Detailed preoperative microsurgical information regarding the scheduled route and the surrounding cisternal space around the aneurysm is mandatory for safe aneurysm surgery. We used constructive interference in steady-state imaging (CISS) to evaluate the microsurgical anatomy around the cerebral aneurysms prior to surgery in addition to three-dimensional computed tomography angiography and digital subtraction angiography. Among 219 patients, 243 intracranial unruptured aneurysms were evaluated using CISS before surgery, and 240 aneurysms in 216 patients were surgically obliterated in 218 procedures. The cranial nerves and other neural structures, and efferent and perforating vessels were confirmed during surgery. The high intensity signal of the cerebrospinal fluid (CSF) was used as an indicator of preserved cisternal space without adhesion between the aneurysm and its surrounding structures.
Microsurgical information regarding the surgical route such as sylvian or interhemispheric fissure, and adhesion or close contact to surrounding tissues including oculomotor, optic and other cranial nerves and the tentorium and other basal dura was very useful for advancing the procedure precisely as planned. Adhesion to large efferent vessels was properly predicted, but identification and description of perforators around the aneurysm was incomplete in some cases, and careful confirmation of these vessels during surgery under direct vision was mandatory. Surgical outcome was excellent with no ischemic complications. Modified Rankin scale (mRS) at six months after surgery was 0 in all but one patient who developed permanent olfactory nerve dysfunction and became mRS1.
Despite its inadequacy, CISS can contribute to safe aneurysm surgery by providing information on the detailed anatomical structure around the aneurysm and surgical route.