Ventricular anatomy: two lateral C-shaped ventricles separated by a midline septum pellucidum; each has a frontal foramen of Monroe which connects into the third ventricle; the third ventricle has an anterior pre-mammillary membrane anterior to the hypothalamic mammillary bodies and posterior to the chiasmatic and infundibular recesses; posteriorly in connects with the fourth ventricle through the Aqueduct of Sylvius; the fourth ventricle sits between the brain stem anteriorly and the cerebellum posteriorly and drains cerebrospinal fluid (CSF) through the central foramen of Magendie and two lateral foramina of Luschka to be spread around the brain and spinal cord.

Cerebrospinal fluid (CSF) physiology: clear colorless fluid produced by choroid plexus within the ventricles (80 %), interstitial space, ventricular ependymal and nerve root sleeves dura mater; resorbed by arachnoid villi of the dural venous sinuses, choroid plexus and cervical lymphatics back into the venous system driven by hydrostatic gradient. Daily CSF production and volumes: Newborns: 25 ml produced per day; total volume of 5 ml; adults: 0.3–0.35 ml/min (450–750 ml/day) produced; total volume 150 ml. The 150 ml volume is reached by age 5 years old. Production is pressure independent.

Hydrocephalus (HCP): abnormal accumulation of CSF, resulting in raised intracranial pressure (ICP). Prevalence 1–1.5 %; incidence of congenital HCP 0.9–1.8/1,000 births.