Color Doppler ultrasound in evaluating the cerebrospinal fluid dynamics before and after duraplasty in patients with Chiari I malformation treated with foramen magnum decompression

Abstract

Objective To evaluate the recovery of circulation of cerebral spinal fluid (CSF)around foramen magnum before and after duraplasty in patients with Chiari Ⅰ malformation (CMI) treated by foramen magnum decompression by using colored Doppler ultrasound (CDU). Methods Twenty patients suffered from CMI, including 17 combined with syringomyelia, admitted to our hospital from December 2008 to June 2009, were performed foramen magnum decompression via posterior midline approach; Neuropatch was used to repair the dura mater. Tarlov's grading scale and MRI was employed to evaluate the efficacy and the improvement of syringomyelia. All patients underwent CDU before and 10-20 d after the duraplasty to evaluate the circulation of CSF in arachnoid space below tonsil of cerebellar (TC). Results Fifteen patients (75%) got improvement and 5 without change after the surgery. Postoperative MRI indicated that 82.4% patients (14/17) combined with syringomyelia enjoyed good results. Cisterna magna reappeared after the surgery. CDU showed that bidirectional flow of CSF was recovered around foramen magnum in all patients with the Caudal-directed flow rate of CSF in dorsal arachnoid space below TC 8.92 ±5.19 cm/s and cephalad-directed flow rate of 6.85 ±2.44 cm./s; as compared with that after the surgery, the bidirectional flow could be found in only 11 patients before duraplasty (55%). Conclusion Foramen magnum decompression with duraplasty can restore the circulation of CSF around foramen magnum effectively in patients with CMI, and CDU, providing accurate data of circulation of CSF during or after the surgery, is a useful tool to evaluate the flow of CSF in patients with CMI. Key words: Arnold-Chiari malformation; Duraplasty; Colored doppler ultrasound; Cerebrospinal fluid dynamics