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ANATOMY FOR DIAGNOSTIC IMAGING
olives give a square configuration to the medulla on this section. The fourth ventricle is seen posteriorly, especially on sagittal sections, with its midline foramen leading to the vallecula. The most inferior part of the fourth ventricle is called the obex. This may be sealed during surgery of the cervical cord syrinx. In the lowest images the hypoglossal nerve may be seen entering the hypoglossal canal of the occipital bone. Cervical myelography Contrast medium may extend into the cranium and outline the medulla anterior to the cisterna magna. The expanded upper medulla with its nerve rootlets can be seen.
CEREBELLUM (Figs 2. 15 and 2. 16) The cerebellum lies in the posterior fossa. It is separated from the occipital lobe by the tentorium and from the pons and midbrain by the fourth ventricle. It is connected to the brainstem by three pairs of cerebellar peduncles: • Superior cerebellar peduncles (brachium conjunctivum) to the midbrain; • Middle cerebellar peduncles (brachium pontis) to the pons; and • Inferior cerebellar peduncles (restiform body) to the medulla. The cerebellum lies on the occipital bone posteriorly and close to the mastoid anteriorly. It is related to the dural sinuses, especially the sigmoid sinuses.
