BIOMECHANICAL CHANGES IN THE HYDROCEPHALIC BRAIN

Year II of this project will focus on the implementation of protocol IV of
the original proposal. The specific aim of this protocol is to study the
amplitude and phase relations of CSF pulse waveforms as they are affected
by two pertubations: alterations of the container property of the brain
and the establishment of active hydrocephalus. The instrumentation
necessary to conduct this phase of research is currently on site and
consists of: 1) An FM-instrumentation tape recorder for capture and
storage of pulse wave signals from experimental subjects; 2) analog to
digital conversion of these signals; and PDP 11/23 computer for analysis of
this data. Signal analysis will be performed in both time and frequency
domains. Software is currently being developed for the fast Fourier
transform of these signals (the method used to enter the frequency domain
from the time domain) and will be operational before year II begins. Pulse waves will be sampled at ventricle, cisterna magna and convexity
subarachnoid cerebrospinal fluid spaces, as well as sagittal sinus and
carotid artery (via lingual artery catheterization). Respiratory
components will be filtered. The analysis of these pulse waveforms will be
conducted in 4 conditions: 1) The intact animal; 2) craniectomy, 3)
durectomy (i.e., conditions 2 and 3 representing altered container
properties) and 4) The hydrocephalic state. Changes in these signals will
also be investigated during pertubations of cerebrospinal fluid. The objectives of data analysis will include the determination of the phase
and amplitude relationships of CSF pulses as container properties of the
brain are altered and during ventricular enlargement. The hypothesis to be
tested is that transient pressure gradients created by phase and amplitude
changes in the CSF pulse accompany progressive ventricular enlargement in
hydrocephalus.