Figure 4.

Plot of cerebrospinal fluid (CSF) and syrinx fluid velocities over one cardiac cycle before and after surgery. Subarachnoid space (SAS) velocities are averaged along the cervical cord at the 1 o’clock location in the SAS. Preoperatively, the SAS has a peak of 3.6 cm per second in the caudal direction, and fluid in the syrinx has a peak velocity of 2.0 cm per second in the cranial direction. The CSF flow has a unimodal pattern, with one peak in the positive direction and one of smaller magnitude and greater duration in the negative direction. Flow in the syrinx fluid has a multimodal pattern with three peaks in each direction. Peak caudal flow in the CSF coincides with peak cranial flow in the syrinx. The heart rate was recorded as 73 beats per minute (bpm). Postoperatively, CSF flow had a peak of 2.7 cm per second in the caudal direction, a 29% reduction from the preoperative study. The fluid in the syrinx had a peak of 1.5 cm per second, also in the caudal direction, a 25% decrease from the preoperative study. The pulse was recorded at 97 bpm. Peak CSF velocity in the same locations in the SAS at 10 months after surgery remained stable at 2.4 cm per second in the caudal direction (no plot shown).