Lateral recess

The lateral recess is a narrow extension of the fourth ventricle on either side projecting laterally posterior and around the inferior cerebellar peduncle, opening into the subarachnoid space at its lateral extremity as the lateral aperture to allow for the passage of cerebrospinal fluid. 

In the area of the lateral recess, the vestibular area (containing the vestibular nuclei) and the cochlear nuclei may be found. In the vicinity, the medullary striae may also be seen.