Cerebrospinal Fluid Pressure Changes in Fractional Pneumoencephalography Without Removal of Cerebrospinal Fluid

Abstract

Although a number of authors (1–3) have reported the performance of pneumoencephalography with minimal removal of cerebrospinal fluid, there is still some opposition to this practice, on the basis that a significant increase in cerebrospinal fluid pressure might result, with an adverse reaction in the patient. The following study was undertaken to determine whether any significant alteration in cerebrospinal fluid pressure, as measured through the lumbar puncture needle, occurs when virtually no cerebrospinal fluid is removed during fractional air encephalography. Material and Technic Seventy-seven pneumoencephalograms were obtained on 73 patients. Eight patients had pituitary tumors extending above the sella, 9 had other intracranial tumors, 1 had undergone removal of a meningioma several years previously, 1 had a brain abscess, and 15 showed enlarged ventricles, or enlarged cerebral sulci, without evidence of ventricular obstruction (“atrophy”). The remaining patients were investigated for seizures, post-traumatic or unusual headaches, etc. (Table I). In 6 instances, 3 in the same patient, all the injected air was in the subarachnoid spaces and no ventricular filling could be obtained. One of this group had post-traumatic headaches and seizures; 1 had cerebral atrophy and a later study was successfully performed; 1 had suprasellar extension of a chromophobe adenoma. A lumbar puncture with an 18-gauge needle was performed with the patient in a sitting position. An average of 3 to 4 ml. of cerebrospinal fluid was removed in the connector tubing and manometer, when pressure was recorded. (Not more than 5 ml. was removed, except in 1 case, in which the amount was 16 ml. This case is included to demonstrate its similarity to the others.) Cerebrospinal fluid pressure was measured in millimeters of water pressure, with the patient seated. The most accurate evaluation of cerebrospinal fluid pressure in such a situation is obtained by noting the level of fluid in the manometer relative to the cisterna magna. Normally, the manometer level of cerebrospinal fluid will not be above the inion or below C-7, except in an occasional patient who is apprehensive and is sweating profusely. In several patients in this series, unusually low cerebrospinal fluid pressures (mid or lower thorax) were noted at the commencement of the procedure, even though blood pressure was normal at the time. One patient was sweating moderately at the time of measurement. In 3 patients (2 with intracranial tumors) there was an elevated cerebrospinal fluid pressure (40 to 100 mm. above the inion) at the commencement of the study. From 12 to 100 ml. of air was injected in fractional amounts, starting with 4 to 10 ml., with increments of varying volumes at five- to ten-minute intervals. The usual total volume of air injected was 40 to 60 ml. Results In 8 cases there was a fall in cerebrospinal fluid pressure of 10 to 90 mm., even though the blood pressure did not drop.