Keyhole Approach and Neuroendoscopy for Cerebral Aneurysms

Abstract

Treating diseases in the field of neurosurgery has progressed concomitantly with technical advances. Here, as a surgical armamentarium for the treatment of cerebral aneurysms, the history and present status of the keyhole approach and the use of neuroendoscopy are reviewed, including our clinical data. The major significance of keyhole approach is to expose an essential space toward a target, and to minimize brain exposure and retraction. Among several kinds of keyhole approaches, representative keyhole approaches for anterior circulation aneurysms include superciliary and lateral supraorbital, frontolateral, mini-pterional and mini-interhemispheric approaches. Because only a fixed and limited approach angle toward a target is permitted via the keyhole, however, specialized surgical devices and preoperative planning are very important. Neuroendoscopy has helped to widen the indications of keyhole approaches because it can supply illumination and visualization of structures beyond the straight line of microscopic view. In addition, endoscopic indocyanine green fluorescence angiography is useful to detect and correct any compromise of the perforators and parent arteries, and incomplete clipping. The authors think that keyhole approach and neuroendoscopy are just an intermediate step and robotic neurosurgery would be realized in the near future.

Keywords: Cerebral aneurysms; Keyhole; Neuroendoscopy.

Fig. 1

Illustrations of various types of keyhole craniotomy. A: Superciliary supraorbital (a, skin incision at the upper margin of eyebrow) and frontolateral (b, skin incision just behind the hairline) keyhole craniotomy. B: Lateral supraorbital craniotomy above the sphenoid ridge, detaching the temporalis muscle. C: mini-pterional keyhole craniotomy exposing the perisylvian area. D: Mini-interhemispheric keyhole craniotomy after linear midline or inverted bowl-shaped skin incisions. Dotted lines indicate the skin incision, black circles indicate the keyhole and solid lines indicate the margin of craniotomy in a size of about 3–4 cm at each plane.

Fig. 2

A case of left anterior choroidal artery (AChA) aneurysm clipped via lateral supraorbital approach with dual channel endoscopic indocyanine green fluorescence angiography (ICGA). A: Aneurysm, AChA (thin arrow) and posterior communicating artery (PCoA, thick arrow) are seen on right lateral projection of 3D reconstructed angiography. B: AChA is not identified even retracting the internal carotid artery (asterisk: left optic nerve). However, a small perforator which seems posterior branch of AChA unseen on preoperative angiography (dotted arrow) is arising from the posterior neck of aneurysm. C: On endoscopic view, the orifices of PCoA (thick arrow), anterior (thin arrow) and posterior branches of AChA (dotted arrow) are shown. D and E: On microscopy, anterior branch of AChA is not seen even after clipping the aneurysm, however, posterior branch of AChA (dotted arrow) is demonstrated. F: On endoscopy, the orifice of anterior branch of AChA (arrow) and tip of clip blade (asterisk) are well identified. G: On microscopic ICGA in the same viewpoint of E, posterior branch of AChA (dotted arrow) is seen. H: On dual channel endoscopic ICGA of ICG image (left) and merging image (right), ICG fluorescence is visualized at the orifices of PCoA (thick black arrows) and anterior branch of AChA (thin white arrows), however not within the aneurysm (asterisk: clip blade). I: On dual channel endoscopic ICGA, ICG fluorescence is shown in posterior branch of AChA (arrow) above the clip blade (asterisk).