A 4-month-old infant has undergone surgical treatment for meningo myelo encephalocele. A CT tomogram of head was made immediately after birth (see Figure below). At birth, an operation was carried out in the posterior cranial fossa to partially replace brain cerebellar contents to an intracranial position. In investigations for progressive hydrocephalus, it is noted that there is herniation of the cerebellar tonsils through the foramen magnum, and a diagnosis of Arnold-Chiari syndrome is established. This syndrome may also include which of the following?Tomogram from CT head taken 4 months previously (immediately after birth). Opening in the posterior cranial fossa showing brain and meninges protruding into sac (axial view).