THE INDICATIONS for pneumoencephalographic and pneumorachiographic studies are well known.1 It is also well known that patients undergoing these procedures complain of severe headache for five days or more and are considerably incapacitated. It is not unusual to hear them referred to by patients in the ward as "skull busters," "nut crackers" and other terms signifying their great dread of and anxiety toward submitting to these diagnostic procedures. Many attempts to overcome such undesirable after-effects have been tried by various workers in the field.2
Liberson3 described the use of various gases in an attempt to reduce the severe headache reactions to encephalographic procedures and concluded:
... whereas the question of safety in encephalography has been dealt with and met in great part by the simultaneous displacement apparatus, nothing substantial has been found to obviate the discomforting post-injection headache. The displacement of the cerebrospinal fluid by gases other than