Keyhole Fenestration for Cerebrospinal Fluid Leaks in the Thoracic Spine: Quantification of Bone Removal and Microsurgical Anatomy

Abstract

BACKGROUND AND OBJECTIVE: A safe working trajectory is mandatory for spinal pathologies, especially in the midline, anterior to the spinal cord. For thoracic cerebrospinal fluid (CSF) leaks, we developed a minimally invasive keyhole fenestration. This study investigates the necessary bone removal for sufficient exposure of different leak types particularly regarding weight-bearing structures. METHODS: In this retrospective case series between January 2022 and June 2023, the volume of bone resection and the axial and sagittal diameter of hemilamina defects after closure through keyhole fenestration were quantified. The involvement of facet joints and pedicles was qualitatively rated. Demographic (age, sex, body mass index, leak type) and surgical data (blood loss, surgery time, discharge after surgery) and complications were analyzed. RESULTS: Thirty-three patients with 34 approaches were included. The volume of resected bone was 1.5 cm3, and the diameter of the hemilamina defect was 17.8 mm in the sagittal and 15.1 mm in the axial plane. Facet joints were uninvolved in 24% and partly resected in 74%, and one facet joint was resected completely. Pedicles remained intact in 71% and were minimally involved in 29%. The median surgery time was 93 minutes, blood loss was 45 mL, and discharge was 4 days after surgery. Three patients (9%) needed revision surgery. No relevant and persisting morbidity occurred. Within the median follow-up period of 10 months, no stabilizing surgery was necessary. No permanent neurological deficit occurred. CONCLUSION: The keyhole fenestration leaves weight-bearing structures like facet joints and pedicles intact in most cases. The limited, penny-sized bone resection is sufficient to reach and close thoracic CSF leaks Type 1, 2, and 3 from the anterior midline to the ganglion. For experienced centers, it is a universal minimally invasive approach for treating all CSF leaks.