Surgical outcomes in Chiari malformation type I: A quality review from a Scandinavian medium-volume neurosurgical center.

Background: Chiari malformation type 1 (CM-I) is characterized by caudal herniation of the cerebellar tonsils through the foramen magnum. Surgical decompression is generally indicated in patients with significant or progressive symptoms, or in clinically relevant or progressing syringomyelia. As CM-I surgery is relatively infrequent in medium-volume neurosurgical centers, outcome data from such settings remain limited. This study evaluates surgical outcomes following CM-I decompression at a Scandinavian medium-sized neurosurgical center. Research question: What are the outcomes of CM-I surgery at the Department of Neurosurgery, Haukeland University Hospital? Material and methods: We performed a retrospective case series of patients with CM-I treated at our department between 2014 and 2023. The primary outcome was the Chicago Chiari Outcome Scale (CCOS) at the last follow-up. Secondary outcomes were 30-day surgical quality indicators. Results: Forty patients comprised of 29 (72.5 %) adults and 11 (27.5 %) pediatric patients. Clinical improvement (CCOS ≥13) was observed in 78 %. The observed 30-day quality indicators were reoperations in three patients (7.5 %), infections in two patients (5.0 %), and readmission in seven patients (18 %). Complications within 30 days occurred in six patients (15 %). The most frequent complication was new-onset hydrocephalus, which occurred in four patients (10 %). The median hospital length of stay was 5.5 days. There was no mortality. Discussion and conclusion: Most patients demonstrated clinical improvement, but complication rates exceeded benchmarks. Hydrocephalus was the most frequent issue. We discuss possible interventions to further strengthen CM-I care in our department, with an emphasis on hydrocephalus management.