CSF-space volumetric change following posterior fossa decompression in paediatric Chiari type-I malformation: a correlation with outcome.

objectiveWe have previously reported inferior post-operative clinical outcomes in younger children with Chiari type-I malformation (CIM). We sought to quantify the CSF volumetric changes pre- and post-decompression, in a paediatric cohort, to determine whether cisternal volume change is associated with clinical outcomes.

methodsIn this retrospective clinical study, the CSF spaces of the posterior fossa (supracerebellar/quadrigeminal, prepontine, fourth ventricle, cisterna magna) were measured on magnetic resonance images pre- and post-operatively using a semi-automated method. Additionally, we describe a novel CSF space of the upper cervical canal incorporating the subarachnoid space from the foramen magnum to the inferior cortex of the C2 body, FM-C2 cistern. Morphometric measurements included the pB-C2 distance, clivoaxial angle, clival length, clival angle and Boogard's angle. Volumetric and morphometric data were correlated with clinical outcomes at 4-12 months post-operatively as measured by the Chicago Chiari Outcome Scale (CCOS).

resultsOf 59 adequate clinical cases, 57 and 36 patients had acceptable imaging for morphometric and volumetric analysis respectively. All CSF spaces measured had a significant increase in volume post-operatively (p < 0.05). There was no correlation between the change in volume or post-operative CSF volumes and CCOS. The pre-operative volume of the FM-C2 was positively correlated with total CCOS (Wald [Formula: see text], [Formula: see text]) and was significantly smaller in the 0-6-year age group (2.38 ± 1.27 ml vs. 3.67 ± 1.56 ml, p = 0.014). No morphometric measurement changed significantly after surgery or demonstrated a relationship with CCOS.

conclusionsVolumetric changes in the CSF cisterns of the posterior cranial fossa and upper cervical canal do not correlate with the age-related differences in clinical outcomes in paediatric CIM. The pre-operative volume of the FM-C2 cistern may have a role in predicting the likelihood of a beneficial post-operative outcome in paediatric CIM.