Paramedian thalamic infarction caused by cisternal drain placement in open clipping for aneurysmal subarachnoid hemorrhage: Two case reports

BACKGROUND: Some complications associated with cisternal drainage have been reported; however, there are few reports on direct vascular injury caused by cisternal drain. We experienced two rare cases of thalamic infarction caused by cisternal drain placement during open clipping for a ruptured anterior communicating artery (AcomA) aneurysm through an anterior interhemispheric approach. CASE DESCRIPTION: Two cases of ruptured AcomA aneurysm were treated by surgical clipping through an anterior interhemispheric approach, and then a cisternal drain was inserted from opticocarotid space toward prepontine cistern. Postoperatively, the magnetic resonance imaging showed unilateral anterior-medial thalamic infarction in both two cases. By reviewing the postoperative computed tomography and digital subtraction angiography, it was suspected that the cisternal drain, which was inserted slightly deep, obstructed the P1 perforator because of an anatomical variation involving a lowered basilar bifurcation and caused postoperative unilateral paramedian thalamic infarction. CONCLUSION: To avoid these complications, neurosurgeons should consider the potential for P1 perforator injury related to cisternal drain placement.