Transcranial Doppler sonography in adult hydrocephalic patients

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.