Morphologic MR imaging results*
| Present | Absent | Unknown | |
|---|---|---|---|
| Triventricular dilation | 17 | 0 | 0 |
| Small/normal 4th V | 17 | 0 | 0 |
| Direct CSF pathway obstruction (sagittal T2) | 10 | 4 | 3 |
| Downward bulging of the floor of the 3rd V | 10 | 7 | 0 |
| Space-occupying lesion | 3 | 14 | 0 |
Note:—4th V indicates fourth ventricle; 3rd V, third ventricle.
* Numbers refer to the patients in each category.