DESPITE extensive research, the factors concerned with the dynamic equilibrium of cerebrospinal fluid are but imperfectly understood. Theories on the formation of cerebrospinal fluid consider the possibilities of dialysis, ultrafiltration,1 or a secretory process, the last theory being supported by more recent data.2 The site of formation of cerebrospinal fluid also remains in doubt. Earlier theories centered it in the choroid plexus,3 while recent studies suggest that the cerebrospinal fluid is formed more diffusely in all perineuronal and perivascular spaces.4 Physiological mechanisms influencing the formation of cerebrospinal fluid and abnormal factors capable of altering its formation remain even more obscure.