Validation of a therapy-oriented complication grading system in cerebral bypass surgery

Cerebral bypass is a niche procedure used in neurosurgery to manage complex cerebrovascular diseases. Bypass surgery can be divided into two distinct categories: flow augmentation and flow preservation. Flow augmentation aims to restore the flow to hypoperfused brain territories of patients with steno-occlusive diseases. Flow preservation aims to replace the blood flow provided by a major intracranial vessel, the occlusion of which is necessary to treat an underlying disease, such as a complex aneurysm or a tumour. The Clavien-Dindo complication Grading (CDG) system rates any adverse event, defined as any deviation from normal postoperative course (CDG≥1), on a scale from one to five, according to the necessary therapy. The aim of this study was to explore the applicability of CDG in a neurosurgical patient population undergoing cerebral bypass surgery. Methods: In total, 58 patients with different cerebrovascular pathologies underwent 59 cerebral bypass surgeries between January 2013 and June 2018 at the Department of Neurosurgery, University Hospital Zurich. Complications were classified according to the CDG system at discharge and at three-month follow-up. Patients’ outcome was assessed using the modified Rankin Scale (mRS) and National Institute of Health Stroke Scale (NIHSS). Results: A total of 42 flow augmentation bypass procedures were performed on 41 patients with Moyamoya disease, symptomatic chronic or subacute large artery occlusion, or acute ischemic strokes. A flow preservation bypass was performed on 17 patients with complex aneurysms or tumours. During the hospital stay, 22 (37,9%) patients developed an adverse event (CDG≥1), with a median CDG of 2 (interquartile range: 1). With 9 (15,5%) patients out of 58, an adverse event (CDG≥1) with new neurological deficit (“d”) occurred. At discharge, the occurrence of a complication and an increase in mRS scale correlated significantly (p=0,003, ρ=0,59). The occurrence of an adverse event (CDG≥1) was higher at discharge than after three months (p < 0,001)