Article
Dynamic magnetic resonance imaging in the postoperative assessment of patients with Chiari I malformation
Dynamische MRT-Untersuchungen zur postoperativen Verlaufskontrolle nach Operation bei Chiari-I-Malformation
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Published: | May 30, 2008 |
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Objective: The objective of surgery for Chiari I malformation is to restore normal cerebrospinal fluid (CSF) flow in the region of the foramen magnum. CSF flow can be visualised using dynamic phase-contrast magnetic resonance imaging (MRI).
Methods: Dynamic phase-contrast MRI was used to investigate the entire central nervous system in 22 patients with Chiari I malformation before surgery and after a mean postoperative period of 12 months (median postoperative period: 12 months; range: 3-33 months). In addition, we measured absolute flow velocities, the extension of the syrinx and tonsillar descent.
Results: In the 22 patients, the mean distance from the cerebellar tonsils to the level of C2 was 1.7 cm before surgery (median distance: 2.0 cm; range: -0.4 to 3.2 cm) and 2.4 cm after surgery (median distance: 2.4 cm; range: 0.7 to 4.0 cm). Mean postoperative tonsillar ascent was thus 0.7 cm (median ascent: 0.7 cm; range: -0.1 to 2.0 cm). This difference is highly significant (p<0.00005). The mean anterior-posterior (AP) diameter ratio decreased from 0.67 (median ratio: 0.69; range: 0.17-1) to 0.2 (median ratio: 0.17; range: 0-0.57). The mean decrease was thus 0.47 (median decrease: 0.46; range: 0-0.92) and highly significant (p<0.00005). The change in pulsation was highly significant in the region of the (enlarged) cistern (p=0.0005). In addition, the maximum and minimum velocities (= pulsation amplitude) considerably increased in the region where the syrinx was largest in diameter. It was interesting to note that the change of pulsation in these patients was significant in the subarachnoid space at all spinal segments but not in the syrinx itself and in the central canal. In 2 cases, there was no postoperative improvement in pulsation in the new cistern. Since the clinical course, too, was unsatisfactory, these patients underwent a second surgerical procedure.
Conclusions: The demonstration of CSF flow pulsations is a useful tool for assessing postoperative outcome in patients with Chiari I malformation. In addition, the results presented here question current theories on the pathogenesis of syringomyelia.