CSF flow measurement in syringomyelia

Abstract

Background and purpose: CSF circulation has been reported to represent a major factor in the pathophysiology of syringomyelia. Our purpose was to determine the CSF flow patterns in spinal cord cysts and in the subararachnoid space in patients with syringomyelia associated with Chiari I malformation and to evaluate the modifications of the flow resulting from surgery.

Methods: Eighteen patients with syringomyelia were examined with a 3D Fourier encoding velocity imaging technique. A prospectively gated 2D axial sequence with velocity encoding in the craniocaudal direction in the cervical region was set at a velocity of +/- 10 cm/s. Velocity measurements were performed in the larger portion of the cysts and, at the same cervical level, in the pericystic subarachnoid spaces. All patients underwent a surgical procedure involving dural opening followed by duroplasty. Pre- and postoperative velocity measurements of all patients were taken, with a mean follow-up of 10.2 months. We compared the velocity measurements with the morphology of the cysts and with the clinical data. Spinal subarachnoid spaces of 19 healthy subjects were also studied using the same technique.

Results: A pulsatile flow was observed in syrinx cavities and in the pericystic subarachnoid spaces (PCSS). Preoperative maximum systolic cyst velocities were higher than were diastolic velocities. A systolic velocity peak was well defined in all cases, first in the cyst and then in the PCSS. Higher systolic and diastolic cyst velocities are observed in large cysts and in patients with a poor clinical status. After surgery, a decrease in cyst volume (evaluated on the basis of the extension of the cyst and the compression of the PCSS) was observed in 13 patients. In the postoperative course, we noticed a decrease of systolic and diastolic cyst velocities and a parallel increase of systolic PCSS velocities. Diastolic cyst velocities correlated with the preoperative clinical status of the patients and, after surgery, in patients with a satisfactory foraminal enlargement evaluated on the basis of the visibility of the cisterna magna.

Conclusion: CSF flow measurement constitutes a direct evaluation for the follow-up of patients with syringomyelic cysts. Diastolic and systolic cyst velocities can assist in the evaluation of the efficacy of surgery.

fig 1.

Cervical syringomyelia. Axial slice, preoperative velocity imaging (patient 11). Six images are obtained 30, 100, 150, 200, 300, and 400 ms after the R-wave. Craniocaudal velocities are represented in red and caudocranial velocites in blue. A pulsatile flow is observed as well in the cyst as in the PCSS.

fig 2.

Normal kinetics of CSF at C2 and C6 levels (volunteer 15). Caudal flow is represented by negative values. A systolic velocity peak is clearly defined, and it occurs in the first third of the RR cycle duration. fig 3. Cystic and pericystic kinetics (patient 1). A systolic peak is observed in the PCSS and in the cyst, but it occurs sooner in the cyst.

fig 4.

Pre- and postoperative evolution (patient 13). Pre- and postoperative cyst morphology (A), pre- (B) and postoperative (C), velocity imaging, evolution of cyst (D), and of PCSS velocities (E) are shown. PCCS velocity increases in the postoperative course. In this case with a partial reduction of the cyst volume, cyst velocity distinctly decreases