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Transcranial Doppler sonography in adult hydrocephalic patients
N G Rainov1, J B Weise, W Burkert
1Department of Neurosurgery, Martin-Luther-University, Halle (Saale), Germany. nikolai.rainov@medizin.uni-halle.de
Insights
Transcranial Doppler sonography (TCD) can indicate elevated intracranial pressure (ICP) in hydrocephalus patients by showing increased resistance indices (RI) and pulsatility indices (PI). While not exact, TCD offers a valuable noninvasive tool for assessing ICP changes.
Area of Science:
- Neurology
- Medical Imaging
- Cerebrovascular Physiology
Background:
- Transcranial Doppler sonography (TCD) noninvasively measures cerebral blood flow velocity (CBFV).
- Pulsatility index (PI) and resistance index (RI) from TCD assess cerebrovascular forces.
- Hypertensive hydrocephalus involves elevated intracranial pressure (ICP) affecting brain vasculature.
Purpose of the Study:
- To investigate the relationship between TCD parameters and ICP changes in adult hydrocephalus patients.
- To assess the utility of TCD in evaluating ICP dynamics before and after intervention.
Main Methods:
- TCD was used to measure CBFV, PI, and RI in the middle cerebral artery (MCA) of 29 hydrocephalus patients and 20 controls.
- ICP was measured in patients before ventricular shunting and correlated with TCD data.
- TCD parameters were re-evaluated immediately after shunting.
Main Results:
- Hydrocephalic patients showed significantly lower mean CBFV and increased distal cerebrovascular resistance compared to controls.
- Pre-shunting ICP positively correlated with RI (r=0.50, P<0.01), but not PI or CBFV.
- Post-shunting normalized ICP, decreased PI/RI, and increased CBFV were observed, with more pronounced changes in severe ICP cases.
Conclusions:
- TCD parameters, particularly RI and PI, are useful indicators of elevated ICP in hydrocephalus.
- TCD may serve as a valuable noninvasive tool for assessing ICP trends in occlusive hydrocephalus.
- Exact noninvasive ICP measurement via TCD remains challenging.
Abstract:
Transcranial Doppler sonography (TCD) is a noninvasive technique for measurement of cerebral blood flow velocity (CBFV) in the major arteries of the circle of Willis. Dynamic changes in the pulsatility index (PI) and the resistance index (RI), as calculated from TCD data, allow for an assessment of the forces acting on the terminal vasculature of the brain. The present study was designed to investigate a possible relationship between TCD parameters and intracranial pressure (ICP) changes in adult patients with hypertensive 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 shunting was significantly lower than in the control group. Compared to normal persons, systolic and end-diastolic CBFV values in patients were significantly decreased, suggesting an increased distal cerebrovascular resistance. PI and RI values in patients with elevated ICP prior to shunting were significantly increased in comparison to those of normal persons. There was a statistically significant positive correlation of preshunting ICP and mean preshunting values of RI (r=0.50, P<0.01) in hydrocephalic patients, but no significant correlation between PI and ICP, and between CBFV and ICP. Immediately 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 subgroup 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 patients 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.