In abnormal IH patients it switches to a negative radial orientation, an important diagnostic feature of central incisural herniation, especially in early stages of IH when findings can otherwise easily be missed.
Central incisural herniation affects the mammillary bodies and the tuber cinereum differently.
In the most advanced state of incisural herniation, the interpeduncular fossa is completely effaced (see Figure 3).
When the mammillary bodies descend to or beyond the level of the incisural line, the patient has substantial caudal migration and is considered grade 2 (if at the line) or grade 3 (ifbelow the line).
In conclusion, this study reveals that IH is always accompanied by central incisural herniation and changes to the visual pathway.
Caption: Figure 1: Incisural and foramen magnum related anatomic planes of reference and their MRI equivalent reference lines.