Description of morphometric measurements
| Morphometric Measurement | Description | |
|---|---|---|
| Area | ||
| 1 | CSF area posterior to PCF (mm2) | CSF area posterior to a line drawn between the IOP and opisthion, and posterior to the cerebellum |
| 2 | Anterior CSF area (mm2) | CSF area in the upper cervical spinal canal anterior to the spinal cord between the FM and inferior limit of the C2 vertebra |
| 3 | Posterior CSF area (mm2) | CSF area in the upper cervical spinal canal posterior to the spinal cord between the FM and inferior limit of the C2 vertebra |
| Length | ||
| 4 | Cerebellar height (mm) | Distance between the most superior point of the superior vermis and the most inferior point of the tonsil |
| 5 | Total dorsal CSF width (mm) | Width of the CSF space measured at the level of the FM, anterior to the cerebellum, posterior to the brainstem and posterior the cerebellum, anterior to the subarachnoid space |
| 6 | Ventral CSF width (mm) | Width of the CSF space measured at the level of the FM, anterior to the brainstem, posterior to the subarachnoid space |
| 7 | Cerebellar tonsillar position (mm) | The perpendicular distance between the most inferior tip of the cerebellar tonsils and the McRae line |
| 8 | Occipital bone length (mm) | Length between a point at the midpoint of the occipital bone at the level of the tentorium and IOP and the most inferior tip of the occipital bone |
| Angle | ||
| 9 | Cerebellum-clivus bone angle (degree) | The angle subtended by the major axis of the cerebellum with the posterior margin of the clivus bone |
Note:—IOP indicates internal occipital protuberance; FM, foramen magnum.