Dural adhesion as a cause of late clip slippage from the medial cerebral artery aneurysm.

BACKGROUND: A properly placed clip may slip off the aneurysm during the postoperative period. Many factors have been attributed to this complication, although clip adherence to the dural stitch has not been reported.

MATERIALS AND METHODS: Following the single occurrence of such unusual complication, 64 similar medial cerebral artery (MCA) aneurysms were retrospectively investigated at a single institution. Clip adherence to the dura demonstrated in early postoperative computer tomography (CT) was a presumed factor of a late clip migration in this study.

RESULTS: In the series, there were 4 aneurysm remnants (6.3%) and one slipped clip that firmly adhered to the dura. In this particular case, the revision surgery revealed the spring coil firmly adhering to the dura in the previous suture line. Neither the occurrence of an aneurysm neck remnant nor clip slippage were related to the clip's adherence to the dura in the analysis of the entire group (p>0.05). On the contrary, application of a fenestrated clip did contribute to that finding in multivariate analysis (p<0.01). Unlike the rest, two surgeons unintentionally tended to position the clip close to the dura (p<0.01). The clip-to-dura distance measured in the follow-up CT angiography one year after the surgery differed from that in the postoperative CT in 83.8% of the cases and decreased by an average of 0.5 millimetres.

CONCLUSIONS: Clip-to-dura adherence should be regarded as a normal finding in the postoperative CT following MCA aneurysm clipping. Surgeons should consider the possibility of clip head protrusion into the dural stitch line.