, surgical indications, and microsurgical technique. We performed subgroup analyses to compare direct clipping versus coil removal and clipping versus parent vessel occlusion, early (<4 weeks post-coiling) versus late surgery and anterior versus posterior circulation.

RESULTS

Twenty-six studies with 466 patients and 471 intracranial aneurysms were included. All of the studies were retrospective and non-comparative case-series. Patients undergoing direct clipping had lower perioperative morbidity (5.0 %, 95 % CI = 2.6-7.4 %) when compared to those undergoing coil removal and clipping (11.1 %, 95 % CI = 5.3-17.0 %) or parent vessel occlusion (13.1 %, 95 % CI = 4.6-21.6 %) (p = 0.05). Patients receiving early surgery (<4 weeks post-coiling) had significantly lower rates of good neurological outcome (77.1 %, 95 % CI = 69.3-84.8 %) when compared to those undergoing late surgery (92.1 %, 95 % CI = 89.0-95.2 %) (p < 0.01). There were higher rates of long-term neurological morbidity in the posterior circulation group (23.1 vs. 4.7 %, p < 0.01) as well as long-term neurological mortality (4.4 vs. 2.8 %, p < 0.01).

CONCLUSIONS

Our meta-analysis suggests that surgical treatment is safe and effective. Our data indicate that aneurysms that are amenable to direct clipping have superior outcomes. Late surgery was also associated with better clinical outcomes. Surgery of recurrent posterior circulation aneurysms was associated with high rates of morbidity and mortality. Given the characteristics of the included studies, the quality of evidence of this meta-analysis is limited.