Monitoring of cerebrospinal fluid flow by intraoperative ultrasound in patients with Chiari I malformation

ObjectiveTo investigate the feasibility of intraoperative ultrasound (IOUS) for monitoring cerebrospinal fluid (CSF) flow in patients with Chiari I malformation.MethodsTwenty patients with Chiari I were scanned by IOUS with color Doppler flow imaging (CDFI). CSF flow status and flow velocity were monitored at different times during the surgery.ResultsCSF flow was detected in all 20 cases by IOUS-CDFI in real time. CSF flow was extremely slow or even ceased following bony decompression (craniectomy + laminectomy) in 19 patients; however, bi-directional flow was observed in the systolic phase and cranially directed flow in the diastolic phase. The maximum flow rate ranged from 4 to 13 cm/s after duraplasty, and this varied with respiratory rhythm. Only 1 patient showed typical CSF flow after craniectomy, suggesting sufficient decompression, and without further duraplasty. All surgeries were terminated when bi-directional CSF flow was observed using IOUS-CDFI. With the exception of 1 patient, all the patients’ symptoms were significantly relieved.ConclusionIOUS-CDFI can monitor CSF flow during posterior fossa decompression, provide information about the re-circulation of CSF flow, and objectively evaluate the efficacy of surgery.