Transcranial Doppler sonography (TCD) is a noninvasive technique for measur
ement of cerebral blood flow velocity (CBFV) in the major arteries of the c
ircle of Willis. Dynamic changes in the pulsatility index (PI) and the resi
stance index (RI), as calculated from TCD data, allow for an assessment of
the forces acting on the terminal vasculature of the brain. The present stu
dy was designed to investigate a possible relationship between TCD paramete
rs and intracranial pressure (ICP) changes in adult patients with hypertens
ive hydrocephalus. Blood flow velocity in the middle cerebral artery (MCA)
was studied by TCD in 29 hydrocephalus patients and in 20 healthy controls.
ICP was measured in the patient group before ventricular shunting and was
correlated with TCD data.
The mean CBFV in hydrocephalic patients prior to ventriculoperitoneal shunt
ing was significantly lower than in the control group. Compared to normal p
ersons, systolic and end-diastolic CBFV values in patients were significant
ly decreased, suggesting an increased distal cerebrovascular resistance. PI
and RT values in patients with elevated ICP prior to shunting were signifi
cantly increased in comparison to those of normal persons. There was a stat
istically significant positive correlation of preshunting ICP and mean pres
hunting values of RI (r=0.50, P<0.01) in hydrocephalic patients, but no sig
nificant correlation between PI and ICP, and between CBFV and ICP. Immediat
ely after shunting, ICP returned to normal, and PI and RI values decreased
significantly, while the mean CBFV increased.
In a subgroup of;hydrocephalic patients with a preshunting ICP value >35 mm
Hg (n=6), the changes described above were more pronounced than in the sub
group with preshunting ICP values <35 mm Hg, which suggests an exponential
degree of influence of ICP on TCD parameters.
In conclusion, TCD may provide a tool for assessment of ICP in adult patien
ts with occlusive hydrocephalus, although an exact noninvasive measurement
of ICP by TCD seems impossible. Changes in the RI and PI indices appear to
be useful indicators of elevated ICP.